Study On The Preparation And Properties Of Germinated Black Rice Instant Powder

As a new type of brewed food,germinated black rice powder is full of nutrition and rich in various functional active substances.In recent years,it has received extensive attention from the cereal food market.However,the polyphenolic compounds in black rice mainly exist in the form of water-soluble pigments,which have poor humidity and thermal stability.Conventional process methods such as wet germination and high-temperature baking will result in a large loss of black rice pigments and phenols.Aiming at the problems of nutrition and quality degradation in the traditional black rice powder processing technology,this paper used semi-dry germination technology to germinate black rice,which effectively avoids the loss of water-soluble nutrients during the germination process.In order to further reduce the loss of active substances of germinated black rice during the heat treatment process,microwave was used to treat the black rice.In addition,this paper also studied the effect of the compound thickeners and granulation technology on the brewing stability of the germinated black rice powder.Finally,the impact of different storage time and packaging methods on the storage stability of germinated black rice powder were studied.This parper aims to explore the preparation process of a new germinated black rice product,and to provide theoretical guidance for the industrial development of grain-based products.The specific research content and results of this article are as follows:First,the effects of semi-dry germination conditions on the quality of germinated black rice were studied.Single factor and orthogonal test were conducted on the germination conditions of black rice to determine the best germination conditions:The germination time is42 h,the germination temperature is 28°C,and the bulk density is 10 g/dm~2.Compared with the traditional germination process,the semi-dry germination significantly avoided the loss of phenolic compounds in the black rice,the total phenol loss was reduced by 91.5%.By measuring the physical and chemical properites of black rice after germination,it was found that the starch content of black rice was significantly reduced after germination,and the protein and dietary fiber content was significantly increased.The GABA content increased from2.25 mg/100g to 17.83 mg/100g,and the amylase activity increased to 41.44 mg/g/min.In addition,the in vitro starch digestibility of black rice decreased significantly after germination.Further stress treatment found that when the germinated black rice was stressed at low temperature and hypoxia environment for 10 hours,the GABA content in the germinated black rice increasing from 17.83 mg/100g to 31.14 mg/100g.Secondly,the germinated black rice was cured by microwave heating.It was found that the total phenol content of the germinated black rice increased significantly from 6.28 mg GAE/g to 6.61 mg GAE/g after the microwave treatment for 4 min.At the same time,with the prolong of microwave treatment time,the amylase activity of germinated black rice continues to decrease,which caused the viscosity of the germinated black rice gelatinization system to continue to increase within 6 min.At 6 min-10 min,due to the starch enzyme was inactivated,the viscosity of the gelatinization system began to decrease.By observing the XRD analysis chart,it was found that the relative crystallinity of germinated black rice starch increased after microwave treatment for 2 min.While treatment exceeded 2 min,the relative starch crystallinity began to decrease.The changes of in vitro digestibility of starch of germinated black rice with the microwave time were similar with the relative starch crystallinity.It was found by DSC measurement that with the prolong of treatment time,the starting temperature and ending temperature of germinated black rice continued to increase,while the gelatinization enthalpy gradually decreased.In addition,the effects of 6 common food thickeners on the stability of germinated black rice powder were studied,and three of them were selected for ternary thickener compounding experiments,the ratio of konjac,xanthan,and carrageenan was determined as 7:4.6:5.With this ratio,the centrifugal sedimentation rate of the germinated black rice powder was 4.05%,and the viscosity was 35.19 m Pa·s.The different ratio of ternary compound thickener with dispersant on the brewing stability were further measured.It was found that when the ratio of compound thickener to dispersant was 4:6,the centrifugal sedimentation rate of the system was3.95%,The viscosity was 39.17 m Pa·s,which has the best suspension stability.However,under this ratio,the dispersibility index of the germinated black rice powder was 17 s,the agglomeration rate was 9.23%,which mean the particle fluidity was poor.After the granulation treatment,the dispersibility index and the agglomeration rate were reduced to 4.3 s and 0,respectively,which solved the problem of poor particle fluidity and agglomeration caused by the addition of thickeners.Finally,the storage stability of germinated black rice instant powder under the accelerated test at 37°C was explored.The results showed that ordinary black rice powder and germinated black rice powder have poor storage stability.With the prolonged storage time,the fatty acid value,oxidation value and malondialdehyde value continue to increase,and the total phenol content continues to decrease.The storage stability of the germinated black rice powder after microwave treatment were improved,the oxidation index and the total phenol content have a lower degree of deterioration.In addition,the use of sealed packaging and the addition of antioxidants can significantly decreased the deterioration of oxidation indicators and the loss of free phenol,however,the effect of differernt packaging on combined phenol of germinated black rice was not obvious.