الفهرس 
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Abstract
Rice bran is a by-product of rice milling industry and constitutes around 8 % of the total weight of rough rice. It is a good natural source of many vital nutrients but has some limitations in food application because of its highly susceptible to rancidity caused by the inherent lipase. The effective utilization of rice bran is possible only by deactivating the lipase enzyme. Moreover using stabilized rice bran oil which has very good fatty acid profile oleic and linoleic and rich in unique natural antioxidant (gamma-Oryzanol) which can be used to extent shelf life of bakery products.
This research focused on1T deactivate lipase activity of rice bran oil by extrusion process depends on two different moisture 15 and 30% and temperature 115°C and 130°C. Corn oil was substituted with different levels (5, 10, 15 and 20%) of stabilized rice bran oil to enhance the shelf life of cupcake; moreover wheat flour was substituted with different levels of defatted stabilized rice bran fiber (DSRBF) to formulate high fiber bran. Study the effect of these additives on physical and sensory properties.
The quality aspects of the formulated cupcake as well as pan bread were evaluated.
The obtained results can be summarized as follow:
6.1. Chemical characteristics of crude rice bran
Crud rice bran contained 9.55% moisture, 17.62% protein, 17.50% fat, 8.00% ash, 30.81% nitrogen free extract and 26.07 total dietary fibers.
6.2. Chemical characteristics and fatty acid profile of crud rice bran oil (RBO)
Rice bran oil had 38.27 % omega 9, 32.15% omega 6 and 1.49% omega 3, Also it had 18.09 saturated fatty acids. The acid value of crude rice bran was 3.12%, meanwhile, peroxide number of crud RBO was 7.11 meq/kg, saponification number of crud RBO was 175 mg/100 gm oil and refractive index was 1.4672.
6.3. Effect of stabilization on lipase activity of rice bran
Stabilization of rice bran at 130°C and 30% completely inhibit lipase activity even after seven days of storage. Rice bran oil has high stability against auto oxidation reached 17h at 100°C.
6.4. characteristics of defatted stabilized rice bran meal (DSRBM)
The functional properties results indicated that water holding capacity of DSRBM was 3.56 g/g, while oil holding capacity was 2.16 g/g.
DSRBM had (1%, 27.6, 6%, 4% and 6%) mlg/100gm of Mn, Zn, iron, Ca and K respectively. The total dietary fiber of defatted stabilized rice bran (DSRBF) was 31.6%. It composed of 29.60% insoluble dietary fiber and 2.05% soluble dietary fiber. Extrusion increased redness and yellowness and reduced lightness of treated rice bran.
6.5. Chemical characteristic and fatty acid profile of stabilized rice bran oil.
Free fatty acid of SRBO was 6.12% meanwhile, peroxide number of SRBO was 12.18 meq/kg, saponification number was 174 mg/100gm oil and refractive index 1.4672. Stabilized rice bran oil had a slight increase in oleic acid and linoleic acid (43.01% and 35.56%), respectively SRBO also had 18.06% saturated fatty acid, 35.56% omega 6 and 43.01 % omega 9 and 1.49% omega 3.
6.6. Effect of rice bran oil substitution levels on cupcake chemical properties and stability.
The acid value decreased significantly (p≤0.05)with increasing the substitution level of stabilized rice bran oil which decreased by 27.30 % by substituting 20% of SRBO. Increasing of stabilized rice bran oil levels in cake decreased acid value and free fatty acids. Substitute corn oil with 20% SRBO in cake samples gave the least acid value (0.82 mlg/g and least % free fatty acids
0.26% after 72 h of storage at room temperature in compare with control 2.70 mlg/g and 0.95% respectively. Substitute corn oil with 20% SRBO in cake samples gave the least peroxide number (2.90 meq/kg) after 72 h of storage at room temperature in compare with control 10.25 meq/kg. Substitute corn oil with 20% SRBO gave highest anti-oxidant activity 14.58% in compare with control 7.12%. Substitute corn oil with 15, 20% SRBO gave highest values of auto-oxidation resistance (rancimat method) 10.04 and 10.14h/100°C, respectively in compare with corn oil 5.6h/100°C. Sensory evaluation of control cupcake had no significant difference (P≤0.05) rating scores of, texture, taste, crust and crumb color, appearance and overall acceptability than cupcake made with rice bran oil with all replacement levels.
6.7. Effect of substitution different levels of DSRBF with wheat flour on quality aspects of ban bread
6.7.1. Rheological characteristics of wheat flour (72%) with different substitution levels of DSRBF.
Farinograph parameters of pan bread dough revealed that water absorption of DSRBF blends was clearly increased by increasing the level of DSRBF. Moreover, dough development time and stability of doughs containing 5% DSRBF was similar to control dough (p≤0.05).
Incorporation of DSRBF into wheat flour decreased resistance to extension (R50), extensibility, but proportional number (R/E) increased.
6.7.2. Proximate composition of pan bread supplemented with stabilized rice bran fiber
Moisture content of control sample of bread was found to be 28%. The moisture content of bread samples increased significantly (p≤0.05) from 28 to 32.1 % with increasing the level of supplementation of stabilized rice bran fiber to 20%. Protein content of bread control sample was found to be 12.4 %. The protein content of bread samples increased significantly (p≤0.05) from 12.4 to 14.6 % with increasing the level of supplementation of stabilized rice bran to 20%. Fat contents of pan bread were not affected (P>0.05) by adding rice bran to the formulation. This is expected since the rice bran added was defatted. Ash content of control sample of pan bread was found to be 0.8 %. The ash content of pan bread samples was increased from 0.8 to 2.68 % with increasing supplementation level of stabilized rice bran fiber. The total fiber content in control sample of pan bread was found to be 0.6 %. The total fiber content of bread samples was increased significantly (P≤0.05) from 0.6 to 6.9 % with increasing supplementation level of stabilized rice bran fiber. Nitrogen free extract content decreased significantly (P≤0.05) from 80.90 to 70.72 % with increasing the level of supplementation. The highest
carbohydrate content 80.90 % was found in control sample of pan bread and the lowest carbohydrate content 70.72 % was recorded for pan bread formulated with 20% DSRBF.
6.7.3. Effect of Different Levels of defatted stabilized rice bran fiber on Crust and crumb Color of pan Bread.
The color differences (ΔE*) between dough containing DSRBF and control were increased by increasing the DSRBF replacement levels.
The crust color as well as the crumb color of pan bread made with different levels of DSRBF were significantly (P≤ 0.05) darker (Lower L* values) and more reddish and yellowish colored than control. The crust and crumb color differences (ΔE*) between bread formulated with DSRBF and control were increased (P≤0.05) by increasing the level of DSRBF. The crust and crumb color differences (ΔE*) were pronounced with bread made with 20% DSRBF replacement level.
6.7.4. Physical properties and Texture profile of bread supplemented with stabilized rice bran fiber
The loaf volume, height and specific volume of pan bread decreased (P≤ 0.05) gradually by increasing the level of DSRBF, while the loaf weight increased (P ≤ 0.05). Pan bread crumb texture results indicated that hardness, firmness, gumminess and chewiness were increased (P ≤ 0.05) by increasing
replacement level of DSRBF, while cohesiveness, springiness and resilience were decreased (P ≤ 0.05). Sensory evaluation of control pan bread had higher (P≤0.05) rating scores of, texture, taste, crust and crumb color, appearance and overall acceptability than pan bread made with DSRBF.
6.7.5. Sensory attributes of pan bread formulated with wheat flour (72% ER) substituted with different levels of DSRBF
Pan bread formulated with DSRBF within 5% showed similar (P> 0.05) taste scores to control, while bread made with DSRBF at level 5% had higher (P≤ 0.05) odor scores similar to control. A significant (p≤0.05) decrease was observed in energy values of pan bread supplemented with stabilized rice bran fiber. The control sample had the highest energy value 420.40 kcal/100 grams followed by sample formulated with 5% DSRBF (414.30) kcal/100 grams. Meanwhile, the Lowest (p≤0.05) energy value (387.18 kcal/100) scored for sample formulated with 20% DSRBF. The hardness, gumminess and chewiness were increased (p≤0.05) by increasing the replacement level of DSRBF, while cohesiveness, springiness and resilience were decreased (p≤0.05). Pan bread formulated with DSRBF had harder (p≤0.05) crumb texture than control. The highest hard crumb value was obtained for bread containing 20% DSRBF. Pan breads made with DSRBF substitution up to 10% were overall acceptable by panelists.