| With the improvement of living standard and pace,the instant rice industry develops rapidly.However,commercially available instant rice products still have problems such as poor rehydration,easy retrogradation,poor taste and insufficient nutrition,which are mainly caused by the rapid retrogradation of rice starch in cooked rice.Aiming at the key technical problems of improving rice quality and anti-retrogradation properties after cooking,the effects of fructo-oligosaccharides and other additives on rice quality and starch retrogradation characteristics were studied,and its regulation effect on intestinal microflora were explored.The main research results are as follows:1.Using sorbitol and maltitol as controls,the effects of different concentrations of fructo-oligosaccharides maceration treatments on the edible quality,anti-retrogradation and digestive properties of rice cooking were studied.The results showed that the maceration treatments of fructo-oligosaccharides,sorbitol and maltitol could improve the water absorption of rice and sensory score of cooked rice,reduce the hardness and hydrolysis rate in vitro digestion of cooked rice.Compared to the control group,the water absorption of rice added with 1.6%fructo-oligosaccharides increased by 15.32%;amylose content,gelatinization enthalpy and hardness of cooked rice after refrigerated for 24 h decreased by 7.36%,22.91%and 21.79%,respectively.Moreover,it significantly reduced the gelatinization enthalpy,and formed a uniform and dense porous structure,which effectively improved the sensory quality.2.In order to further explore the mechanism of fructo-oligosaccharides maceration treatment improving anti-retrogradation quality of cooked rice,theβ-cyclodextrin was used as the control to study the effects of fructo-oligosaccharides on the anti-retrogradation properties of rice starch.The results showed that compared to the blank control group（rice starch）,fructo-oligosaccharides treatment significantly decreased the peak viscosity,final viscosity and setback value of gelatinized rice starch.In addition,the short-time refrigeration of rice starch exhibited lower syneresis rate（21.82%）,hardness（16.26%）and amylose leaching（17.25%）,indicating that fructo-oligosaccharides could improve its water retention and stability.Also,fructose-oligosaccharides decreased the storage modulus,water fluidity,relative crystallinity,and transmittance ratio in the wavelength of 1047 cm-1and 1022 cm-1 from rice starch,and the network structure was more compact,showing better anti-retrogradation properties.Compared toβ-cyclodextrin,fructo-oligosaccharides had more advantages in delaying the retrogradation of rice starch.The results proved that the addition of fructo-oligosaccharides could significantly improve the anti-retrogradation properties of rice starch.3.By inoculating human intestinal bacteria to anaerobic culture in vitro,the changes of total carbohydrate content during in vitro digestion,p H value and concentration of short-chain fatty acids during in vitro fermentation,as well as the changes of bacterial flora distribution after fermentation on cooked rice added with fructo-oligosaccharides were studied.The results showed that the total carbohydrate content of fructo-oligosaccharides maceration treatment group in digestive juice was lower than that of the control group,and there were no significant changes in fructo-oligosaccharides contents.Meanwhile,the p H value of the fructo-oligosaccharides maceration treatment group decreased and the short-chain fatty acids concentration increased significantly compared to those of the control group in the fermentation process.In addition,the fructo-oligosaccharides maceration treatment group could significantly promote the proliferation of probiotics in fermentation broth such as Bifidobacterium and Lactobacillus,and effectively improved the distribution of intestinal flora.It provides a theoretical basis for the deep processing of rice and the development of high quality,healthy and convenient rice products. |
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