| Resistant starch (RS) can not be digested in the small intestine, so it can be fermented in the large intestine by intestinal microorganisms to produce some short chain fatty acids, which can stimulate the growth of the probiotics and inhibit the growth of cancer cells. Because of its low water retention property and no effect on mineral absorption, RS is a suitable material of dietary fiber and processed food. So using rice starch to produce resistant starch will further boost rice processing and utilization, moreover, it will provide a practical strategy to prevent modern civilized illness.Considered from the novel role, in this thesis, the effect of food gums on the rice starch gel property, yield and formation mechanism of resistant starch were investigated with emphasis on the effect of hydrophilic gel on the process. Offer good taste resistant starch for especial people, and give theory basis and experimental support. The thesis were divided into four parts: firstly, a texture profile analysis on characters of rice starch gel modified by three normal food gums; secondly, influence of adding food gums to indica rice starch on resistant starch yield; thirdly, influence of adding konjac glucomannan to indica rice starch on formation mechanism of resistant starch; fourthly, primary study of influence of adding food gums to indica rice starch on the structure of resistant starch.The main research results:1 The texture profile of the rice starch/food gums mixed gel(such as hardness, adhesiveness and chewiness) depends not only on the variety of rice and food gums, but also on the concentration of the food gums. The addition of unsuitable food gum or gum with improper concentration would lead to deterioration of the gel. Only the suitable food gum at a proper concentration would endow the gel an excellent quality. Low concentration (＜0.2% (w/w)) of carrageenan and high concentration of gellan (＞0.3% w/w)) could increase the hardness and adhesiveness significantly; the indica rice starch/polysaccharides always had the largest hardness, adhesiveness and chewiness comparing with other starches. Considering the economic factor, adding 0.2% (w/w) carrageen to the indica rice starch was valuable for improving the texture of rice gel food. When a higher adhesiveness/hardness ratio was needed, 0.3% (w/w) gellan could be add to indica rice starch. The konjac glucomannan could not improve the adhesiveness, chewiness and hardness significantly for any kind of the rice starches. The three varieties of rice starch, food gums and their concentration had no significant effect on the springiness of the mixed gel.2 The mono-factor experiments indicate autoclaving treatment is better than acid-modifying. These experiments were conducted to investigate the effects of food gums concentration, NaCl concentration, autoclaving time, storage time and pH on the yields of rice resistant starch. The results show pH has little effect on yields. For these factors in resistant starch preparation, the subsequence of importance was NaCl concentration＞food gums concentration＞autoclaving time＞retrogradation time＞pH. The optimum technology parameters and conditions were obtained from poly-factor experiment, the concentration of konjac glucomannan is 0.2%, the concentration of NaCl is 5%, autoclaving time is 60min, and storage time is 12h. Resistant starch yields are correlative with the texture of the food gums added with different concentration. With the increasing of the food gums concentration, hydrogen bonds between starch molecules links strengthened, or offer a series of water molecules strengthening retrogradation, so resistant starch yield increased. But when the gum concentration was increased to＞0.2%, the gum and starch molecules mixed uniformly, which interfered mutual combining of the starch molecules, thus lowered producing of resistant starch yield.3 The forming mechanism of konjac glucomannan/India rice starch resistant starch was studied by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction. Autoclaving time, retrogradation time and methods of anneal affected the productivity of resistant starch insignificantly, but the productivity was higher when konjac glucomannan was added. DSC suggested that crystal melting temperature was the highest (94～146℃) with the autoclaving 60min, retrogradation 12h and storage in 4℃after cooling to room temperature. The WXRD showed that the crystallinity of resistant starch was the highest when retrogradation for 12h. And the results suggested that the resistant starch had B-type and V-type X-ray diffraction patterns.4 The cause of formation of resistant starch is that amylase molecular resetting, and causing change of microstructure and thermodynamice character. So, the structure of purified resistant starch was studied by wide-angle X-ray diffraction (WXRD), differential scanning calorimetry, and scanning electron microscopy (SEM). The WXRD showed that the crystallines degree of the rice starch were higher than those obtained from autoclaved starches, and the peaks shifted rightwards with increased crystallinities. DSC curves presented two peaks, one was crystal melting peak, the other was amylose-fat compound melting peak. SEM showed that the shape of rice starch granule was polyhedral, but autoclaved resistant starch combined with polysaccharides were irregular sheet (shape of resistant starch with carrageenan is round), and the shape became more and more rugular with the increasing of the content of resistant starch.
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