Differences Of Resistant Starch Content And Its Its Correlation With Flour Quality In Different Wheat Cultivars

Resistant starch (RS) Performs better physiological function than dietary fibreplaying a key role in protecting gut function and reducing glycemic concentration after meal. Wheat is the third food crops and its made-up products such as noodles, bread and steamed bread are staple foods in our country. To provide theory basis on the new quality trait-RS content for cultural regulation and breeding, differences of RS content in wheat cultivars and its correlation with flour quality should be studied, and nitrogen fertilizer on RS content and its correlation with starch physicochemical properties should also be discussed. It has great significance in increasing RS content of wheat-products and satisfying the peoples healthy needs for this unique dietary fibre. In this study, the field experiment was conducted using 10 wheat cultivars planted widely since 1990s to investigate differences of RS content in wheat flour and extracted starches and its correlation with flour quality and starch physicochemical properties. Morever,the effects of different conditions on RS formation in wheat starch was studied by the method of single factor experiments and response surface experimention. The main results were as follows:1. Differences of resistant starch content in wheat flours and its correlation with flour quality. Differences of RS content both in raw and cooked flour from different wheat cultivars were significant. RS content in raw flour was lower than in the cooked flour and their relationships were positively significant. For raw flour,RS ranged from 0.17% to 0.84% under N225 and 0.33% to 0.89% under zero nitrogen, while for cooked flour, those were 1.07% to 1.84% under N 225 and 1.38% to 2.02%. Nitrogen fertilization significantly-reduced RS content in raw and cooked flours as well as amylose content,which indicated that nitrogen fertilization obviously regulated RS formation, morever increased variation among wheat culitivars. Based on variation of RS content in raw and cooked flours,10 culitivars could be clustered to two groups with significant differences.RS content in cooked or raw flour had significantly positive correlation with amylose content. RS content in raw flour had remarkable negative correlation with trough viscosity and final viscosity, while RS content in cooked flour had remarkable negative correlation with peak viscosity, trough viscosity and final viscosity. The results indicate that the formation of RS is closely associated with that of amylase,and higher RS content in flours would be unfavorable for pasting properties.2. Differences of resistant starch content in wheat starch and its correlation with starch physicochemical properties. Differences of RS content both in raw and cooked starches from different wheat cultivars were significant. RS content in raw starches was lower than in the cooked starches and their relationship was positively significant. For raw starch,RS ranged from 0.46% to 1.32% under N225 and 0.17% to 1.22% under zero nitrogen, while for cooked starches,those were 1.88% to 3.71% under N225 and 2.45% to 3.64%. RS content in cooked or raw starches had significantly positive correlation with amylose content, amylopectin/amylase and retrogradation value while it had significantly negative correlation with protein content. RS content in raw starches had significant negative correlation with the average diameter of the starch. The results indicate that higher amylase content,higher amylopectin/amylose, smaller average diameter,lower protein content and easier retrogradation property were good for RS formation. Nitrogen fertilization significantly reduced RS content in raw and cooked starches, which indicated that nitrogen fertilization obviously regulated RS formation, morever increased variation among wheat culitivars. At the same time,nitrogen fertilization increased protein content, average diameter, number peak diameter, A-style starch granule volume percent and A-style starch granule number percent, but reduced B-style starch granule volume percent, and the amylose content and the retrogradation property had no remakable changes.3.Effects of retrogradation conditions on resistant starch formation in wheat starch. With starch solution concentration increased (10%-50%). RS content of wheat starch from Zhengmai 9023,Yangmai 158 and Yangmai 13 changed in the form of single peak curve and the maximum appeared when the concentration was between 20% and 30%. At the temperature of 4℃. RS content changed in the form of S-style curve when the storage time increased. After 20-26h. RS in these three wheat turn into the stage of stagnancy.4℃was a better condition than 25℃for the RS in wheat starch to form. RS content changed in the form of single peak curve when pH value increased.and the pH values between 5 and 7 was good for RS formation. RS formation effects were different among different wheat cultivars and RS formation effects of starch in zhengmai 9023 was stronger than that in Yangmai 158 and the effect of stach in Yangmai 13 was the weakest. RS content of Yangmai 13 could be improved to 6.27%. The optimum condition for getting the highest RS content was as bellow:starch concentration 24.19%, pH 6.23, srorage time 28h and 4℃.