Effects Of Degree Of Milling On Physicochemical Properties And Cooking And Eating Quality Of Indica Rice

The phenomenon of post-harvest loss and waste of rice nutrients in my country is prominent,especially in the processing link.Excessive processing makes the rice"refined,white and bright",but it results in a decline in the yield of rice,waste of food resources and a decline in corporate efficiency."Moderate processing" can reduce the processing loss and energy consumption of rice,and retain the nutrients more completely.In this paper,the grinding characteristics and appearance quality of 24 kinds of indica rice were firstly studied.On this basis,the early indica rice "Longkezao No.1" and the late indica rice "Xing No.2" were selected as the research objects.The influence of physical and chemical properties,cooking quality,digestive characteristics and sensory quality of indica rice was determined,and the appropriate processing accuracy of indica rice was determined,thus providing a theoretical basis for realizing moderate processing of indica rice.The main results are as follows:The milling characteristics and appearance quality of 24 different indica varieties were studied.The results showed that with the extension of milling time,the reduction rate of indica rice increased,and degree of milling(DOM)characteristics of different varieties of indica rice were different.When the milling time was 90 s,the g degree of milling(DOM)"Jade Needle Fragrance" was the highest,while that of "Wuyou 308,Longkezao No.1,and Xing No.2" were lower.The degree of milling(DOM)had a significant effect on the broken rice rate,L value,a*value,b*value and whiteness of rice,but had no significant effect on the aspect ratio of rice.Correlation analysis showed that degree of milling(DOM)was significantly positively correlated with L value,whiteness,broken rice rate,but was significantly negatively correlated with a*value and b*value(P<0.05)..Taking "Longkezao No.1" and "Xing No.2" as representatives,the effect of degree of milling(DOM)on the physicochemical properties of indica rice was studied.With the increase of degree of milling(DOM),the skin retention and skin residual ratio of indica rice decreased,the moisture content,crude protein,crude fat,dietary fiber,minerals and total phenols content of indica rice decreased,while the content of crude starch and amylose increased.Compared with brown rice,when the ideal grinding rate was 14%,the crude protein,crude fat,dietary fiber,minerals and total phenolic content of"Longkezao No.1" and "Xing No.2" decreased by 85%and 85%,respectively.71%,48%and 65%,73%and 61%,32%and 28%,47%and 44%.With the increase of degree of milling(DOM),the gelatinization enthalpy ΔH value,viscosity and decay value of indica rice flour increased,while the gelatinization temperature and retro gradation value decreased.The study of rheological properties showed that the indica rice flour paste was a shear thinning fluid,and the flow index decreased with the increase of degree of milling(DOM).The starch crystallinity of indica rice flour increased with the increase of degree of milling(DOM),and there was no significant difference between the crystallinity of Longkezao 1 and Xing 2.Taking "Longkezao No.1" and "Xing No.2" as representatives,the effects of degree of milling(DOM)on the cooking characteristics,hardness,digestibility,volatile substances and consumer acceptance of indica rice were studied.The results show that increasing degree of milling(DOM)rice can shorten the cooking time of rice,and increase the water absorption rate of rice and the solid content of rice soup during the cooking process.When the reduction rate was 0-8%,the hardness of rice decreased with the increase of degree of milling(DOM).Continuing to increase the reduction rate had no significant effect on the hardness of the rice.With the increase of degree of milling(DOM),the rapidly digestible starch(SDF)content of indica rice increased and the starch digestibility increased.47 monomers and dimers of some substances in rice were identified by gas chromatography-ion mobility spectrometry(GC-IMS),mainly including aldehydes,ketones and alcohols.Most of the volatile substances were higher in indica rice with a milling ratio of 0%to 6%,while the contents of hexanal,valeraldehyde and phenylethyl alcohol increased with the milling ratio,and the milling ratio was 14%.The highest content in rice.The 2%～6%degree of milling(DOM)can retain most of the volatile substances in the rice,and the volatile substance composition of the 10%～14%degree of milling(DOM)has no significant difference.The results of the consumer preference test showed that with the increase of degree of milling(DOM),the preference of indica rice gradually changed from a high degree of dislike to a preference.The"Longkezao No.1" and "Xing No.2" with a depreciation rate of 8%have a higher degree of acceptance.At this time,the crude protein,crude fat,dietary fiber,minerals and total phenolic content of "Longkezao No.1" and "Xing No.2" retained 87.83%and 76.43%,82.76%and 72.92%,84.82%and 84.82%,respectively.78.26%,50.12%and 35.71%,80.31%and 79.17%.