Indian Journal of Traditional Knowledge Vol. 15 (4), October 2016, pp. 659-668
Assessment of physicochemical, functional and nutritional properties of raw and traditional popped rice TB Bagchi*, P Sanghamitra, J Berliner, K Chattopadhyay, A Sarkar2, A Kumar, S Ray & SG Sharma ICAR- National Rice Research Institute, Cuttack-753006, India; ICAR-Central Institute for Women in Agriculture, Bhubaneshwar-751003, India E-mail:
[email protected]
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Received 02 November 2015, revised 20 January 2016, updated 03 June 2016 Popped rice is a common, chip and nutritious breakfast item widely consumed in India. We analyzed functional, physicochemical and nutritional properties of raw rice (RR) and popped rice (PR) of some Indian rice cultivars (Kalabhat, Banskathi, JP-73, Kabirajsal, Dehradun Gandheswari). RR of Kabirajisal showed better physical grain quality among all whereas Banskathi and Dehradun gandheswari was found to be better with respect to physical quality of popped rice. Amylose content (AC), phytic acid content (PA) and total antioxidant capacity were also higher in both RR and PR of Banskathi. In vitro starch digestibility (IVSD) of RR was higher in JP-73 followed by Dehradun gandheswari while in PR, it was higher in Kalabhat. Therefore, Banskathi, Dehradun gandheswari and Kalabhat are most suitable for popping. This study provides knowledge about different functional, physicochemical and nutritional properties of RR and PR and their relationship. Keywords: Raw rice, Popped rice, Physicochemical properties, Functional properties, Starch granules IPC Int. Cl.8: A01G 9/00, A01G 16/00, A47G 19/26, A47J 39/02, A23L C09K 15/00
Among the various value added products of rice, popped rice (PR) is one of the earliest known and highly popular snacks in India. It is generally consumed at the time of sacred ceremony like wedding, worship, etc. It is also a popular breakfast item of India as it is readily digestible and convenient to make several delicious preparations with minimum processing. Many traditional food items are prepared from PR, especially in the eastern part of India, having excellent sensory properties. Besides, PR powder can be used as a substitute of glucose in ORS formulation1. Popping of rice is performed by heating the kernel (intact rice grain without removing the hull) in sand at more than 177 ºC. This heat gradually vaporizes the water contained in the kernel which leads to gradual build up of vapor pressure. When the vapour pressure exceeds ~135 psi the kernel ruptures suddenly leading to kernel expansion by 6-8 times its original volume. The expanded state is then fixed by dehydration resulting from rapid diffusion of water vapor out of it. The popped product is to be maintained at about 3% moisture to retain the desired crispness. The popped rice is very porous, and, therefore, becomes very soft in a few seconds of —————— * Corresponding author
wetting and hence can be consumed with milk or curd. Volume expansion is the most important quality parameter for popped rice. Wide varietal difference in volume expansion during popping of rice has been reported by many authors. Tightness of husk (lemma-palea) interlocking and grain hardness is positively and chalkiness is negatively correlated with popping2. Proper moisture content (14%) is known to govern expansion value as it creates the necessary vapour pressure inside the kernels immediately before popping. Moisture loss decreases popping performance, where as excess moisture produces low popped volume3. Unfortunately, unlike in maize where several physico-chemical properties of the kernel related to popping are well studied4, not much is known, except the above mentioned few factors influencing poppability in rice. Generally the specialty rice types are native landraces or folk cultivars of India and PR are prepared from specific specialty rice cultivars. Consequently the objective of this research was (a) to evaluate the functional and physicochemical attributes of RR and PR of 5 Indian cultivars in order to identify the physico-chemical properties related to good poppability and (b) evaluate the nutritional parameters after making PR.
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Materials and methods The 26 quality rice cultivars, mostly landraces of West Bengal were collected from the farmers and after making popped rice, 5 cultivars (Kalabhat, Banskathi, JP-73, Kabirajsal and Dehradun Gandheswari) were selected on the basis of sensory evaluation and their subsequent physicochemical and nutritional analysis was performed as follows. These cultivars were suitable for irrigated low land ecology and commonly cultivated in clay loam soil of Indo-Gangatic plain.
Determination of loose and packed bulk densities of PRF
Raw rice (RR) and popped rice (PR) preparation
Determination of water (WAC) and oil (OAC) absorption capacities of PRF
Rice grains were harvested at maturity and sundried naturally for further processing to grain moisture content of 12-13%. The dried grains were stored at 20 °C and 177 ºC) in an iron pan for 4050 seconds with continuous stirring. Almost all the husk was separated from popped kernel, which was already detached during heating (Fig.1). Physical characteristics of rice kernels
The rough rice was dehulled and the brown rice, obtained was polished for 60 seconds. Milled rice outturn was expressed as per cent of milled rice. The digital image analyzer (Annadarpan, India) was used for measurement of grain length, breadth, L/B ratio in case of both grain and popped paddy. Determination of hundred grain weight for RR and PR
A hundred grain weight of randomly selected rice kernels and PR was determined using an automatic grain counter and afterwards the analytical balance.
A measuring cylinder (100 mL) was filled with the sample to the 100 mL mark and the weight was obtained with a digital weighing balance. Loose and packed bulk densities of the PR flour were determined, but packed density was with additional tapping (x 50) of the edge of the work bench prior to re-weighing. The densities were calculated as the ratio of the bulk weight to the volume (gm/mL).
One gram of sample was suspended in 10 mL distilled water (or refined rice bran oil) in a weighed centrifuge tube. The suspension was vortexed three times and 10 min rest periods were allowed between each mixing. This suspension was centrifuged at 2000x gm for 30 min and the supernatant was decanted, and the tubes were air-dried. The bound water was calculated from the increase in the weight of the samples. Water (or oil) absorption capacity was expressed as percentage of water (or oil) adsorbed by 100 gm of sample. Determination of swelling power, solubility, foam capacity and foam stability of PRF
PRF-water slurry (0.35 gm in 12.5 mL distilled water) was heated in a water bath at 60 ºC for 30 min with constant agitation. After centrifugation at 3500 x gm for 20 min, the supernatant was decanted in pre weighed evaporating dish and dried at 100 ºC for 20 min. The difference in weight of the evaporating dish was used to calculate the solubility. Swelling power was calculated by weighing the residue after centrifugation and dividing by the original weight of the flour5. Foam capacity and foam stability were determined by the standard methods. Popping percentage of PR
Hundred rough rice grains were popped by the above mentioned method and number of popped grain was measured. The percentage of popping was calculated. Length and breadth elongation ratio and volume expansion ratio (VER) of PR
Fig. 1—Morphology of different processed products of five rice cultivars.
Length (L) and breadth (B) of randomly selected 100 unbroken milled rice grains and PRs grain were measured using a manual veneer caliper with accuracy of ±0.02 mm and the average length/breadth (L/B) ratio was calculated. Volume of PR was
BAGCHI et al.: POPPING QUALITY OF RICE
measured by the following formula: V PR =πr2h (r= radius of each PR, h= length). Volume of 30 PR for each cultivar was measured and average data was presented here.
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left for 45 min at 60 °C with shaking (100 rpm). After centrifugation, supernatant was separated and both the supernatants were tested for a total soluble sugar (TSS) by previously described anthrone method and result was expressed as mg TSS/gm sample.
Starch granule morphology
The starch was extracted from dehulled rice by alkali extraction with steeping in NaOH solution6 (0.2%, 2 L). The starch obtained as sediment was dried in an air convection oven at 40 0C for 48 hrs. The dried starch was pulverized into a smooth flowing powder using the dry mill of the commercial blender. Light microscopy method7 was used in assessing the morphology of rice starch samples under 20 X magnifications. Chemical properties of raw grain and popped rice
The moisture content of rough rice was measured through digital moisture meter (Kett moisture meter, Japan).The total protein content was determined by taking ten brown rice sample in three replication and as described in the AOAC methodology (Kjeldahl digestion) using the formula N × 5.95. Total soluble sugars
The total soluble sugar was measured by anthrone method. Phytic acid content (PAC)
PAC of brown rice was estimated using wade reagent (0.03% FeCl3, 6H20+0.3% Sulpho- salicylic acid)8. Standard curve was prepared by sodium phytate so that the blank OD will be 0.453+ 0.002. PAC can be determined through standard curve. In vitro starch digestibility (IVSD)
It was measured with some modifications of previous one9. About 0.1 gm of ground sample (100 mesh sheaving) was weighted and mixed with 10 ml KCl-HCl buffer (pH 1.5) and incubate for 10 min. After adding 0.1 ml pepsin solution (1% W/V in KCl- HCl buffer) it was shaken at 40 °C for one hour. After cooling at room temperature, 9 ml phosphate buffer (pH 6.9) was added. 1ml porcine αamylase (Sigma A3176 Type VI-B) solution (4%) was also added in it and it was shaken for one hour at 37 °C. Then after centrifugation (4000 rpm), supernatant was kept separately and 10ml 2M HCL solution was added to the remaining digesta. 4 ml amyloglucosidase (Sigma) solution (0.833 µL in 4 ml Na-acetate buffer pH 4.75) was added with it and
Antioxidant capacity by ABTS
ABTS radical scavenging assay was performed through modified protocol of the previous10. The antioxidant capacity was expressed as ascorbic acid equivalent/gm. Statistical analysis All the analysis was performed using SAS 9.3 Software and MS-Excel. The data were presented as mean of three replications. Pearson's correlation coefficient (PROC CORR of SAS) was used to measure strength and direction of the linear relationship between any two quantitative variables. Results and discussion Physical properties of RR and PR
In order to understand the influence of different physical properties of RR in popping we studied parameters like hulling, milling, HRR, Kernel length, breadth, 100-kernel weight and length-breadth (L/B) ratio of the milled RR obtained from various cultivars. The varieties under study differed from each other significantly in all the parameters (Table 1). For example, Kabirajisal showed the highest Hulling, milling and HRR (76.5%, 65% and 60% respectively) while JP-73 had the lowest (72%, 60% and 40%). Grain weight is a very important parameter in case of cereal crops from the evolutionary perspective. Large grain type was preferentially selected during early domestication11. Among the different cultivars, 100 RR grain wt of Kabirajisal was observed to be highest (2.49 gm), followed by Kalabhat (1.95 gm) and JP-73 (1.94 gm), whereas Banskathi had the lowest (1.56 gm). L/B ratio was observed to be highest for Dehradun Gandheswari (4.36) and categorized as long slender (LS) type but highest length and breadth was observed in Kabirajisal (7.99 mm and 2.19 mm). Moisture content of rough rice is an important factor which should be maintained at 12-14% to obtain optimum HRR and for good popping12. Moisture content of raw paddy was highest (12.71%) in Dehradun Gandheswari and lowest (12.01%) in JP-73. All the cultivars showed better results with respect to hulling, milling, HRR, length and breadth as compared to previous
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Table 1— Physical properties of Raw Rice (RR) and Popped Rice (PR). All the values are means of three replications. All the grains are long slender type (LS) except kalabhat (i.e. short slender type). Cultivers
Hulling (%)
Milling (%)
HRR (%)
Moisture Length (%) /mm
Breadth /mm
L/B
100 kernel Loose Wt BD (g) (g/ml
Packed BD (g/ml
Popping %
Kalabhat RR 73.67B 63.67B 53.33B 12.25C 6.75B 2.21A 3.06D 1.95B 0.67C 0.81A ND B C B B B BC AB C A Banskathi RR 74.67 62.00 54.00 12.31 7.06A 1.67 4.22 1.56 0.72 0.77B ND JP-73 RR 72.00C 60.00D 40.00D 12.01E 7.02B 1.90B 3.70BC 1.94B 0.69B 0.74C ND A A A D A A C A CD Kabirajisal RR 76.50 65.00 60.50 12.07 7.99 2.19 3.65 2.49 0.67 0.69D ND Dehradun B D C A B C A BC D C RR 74.50 60.50 46.50 12.71 6.80 1.53 4.36 1.63 0.67 0.74 ND Gandheswari p-Value
