Research On Drying Technology Of Nutritious Restructuring Rice

Nutritious restructuring rice is produced with twin-screw extrusion processes,and is mainly composed of low-cost brown rice(or broken rice) and a few other cereals or vegetables.Compared to the ordinary rice,it contains more vitamin B,minerals,dietary fiber and has the effect of preventing people from diseases.So it suits well citizen who always eat the polished rice.Firstly,parameters in hot air drying and microwave drying processes were studied,especially how they influence dehydration time and drying quality.The results showed optimal parameters:for hot air drying,the temperature was 50℃,the wind speed was1.5m/s,the drying time was 175 min,under this condition the crack percentage was 2%;for microwave drying,the microwave power was 350 W,the drying time was 5min,under this condition the crack percentage was 2.33%.By comparing the produced rice of the two drying methods,it could be found that the dehydration time for hot air drying method was too long and resulted in hardening of rice skin;the microwave drying method would make the underlying rice charry or dissilient,even arose white points inside few rice.So a hot air-microwave two stage drying method was created by combining two drying methods.Meanwhile a sensory evaluation criteria was made to value charry and dissilient condition.Then a response surface method was conducted to get the following optimal parameters:the hot air temperature was 53℃,the transform moisture content was 22%(hot air drying for 35 min, microwave drying for4min),the microwave power was 280 W.Through the proof test proves,dying total time was 39 min,the crack percentage was 2%,the sensory evaluation score was 84.Hot air-microwave two stage drying method is the best drying process for producing nutritious restructuring rice. its advantage is that the drying last short and the rice quality after dehydration is still high.The scanning electron microscopy(SEM) was used to examine the influence of the drying methods on inner microstructure and surface microstructure of Nutritious restructuring rice.The results of photographs from the 500× scanning texture electron microscope showed:on the image of hot air drying samples,there were large numbers of holes on the surfaces of rice.By contrast,rice surfaces of microwave drying and hot air-microwave two stage drying were slick;From the 1000×scanning electron microscope photographs,the nutritious restructuring rice of air drying had dense structure,there were hardly no hole inside rice;the nutritious restructuring rice of the microwave drying hadmany deep holes inside; there were some relatively shallow holes inside the hot air-microwave two stage drying samples.