Process Optimization of Enzyme-assisted Pregelatinization Technology and Analysis of Flavor Substance Difference

The response surface experiment was used to design and optimize the enzyme-assisted pregelatinization process of brown rice. The optimum conditions of enzyme-assisted pregelatinization process were obtained through the cooking time: The enzymatic hydrolysis time was 4 h, the amount of enzyme added was 0.1%, the pregelatinization time was 10 min and the enzymatic hydrolysis temperature was 39 ℃. Gas chromatography-ion migration spectrometry (GC-IMS) was used to determine the volatile substances of white rice, brown rice and enzyme-assisted pregelatinized brown rice before and after cooking. 56 kinds of volatile substances were detected in enzymolysis assisted pregelatinized brown rice, including 19 kinds of aldehydes, 8 kinds of ketones, 6 kinds of esters, 12 kinds of alcohols and 11 kinds of other compounds. Forty-four kinds of volatile substances were detected in the pregelatinized brown rice assisted by enzymatic hydrolysis after cooking, including 18 kinds of aldehydes, 8 kinds of ketones, 3 kinds of esters, 11 kinds of alcohols and 4 kinds of other compounds, and 2-octenal, phenylacetaldehyde, acetophenone, acetoin, gamma-butyralide, pentanoic acid, hexanoic acid, butyric acid and hexadiene disulfide and other volatile substances disappeared after cooking.Aldehydes, ketones and alcohols showed the largest changes in the volatile flavor components of brown rice before and after the enzymatic hydrolysis assisted pregelatinization. The acids in esters and other groups showed the greatest changes in the volatile flavor components of brown rice before and after cooking assisted by enzymatic hydrolysis.