| China accounts for 35% of global rice production and 2/5 of total domestic grain production.About 55% of rice yield is consumed directly as cooked rice.Only 6% is used for processing in China. There is a large number of rice overstocked, and leaded to great losses. Identification of further processing for rice is necessary to generate great demand for it. Yinmi as a traditional Chinese food is a intensive processing production which has high nutritional value, such as maintain stomach,reinforce the spleen,to benefit the lung, Which is considered by the TMC. The primary technical process of yinmi is soaked in warter for a few days. Steaminged and than dryed in the shade, where is the name "yinmi" come from. The content of starch in yinmi is above 60%. Compared with the raw rice starch, yinmi starch has high degesty. So the properties of starch in yinmi has direct effection on the physical properties of yinmi.In this study, there are two materials made from liangyoupeijiu and jingnuoliuhao respectively, which is called liangyoupeiju yinmi and jingnuoliuhao yinmi in the following for short. In this article, the granular properties, physical Properties,vitro digestibility and degradation kinetics of yinmi starch was thoroughly investigated. The main contents and results are as follow:1. The composition and granular properties of yinmi starchCompared with the raw rice, the content of moisture increased, total starch decreased and amylase decreased. The granular properties of rice starches have been characterized by the means of X-ray diffraction analysis,Zetasizer analysis, the results were as follows:Compared with the raw starch, the crystallinity of yinmi starch decreased; the size of rice starch granules showed significant differences, the AD range of yinmi starch is 45～60μm, while raw starch is 10～12μm. The granular properties had a significant effect on physicochemical properties and vitro degestibility:the AD granule diameter of rice starch showed positive correlation with rehydration and negative correlation with pasting temperature; The amylase contents showed positive correlation with pasting temperature.2. The physicochemical properties of yinmi starchThe physicochemical properties of yinmi starch were studied, including solubility and swelling power, graphical analysis by rapid viscosity analyzer, thermal properties by differential scanning calorimeter (DSC), gel firmness by texture analyzer (TA) and rheological properties by dynamic mechanical analysis (DMA). Compared with raw starch, the results showed that yinmi starch has higher solubility curve, swelling power and rehydration, lower pasting temperature and lower enthalpy value; Compared with liangyoupeijiu yinmi starch, jingnuoliuhao yinmi starch showed higher freeze-thaw stability, while yinmi starch showed lower freeze-thaw stability than raw starch; Typical pasting curve and rheological properties were determined by RVA,DMA, the results of finally viscosity and disintegration, storage modulus (G') and loss modulus (G") have different degrees changes.3. In vitro digestion kinetic and retrogradation kinetic of yinmi starchThe resistant starch and hydrolysis index were determined by the method suggested by Goni et al. The glycemic index (GI) estimated using an equation (GI=39.71+0.549HI) build by Goni et al, the GI and HI are negative correlated with resistant starch content. The results are as follows:The resistant starch content showed negative correlation with GI and HI; The effect of moisture content on retrogradation of yinmi starch was studied by wide-angle X-ray powder diffraction and differential scanning calorimetry. The results showed that yinmi starch has obvious diffraction peak and the highest degradation rate with the 55% moisture content, and liangyoupeijiu yinmi starch showed higher degradation rate than jingnuoliuhao yinmi starch.
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