Effect Of Resistant Starch On The Quality Of Quick-Frozen Steamed Bread

Resistant starch (RS) is defined as starch and starch degraded products that are not absorbed by the small intestine. It has a similar physiological function as dietary fiber, but has better processing characteristics, and it is an excellent food additives. As one of Chinese traditional staple food, steamed bread has gone through a great development because of frozen technology, which helped solve the shelf stability problem and made the quick-frozen steamed bread very popular in our daily life. Adding RS to the quick-frozen steamed bread will make it more healthy and nutrition, while still with great texture and flavor.In this thesis, the distribution and migration of moisture in dough and steamed bread were studied using nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) techniques, and the relationship between the quality of bread and the relaxation time of bread was established. The mathematical models were also developed and used to explore the optimum RS for content and other quality-enhancers for the quick-frozen steamed bread. The main results are as follows:1. Through study of the traditional fermentation produced dough using NMR, MRI, it was found that, to some extent, resistant starch (RS) had a favorable influence in the water holding capacity of dough, and it could also have a positive effect on the fermentation. However, if too much RS was added, the formation of gluten network would be hindered, and the appropriate amount found was about 10%. It did little influence on dough fermentation when 10% RS addition,60% water content and 1.0% yeast content were added.2. Through the analysis of NMR relaxation properties, it was observed that the detrimental effects on the sensory quality of the quick-frozen steamed bread brought by RS could be decrease, when increasing the amount of water addition in dough. A higher sensory evaluation for the quick-frozen steamed bread could be achieved with 12% RS addition,62% water content and 1.0% yeast fermentation at 32℃for 1.0 hour according to the orthogonal experiment with five factors and four levels. There were significantly correlations between the sensory scores and the relaxation characteristics of the steamed bread, and the distribution of water is one of the main factors affecting the sensory quality of steamed bread.3. The complex formulation of the quality enhancers used in the steamed bread with RS additions was studied. The regression equation, contour plots and response surface plots were acquired. The response surface experimental design four factors and three levels was developed based on the results of the single factor experiments. Considering the actual operations, the optimum contents of the composition in the quality enhancers obtained were:10.05 g/kg monoglycerides content,4.90 g/kg compound phosphate content,27.9 mg/kg lipase content and 24.4 mg/kg VC content. With the addition of these quality enhancers, the steamed bread had a much higher sensory score and improved quality.