The present experiment was carried out at Cereal Technology Laboratory, Institute of Food Science Technology (IFST), Bangladesh Council of Scientific and Industrial Research (BCSIR), Dhaka 1205, Bangladesh.
Sample Collection and Preparation: Freshly milled rice bran of parboiled paddy, BRRI-28 variety was obtained from Rashid Agro Food Products Ltd at Poradah, Ballobpur, Kushtia, Bangladesh. The collected bran was processed within 1/2 h of collection to inactivate the endogenous lipase enzyme and denature the trypsininhibitors. To achieve this objective the bran subjected to cold treatment. Before starting this experiment, the rice bran of the first, second , third and silky polishes have been screened through 80-mesh screen .
Stabilization of Rice Bran: To obtain parboiled rice bran, the BRRI-28 variety of paddy was soaked and steamed followed by drying and milling (Saunder 1990). The bran was then removed to yield parboiled white rice through 2-3 cycles polishing. All the fractions of rice bran were subjected independently to cold treatment for stabilization. For the cold treatment process, 500g of collected rice bran was placed in an airtight zip lock polythene cover ed bag , and kept under ice immediately after the milling process. Then it stored in refrigerator at -20oC for further analysis. The same fraction of rice bran was also kept at room temperature for same period of time as a control (untreated bran).
Shelf - life of Rice Bran: The stored samples were assessed in triplicates for free fatty acid (FFA) content at 15 day intervals for a period of 90 days. FFA was determined by the titrimetric procedure by titrating against potassium hydroxide (1 mol L-l) after extracting with hot neutral alcohol (AACC, 1983).
Proximate Composition: The proximate composition of all the fractions of BRRI-28 variety parboiled rice bran was carried out as follows:
Moisture Content: Moisture content was determined by oven dry method as the loss in weight due to evaporation fro m sample at a temperature of 100 ± 20C. The weight loss in each case represented the amount of moisture present in the sample.
Moisture (%) = {(Weight of original sample – weight of dried sample)} × 100/(Weight of original sample)
Crude Protein: The crude protein content was determined following the micro Kjeldahl method (AOAC 2005). Percentage of nitrogen (N) was calculated using the following equation.
Nitrogen (%) = {(S - B) × N × 0.014 × D× 100} / (weight of sample × V)
Where D = Dilution factor, T = Titration value = (S - B), W = weight of sample, 0.014 = Constant value. Crude protein was obtained by multiplying the corresponding total nitrogen content by a conventional factor of 6.25. Thus crude protein (%) = % of N × 6.25.
Crude Fat: Crude fat was determined by the Soxhlet extraction technique followed by AOAC (2005). Fat content of the dried samples can easily extracted into organic solvent (petroleum ether) at 40 - 600C and followed to reflux for 6 h. Percentage of fat content was calculated using the following formula.
Crude Fat (%) = Weight of fat in sample × 100/ Weight of dry sample.
Ash Content: Ash content was determined by combusting the samples in a muffle furnace at 6000C for 8 h according to the method of AOAC (2005).
Ash content (%) = Weight of Ash × 100/ Weight of sample
Acid Insoluble: Ash (silica) Acid insoluble ash was determined by adding 25 ml of dilute HCI to the ash and boiled for 10 minutes and then filtered, incinerate, cool and weight according to the method of AOAC (2005).
Crude Fiber: The bulk of roughage in food is referred to as the fiber and is called crude fiber. Milled sample was dried, defatted with ethanol acetone mixture and then the experiment was carried out using the standard method as described in AOAC (2005).
Crude Fiber (%) = (Weight of residue – weight of Ash) × 100 / Weight of sample.
Carbohydrate: The carbohydrate content was estimated by the difference method. It was calculated by subtracting the sum of percentage of moisture, fat, protein and ash contents f rom 100% according to AOAC (2005).
Carbohydrate (%) = 100 – (moisture% + Fat% + Protein% + Ash%)
Total Energy: The total energy value of the food formulation was calculated according to the method of Mahgoub (1999) using the formula as shown in equation:
Total energy (kcal/100g) = [(% available carbohydrates X4. 1) + (% protein X4.1) + (% fat X 9.3)]
Vitamin and Mineral: The vitamins thiamin (B1), niacin (B5) and pyridoxine (B6) were analyzed according to the method of AOAC (1993). The minerals Fe, Mn, Zn and Ca were determined after acid digestion by using atomic absorption spectrophotometer according to the method of AACC (2000).
Statistical Analysis: Collected data obtained from various parameters of processed rice bran were subjected to statistically analysis using “SPSS (Version 12.00)” computer programmed to compute analysis of variance (ANOVA) techniques according to the method of Steel et al . (1997)