Nutritional values, consumption and utilization of ...

Proc. Regional Workshop on Hilsa: Potential for Aquaculture. 16-17 September 2012. Dhaka, Bangladesh

Nutritional values, consumption and utilization of Hilsa Tenualosa ilisha (Hamilton 1822) A K M Nowsad Alam1, Bimal P. Mohanty2, M. Enamul Hoq3 and Shakuntala Thilshed4 1

Department of Fisheries Technology, Bangladesh Agricultural University, Mymensingh, Bangladesh Biochemistry Laboratory, ICAR-Central Inland Fisheries Research Institute, Barrackpore, Kolkata, India 3 Bangladesh Fisheries Research Institute, Mymensingh, Bangladesh 4 The WorldFish Center, Bangladesh & South Asia Office, Dhaka, Bangladesh 2

Abstract The Indian shad hilsa, Tenualosa ilisha (Hamilton, 1822), is one of the most important tropical fishes in the IndoPacific region and has occupied a top position among the edible fishes due to its superb taste, mouthwatering flavor and delicate culinary properties. Hilsa is rich in amino acids, minerals and lipids, especially with many essential and poly-unsaturated fatty acids (PUFA). It is found to be beneficial to human health because of very high level of high density lipoprotein and low level of low density lipoprotein in PUFA that reduce the risk of heart disease, diabetes, cancer, obesity, etc. The unique taste of hilsa has been attributed to the presence of many mono and poly unsaturated fatty acids, viz., oleic, lenoleic, lenoleneic, arachidonic, eicosapentaenoeic and docosa-hexaenoeic acids. Hilsa is tastier during pre-spawning than post-spawning or maturing stages. Female hilsa grows faster, attains larger and becomes more tastier than the male of same age group. Riverine hilsa, especially those from the river Padma, are more tastier than marine ones. Transformation of saturated and mono unsaturated fatty acids into PUFA are believed to be the key important phenomena that controls the unique taste of riverine hilsa. About 60-70% of hilsa are consumed fresh in Bangladesh and the rest are exported to India, USA, EU, Japan and the Middle-east. Due to high price paid in both domestic and international markets, post-harvest handling and icing of the fish are found to be adequate, while post-harvest loss was minimum, except in some glut catches when ice production can not keep pace with very high demand. Hilsa is processed through semi-IQF (individual quick freezing), plain salting, saltfermenting and wood-smoking. Hilsa is consumed by so many ways with several lovely dishes are prepared as delicacy, viz., shorshe ilish, bhapa ilish, ilish polao, ilish paturi, panta ilish, etc. The present paper reviews the nutritional importance, consumption, post-harvest handling, processing and utilization of hilsa as the most popular and commercially important food fish in the Indian subcontinent.

1.

Introduction Fish is one of the important sources of quality animal proteins and availability and

affordability is better for fish in comparison to other animal protein sources. Fish serves as a health-food for the affluent world owing to the fish oils which are rich in polyunsaturated fatty acids (PUFAs), especially ω-3 PUFAs and at the same time, it is a health-food for the people in the other extreme of the nutritional scale owing to its proteins, oils, vitamins and minerals and the benefits associated with the consumption of small indigenous fishes (Mohanty, 2011). Fish, especially saltwater fish, is high in ω-3 fatty acids, which are heart-friendly, and a regular diet of fish is highly recommended by the nutritionists. This is conjectured to be one of the major causes of reduced risk of cardiovascular diseases in Eskimos (Bang et al. 1976). It has been suggested that the longer lifespan of Japanese and Nordic populations may be partially due to their higher consumption of fish and seafood. Oily fish is claimed to help prevent a range of other health problems from mental illness to blindness. Thus fish has medicinal and therapeutic value


(Mohanty et al. 2011a) and the health benefits of eating fish are now being increasingly understood (FISHupdate.com). Tenualosa ilisha (Hamilton, 1822) of the subfamily Alosinae, family Clupeidae, order Clupeiformes, is one of the most important tropical fishes of the Indo-Pacific region and has occupied a top position among the edible fishes owing to its taste, flavor and culinary properties. Popularly known as hilsa, it is a fast swimming euryhaline known for its cosmopolitan distribution in brackish water estuaries and marine environment in the Indo-pacific faunistic region and in the riverine environments where it migrates for breeding. Major catch of hilsa, about 95%, comes from Bangladesh, India and Myanmar. Naturally hilsa is in great demand globally, specifically in the oriental world and enjoys high consumer preference. Its high commercial demand makes it a good forex earner. Five varieties of Tenualosa sp (T. toli from Malaysia, T. macrura from Indonesia, T. thibaudeaui from Mekong, T. reevesii from Southern China and T. ilisha from India, Bangladesh and Myanmar) are found in tropical Asian region (Blaber et al. 1997) out of which T. ilisha and to some extent T. toli and T. kelee are prevalent in the Indian waters. The normal habitat, age and growth and trend of migratory habit differ from species to species. Among the five species, T. ilisha is the major component of fishery in the Ganga-Brahmaputra-Padma river system. In Hooghly estuary, hilsa, the state fish of West Bengal, accounts for 15-20% of the total fish landing (Bhaumik 2010). Hilsa, the national fish of Bangladesh, contributes 12-13% of the total fish production and about 1% to the GDP. Hilsa is oblong and compressed having 30-33 spine like scutes on abdomen. Difference between two major hilsa species is very minute. In T. ilisha dorsal and ventral profile of the body is equally convex, while in T. toli abdominal profile is more convex than that of dorsal. There are 150 to 200 straight to slightly curved gill rakers on the lower part of first arch in T. ilisha, while gill rakers are curved and number of gill rakers are 80 to 90 in T. toli ( Huda and Haque, 2003). There are two bundles of muscles on each side of the vertebral column and each of the bundles is further separated into an upper mass above the horizontal axial septum and a ventral mass below this septum. In between the upper and lower bundle mass, along the axial septum, a thick sheet of dark muscles develops, spreading widely on the surface beneath the skin but extending conically up to back bone (Nowsad, 2010). Branched pin bones extend horizontally from the neural or hemal spines into the white muscle tissue. Abdominal portion of lower bundles are devoid of pin bones. Due to pin bones hilsa can not be filleted.

Most of the muscle tissue is


white (65-70%). White muscles have lower level of lipids, haemoglobin, glycogen and vitamins compared to dark muscles. The dark muscle, about 30 to 35 % of total muscle, is located just beneath the skin, originates from the base of caudal region and extends along the horizontal axial septum up to cranium. The darkness in muscles originates from the colour due to chemical combination of haemoglobin with myofibrillar proteins, called myoglobin. Dark muscles are generally devoid of pin bones and

characterized with higher levels of lipids, haemoglobin,

glycogen and most vitamins. Dark muscle also contains more trimethylamine oxide and amino acids. The high lipid content of dark muscle in hilsa is important because of problems with rancidity. Dark muscle also inhibits gel forming ability of muscle tissue which is an important characteristic of fish for heat treated textured foods. The dark muscle primarily functions as a cruising muscle, i.e., for slow continuous movement, characteristics of migratory species (Huss, 1988). Due to high lipid content, hilsa can not be sun dried. Therefore, most preferred short term method of preservation is icing and long term one is salting or salt-fermenting. Some of the hilsa are frozen. A few are smoked but, although available before, are not found in the market now (Nowsad, 2007). High lipid content makes the hilsa very susceptible to oxidative rancidity, along with rapid autolytic and bacteriological decomposition (Nowsad, 2010).

So, adequate handling and

immediate icing for the fish are required. Premium quality fresh hilsa is silver shinny with transparent watery slime and pleasant odour. There is often found a reddish colouration on abdominal surface on each side of the fish in the market. Newly caught fish do not have this colouration. The dark and associated surface muscles are supplied with enormous blood through network of capillaries, in order to supply energy for continuous movement. The redness appears after death when a portion of hemoglobin molecule is separated from the blood and flood the musculature beneath the skin. But the redness is not an indicator of quality deterioration in fish (Nowsad, 2010). Hilsa fishery plays a critical role in terms of the generation of employment and income for those involved, as well as earning foreign exchange for the country. Recent estimates have suggested that, in Bangladesh alone, about 500,000 fishers catch hilsa; there may be another 2-2.5 million people indirectly involved in the distribution, sale and other ancillary activities like net and boat making, ice production, processing and export. The present paper reviews the nutritional


importance, consumption, post-harvest handling, processing and utilization of hilsa as the most popular and commercially important food fish in the Indian subcontinent. 2. Nutritional values of hilsa Fish contains proteins and other nitrogenous compounds, lipids, minerals and vitamins and very low level of carbohydrates (Gopakumar, 1997). Protein content of fish varies from 15-20% of the live body weight. Fish proteins contain the essential amino acids in the required proportion and thus, improve the overall protein quality of a mixed diet. The superior nutritional quality of fish lipids (oils) is well known. Fish lipids differ greatly from mammalian lipids in that they include up to 40% of the long-chain fatty acids (C14-C22) that are highly unsaturated and contain 5 or 6 double bonds; on the other hand, mammalian fats generally contains not more than 2 double bonds per fatty acid molecule. Fish is generally a good source of vitamin B complex and the species with good amount of liver oils are good source of minerals like calcium, phosphorous, iron, copper and trace elements like selenium and zinc. Besides, saltwater fish contains high levels of iodine also. In fact, fish is a good source of all nutrients except carbohydrates and vitamin C. Some inland fish species like singhi (Heteropnestus fosslis), magur (Clarius batrachus), murrels (Channa sp.) and koi (Anabas testudineus) have therapeutic properties (Mohanty et al, 2011a). The importance of fish in providing easily digested proteins of high biological value is well documented. In comparison to other sources of dietary proteins of animal origin, such as chicken, mutton, pork, beef etc. the unit cost of production of fish is much cheaper. Fish also come in a wide range of prices making it affordable to the poor. A common man can afford to meet the family‟s dietary requirement of animal proteins because he has the option to choose from a fairly large number of fish species available (Mohanty et al, 2012b). A portion of fish provides with one-third to one-half of one‟s daily protein requirement. This explains how fish plays an important role in meeting the nutritional food security, especially in preventing the protein-calorie malnutrition. In the past this has served as a justification for promoting fisheries and aquaculture activities in several countries. On a fresh-weight basis, fish contains a good quantity of protein, about 18-20%, and contains all the eight essential amino acids including the sulphur-containing lysine, methionine, and cystein. The greatest advantage of *eating fish* is that, unlike meat, it has minimal content of saturated fat. The most important fat in fish is omega-3 fatty acid.

Hilsa is endowed with this


valuable fatty acids and lipids which play a major role in providing pharmaceutical elements for physiological maintenance of body tissue. The fats found in hilsa are of the unsaturated kind, which is good for health. Cooked hilsa is known for its easy digestion and is also used as a recuperating food. Polyunsaturated omega-3 fatty acids (ω-3 PUFAs), EPA and DHA especially obtained from fish oil are reported to be potential in curing coronary heart diseases, stroke, hypertension,

cardiac

arrhythmias,

diabetes,

rheumatoid

arthritis,

brain

development,

photoreception system, cancer and depression. A 100 g hilsa contain 22.0 g Protein, 19.5 g Fat. Highest fat content of 20% has been observed in hilsa captured from Mahanadi river mouth, while it was lower in Narmada catches along Indian coast. Fatty acid profiling of small pelagic fishes of Sri Lanka have shown highest amount of saturated fatty acids in hilsa shad (5844.5 mg/100g fish and palmitic acid contributed 3345 mg/100g fish as compared to other pelagic in North-West coast of Sri Lanka (Edirisinghe et al. 1998). Table 1. Nutritional value of raw hilsa Nutrients Calories Calories from fat Protein Total fat Total carbohydrate Vitamin C Calcium Iron

Value 309.58 200.00 24.72 g/100 g 22 g/100 g 3.29 g/100 g 27.22 mg/100g 204.12 mg/100 g 2.38 mg/100 g

The chemical characteristics of oil extracted from different body parts of hilsa fish showed variation among different body parts (Table 2). The saturated and unsaturated fatty acids present in hilsa oil are mainly myristic, palmitic, stearic, palmitolenic and oleic acids. The contents of % FFA are initially low but increased rapidly on storage at room temperature (Salam et al. 2005). Table 2. Chemical characteristics of hilsa fish oil extracted from different body parts Parameters Saponification value Iodine value Peroxide value (m.eq.O2/kg oil) Acid value % FFA (as oleic)

Body parts Dorsal 194.00 101.30 8.00

Ventral 194.00 102.00 8.60

Caudal 192.00 101.40 8.00

Egg 180.28 100.22 9.28

Liver 180.76 126.40 10.00

Brain 182.24 80.70 7.00

4.28 2.14

4.16 2.08

4.30 2.15

7.16 3.58

12.00 6.00

8.72 4.36

Proc. Regional Workshop on Hilsa: Potential for Aquaculture. 16-17 September 2012. Dhaka, Bangladesh 1.66

Unsaponifiable matter (%)

1.58

1.82

4.60

3.72

7.00

The fatty acids composition of the oil from six different parts of hilsa showed that the saturated fatty acids present in the oil are mainly myristic acid, palmitic acid and stearic acid. The unsaturated fatty acids present in the hilsa oil are palmitolenic acid, oleic acid, linoleic acid, linolenic acid etc. and present in highest amount in egg (Table 3) (Salam et al. 2005). Table 3. Fatty acid compositions of hilsa oil extracted from different body parts Fatty acids C14:0 C16:0 C18:0 C16:1 C18:1 C18:2 C18:3

Body parts Dorsal 5.44 24.70 6.20 13.00 28.32 1.16 0.92

Ventral 5.70 25.30 6.32 12.30 28.00 1.10 0.96

Caudal 5.50 24.86 6.30 13.11 28.40 1.02 0.92

Egg 6.60 26.40 5.70 14.00 29.78 2.18 0.90

Liver 5.90 27.08 5.00 12.00 29.44 2.20 1.08

Brain 7.24 22.00 4.00 12.18 26.08 0.92 0.82

The fatty acid composition of different size hilsa is given in Table 4. Analysis showed that medium-sized fish contained the highest amount of unsaturated fatty acids as well as ω-3 PUFAs (EPA+DHA) and the lowest amount of saturated fatty acids (SFAs). PUFA content was highest in small-sized hilsa; however, ω-3 PUFA content was lower and SFAs content was higher in medium-sized fish. In the large-sized fish, although ω3/ω6 ratio was highest, quantitatively they contained the lowest amount of PUFAs and highest amount of SFAs. Thus on the basis of fatty acid profiles, medium-sized hilsa is the best followed by the small-sized fish for human health and nutrition. Myristic acid (C14:0) was the dominant SFA in small and medium size fish whereas palmitic acid was the dominant SFA in large sized fish. The highest amount of stearic acid (C18) was found in large sized hilsa, however, there is no significant differences in stearic acid content of small and medium sized hilsa. Oleic acid (C18:1; n-9) was found to be the major monounsaturated fatty acid in all three different size fish (Mohanty et al, 2012a). Oleic acid (OA) is clinically important unsaturated fatty acid with great therapeutic value. It has been reported that OA suppresses over expression of the oncoprotein (Her-2/neu-coded) p185Her-2/neu in vitro and a higher level of OA in breast tissue provide an effective means of influencing the outcome of breast cancer (Menendez et al. 2005).


Table 4: Fatty acid composition of different size-groups of hilsa (Source: Mohanty et al. 2012a) Fatty acid Saturated 8:0 10:0 12:0 13:0 14:0 15:0 16:0 17:0 18:0 20:0 22:0 24:0 ΣSFA Monounsaturated 14:1 15:1 16:1n-7 17:1 18:1n-9 20:1n-9 22:1n-9 24:1 ΣMUFA Polyunsaturated 18:2n-6 18:2tr 20:2n-6 22:2n-6 18:3n-3 18:3tr 20:3n-6 20:3 and 21 20:4n-6 20:5n-3 22:6n-3 ΣPUFA Σω-3 Σω-6 EPA+DHA Σω-3/ Σω-6 ΣPUFA/ΣSFA AI TI

Small size

Medium sized (% of total fatty acids)

Large size

0.05±0.04a 0.06±0.02 a 0.41±0.01 a 0.24±0.25 a 38.78±0.12 a 1.69±0.04 a 0.81±0.05 a 0.82±0.03 a 0.24±0.02 a 0.62±0.06 a 0.48±0.09 a 0.43±0.02 a 44.64±0.09 a

0.03±0.03 a 0.05±0.01 a 0.37±0.23 a 0.05±0.01 a 37.77±0.02b 1.48±0.01 b 0.21±0.06 a 1.05±0.03 b 0.26±0.06 b 0.67±0.03 b 0.45±0.02 a 0.44±0.04 a 42.82±0.07 b

0.03±0.01 a 0.02±0.01 b 0.09±0.03 b 0.02±0.01 a 9.67±0.48 b 0.34±0.12c 38.26±0.05 c 0.19±0.05 c 8.86±0.16 b 0.20±0.02 c 0.22±0.09 b 0.11±0.05 b 57.99±0.15 c

0.26±0.05 a 0.08±0.02 a 0.06±0.01 a 0.25±0.08 a 26.55±0.51 a 3.47±0.06 a 0.38±0.06 a 0.55±0.13 a 31.60±0.19 a

0.18±0.08 a 0.05±0.02 a 0.48±0.05 b 0.29±0.09 a 30.66±0.19 b 2.27±0.36 b 0.64±0.02 b 0.78±0.05 b 35.36±0.20 b

0.07±0.04 b 0.01±0.01 b 0.22±0.06 c 0.07±0.05 b 25.42±0.25 c 1.23±0.40 c 0.09±0.04 c 0.20±0.13 c 27.59±0.18 c

0.66±0.12 a 2.66±0.11 a 0.13±0.02 a 0.07±0.01 a 2.61±0.06 a 0.86±0.16 a 1.11±0.06 a 0.13±0.02 a 4.66±0.03 a 2.49±0.03 a 8.41±0.01 a 23.78±0.08 a 13.51±0.09 a 6.62±0.12 a 10.90±0.03 a 2.18±0.26 a 0.54±0.01 a 3.02±0.01 0.62±0.01

0.88±0.03 b 1.84±0.66 b 0.12±0.03 a 0.07±0.01 a 2.23±0.04 b 0.68±0.05 a 0.14±0.004 b 0.17±0.03 b 4.14±0.06 b 2.87±0.09 b 8.95±0.03 b 22.11±0.25 b 14.06±0.05 b 5.36±0.09 b 11.83±0.09 b 2.62±0.04 a 0.52±0.02 a 2.77±0.03 0.59±0.01

0.29±0.45 a 0.88±0.09 c 0.03±0.02 b 0.15±0.04 a 0.59±0.13 c 0.74±0.72 a 0.08±0.04 b 0.03±0.09 c 1.21±0.33 c 8.22±0.25 c 2.02±0.42 c 14.75±0.39 c 10.83±0.68 c 1.76±0.37 c 10.24±0.57 a 6.41±1.86 b 0.25±0.02 b 2.25±0.55 1.18±0.02

Proc. Regional Workshop on Hilsa: Potential for Aquaculture. 16-17 September 2012. Dhaka, Bangladesh SFA-saturated fatty acid; MUFA- monounsaturated fatty acids; PUFA-polyunsaturated fatty acids; EPAEicosapentaenoic acid; DHA- Docosahexaenoic acid; AI- atherogenic index, TI- thromobogenic index

2.1 Changes in proximate and fatty acid composition of hilsa Nutrient composition of hilsa fish varies among their body parts and also in different habitats. Hilsa from the major landings sites of Chittagong and Kulna, Bangladesh showed that proximate compositions varied among the different portions of fish body (Shamim et al. 2011). The protein content was estimated to be 20.56, 21.89, 21.33, 20.87 and 20.50% in the dorsal portion (Chittagong), ventral portions (Chittagong), caudal portion (Chittagong), dorsal portion (Kulna), ventral portion (Kulna) and caudal portion (Kulna), respectively. Highest protein and fat contents were recorded as in ventral portion of fish from the Chittagong region (21.89% and 20.28% respectively). Proximate composition of the hilsa changes during their anadromous migration in river Godavari, India (Table 5) (Rao et al. 2012). The variation in the protein content of hilsa during anadromous migration was not very conspicuous. However, there was wide variation in the fat content of hilsa during its anadromous migration. The fat content in the marine hilsa was 12.4%. The fat content increased to 17.3% in brackish water hilsa. The fat gradually decreased in Godavari hilsa (14.51 to 8.78%). The results suggest that hilsa gains significant fat content in the brackish water environment. This is in contrast to other anadromous fishes which accumulate fat in the marine environment and do not feed during their upward migration. Table 5. Changes in the proximate composition of Godavari hilsa during anadromous migration to river Godavari during June to November Proximate composition Moisture (%) Protein (%) Fat (%) Ash (%)

Marine

Brackish water

June 63.5 22.69 12.4 1.43

July 62.31 18.14 17.38 1.68

Freshwater Aug 64.63 19.92 14.51 1.03

Sep 66.3 21.53 11.18 1.15

Oct 69.29 20.15 9.83 0.73

Nov 66.64 22.38 8.78 1.66

The Godavari hilsa showed decreasing fat content with time. It is likely that fatter fish move first from the brackish water location to the Godavari barrage. Hilsa must accumulate energy reserves during their growth phase in the form of lipids, mainly as triglycerides which are catabolized to provide the energy necessary for anadromous migration and spawning. Jonsson et


al. (1997) reported a decrease in lipid content during the course of upward migration of Atlantic salmon. Again the changes in the saturated and unsaturated fatty acid content during migration of Godavari hilsa were determined (Table 6). The saturated fatty acid (SFA) content was lower in Godavari hilsa (24.98%) than in brackish water hilsa (36.76%) and marine hilsa (36.03%). The distinctly higher content of SFA in marine and brackish water hilsa is obvious as the hilsa is gearing up for migration and storing saturated fat. Even though the total unsaturated fatty acid (USFA) content of marine hilsa (63.98%) and brackish water hilsa (63.14%) was almost similar, marine hilsa had higher levels of monounsaturated fatty acid (MUFA) content (52.57%). Polyunsaturated fatty acid (PUFA) content showed an increasing trend with lowest in marine hilsa (11.41%) and highest in freshwater hilsa (26.87%). The distinctly higher content of SFA in marine and brackish water hilsa is obvious as it is gearing up for migration by storing saturated fat. PUFA content was higher in freshwater hilsa. The results suggest the transformation of fat, towards PUFA, during the migration of the hilsa. PUFA was formed at the expense of either MUFA or both SFA and MUFA. PUFA are integral constituents of the cell membranes. The migration of hilsa from the salty marine environment (30-35 ppt) to the low saline brackish water or zero saline freshwater environments changes the osmotic balance of the cells. Increased PUFA is necessary to reorganize the composition of vital membrane to maintain homeostasis. The change in fatty acid composition of hilsa towards PUFA might be possibly a physiological mechanism to counter the changes in salinity of water during migration. The study showed that Godavari hilsa is a nutritionally rich fish with adequate amounts of protein, minerals and fat. Increase in PUFA was observed during the anadromous migration of hilsa. The nutritional composition of freshwater hilsa from River Godavari appears to be better than the marine hilsa from Bay of Bengal. Table 6. Changes in the saturated (SFA) and unsaturated (USFA) fats during migration of hilsa from marine to freshwater during June to November Hilsa origin Marine Brackish water Freshwater(Godavari river)

SFA* 36.03 36.76 24.98

USFA* 63.98 63.14 75.02

*All values are expressed as % fatty acid/total fatty acids

The crude fat content of small, medium and large size fish was found to 6.74-9.43, 8.9412.56, and 11.25-17.87%. Substantial differences between the seasons were observed in three


different size groups of hilsa. The highest level of fat content was found during the quarter July– October (Q1) while lowest during the quarter November– February in all three different size groups of hilsa. The crude fat content of small, medium and large size fish was found to be 6.74– 9.43, 8.94–12.56 and 11.25–17.87 %, respectively, showing a direct positive relation to the size of the fish (Table 7) (Mohanty et al. 2012a). Table 7. Seasonal variation in crude fat content of Hilsa (Source: Mohanty et al. 2012a) Size/Season

Small (200-400 g) Medium (800-1000 g) Large (1400-1600 g)

July-October (Q1) 9.43 12.56 17.87

November-February (Q2) (g/100 g of wet muscle) 6.74 8.94 11.25

March-June (Q3) 7.56 9.91 14.73

Besides fatty acids, hilsa is also rich in amino acids (Table 8). The amino acids are the building blocks of the body protein. Essential amino acids (EAA) must be obtained from the diet, while non essential amino acids (NEAA) can be produce from the other source in the body. The major amino acid in small size, medium size and large size fish are histidine, glutamic acid and aspartic acid ranging from (5.47 ± 0.41)% to (6.31 ± 0.10)% , (13.06 ± 0.06)% to (15.39 ± 0.22)%, (10.21± 0.06)% to (11.25 ± 0.40)%, respectively. The level of different amino acids was from (0.20±0.05)% to (15.16±0.47)% in small size hilsa, (0.95±0.04)% to (15.39±0.22)% in medium size hilsa and from (0.72±0.01)% to (10.21±0.06)% in large size fish, respectively. Aspartic acid, glycine and glutamic acid content in small size fish was (10.48±0.04) %, (8.46±0.39) % and (15.16±0.47) % respectively. The essential amino acids such as isolucine, leucine, phenylalanine, histidine, lysine, and arginine were (5.35 ± 0.12)%, (9.25 ± 0.33)%, (4.16 ± 0.14)%, (6.31 ±0.10)%, (3.22±0.03)% and (1.25±0.13)%, respectively in small size hilsa. A high plasma EAA-to-NEAA ratio is considered to be an index of positive protein nutritional status (Swendseid, Villalobos & Friedrich, 1963). The favorable ratio of EAA to NEAA, about 0.70, indicates high quality protein content (Bandarra, et al., 2004). The highest value recorded for squid‟s roe (0.93) and was lowest for sea urchin roe (0.65). Amino acid metabolism also depicts the physiological function of rat plasma and erythrocyte EAA-to-NEAA ratio showed a positive correlation to IGF-I and insulin whereas an inverse correlated to IGFBP-1 (Filho, et al., 1999).


Table 8: Total amino acid profiles of Tenualosa ilisha. (Source: Mohanty et al. 2011b) Amino Acid

Small Size

Medium Size

Large Size

(% of total amino acid) Essential ND

6.32 ±0.17a

7.10 ±0.03a

6.58 ± 0.81a 3.30 ±0.29a 5.35 ±0.12a 9.25 ±0.33a 4.16 ±0.14a 6.31 ±0.10a 3.22 ±0.03a 1.25 ±0.13a 39.42

6.35 ± 0.21a 1.63 ±0.10b 6.20 ±0.21b 9.33 ±0.35a 3.71 ±0.42b 5.47 ±0.41b 2.35 ±0.25b 0.94 ±0.03b 42.3

5.80 ±0.81a 2.72 ±0.02c 4.69 ±0.58a 8.03 ±0.06b 3.43 ±0.38b 5.94 ±0.21a 10.15 ±0.05c 0.72 ±0.01c 48.58

Aspartic acid Serine Glutamic acid Glycine Alanine Tyrosine Proline Cysteine ∑NEAA

10.48 ± 0.04a 6.56 ± 0.13a 15.16 ± 0.47a 8.46 ± 0.39a 9.34 ± 0.28a 1.92 ± 0.54a 0.20 ± 0.05a 0.32 ± 0.03a 52.44

11.25 ±0.40b 7.02 ±0.31b 15.39 ±0.22a 9.01 ±0.21b 9.59 ±0.15a 1.39 ±0.16a 1.34 ±0.39b 0.95 ±0.04b 55.94

10.21 ± 0.06c 5.99 ±0.13c 13.06 ±0.06b 8.22 ±0.25a 8.45 ±0.04b 0.84 ±0.16b 0.91 ±0.10b 2.11 ±0.06c 49.79

EAA/NEAA

0.75

0.76

0.98

Threonine Valine Methionine Iso leucine Leucine Phenylalanine Histidine Lysine Arginine ∑EAA Non-essential

Values are shown as average ± standard deviation. ND- not detected, EAA- essential amino acid, NEAA- non essential amino acid

The paramount importance of the hilsa in nutritional point of view is all the more enhanced by the presence of minerals. These micronutrients play a major role in the metabolic activity of the human body, by serving as co-factor of enzymes. The macro minerals (Na, K, Ca, Mg) and trace minerals (F, Cu, Zn, Mn) are present in hilsa in good amount (Table 9). Table 9: Mineral content in medium size hilsa (Source: Mohanty et al. 2012c) Minerals

Concentration (mg/100g wet weight)

Macro minerals Na Mg K

63.07±5.11 38.33±8.12 695.13±17.25

Ca

119.03±14.56

Proc. Regional Workshop on Hilsa: Potential for Aquaculture. 16-17 September 2012. Dhaka, Bangladesh Micro minerals Mn Fe Cu Zn

0.28±0.03 3.06±0.72 0.31±0.06 0.96±0.09

Values are shown as average ± standard deviation

Fish is a rich source of vitamins, particularly vitamins A, D, E from fatty fish species, as well as thiamin, riboflavin and niacin (vitamins B1, B2, B3). Vitamin A from fish is readily available to the body than from plant source. Among all the fish species, fatty fish contain more vitamin A. The vitamin content of medium size hilsa (Mohanty et al, 2012c). is given below (Table 9). Table 10: Fat soluble vitamin content of medium size Hilsa (Mohanty et al. 2012c ) Vitamins

A D E K

Concentration (µg/100g)

IU/100g

712.93±0.59 133.6±0.60 841545.45±0.47 1163.85±0.62

2376.43 5344.0 925.70 -

2.2 Nutrigenomics of hilsa Study of physical structure of fish is important in order to understand the nutrition profile and quality changes of fish during handling, transportation, processing, storage and heat treatment. Like other teleosts, in hilsa there are two bundles of muscles on each side of the vertebral column and each of the bundles is further separated into an upper mass above the horizontal axial septum and a ventral mass below this septum. In between the upper and lower bundle mass, along the axial septum, a thick sheet of dark muscles develops, spreading widely on the surface beneath the skin but extending conically up to back bone (Fig. 1 & 2). Bundles of muscles, mostly upper bundles, are characterized with huge Y- shaped branched pin bones. Pin bones extend horizontally from the neural or hemal spines into the muscle tissue (Nowsad, 2010). Abdominal portion of lower bundles are devoid of pin bones. Due to pin bones hilsa can not be filleted. Patient separation of cooked flesh from bones is required, that may restrict fish loving people, unfamiliar to hilsa taste, to eat this fish at the first time. There are two types of muscles: white muscle and dark or red muscle. Most of the muscle tissue is white (65-70%). White muscles are full of pin bones and have lower level of lipids, hemoglobin, glycogen and vitamins compared to dark


muscles. White muscle is sprinting muscle in function, used for sudden, quick movements needed for escaping from a predator or for other reasons. Hilsa has 30-35% dark tissue of brown or reddish colour. The dark muscle originates from the base of caudal region and extends along the horizontal axial septum up to cranium. This darkness in muscles appears from the colour due myoglobin. Dark muscle, generally devoid of pin bones, is characterized by higher levels of lipids, hemoglobin, glycogen and most vitamins and usually contains more trimethylamine oxide and amino acids. From technological point of view, the high lipid content of dark muscle in hilsa is important because of problems with rancidity. The dark muscle primarily functions as a cruising muscle, i.e., for slow continuous movement (Huss, 1988).

a.

b. Fig. 1. Hilsa, Tenualosa ilisha. (a) Tenualosa ilisha; (b) Sketch of hilsa showing distribution of dark muscles along the lateral line (Curtsy: Nowsad, 2010))


a. b. Fig. 2. Skeletal musculature of hilsa. (a) Musculature; (b) Sketch showing the distribution of dark and white muscles (Curtsy: Nowsad, 2010)

Skeletal muscle is the largest organ system in fish and represents the edible part. In fish, the skeletal muscle constitutes the 34-48% of the total body weight (Addis, 2010). Muscle composition contributes strongly to quality. In fact texture, elasticity, and water holding capacity, all features highly related to quality, are dependent on number and integrity of muscular fibres (Johnston, 1999). The number of muscle fibre recruited during growth is subjected to variation depending on several factors, such as the fish strain, diet, exercise training and temperature (Addis, 2010). Muscle proteins are the important repository of much of the biological information. Since the proteins, not the genes, directly take part in various metabolic processes and physiological activities depending upon whether it is a structural protein, an enzyme, a signaling molecule or growth factor or a defense protein like immunoglobulins, they can potentially provide most, if not all, of the vital information on the organism (Mohanty and Mohanty, 2004; Mohanty et al. 2005; Ohlendieck, 2011). All the proteins expressed by a cell or tissue or organ comprise the proteome and study of the proteome is called „proteomics‟. Proteomics is functional genomics, meaning it focus on those 10% of genes (or gene products) which are expressed/functional; about 90% of genes are not expressed and they are, therefore, not well understood. It is a highly powerful tool in protein analysis which supplements gene sequence data with protein information about where, in which ratio and under what condition proteins are expressed. Proteomics is an unbiased and technology-driven approach for the comprehensive cataloging of entire protein complements and represents an ideal analytical tool for the highthroughput discovery of protein alterations in health and disease (Hochstrasser et al., 2002; Martin et al. 2007). Mass spectrometry-based proteomics is concerned with the global analysis of protein composition, posttranslational modifications and the dynamic nature of expression levels. The


generation of large data sets on protein expression levels makes proteomics a preeminent hypothesis-generating approach in modern biology (Cravatt, 2007; Ohlendieck, 2011). Aiming to better understand proteome alterations, it is vital to have a „reference proteome map‟ for a specific tissue and species and the muscle proteome map may in fact represent a general „fingerprint‟ of the fish species (Fig.3. Mohanty, B. P. 2012; unpublished data) (Mohanty et al. 2009; Ohlendieck, 2011). Tenualosa ilisha is a commercially important food fish species and enjoys high consumer preference. Proteomics analysis of muscle is an important approach for gaining insight into the comparative muscle physiology and biochemistry under normal and pathophysiological conditions (Yi et al., 2008). Skeletal muscle proteomics will also help to establish the global identification and biochemical characterization of all members of the muscle-associated proteins. For example, if in hilsa it is found that the medium size fish contains the highest amount of w-3 PUFAs EPA and DHA, as compared to the small and large size fishes, muscle/liver proteomic analysis at that stage of the fish can explain why it is so by providing biochemical evidence at the proteome level, by showing the expression level and quantity/abundance of the enzymes (proteins) elongases and desaturase (Mohanty et al. 2012a). Thus muscle proteomics and transcriptomics needs to be studied in detail for understanding the nutrigenomics of this important food fish for optimal utilization of the health benefits associated with consumption of hilsa.

Proc. Regional Workshop on Hilsa: Potential for Aquaculture. 16-17 September 2012. Dhaka, Bangladesh Fig.3. 1- and 2-Dimensional Gel Eectrophoresis profiles of Tenualosa ilisha white muscle protein extract. 12% Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) profile and 2-D gel electrophoresis profile. (Mohanty, B. P. 2012; unpublished data).

2.3 Hilsa for betterment of human health Fatty acids of fish oil are currently being championed as beneficial for human health (British Nutrition Foundation 1992). The most efficient way to add these important oils to one‟s diet is to take at least two/three, servings of fatty fish per week. Hilsa is a highly preferred foodfish in Kolkata, India, and is always in great demand due to its taste and other culinary properties. Comparing the fatty acid profile of hilsa with other marine fishes, we found that ω-3 and EPA + DHA content of hilsa (14.06 and 11.83 %) is higher than that of Indian Mackerel (11.2 and 6.42 %) (Marichamy et al. 2009). Moreover considering ω-6 content, hilsa (5.36 %) also have an advantage over herring (2.93 %) (Huynh et al. 2007) and Atlantic salmon (3.2 %) (Blanchet et al. 2005). Assuming that hilsa is consumed four times a week and one piece (weight 40–45 g) each time, the consumption per head per week comes to 160–180 g. The commonly available size of hilsa in local fish markets varies from 400 to 900 g i.e. medium size. As this size of hilsa contains 1.55 g EPA + DHA per 100 g of fish meat, 2.48–2.79 g of EPA + DHA is consumed per week; this means, about 354–398 mg EPA + DHA is consumed per day against a requirement 650 mg per day of these two ω-3 fatty acids, as per the National Institutes of Health, USA as studied by Mohanty et al. 2012a. However, this projection of the consumption pattern is for the peak seasons, when hilsa is plentily available in the market. Therefore, hilsa can be a good food supplement for providing the PUFAs, especially the ω-3 fatty acids. However, there is a line of caution for the affluent class of consumers who can afford to eat hilsa ad libitum. As mentioned before and as has been reported by other workers earlier (Rahman and Salimon 2006), hilsa contains higher amount of SFAs (42.82 %) owing to which it has a higher value for atherogenic index (AI) and thrombogenic index (TI) and therefore, moderate consumption is good for the heart (Mohanty et al. 2012a). Effect of eating hilsa fish in hypercholesterolemic subjects revealed that hilsa fish although is fatty and contains cholesterol, but it may reduce blood cholesterol level. A study by Quazi et al. (1994) showed that after 10 months of eating 100g hilsa fish per day, serum total cholesterol level fell from 285.1 to 244.6 mg/dl (14.2% decrease) in the hypercholesterolemic subjects. The fall in total cholesterol was exclusively due to fall in LDL-cholesterol. Serum triglyceride, serum HDL-


cholesterol increased in the experimental subjects by 12.5%. On the other hand, serum total cholesterol, HDL-cholesterol, LDL-cholesterol and triglyceride levels were not changed in control subjects. Both in control and experimental subjects there were no changes in body weight and blood pressure during the study period. 3. Why hilsa is called “Macher Raja” – the reasons behind its unique tastiness Hilsa is considered as one of the most tastiest fish due to its distinctly soft oily texture, mouthwatering flavour and superb mouthfeel. The fish is locally called “Macher Raja” means the king of fish. The human tongue recognizes four basic tastes as sensory responses in different taste buds, viz., sweet, sour, salty and bitter (Keller, 1985). The sweet taste is sensed at the tip of the tongue, the salty taste at the tip and edges, the sour at the edges and the bitter at the deep back. Bitter sensation takes longer time to perceive and tends to linger. Flavour is perceived when volatile flavor compounds stimulate the olfactory fibers in nasal air passages. Mouthfeel occurs at a variety of nerve endings in the oral cavity. When tasting, human sensory organs perceive not only the four basic tastes, but also warm, cold, pain, tactile and pressure sensations. When food is taken into the mouth, all the sensations are usually recognized to verifying the degree of tastiness (Keller, 1985). Konosu (1979) and Konosu and Yamaguchi (1982) reviewed the taste of fish and shellfishes and concluded that the flavor of fish are distributed to extremely great variety of flavor compounds that are variable according to species and biological conditions. The nucleus of taste and flavor in fish is constructed by the synergistic effects of glutamic acid and neocleotides along with sodium and chloride ions. The core flavor is enhanced by other taste active amino-acids, mainly taurine and arginine, and nucleotides and inorganic ions. Peptides, organic bases, organic acids and sugars are also responsible for characteristic taste of some fish species. Flavour volatiles, lipids, fatty acids and glycogen also play important role in producing overall flavor. Konosu and Yamaguchi (1985) found large amount of anserine in five species of Atlantic salmon, a great tasty fish, and suggested that anserine present in the muscle of salmon should play a significant role in its taste. The unique taste of hilsa has often been attributed to the presence of certain fatty acids like steareic acid, oleic acid and many poly unsaturated fatty acids (ω3, ω6 ), viz., lenoleic, lenoleneic, arachidonic, eicosapentanoeic and docosa-hexanoeic acids (Mohanty, et al. 2011;


Nath and Banerjee, 2012; Madhushudhana Rao et al. 2012). It is very widely accepted hypothesis, but the correlation between the content of these fatty acids and the tastiness has not been studied. However, some clues are there that clearly defines a close linkage between the polyunsaturation of fatty acids and the taste of the fish. Hilsa is tastier just before the spawning than post-spawning or maturing stages. During pre-spawning time, lipid content in female hilsa generally range from 16 to 22 percent (Mohanty et al. 2011; Madhushudhana Rao et al. 2012). Female hilsa grows faster, becomes larger and more tastier than the male of same age group. Riverine hilsa, specially those from the river Padma, are more tastier than marine ones. Several researchers claimed that a sub-stock of hilsa exists in the Padma river, although many authors described hilsa as a single stock in the regions shared by Bangladesh, India and Myanmar (BOLME, 2011). Ahmed et al. (2004) found very distinct genetic difference between Chandpur-Kuwakata and Cox‟s Bazar population of T. ilisha. The sub-stock of the Padma river might have been rich with characteristic type of taste-active compounds those impart further taste to this river population. The taste and flavor of many fish was sometimes depended on their food and feeding behaviour (Connell, 1975; Love, 1992). Planktonic mollusk, Spiratella helicinia fed by fish gives rise to an off-flavor in marine fish muscle, often described as „petrol‟ flavor. The larvae of Mytilus sp. give a bitter taste in herring (Connell, 1975). The texture, colour and flavour of fish flesh depend on food and feeding habits (Tangeras and Slinde, 1994). The nature of habitat where it lives also influences the taste of muscles (Huss, 1988). Tastes of cultured pungus, anabas, major carps, etc differ greatly from wild ones due to the type and quantity of supplemental feed administered. Farmed salmon are not as colourful due to astaxanthin deposition as the wild one and therefore receives low price in the market. Salmonids are not able to synthesize astaxanthin and depend on adequate supply through feed to obtain colour (Foss et al. 1987). Carps from lotic environment or from big reservoirs impart characteristic taste and color in flesh than carps of small confined water bodies. The unique taste of hilsa was also believed to be attributed to the environment where it grazes or to the feed it takes. Hilsa of freshwater origin is tastier than those of the sea. Godavari hilsa was found to be testier than marine hilsa in Indian waters of the Bay of Bengal (Madhushudhana Rao et al. 2012). During its time at sea hilsa remains short, thin and less tasty but when it enters in freshwater its taste and growth increases. Hilsa feed on plankton, mainly blue green algae, diatoms copepods, cladocera, rotifer, organic detritus, mud, sand, etc. (Hora and Nair, 1940). The stomach of spawning hilsa was found to contain a considerable amount of mud and sand also (Pillay, 1958). Hilsa filters planktons but also grubs on muddy


bottom in the sea and brackish water environment (Madhushudhana Rao, et al. 2012). But it does not feed at all or takes less feed during its further upward migration from brackish waters (Pillay, 1964). During migration it is sustained by the accumulated fat in its body. Therefore, fat content decreased from the sea to the brackish water, then further to the rivers. Fatter hilsa migrates faster and losses fats prompter in the rivers. Comparatively lesser fats in the river than their accumulation in the marine environment makes the flesh more soft and relaxed. During low salinity directed spawning migration, saturated fatty acids (depot fat) are converted first into mono- and then into poly unsaturated fatty acids. More the upward migration towards zero salinity, more the conversion into polyunsaturation was observed in many migratory fish like, hilsa, Atlantic salmon, chum salmon and sockeye salmon (Jonsson et al. 1997; Magnoni et al. 2006; Sasaki et al. 1989). Probably more the poly unsaturation in fish lipid, more the development of characteristic texture and pleasant flavour in the muscles. Probably, that is why abdominal part is tastier than the dorsal, where both lipid content and level of unsaturation are higher (Salam et al. 2005; Shamim et at. 2011). Polyunsaturated fatty acid content was found to be lowest of 11.41% in marine hilsa and highest of 26.87% in freshwater hilsa (Madhushudhana Rao et al. 2012).

Therefore, the transformation of saturated and mono unsaturated fatty acids into poly-

unsaturated fatty acids are believed to be the key important phenomena that controls the unique taste of freshwater hilsa. More over, among the PUFA, the quantity of docosa-hexaenoic acid (DHA, C22: 6ω3) was found to be 5.4 times higher than eicosa-pentaenoic acid (EPA, C20:5ω3)) content in Godavari river hilsa, while they were in smaller quantity in brackish water hilsa. In the sweet-water environment, due to changed osmotic balance from the 30-35 ppt salinity to almost zero salinity, fish takes more water through mouth, gills and skin to produce and expel large volume of urine. Thus the musculatory system of the fish gets relaxed, muscle cells become soft and flexible and the fat-protein inter molecular adjustment becomes more comfortable. As the fish swims up the river, it flexes it muscles, leading to loss of body fat and makes herself more tasty (Mondal, 2012). The PUFA acts as the integral components of the cell membrane during the new osmotic balance in sweet-water system, the conversion of which is necessary to counter the changes in salinity of water during migration. On the other hand, as the fish does not take food or take less food while in the rivers, most of the off-flavours imparted in the muscles from the food and mud in marine/brackish water habitat are eliminated through continuous dialysis by the sweet water threshold. All these impart unique taste and flavour in the hilsa muscles and make it the “Macher Raja” – the king of fish.


4.

Consumption and Utilization of Hilsa

4.1. Post harvest handling of hilsa Since hilsa is a high-lipid, rapidly perishable tropical fish, proper handling is necessary to control and slow down spoilage so that this popular high-priced fish can reach the consumer fresh. Due to delicate nature and rapid deterioration of muscles, that occurs if treated badly, it is extremely important to handle this fish very carefully during all stages of transportation, retail distribution, processing, preservation and marketing. Fishing gears determines the initial quality of harvested fish (Nowsad, 2010).

In

Bangladesh, the crafts and gears for harvesting of hilsa differ from place to place and season to season. The most effective and popular net for harvesting medium to large size hilsa in marine and brackish waters are drift gill net, locally called „vasha jal‟ and seine net, called „ber jal‟. Small mesh mono-filament gill nets, locally called „current jal‟ are mostly used to catch juvenile hilsa in the river mouth, estuary and

brackish waters.

Nets are usually made of synthetic and

monofilament fibre. Beside gill nets and seine nets, hilsa is also caught by setbag net, shangla jal and khora jal or vesal jal (lift net). Usually motorized boats, locally called „trawler‟ are used to catch hilsa in the sea and river. Motorized boats use inboard engines with capacity ranging from 18 to 65 HP. Generally three types of motorized boats are operated in the estuarine and brackish water hilsa fishing.

Small day fishing boats operating in the estuary or near shore have a

maximum of 4 crews on board. Some boats make a voyage for 3-4 days in the sea with 5-8 crews, while many large boats of 65 HP engine sail for 10-15 days with number of crews raging from 15 to 18. The boat owners generally hire fishermen to catch fish against pre-set little share of the catch.

Big merchants or „Mahajons’ give cash loan and boats/nets to the fishermen against the

promise to sell the fish to them at tangibly lower price than the market. Mahajons/commission agents deploy collectors or „bepari‟ to collect fish. They then sell the fish at wholesale markets. Traders purchase hilsa through the commission agents and transport them to big cities where it is re-auctioned through second commission agents to the retailers. So the quality of hilsa also depends on the capital flow, input and infrastructures and the awareness and attitude of the market actors. Hilsa was landed in major landing centers in most of the main rivers in Bangladesh several years back (Haldar et al., 2004). Even during inundation when flood water overflew the


river bank, huge number of hilsa came out from the rivers and

found in some beels or haors

(Mazid et al. 2005). Most of those hilsa were marketed locally within few hours and did not require much care for quality. Upward migration of hilsa declines now-a-days. Haldar et al. (2004) found hilsa and jatka only in 100 down-stream rivers in Bangladesh. Catch situation is further aggravated at present. The landing of hilsa is now confined at the lower shore areas of Meghna river, Tetulia, Kalabodor, down reaches of Arial Kha river, estuary of Dharmagonj and Nayabhangani river, other estuaries and coastal areas of Bangladesh (Hasan, 2009). Contrary to freshwater landing, marine landing of hilsa has been increased (DoF, 2011). Hilsa is landed almost round the year in many landing centers of Teknaf, Cox‟s Bazar, Bashkhali, Chittagong, Hatia, Patharghata, Kuwakata and Rangabali coasts and Khulna BFDC Ghat (Nowsad, 2010). Harvesting period also determines the quality of hilsa. Although migrate seasonally to the rivers during May to October, hilsa are caught in smaller quantity more or less all year round in the estuary and brackish water areas. The main harvest time of hilsa is August to October. Nearly 60% of total hilsa are caught during this time, with a lesser season between May to June (DoF, 2011). The fishing season varies from area to area. Fishing in the rivers starts from the beginning of South-west monsoon and continues up to 2-3 months after the monsoon. The winter fishing is limited and starts from December and continues up to March (Haldar et al. 2004). In the Northern region hilsa is caught during summer and in the Eastern region it is caught in the winter months. Dunn (1982) contradicted as saying that there are three peak seasons - one is around February, another is June and the major peak is September. Due to highly humid hotter climate, majority of hilsa caught in Bangladesh requires proper handling and adequate icing. As it is sold at very high price in both domestic and international markets, generally very special care is taken in postharvest handling and marketing unless any sudden glut catch disrupts ice supply and other facilities (Nowsad, 2010). Glut catch occurs one or twice in a year, mostly during SeptemberOctober. Handling of hilsa on-board fishing vessel, at landing and in different steps of distribution and marketing is more or less adequate (Nowsad, 2010). This is geared partly because of the awareness developed, but mostly due to the high price in the market. The price of inputs like ice and fish box is high, adequate transportion is costly, but the traders do not hesitate to afford because the extra cost can be easily realised through additional price-hiking. This is true for the big traders and suppliers who monopolize hilsa market. But there are small fishers and fish traders, where handling of hilsa is not often up to the mark.


Lack of awareness and skill often creates real problem when fishermen do not know how to behave with their hervest from different gears. Fish in “current jal”, “vasha jal” (drift gill net) and other gill nets spoil rapidly as they struggle much during fishing. Juvenile hilsa caught in the coast and river mouths by monofilament –„current jal’ are most susceptable to spoilage. In hotter months, if not treated with ice, these fish spoil within a few hours of hauling. Field study reveals that icing in traditional fashion is often sufficient in case of market size hilsa, except during glut catch when ice supply can not meet the huge demand (Nowsad, 2010). In traditional hilsa fishery in Bangladesh, fish are bulk-iced in the fish hold of the motorized artisanal fishing boats. The size of fish holds depends on the size of boat. Generally, it varies from 10 x 8 feet with a depth of 4-5 feet in 18 HP engine boat to 12.5 x 10 feet with a depth of 6-7 feet in 65 HP engine boat. Fish are stock-piled with ice in such a big room. Sometimes, this big room is divided into sections using pound boards supported by stanchions. During glut catch when the fish holds are full, because of the pressure of huge quantity of fish and ice from the top, the fish at the bottom of the fish hold are deteriorated rapidly, although they are kept in ice.

To overcome these problems, now small boxes made of plastic or steel and/or empty

plastic drums are used to keep hilsa in the hold. This type of icing is limited to only hilsa and other high priced species in coastal and matrine fishing. Large fishing boats operating large drift gill net (8-10 ton capacity) stay at the sea for about 10-15 days. Small boats (0.5-1.5 tons capacity) return to the land within 2-4 days. The boats generally carry ice block less than their capacity due to high price of ice and uncertainty in getting fish. For example, large boat carries only about 70-80 blocks of ice, each of 75 kg wight, which is not sufficient for 6-8 tons of fish to be kept chilled for 10-12 days. Most of the time fish holds are not full, so the quantity of ice carried do not hamper the quality of icing, except in glut catch which was found only for a few days in a fishing season. In Bangladesh, hilsa are iced in different types of containers and trnasported in many ways (Nowsad, 2010). Majority of the hilsa are transported by bamboo baskets of different shapes and sizes, with or without hogla mat or polythene covered and with sufficient ices. Fish transportation by bamboo baskets may cover a distance from a few kilometers to several hundred kilometers and the content from a few kg fish to several hundred kg. A quantity of 180 to 250 kg are often transported inter-district by a large size bamboo basket with 2-3 feet elevation made by split bamboo and polythene gunny sacs. When two of such baskets are placed one top another on the truck and transported a few hundred kilometers, the quality of fish really goes bad.


Locally made large ice boxes placed one-top-another on the truck are now used by innovative traders to carry fish from Khulna, Jessore, Chittagong, Cox‟s Bazar and many other places. These boxes were initially designed to preserve ice blocks and unsold fish in the market to sell on the next day or after (Nowsad, 2007). These were named community ice box since 5 community traders used the box on community based approach. That technology has been successfully adopted into bulk fish transportation over the time passed (Nowsad, 2011). Hilsa landed in Barishal-Barguna-Patharghata-Kuakata-Sundarban coasts are mainly transported in water-ways by country boat.

For this purpose, the open boats are specially

partitioned into several semi-insulated rectangular blocks with or without wood boards, hogla (a kind of aquatic plant leaves) mat and polythene sheet. Sometimes, styrofoam sheets are placed in bewteen the wooden boards. The rectangular partition blocks are wrapped with layers of polythene sheet. Hilsa are kept in these holds with sufficient ice and fish in alternate. Top of the fish are covered with a layer of ice, polythene and hogla mat. Generally,

fish landed in riverine stations

like, Chittagong, Pathaghata, Chandpur or Showarighat of Dhaka city are coming in this way. Hilsa are also being transported by plastic drum, steel made half-drum, country boat, sac made of hogla and polythene sheet, aluminium container with or without lid, wooden, fibre glass or plastic craters, styrofoam box and ideal ice boxes. Post-harvest condition of wet fish along with percent consumption of harvested fish is shown in Table 11. Hilsa was found to be nicely handled post-harvest, along with other high-valued species like prawn, shrimp and pomfret.

Table 11. Post-harvest situation of wet fish in Bangladesh (Source: Nowsad, 2010) Fish groups

Pretreatment (% practice)

Icing

Sorting Gutting Washing Dressing/ BCM (% 1 filleting practice)*

Process pattern

Market pattern

% consumed as wet fish *2

Giant prawn Hilsa Pomfret Bombay duck Ribbon Fish Jewfish Tuna/Mackerel Sea bass Penaeid shrimp

*1

97±1 97±2 98±0 22±9 27±4 65±12 69±11 78±13 100

Nil 8±2 Nil Nil Nil Nil Nil Nil Nil

95±3 77±18 87±12 82±3 87±4 86±5 75±7 65±2 100

Nil Nil Nil Nil Nil Nil Nil Nil Nil

87±9 88±3 91±4 38±5 42±8 72±12 47±7 69±6 92±3

Fre/Fro Fre/Fro/Salt Fre/Fro Fre/Dry Fre/Dry Fre/Fro/Dry Fre/Fro Fre/Fro/Dry Fre/Fro/Dry

Icing BCM: Icing before consumer market *2 Estimated from interview checklist, RRA and RMA data Fre: fresh; Fro: frozen; Dry: drying; Fer: fermentation: Dom: domestic; Expt: export Data Source: RRA, SWOT analysis and questionnaire interview of the current study

Dom/Expt Dom/Expt Dom/Expt Dom/Expt Dom/Expt Dom/Expt Dom/Expt Dom/Expt Dom/Expt

19±9 68±5 33±8 27±7 14±4 18±7 68±4 73±5 16±9


About 68% of harvested hilsa are consumed as wet fish. Hilsa is brought to the retail markets

with sufficient ice. Hilsa is displayed on large circular aluminium or GI sheet tray with ice around in the market for sale. Fish those are not displayed are kept in ice box or bamboo basket wrapped with polythene with sufficient crushed ice around the fish. The fish mongers or nikeries take extra care for quality maintenance in order to attract buyer and thus demand higher price. Premium quality fresh hilsa is silver shinny with transparent watery slime and pleasant odour. There is often found a reddish or pink colouration on the ventral surface on each side of the fish in the market. Newly caught fish do not have these colour bands. As stated, the redness is not an indicator of quality deterioration in hilsa. 4.2.

Post harvest loss in hilsa Hilsa is a high-lipid, high-protein fish. In addition, it has 30-35% dark muscles having

higher levels of lipids, hemoglobin, glycogen, vitamins, trimethylamine oxide and amino acids. These compositions make hilsa very much prone to spoilage at ambient temperature.

In hilsa,

rigor comes early, within 15 minutes of death and the fish achieves full rigor within 2 hours at ambient temperature (33oC). Rigor lasts for 15-16 hours after attainment of full rigor (Haque et al. 1997). After rigor is over, the decomposition of nitrogenous compounds leads to an increase in pH in the flesh and spoilage starts with autolysis and bacterial action in association with oxidation of lipids. As the fish is carefully handled by ice during transportation and marketing, spoilage or quality deterioration is not enormous in hilsa. The quality loss of hilsa was determined in different steps of distribution channel (Table 12). In estimating quality loss of wet fish, primarily a sensory method (Howgate et al. 1992) was used where the sensory indicators were rationally revised for getting more accurate results. A model was developed to standardize sensory data by chemical and microbiological quality indicators for greater accuracy (Nowsad, 2010). The assessments were conducted in different steps of its major distribution channels throughout the country for an entire year from March 2009 to February 2010 to find out the seasonal and spatial variations of quality loss. In every distribution step, at least five lots of fish and 3 individual measurements for each lot were assessed. The quality deteriorations of the same fish or same lot of fish were assessed during its movement from the fishermen at harvest to commission agent-1 (commission agent in primary


market) to transporter/wholesaler to commission agent -2 in secondary market to retailer and vendor.

Field data collectors moved along with hilsa from the origin of harvest or landing

through these value chains up to retailers and vendors and assessed the quality deterioration of same fish or lot of fish in different steps. In case of determining percent quality loss, the distance of consumer market from origin was considered and an average of loss due to handling of fish in hotter and colder months was taken. Neither of the fish lost their quality when they were in fishermen, landing centers or commission agents in primary fish market.

A 2% and 5% loss in hilsa destined for consumer

market as wet fish was, however, recognized in landing centers and Aratders (Table 12). This might be due to unavailability of ice or transport in glut season catch. Uddin et al. (1999) reported significant loss of ilish during glut period, mainly in August-September. But these huge catches cannot be taken care of with adequate supply of fishing boat, manpower for handling, icing, ice box and transportation. In this time, most of the quality deteriorated hilsa are processed into salting.

Hilsa used for salting suffered a substantial loss while they are in fishermen (14%) or

landing center (43%). Table 12. Percent quality loss of fish in different stages of distribution channel (Source: Nowsad, 2010). Fish

Month

Hilsa (wet fish) Hilsa (for salting) Roi

August September

Catla

February August

Mrigel

February July

Kalibaush

February July

Grass carp Silver carp Tilapia

March July

Pungas Bambay duck Ribbon

September February July

March May February May June January April December February

Distanc e of market (km)

% Loss*1 Fisherme n/ Farmer

Landing centre

Aratde r1

Transpor ter/Piker

Aratder – 2/ Processor

Retailer

Fish vendor

-

2±0.4

5±2

-

7±2

9±2

19±4

14±3

43±5

-

-

61±7

-

-

150400 150340 150350 150400 150350 150400 150

-

-

-

4±2

6±0.4

16±4

19±3

-

-

-

3±2

4±3

12±3

17±2

-

-

-

6±1

7±1

11±3

16±2

-

-

-

4±1

8±2

9±2

12±3

-

-

-

3±2

12±3

12±2

14±0.5

-

-

-

3±0.1

4±2

13±3

15±3

-

-

-

5±2

11±0.5

16±2

13±2

400450 250

-

-

-

-

4±2

7±3

10±4

3±0.2

4±0.8

-

11±1

17±2

19±2

-

50

8-10

10-14

400500 70- 150

20% in drying yard

Proc. Regional Workshop on Hilsa: Potential for Aquaculture. 16-17 September 2012. Dhaka, Bangladesh fish

4.3. Freezing of Hilsa Both jatka and medium sized hilsa of the glut catch are frozen into block on board in mechanized trawlers. Small hilsa are packed in polythene gunny sacs in orderly fashion and frozen into large block, preferably 40-60 kg in the trawler. Frozen blocks of small sized hilsa and jatka are frozen, stored in land-based cold storages and suitably sold in domestic markets throughout the country at reasonably cheaper price. Low income people are the major buyers of these small frozen hilsa. While selling in rural and urban markets, thawing of such large blocks is not adequately performed, mostly due to negligence. Whereby, sign of muscle distortion, head-cut, loss of operculum, torn up belly, etc. were observed with deterioration in quality (Nowsad, 2010). Hilsa exported to foreign countries are frozen whole, mainly in batch type air blast rack freezer as semi-IQF freezing. Air blast spiral freezer and contact plate freezer are also used. Long time frozen storage deteriorates hilsa quality due to oxidation of lipid and disintegration of myoglobin along the lateral line.

Oxidation was found to take place in lipid fish slowly even

during freezing and frozen storage (Clucas and Ward, 1996). Semi IQF of Hilsa Semi-IQF (individual quick freezing) hilsa are produced in the shrimp processing plants. After receiving moderate to large sized premium quality hilsa in iced condition, they are weighed, washed, re-iced, dressed, re-washed with chilled chlorinated (5 to 10 ppm) water (4oC) and weighed again. Hilsa is not gutted but processed whole for semi-IQF product. Adhered waters after washing are dried by fanning and then kept naked on SS pans or racks placed on the freezer pipe of air blast freezer. The fish is frozen at –30oC for 6 hours. Freezing plants that freeze white fish are equipped with air blast freezing equipment. Exclusive shrimp processing plants generally do not require batch or continuous type air blast freezer. But hilsa is also processed in shrimp/prawn processing plants. In the absence of continuous or batch type air-blast freezer, dressed hilsa are often kept on wire mesh of spiral freezer for freezing. In case of plate freezer, fish are placed on the freezing tray side by side and frozen as individual unit without making block. After freezing, the fishes are individually glazed, wrapped by thin polythene sac and packed in 20 kg carton under various grades like 10/12, 12/14, 14/16, 16/18, 18/20, 20/22, etc


according to buyers demand. A 10/12 grade means that there are ten to twelve fishes in a 20-kg package. Hilsa are also packed as 1000 g+, 1200 g+, etc. The carton is packed in durable poly bag and frozen stored at –25oC. 4.4. Salting of Hilsa Salting is a process of fish preservation where the water content is reduced by the penetration of salt, whereby the activity of most of the spoilage bacteria is stopped or reduced. Two basic principles describe the mode of action of salting as well as its importance in preservation of fish: i. removal of water from the deepest part of the flesh quickly enough to reduce water activity; ii. penetration of salt quickly enough in the deepest part of the flesh to lower the water activity (Clucas and Ward, 1996). A concentration of 6-10% salt in fish tissue can prevent the action of most spoilage bacteria. 4.4.1 Dry-salting of hilsa In dry-salting, solar salt and turmeric powder are sprinkled over the dressed and cut fish. In large commercial application, salted fish are piled up in circle in bulk quantity in a big room. In small-scale operation salt-treated fish are kept in a dry bamboo basket or perforated tin and the exudates are allowed to run away through the bottom holes. At first, the fish is scaled and the fins and gills are removed. The fish is cut transversely, from the dorsal to the ventral, by a sharp knife or „Boti‟ in such a way that the chunks remain attached at the abdominal „keel bone‟ region. The thickness of the piece ranges from 0.75-1.0 cm. Sometimes one triangular chunk from the neck is removed to widen the space between the chunks to ease spreading of the fish in crescentic fashion on the pile.

This also helps to ease the mixing and penetration of salt as well as removal of

exudates. Head remains intact with the body. The entrails are removed from the abdomen. Salt is added to the fish in sufficient amount, in its gills and mouths, in eyes and abdomen and in between each chunk. One part salt is used for a four-part fish. Along with solar salt, a small amount of turmeric powder is used to develop a colour in the product. Turmeric has got preservative value too. Storage is done in piles as in the case of large commercial production or in bamboo baskets and tin containers for small-scale production. In both cases,

dry-salted hilsa are kept for 3-6

months that allows rigorous changes in sensory properties. There are chances of contamination in every step of dry salting and the salt used and the salting method itself is not hygienic. The raw


material used was found to be stale, more than 60% of the raw material hilsa lost freshness quality (Table 12) and hence, the overall quality of the final product was not found good. 4.4.2 Wet-salting of hilsa In this method, the fish is dressed as in case of dry salting but the head is completely removed from the body. The dressed fish is either cut into small chunks or kept intact and salted either in brine or in dry solar salt. For brine salting, the whole fish or chunk is kept in a previously prepared saturated brine solution. Additional salt is incorporated to maintain the saturation of the brine as blood, slimes and other exudates of the fish body dilute the brine. In case of the fish in dry solar salt, the fish is kept in a leak-proof tin container with alternate salt and fish layers. Sufficient salt is given at the top layer. The tin is covered and kept for a few weeks in a cool and dry place. The exudates come out of the fish body due to salt penetration dissolves the surrounding salts and make a concentrated salt solution in which the fish floats. The ripening comes in within 7-10 days. In either of such wet salting processes, the removed water, blood, slimes and other exudates cannot pass out but directly mix with the brine solution, thus forming a complex biochemical high salt mixture that probably helps to develop characteristic texture, colour and flavour of the wet-salted product. The keeping quality of wet-salted hilsa was found to be longer compared to dry-salted one (Nowsad, 2005). 4.4.3 Salt-fermentation of hilsa Airtight pot is kept underground for 2-3 months. Before filling, the pot is prepared well by polishing with mustard oil several times and subsequently by sun-drying. Turmeric powder is sometimes used with salt during fermentation. A semi-fermentation in the fish tissue takes place, as the muscle softens but the fish remains intact after 2-3 months with the development of a characteristic texture and attractive flavour. 4.4.4 Under-ground salting of hilsa Undressed, unwashed hilsa is cut longitudinally along the base of the dorsal fin from the lumber region up to the cranium. For this purpose, the fish is kept flat on a uniform surface and the tip of a sharp knife is inserted through the base of dorsal fin up to abdominal cavity. The knife is extended, parallel to the surface, to the front up to the cranium and to the back up to the lumber region and the entrails is taken out through dorsal opening. The fish remains intact along the ventral line. Salt is put inside the fish muscle and in the abdomen through the dorsal opening.


Sufficient salt is pressed in the gills, eyes and mouth and on the body surface. A 2 x 2 x 3 feet deep hold is dug in the floor under a shed where rain water cannot enter. The underground hold is protected all around inside with a mat made of split bamboo, locally called “chatai” and a polythene sheet. Salted fish are kept in layers in an orderly fashion in the hold and sufficient salt is given in between layers. When the hold is filled up with fish, it is covered by a final layer of salt and a mat is placed on the top. The top surface of the hold is covered with a clay layer of about 1 feet and heavy objects like stone, wood-block, brick, etc. are kept on the surface to press the fish from the top. The mouth of the hold is always maintained 1-1.5 feet high from the floor. As the hold is dug under a shed it remains protected from the rain. Open shed (no fence around) also keeps the underground hold cool and dry. The exudates come out of the fish due to salt uptake are absorbed by the surrounding soil. After 1-1.5 months, the flesh becomes slightly reddish and off-flavours due to pre-processing spoilage disappear with the development of a characteristic attractive flavour. The final product becomes more flattened, wider and longer than the unsalted one. 4.4.5 Salt-fermentation of hilsa in basket Salting in the underground hold generally requires a large quantity of fish. To process small catch, however, hilsa is salted and aged by semifermentation in bamboo basket instead of earthen hold. Hilsa is prepared as the same way as in the case of underground hold and kept in layers in polythene sheet with sufficient salt all around.

Finally,

the

polythene is closed well and kept in a woven bamboo basket for 1.5 to 2 months. Fig. 4 Aging of hilsa after dry-salting in Chittagong (Curtsy: Nowsad, 2010)


A small mat covers the basket and heavy stones or bricks kept on the top press the fish inside the basket to release exudates.

Polythene sheet that covers the fish is punctured at the bottom to

allow exudates to drain out. The product is opened after 1 month and more salt is added if required. 4.4.6. Maturing or ripening in salted fish Maturing or ripening is a physico-chemical process where a characteristic texture and flavour are developed in salted product due to complex autolytic, enzymatic and microbial actions. In either of dry or wet salting, salt uptake and water removal do not continue indefinitely; sodium and chlorine ions form a water binding complex with proteins which exerts an endosmotic pressure that eventually balances the exosmotic pressure due to surrounding brine and equilibrium is reached. Under this equilibrium state, within 8 to 15 days of salting, depending on the species and size of fish, a maturing or ripening occurs in salted products (Horner 1992). Having lost up to 20% of its weight through exosmosis of water to the brine, Hilsa regains original weight through salt uptake within 10-12 days. The enzyme responsible for maturing is derived mainly from the digestive system of the fish, the fish muscles and bacteria growing on the fish and in the salt. The products of proteolysis and lipolysis are also predominant in the ripened products. Lipolysis and oxidative rancidity play an important role in the flavour development of salted fish products. The products of Maillard browning reactions also make a significant contribution to the flavour of wet salted fish (Jones, 1962). In dry-salted hilsa, however, any browning is undesirable and can render the product unfit for sale. Various researchers studied the quality of ripened products produced under different ways, in order to improve the traditional hilsa salting practice. Siddiqui (1993) found that the shelf-life of salted hilsa packed in polythene bag and preserved at 4°C had better quality than those kept in room temperature. Khan (1993) studied the changes in physical, biological and microbial quality of dry-salted, wet-salted and sun-dried & salted hilsa prepared in laboratory conditions and found that the combined curing method of sun drying and salting produced more attractive yellowish color with characteristics odor compared to those produced by the traditional and other laboratory methods. While comparing the four types salted products, Mustafa et al. (2012) found better quality in the order of mixed salting > dry salting > pickle salting > brine salting. Rahman (1996) found a considerable loss of lipid during salting, in addition to moisture loss, but essential amino acids were found unchanged. Salted hilsa showed significant variations in the amino acid profile


of the product as compared to that of raw hilsa as shown in Table 13 (Majumder et al. 2005). This might be due to the formation of derivatives of amino acids such as amines and gluconeogenic substances. Lysine was reduced to a great extent, while cysteine was not present or detectable in the product. Table 13. Amino acid composition (g amino acid per 100 g protein) of salted hilsa Amino acids Aspartic acid Threonine Serine Glutamic acid Proline Glycine Alanine Cysteine Valine Methionine Isoleucine Leucine Tyrosine Phenylalanine Histidine Lysine Arginine Tryptophan

Raw hilsa Salted hilsa 9.93 4.11 3.37 16.59 0.99 4.59 6.34 0.68 4.65 1.56 4.04 7.91 1.58 4.09 3.58 11.52 4.39 1.17

% Loss during ripening

7.27 3.31 2.67 11.21 0.72 4.51 5.03 ND 3.66 1.44 3.10 5.70 1.57 2.88 1.86 3.72 3.49 1.05

26.7 19.4 20.7 32.4 27.2 1.70 20.6 100 21.3 7.70 23.2 27.9 0.63 29.6 48.0 67.7 20.5 10.2

4.4.7 Problems of hilsa salting Hilsa is a dark-fleshed high lipid species. Icing is an effective short-term preservation method for the fish. Sun-drying cannot be performed for the species because of atmospheric oxidation or rancidity problems. Long term chilling and freezing are not useful due to texture degradation for spoilage of dark muscles. Considering the compositional characteristics of the species, comparative advantage and acceptability of different fish preservation methods and socioeconomic conditions and food habit of the local consumers, salting seems to be the best suited method for the preservation of hilsa. The following problem, however, have been found to be associated with the process and the products (Nowsad, 2010): i.

The producers do not follow the regulations regarding public health and sanitation.

ii.

In glut period, the fish only those are spoiled or partially spoiled and cannot be sold in the fresh wet fish market are used for salting.

iii.

The fish or the cut pieces are not washed before salting in most of the cases.


iv.

The raw material is contaminated by pathogens or other bacteria during scaling, gutting, dressing and cutting by unclean knife, container or tools.

v.

Low quality solar-salt is used that inhibits the development of good texture, attractive colour and nice flavour of the product.

vi.

Salt:fish ratio is not properly maintained. So rancidity occurs in fish during dry salting.

vii. Sometimes excess salting may denature protein and impact upon the sensory and biochemical properties of the final product. viii. In wet salting, cut pieces are often floated on the surface of the brine, come in contact of air and become rancid. ix.

Semi-fermented ilish is not always well protected in the underground hold. Rain water and mud enter and insects and rodents attack and spoil or contaminate the products.

x.

Packaging and storage are not appropriate and hygienic. Very often rancid off flavour develops in the products those are kept in the basket for long time.

4.4.8 Post-harvest loss in salted hilsa Post-harvest loss was estimated in 2 types of salted products, i. dry salted hilsa and ii. wet salted hilsa (Nowsad, 2010). In both cases, 60% of the raw material lost their quality. Pre-process (handling, washing) and in-process (dressing, cutting, salting, piling, etc.) losses ranged between 5-7%. Quality losses in final products were 65.6% and 67% respectively in dry and wet salted hilsa. Wet salted chunks were found to float up on the surface of the brine in salting container and become rancid due to partial contact with air. This might be a reason of comparative higher qualitative loss in wet salting. There was no quantitative loss found during packaging of wet salted hilsa and also, the transportation, storage and marketing loss were minimum (2.5%, 2.8% and 2.3 % respectively). Therefore, the total quantitative loss in wet salted hilsa was only 7.6%. The reason behind such little loss in wet salting might be due to lesser chance of drying-up the product during in-process and post-process operations, compared to dry salting. Quantitative loss in dry salted hilsa was 23.2%, might be due to wet loss in storage and during marketing. Storage and marketing loss was estimated to be 12.2% and 5.4% respectively. 4.5 Smoked Hilsa


With present day‟s reduction of the catch and increased availability of ice, the extent of smoking of the species has been reduced significantly. Higher price paid for wet fish might be another reason for such reduced smoking.

This product is no longer found in the market. But

local people of Teknaf have been found to prepare this delicate dish at home for own consumption. Brilliant colour and delicious flavour have made it one of the cherished food items and a delicacy in this area. 4.5.1 Smoking process For smoking, the fish is scaled and gutted and then thoroughly washed with clear sea water. Washed fish is split through dorsal lining to widen and expose the anterior part to smoking, keeping the ventral lining of the fish intact. After 3-6% salt treatment, split fish is fixed in between two triangular frames made of split bamboo. The fish is so fixed in order to handle and turn it easily on fire or smoke that allows uniform smoking. Sometimes, fishes are framed by triangular fine mesh made of split bamboo. Bamboo mesh is used mainly to frame small hilsa. Now, the framed fish is kept on the narrow-meshed smoking rack made of split bamboo in such a way that the anterior split portion of fish receives smoke directly. The smoking rack is placed 2.5 feet above the earthen oven. Smoke is produced by local woods. No flame but only smoke is allowed and if any fire breaks out, it is stopped immediately. Fire burns the flesh and develops a brittle texture of muscle that comes out of the bones. But exclusive smoke makes the texture rigid and elastic that is relished by the consumers. Green or semi green woods are used for intense smoke. Smoking is done in a two-step process. In the first step, smoking is done for 4-5 hours. For good quality and longer shelf life, the product is again smoked for 2 hours after 2-3 days of first smoking. Due to such repeated smoking, the bones are softened. The final product becomes brilliant red inside (split part), while the upper surface (skin part) remains transparent. Products within the triangular frame are stored or marketed as such. Storage is done in open-mouth big basket made of bamboo split, locally called lai. Field study suggests that smoked hilsa has already gone to the oblivion memory because of the easy availability of ice and development of other low-cost improved preservation methods (Nowsad, 2007). Improvement in the quality and adequate but lucrative packaging might be necessary to regain their importance in the competitive markets. Attempt has been made to produce smoked hilsa as a ready food item. Smoked hilsa made from 10% salt and garlic resulted quality product than fish treated with 10% salt, garlic and coriander, and only 10% salt. Smoked


hilsa contain 39.65% moisture, 25.65% protein, 24.85% fat, 3.5% ash and 16.2% salt (Hossain et al. 2012). 5. Hilsa Consumption Fish is not only important for human nutrition; it is also part of the Bengali culture. Fish demand remains unmet, and fish consumption is still below the recommended dietary allowance. After a dramatic increase in aquaculture production during 1980s and 1990s, the pattern of fish production and the shares of different species in national production have remained relatively unchanged during the last decade. In many developing countries, official national statistics on per capita fish consumption are commonly based on the total availability of commercial fish in the country and do not include the consumption of many small and non-commercial fish species obtained from the artisanal and subsistence fisheries. It is generally assumed that actual per capita fish consumption is higher than the national average reported in official database (Dey et al. 2005). Fish consumption in Bangladesh varies across different income groups. For example, the monthly consumption of the bottom income quartile is only 1.10 kg/capita, which is less than half that of the highest quartile group. Fish consumption also varies across different types of consumers. Urban consumers appear to have the highest fish consumption (1.96 kg/capita/month), followed by producer consumers (1.92 kg/capita/month) and rural consumers (1.69 kg/capita/month). As for specific species, the highest consumption is of assorted small fish, accounting for 29% of the total fish consumption. This is followed by Indian carp (22%) and exotic carp (21%). The shares of the other species are: 9% for hilsa, 7.6% for live fish, 4.7% for tilapia, 4% for shrimp and prawn, and 3.5% for high-valued species. There is a seasonality pattern of per capita fish consumption, which is in inverse relation to the weighted average price of fish supply. Expert for shrimp and prawn, all species similarly follow the seasonal patter (Fig.1). The assorted small fish, which are mostly from freshwater capture fisheries, seem to be major driving factor for this seasonality pattern, followed by cultured Indian carp and exotic carp. However, consumption can vary very substantially depending on income, season and location. Dey et al. (2010) report that an average consumer in the poorest quartile consumes just 39% of the fish consumed by an average consumer in the richest quartile. This indicates that consumption choices are closely linked to the price of fish; poorer consumers buying cheaper species, and fish of smaller sizes or of poorer quality. A survey of 150 consumers in Dhaka


conducted by the WorldFish Centre in November 2010 (Fig. 1) reveals a number of interesting patterns with respect to unban fish consumption. This is also the case for quantity consumed. When consumption is disaggregated further by origin and species some interesting patterns emerge. Medium sized freshwater capture species and hilsa (including jatka) are the first and second most important categories of fish, being eaten in large quantities by consumers in all income groups. Cultured fish accounted for 31% of total consumption at the time of the survey. When cultured fish are broken down into their composite species it is evident that Indian major carp, pangus and tilapia account for three quarters of total consumption, each with an almost equal share. Exotic carps, including silver carp, account for only 8% of the total, behind climbing perch, which accounts for 12%. This points to an emerging division between rural and urban consumption patterns, suggesting a tendency for high value wild fish and commercially cultured species (pangus, tilapia and climbing perch) to be exported from rural areas to Dhaka, while cultured carps are mainly consumed in rural areas. This conclusions also appears to be supported by a survey of markets conducted during the research that informs this report, which indicated that a smaller farmed fish (roi, silver carp, etc.) and small capture fish (puti, baim, etc.) are the most commonly available species in rural markets, while larger farmed and wild fish are more abundant in urban markets.

Delicacy in hilsa dishes About 68% of the harvested hilsa are consumed as wet fish. Cooking methods applied for the fish in Bangladesh and West Bengal of India are often common. Some of the highly preferred


dishes are shorshe ilish, bhapa ilish, ilish polao, ilish paturi, bhaja ilish, panta ilish, etc. Some of them like shorshe ilish, bhapa ilish or ilish polao are of great delicacy, often cooked to celebrate special occasions in Bengali culture. Panta ilish - a traditional platter of congee with fried hilsa slice, supplemented with dry fish pickles, sour fruit pickles, varieties of pulses (dal), roasted leaf vegetables-like jute, green chili and onion - is a popular serving for the Bengali New Year‟s Day (Pohela Boishakh) festival. 6.

Epilogue

The oily fish hilsa is known worldwide for its unique flavor and delicious taste that last for long time. It possesses an aroma of its own. Hilsa is very favourite fish for its easily digestible proteins (amino acids), fatty acids like omega-3 fatty acids triglyceride, vitamins like vitamin-D, vitamin-A and some members of vitamin-B family and minerals like selenium, zinc, phosphorus, calcium and iron. Like salmon, hilsa is also a rich source of omega-3 fatty acids such as EPA and DHA, although the PUFA content is lower as compared to salmon. Hilsa is also known for its appetizing and culinary properties. The highly nutritive and culinary properties of hilsa amply justify the adage „macher raja ilish‟. This also makes hilsa a strong candidate for aquaculture and justifies the urgency in standardizing the breeding technology and management practice for this prized food fish for early domestication. 7.

Acknowledgements Some of the data used in this paper were generated under the ICAR-sponsored Outreach

Activity on Nutrient profiling and evaluation of fish as a dietary component (BPM). Data on post harvest handling and processing of hilsa were the outcomes of the research project, “Post-harvest loss reduction in fisheries in Bangladesh-A way forward to food security”, funded by the FAO (FAO-NFPCSP-PR#5, 2008).

8.

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Proc. Regional Workshop on Hilsa: Potential for Aquaculture. 16-17 September 2012. Dhaka, Bangladesh Majumdar, P.K. and Basu, S. 2010. Characterization of the traditional fermented fish product Lona ilish of North West India, Indian J Traditional Knw 9(3): 453-458. Majumdar, P.K., Kumar, R., Basu, S. and Anandan, R. 2005. Biochemical and microbiological characteristics of salt fermented Hilsa (Tenualosa ilisha). Fishery Technology 42(1):67-70. Marichamy, G., Raja, P.S., Veerasingam, S., Rajagopal and Venkatachalapathy, R. 2009. Fatty acids composition of Indian mackerel Rastrilliger kanagurta under different cooking methods. Curr. Res. J. Biol. Sci 1:109–112. Martin, S.A.M., Mohanty, B.P., Cash, P., Houlihan, D.F., and Secombes, C. 2007. Proteome analysis of Atlantic salmon, Salmo salar, cell line SHK-1 following recombinant IFN- Stimulation. Proteomics 7(13):2275-2286. Menendez, J.A., Vellon, L., Colomer, R. and Lupu, R. 2005. Oleic acid, the main monounsaturated fatty acid of olive oil, suppresses Her-2/neu (erb B-2) expression and synergistically enhances the growth inhibitory effects of trastuzumab (Herceptin) in breast cancer cells with Her-2/neu oncogene amplication. Ann Oncol 16:359-371. Mohanty, B. P., Banerjee, S., Bhattacharjee, S. and Sharma, A. P. 2009. The muscle proteome of Catla catla. Asstract, 9th Indian Fisheries Forum, organized by Central Marine Fisheries Research Institute (ICAR), Chennai, India,19-23 December 2009. Mohanty, B.P. 2011. Fish as Health Food. Ch. 35, pp. 843-861, In: Handbook of Fisheries and Aquaculture, DKMA, Indian Council of Agricultural Research, New Delhi. ISBN: 978-81-7164-1062. Mohanty, B.P. and Mohanty, S. 2004. Proteomics and human proteome organization. Natl. Acad. Sci. Lett. 27(7&8):249-256. Mohanty, B.P., Mohanty, S. and Panwar, R. S. 2005. Proteomics and its applications in fisheries sector. Fishing Chimes. 25 (4): 35-38. http://www.fishingchimes.com/proteomics.htm?isu=v02i06&art=student Mohanty, B.P., Das, S., Bhaumik, U. and Sharma, A.P. 2011b. Tenualosa ilisha - A rich source of -3 fatty acids. Bulletin No. 171, Central Inland Fisheries Research Institute (ICAR), Barrackpore, India, ISSN: 0970-616X. http://www.cifri.ernet.in/171.pdf Mohanty, B.P., Ganguly, S. and Mahanty, A. 2012c. Micronutrient profile of the Indian shad, Tenualosa ilisha (Hamilton, 1822), hilsa from the river Ganga, India. Natl. Acad. Sci. Lett (in press). 35:00-00 (in press). Add vol/issue no. Mohanty, B.P., Ganguly, S., Chakraborty, K., Karunakaran, D., Mohapatra, P.K.R. and Nayakand Nayak, N.R. 2012b. Maternal fish consumption and prevention of low birth weight in the developing world. Natl. Acad. Sci. Lett 35:00-00 (in press). Mohanty, B.P., Paria, P., Mahanty, A., Behera, B.K., Mathew, S., Sankar, T.V. and Sharma, A.P. 2012a. Fatty acid profile of Indian shad Tenualosa ilisha oil and its dietary significance. Natl. Acad. Sci. Lett. 35(4):263-269. Mohanty, B.P., Sudheesan, D., Sankar, T. V., Das, M.K. and Sharma, A. P. 2011a. Therapeutic value of fish. Bulletin No. 170, Central Inland Fisheries Research Institute (ICAR), Barrackpore, India, ISSN: 0970-616X. http://www.cifri.ernet.in/170.pdf Mondal, B.K. 2012. Delicious hilsa turns 'bland' due to early maturity. National Fisheries Development Board of India. Cited by Niyogi, S. 2012. http://timesofindia.indiatimes.com/topic. Mustafa, M., Ghulam, S.R., Begum, M.A., Khaleque, M. and Ahsan, D.A. 2012. Nutritional qualities of Hilsha and Sarpunti in different salt curing methods. Dhaka Univ. J. Biol. Sci 21(1): 97‐104. Nath, A.K. and Banerjee, B. 2012. Comparative evaluation of body composition of hilsa, Tenualosa ilisha (Hamilton, 1822) in different size groups with special reference to fatty acids, in Hoogly estuarine system, West Bengal, India. Indian J. Fish 59(2):141-146. Nowsad, A.K.M.A. 2005. Low cost processing of fish in coastal Bangladesh, BGD/97/017 Field Doc: 05/2005, Food and Agriculture Organization of the United Nations, Dhaka, 88 pp. Nowsad, A.K.M.A. 2007. Participatory Training of Trainers: A New Approach Applied In the fish processing. Bangladesh Fisheries Research Forum, 213p.

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