Isolation, Physicochemical Properties And Processing Characterostic Of Wheat Bran Starch

Wheat is the biggest grain crop in the world, playing an important role in development of food productions and national economy. Wheat bran usually accounts for about the entire15%of the wheat grain weight after milling. Starch presented in wheat bran at10%-15%is good source of starch. Starch is the main material of flour, which is one of the decisive factors of wheat flour. Starch and A-, B-type starch granule were extracted from commercial bran passing through20mesh sieve using low concentration of NaOH and neutral protease, and was also shown to have different physicochemical properties and processing characteristic in this study. The main results were as follows.1Optimization of isolation of wheat bran starchResponse surface analysis methodology (RSM) was used for optimizing the extraction technology of starch from wheat bran by aqueous alkali, and neutral protease. Based on single-factor experiments, the conditions of optimizing extracting were concluded according to Box-Behnken central composite experiment design. By the methods, the optimum extraction condition were obtained as follows:concentration of NaOH0.06mol/L, extraction time50min and extraction temperature40℃, starch extraction yield12.4%; concentration of neutral protease1.0%(E/S), extraction time50min and extraction temperature60℃, starch extraction yield14.55%. Two different extracting methods for bran starch gave a guideline to improve the comprehensive utilization of wheat bran.2Physicochemical properties of wheat bran starch, A-and B-type starch granulesThere were obviously different physicochemical properties of starch and A-, B-type starch granule by different extracting methods. In comparison with starch and A-, B-type starch granule isolating by neutral protease, starch isolating by low concentration of NaOH exhibited higher total starch content, amylopectin content, swelling power and viscosities of peak, through, breakdown, final and setback, less amylose content and pasting temperature; A-type starch granule significantly showed higher total starch and amylopectin content, swelling power and viscosity of through, setback and breakdown, lower protein content final viscosity and pasting temperature; while the method of using NaOH extracting might damage the structure of B-type starch granule, leading to the total starch, amylose, amylopectin content, swelling power, viscosity of peak, through, final, setback and breakdown lower but pasting temperature higher.3Processing characteristic of wheat bran starch, A-and B-type starch granulesPhysicochemical properties of wheat flour by adding bran starch and A-, B-type starch granule from0%to15%were influenced significantly. Sedimentation and falling number value of wheat flour mixed with wheat bran starch presented increased first slowly then down fast. There was significantly trend that the peak viscosity, through viscosity, final viscosity, setback, breakdown and pasting temperature increased with an increasing wheat bran starch. Development time, stability and farinograph quality number raised and degree of soften decreased as the content of starch isolating by NaOH in the mixture increased. At the same time, water absorption of flour added starch isolating by neutral protease also increased and development time was up to down. Meanwhile, the falling number value and sedimentation value of flour showed raised first then down increasing the addition of A-, B-type starch granule. A-, B-type starch granule isolating by neutral protease effected falling number greater and sedimentation value smaller. There was significantly trend that viscosity of peak, through, final, setback, breakdown and pasting temperature increased with an increasing in wheat bran A-, B-type starch granule from0to15%in blends. However, Ihere was different degree on different extraction methods obtaining wheat bran starch and A-, B-type starch granule impacted on the physicochemical properties significantly.In conclusion, wheat bran starch, A-and B-type starch granule have difference in total starch, amylose, amylopectin content. And these differences not only affect physicochemical properties, but also the processing characteristics.