Effect of Processing on the Proximate and Mineral Compositions of ...

Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 4(3): 378-385 © Scholarlink Research Institute Journals, 2013 (ISSN: 2141-7016) jeteas.scholarlinkresearch.org Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 4(3):378-385 (ISSN: 2141-7016)

Effect of Processing on the Proximate and Mineral Compositions of Trachurus Trachurus: A Fish Commonly Consumed in Nigeria O.T. Adeyemi1, O.O. Osilesi1, F. Onajobi1, O. Adebawo1, S.O. Oyedemi2 and A. J. Afolayan2 1

Department of Biochemistry, Babcock University, Ilishan Remo, Ogun state, Nigeria. 2 Botany Department, University of Fort Hare, Alice 5700, South Africa Corresponding Author: A. J. Afolayan __________________________________________________________________________________________ Abstract The present study assessed the effect of processing on the sensory qualities, proximate and mineral compositions in the fillet and SHB (skin, head and bone) of Trachurus trachurus. The fish samples were prepared by smoking (wood and coal) or poaching while proximate and mineral analysis was done by standard methods. A sensory quality of the processed fish was conducted via categorical ranking. All processing methods significantly (p Ca > Na > Mg while that of SHB was Ca > K > Na > Mg. The trace elements in both samples increased in this order Fe > Zn > Cu > Mn > Cr. Wood and charcoal smoked fish samples were found most palatable by the panelists. The data obtained from this study demonstrated that processed SHB and fillet could be a veritable source of valuable ingredients for human consumption and animal feeds. __________________________________________________________________________________________ Keywords: effect of processing; trachurus trachurus; proximate; mineral; sensory evaluation. (Olayemi et al, 2011). Most processing methods often times involve removal of the head, viscera and other parts of the fish which may have either negative or positive effect on the total nutritive values of the fish (Saliu, 2008). Previous works reported the effect of processing methods on different fish types (SanchezMuniz et al, 1992; Oluwaniyi & Dosum,u 2008; Osibona, 2011). However, there is a paucity of scientific information on the nutrient and mineral compositions of processed T. trachurus (fillet and SHB). In this study, T. trachurus was chosen due to good consumer acceptance and economic availability (Nadcisa et al, 2001). Since, T. trachurus is imported to Nigeria without full understanding of their feed composition, there is need to assess its nutrient and mineral compositions.

INTRODUCTION The number of undernourished people worldwide has been estimated to have increased to 963 million compared to 923million in 2007 (FAO, 2008). This estimation confirms the need for immediate attention considering the ongoing financial and economic crisis. In recent times, fish has been reported as the cheapest source of protein used to correct protein deficiency in human diets in the tropic region (Akinwumi, 2011). It also contains some bioactive compounds with therapeutic properties that are beneficial to human health (Nnaji et al, 2010; Lordan et al, 2011). Trachurus trachurus (Atlantic horse mackerel or Kote) is an important commercial marine fish, pelagic in nature, said to originate from off the coast of Portugal (Nadcisa et al, 2001). Despite its nutritive value, fish is highly susceptible to damage once caught and so have become source of pollution in the environment (Vignesh & Srinivan, 2012). However, processing methods such as salting, boiling, frying, sun drying, roasting and smoking have been used to preserve and increase its availability to consumers

The present study therefore was conducted to provide scientific information on the effect of processing methods on the proximate and mineral compositions in the raw, poached and smoked (coal and wood) fillet and SHB of T. trachurus together with their sensory abilities. 378

Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 4(3):378-385 (ISSN: 2141-7016) and Cr) were determined by atomic absorption spectrophotometry (AOAC, 2002).

MATERIALS AND METHODS Sample Collection A total of 20 kg of Trachurus trachurus was purchased from two popular major cold fish distributors (Asake and Heritage fisheries) in Ipata market, Ilorin, Nigeria. The mean length and weight of the fish was 30.52 ± 0.22 cm and 197.66 ± 3.67g respectively. T. trachurus was prepared using handling process, i.e. thoroughly washed, eviscerated, and cooked by boiling and smoking using either firewood or charcoal. The processing methods were grouped into four (WSK: Wood Smoked Kote; CSK: Charcoal Smoked Kote; PK: Poached Kote; RK: Raw Kote).

Sensory Evaluation Sensory evaluation was conducted using the categorical ranking (highest, good, fair and rejected quality), by taste panel consisting of ten experienced judges using the guidelines described by DOCE (1989) and Eyo (2001). Statistical Analysis Significant differences between means of experiments were determined by least significant difference. SPSS 14.0 statistical tool was used to analyze the data obtained. Results were considered statistically significant at p < 0.05 with Duncan’s multiple range test (Duncan 1955).

Sample Processing A portion of the fish was poached in water at 60o C for 15 min and the remaining portion hot smoked using either charcoal or firewood in a conventional smoke kiln as described by FAO/UN (2007). All cooking processes were done without addition of any ingredient.

RESULTS Proximate Analysis The results of proximate analysis of processed fillet are presented in Table 1. The percentage moisture content of poached fillet had the highest value followed by raw fish fillet, while the least value was obtained in wood smoked fillet compared with the charcoal smoked fillet. Among the processing methods, CSKF had the least crude fibre content, whereas others had comparable amount to the raw fish. With respect to percentage crude protein content, all processing methods increased (p P > K > Na > Mg was observed in SHB. The difference in the order could be linked to higher concentration of calcium in the bones and cartilages of SHB. Generally, the data obtained for the major minerals from both processed fish samples were significantly different from the raw fish which could be assigned to the effect of processing methods in the fish samples.

surface. The significant reduction of crude fibre observed in the samples posed no threat because fish is usually consumed as adjuncts or additives to other foods. This observation concurred with the report of Ewing (1951) and NRLA (1995) who demonstrated that higher crude fiber is poorly digested by animals and interferes with other nutrients. Recently, the interest in dietary fiber has been stimulated due to its ability to prevent chronic diseases such as cardiovascular disease, cancer and diabetes mellitus (Bowmen & Russell 2001). However, inadequate intake of fiber may results to bowel irritation and possibly colon cancer (Mbaebie et al, 2010). Ash content was significantly (p < 0.05) high in SHB than the fish fillet which indicate an increased inorganic content (Oloyede, 2005).

Sensory Evaluation Figure 1 illustrates the sensory scores assigned to raw and processed fish samples as determined by the trained panelists. Data obtained indicated that WSKF had significantly high values in odour, flavor and texture in all cooking methods. Likewise, data as shown in Figure 1 demonstrated that all processing methods did not alter the quality of fish as reported by the panelists.

Mineral Composition A considerable amount of total marine fish catch is discarded as processing leftovers, which include skin, bones and the head (SHB). It has been suggested that about 25% of the total production of marine captured fisheries are discarded worldwide (AOAC, 2000). Our observation on the major minerals is contrary to the report of Oladimeji & Sadiku (1991); Teeny et al (1984) who reported decreasing order K >Na>P>Mg>Ca in oven-dried of several fishes but correspond to the report of Kirchgessner & Schwall (1986) who observed a well-defined order; Ca>P>K>Na>Mg. The significant increase in the concentration of calcium found in the SHB is expected because of its deposit in the bone. Our findings suggest that these discards could be a veritable source of calcium to reduce the risk of osteoporosis and osteomalacia in adults and infants respectively, if transformed into high valued products for human consumption. The significant reduction in the level of calcium of both fillet and SHB could be associated with heat flow of gases and interaction of the smoke components with the minerals (Moriss et al, 2006). Potassium is an essential element in the body system that plays a vital role in protein synthesis, nerve conduction; control of heart beat, muscle contraction and synthesis of nucleic acids (Soetan et al, 2010). However, deficiency of this element could result to tiredness and muscle weakness.

DISCUSSION A large percentage of Nigeria population and neighboring countries consume T. trachurus as a substitute for animal protein in their daily diets (Adewoye et al, 2003). However, there is inadequate technique to preserve these fishes without affecting the proximate and mineral compositions. Some of the methods commonly used for preservation lack adequate scientific information on their effect on nutritive and mineral compositions. The findings from this study showed that different methods had selective effect on the parameters investigated. Proximate content of Fish fillet It is well established that water activity determines the storage life of fish due to limited microbial contamination. The moisture content of smoked T. trachurus was significantly (p Zn > Cu > Cr > Mn). Most concentrations are within World Health Organization limits for human consumption per day (WHO 2002) but tend to become harmful when exceed the metabolic demands (Hogstrand & Wood, 1996; Ako & Salihu, 2004). The difference observed in the concentrations of these trace elements concurred with the report of Windom et al (1987). In the previous studies it was found that the processing and cooking methods had little or no effect on the elements (Ackurt, 1991; Gall et al., 1983; Steiner-Asieduet al., 1991), but Ackurt (1991) reported that mineral levels in some fish samples were affected by cooking methods. Generally, processing methods decreased the levels of all minerals except Zn, Cu, MN and Cr in the fillet; K, F, Zn, Mg, Cu, and Cr in the SHB, decrease observed in present study is in agreement with the findings of (Gokoglu et al, 2004). Sensory evaluation The data obtained from sensory evaluation revealed that both fish and the products were in good quality that warrant general acceptance as shown in Figure 1. Conclusion We conclude from our studies that all the processing methods used for the preservation of fish for human consumption had selective effect on the proximate and mineral compositions. However, among the processing methods, wood smoked showed the best result for mineral analysis while steaming had the best nutrient conservation. Our data revealed that leftovers or discards (SHB) are rich in some nutrients and minerals and thus could be an appropriate item for human diet or potential ingredient for animal feeds. Further studies are highly needed to evaluate the toxic effect of these methods in animal models.

Table 1: Proximate Composition (%) of Processed T. trachurus Fillet. Data= Mean ± SD, n=3 GROUPS (%)

RKF

PKF

CSKF

WSKF

PROTEIN FAT ASH CRUDE FIBRE MOISTURE

65.65±1.01 b 3.32± 0.01c 8.60± 0.20 a 2.13± 1.09a 73.56±0.01b

66.68±1.19 a 3.46± 0.01c 4.93± 0.68 c 2.06± 0.24b 74.02± 0.02a

66.80±0.54a 4.06±0.00b 4.40± 0.81 c 1.40± 0.12c 69.78± 0.01c

66.24±2.70 a 8.87± 0.01a 6.50± 0.06 b 2.26± 0.67a 52.76±0.02d

Table 2: Proximate Composition (%) of Processed Skin Head Bone (SHB). Data= Mean ± SD, n=3 GROUPS (%) PROTEIN FAT ASH CRUDE FIBRE MOISTURE

RSHB 58.15±3.77 a 5.67± 0.01b 22.00± 1.02 b 15.73± 0.57b 73.56± 0.01b

PSHB 54.48±7.05 c 7.28± 0.02a 26.20± 1.80 a 17.33±0.48a 74.03± 0.10a

CSSHB 55.78±6.71 b 6.08± 0.01b 17.73± 0.24 d 14.46± 0.66c 69.77± 0.00c

WSSHB 55.80±3.50 b 7.45± 0.02a 19.40± 1.80 c 13.26± 1.75d 52.76± 0.04d

Values with different superscripts along a row are significantly different (p < 0.05). CSSHB: charcoal smoked kote SHB; WSSHB: wood smoked kote SHB; PSHB: poached kote SHB; RSHB: Raw kote SHB.

381

Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 4(3):378-385 (ISSN: 2141-7016) Table 3: Mineral Composition (mg/l) of Processed Trachurus trachurus Fillet. Data = Mean ±SD, n=3 GROUPS

PKF

RKF

CSKF

WSKF

Ca (mg/litre)

80.16±3.13 c

181.97±5.07 a

108.69±4.84b

79.47±6.57 c

P (mg/litre)

62.38±2.99 d

77.85±3.36 a

65.87±1.00 b

63.29±5.23 c

K (mg/litre)

242.43±8.91 c

515.57±252.05a

275.09±12.67 b

251.23±15.14 c

Na (mg/litre)

49.34±1.22 c

66.33±1.26 a

57.99±0.45 b

44.02±1.95 d

Mg (mg/litre)

13.66±0.25 b

16.88±0.18 a

13.38±0.21 b

13.56±0.20 b

Cu (mg/litre)

0.04±0.00 a

0.04±0.00 a

0.04±0.00 a

0.04±0.00 a

Mn (mg/litre)

0.00±0.00 b

0.01±0.00 a

0.01±0.00 a

0.01±0.00 a

Fe (mg/litre)

0.01±0.00 c

0.10±0.05 a

0.10±0.01 a

0.07±0.05 b

Zn (mg/litre)

0.08±0.29 c

0.10±0.26 b

0.17±0.99 a

0.04±0.01 d

Cr (µg/litre)

23.31±3.35 c

21.32±1.58 d

30.13±2.66 a

27.57±2.39 b

* Values with different superscripts along a row are significantly different (p