Research On The Appropriate Degree Of Milling Of Rice Products

The raw materials of all kinds of rice products currently on China are still based on white rice.Excessive pursuit of "precision,fine,white" rice milling process has caused a lot of food and nutrition waste which is contrary to the national conditions and people's increasing health awareness.In response to the current situation,our country has proposed a moderate grain processing policy,but the range of suitable degree of milling(DOM)for various types of rice products is not yet clear,and resulting in a lack of theoretical support for the policy.Therefore,In order to investigate the influence and mechanism of DOM changes(0%,3%,6%,9%,and 12%)on the core physiochemical properties of various rice products,superheated steam-light milled rice(SS-LMR),instant rice and frozen rice gel were used as the three types of common rice products in this article,the main conclusions are as follows:(1)The influence of DOM on the cooking behavior of SS-LMR,the results showed that:Milling could increase the water absorption rate,water content and gelatinization rate of SS-LMR during cooking,and reduce the order of starch crystallization.When DOM?6%,SS-LMR has a similar moisture absorption rate and moisture content as white rice(DOM 12%),and the cooking time is about 21 minutes.And the relative crystallinity,absorbance ratio,thermal stability structure and internal microstructure of SS-LMR also have no significant difference with white rice.The appropriate DOM of SS-LMR should be DOM?6%.(2)The influence of DOM on the rehydration and edible quality of instant rice.The results showed that when DOM?3%,the water absorption rate,water distribution and morphological characteristics of instant rice were similar to that of white rice(DOM 12%).When the DOM reached to 6%,the morphological characteristics,total color difference(?E),hardness,and microstructure of instant rice were similar to that of white rice.When the DOM reached 9%,the viscosity of instant rice was not significantly different from that of white rice.It can be seen that the adaptation range of DOM for producing instant rice should be 6-9%.(3)The influence of DOM on the freeze-thaw stability of rice gel.The results show that reduced DOM can inhibit starch retrogradation during FTC,including the formation of long-range,short-range and thermally stable molecular structures.At the same time,water-solid phase separation and the shifting of partial loosely-bound water to tightly-bound water could also be suppressed,thereby reducing the water mobility of the rice gel.This result can be attributed to the enrichment of hydrophilic macromolecules(fiber,etc.)in the rice gel with low DOM which probably improve the anti-retrogradation ability and water holding capacity of rice gel.Therefore,the freeze-thaw stability of rice gel could be significantly improved by simply reducing DOM of rice.That is,DOM 0%-3%is the suitable of frozen rice gel products.Based on the above results,the appropriate DOM of SS-LMR?instant rice and frozen rice gel are DOM?6%,DOM 6%-9%,DOM 0%-3%respectively.The preparation of rice products within the range of DOM of rice can save 4%-10%of food,retain part of the bran layer nutrition,and obtain the core physiochemical properties which similar to those prepared with white rice as raw materials.The results of this study provide a theoretical basis for the implementation of moderate grain processing policy in China.