Research On Processing Optimization And Flavor Quality Of Traditional Doushen

As a traditional folk snacks with strong regionalism in the east of Henan province, limited reports on Doushen is available.The reasons could be attributed to the traditional koji and multi-strain mixed fermentation of this product. Additionally, little knowledge on the microbes responsible for the fermentation of this product, also hampered the standardization of the production process.We find the content of free amino acids was higher in 10% salt concentration relatively during simulate temperature fermentation. Variable-temperature fermentation was performed by simulate traditional fermentation of sun and dew, the conclusion is that the trend of main ingredient was similar with high-temperature fermentation and traditional fermentation. But the content of free amino acids was significantly better than single high-temperature fermentation,which shows the advantage of traditional fermentation. At the end of the Variable-temperature fermentation, the amino acid content of sweet and umami was rich, for 20.39% and 14.81%,respectively. The total acidity were 5.31 and 4.57%, protein was 25.24%, sugar was 8.10%, the amino nitrogen was 1.79% in the traditional fermentation products(dry basis). The glutamic acid and aspartic acids in the umami and the sweet, bitter, tasteless in the the total amino acids was 14.77% 15.11%, 59.12% and 11.00%, respectively. The proportion between four types of free amino acids during fermentation process essentially unchanged.The content of alcohols of volatile substances was found higher in three ways of fermentation by identified of SPME-GC-MS, and traditional fermentation> variable-temperature fermentation> high temperature fermentation.We can find that the percentage of aldehydes, esters and furans was increased then decreased during traditional fermentation, however, phenolic was the opposite, the percentage of ketones and nitrogen were changed by fluctuating. The type of volatile flavor compounds was the most in low salt concentration at the end of the high-temperature fermentation. For variable temperature fermentation, the percentage of aldehydes and ethers were increased then decreased, the percentage of ketones and furans were contrary, for the alcohols, phenols and nitrogenous substances, the percentage were continued to decline.So we can say that variable temperature fermentation could achieve at the basic requirements of traditional fermentation, but the formation mechanism of flavor and amino acids have yet to be studied.Using PCR-DGGE technique to identify the microbial flora during koji by different conditions in this study. Eleven species were detected in the samples, including Rhizopus oryzae, Lichtheimia ramosa, Absidia corymbifera, Rhizopus stolonifer, Amylomyces rouxii, Galactomyces geotrichum, Wickerhamomyces anomalus, Candida athensensis, Cladosporium herbarum, Neurospora crassa, Aspergillus tamarii, and we can see the microorganism is richer by traditional koji.