The Research On Protein Hydrolysate Of Yongchuan Douchi And Melanin Formation

Douchi is one of the Chinese traditional fermented foods.It is loved by consumers for unique flavor. Yongchuan douchi,as a typical example of mucor type fermented food, is popular with by the Chongqing area and even the whole country. Douchi will produce a series of composition changes in the fermentation process.These changes give it to sensory quality such as colour, aroma, taste and produce many active substances.Douchi’s color, to a certain extent, can be used as evaluation criteria of douchi quality and maturity.Ripe douche is usually sheen.Studies suggest that the douche color mainly derived from protein hydrolysate of maillard reaction during fermentation, and protein hydrolysis is core of the change mechanism of douchi fermentation.It main provides nutrients, flavor substance and function of the active materials.Nowadays the current domestic research focuses on the production process and active ingredient’s research.But the research of douchi fermentation process in the relationship between protein hydrolysate and melanin formation has not to report yet.This paper will research relationship between protein hydrolysis and melanin formation in the process of traditional Yongchuan douchi fermentation.Aimed at quality of douchi quickly identify and the development of protein source of functional food and even to lay the theoretical basis rapid production technology. Through analysing dynamic process,which contains traditional Yongchuan douchi fermentation amino nitrogen, total amino acid content, free amino acids, peptide content changes and color change rule, for color value index to establish regression model, in order to make clear the dynamic process of protein degradation and melanin formation mechanism. This article main research conclusion is as follows:(1) The Yongchuan douchi color is on the rise in the fermentation process and late in the starter propagation to the early stage of the secondary fermentation generated melanin in great quantities,suggests that this period of time is stage of rapid formation of melanin. During fermentation, the crude protein content changed little and the protein hydrolysis is always throughout the fermentation stage. For enhanced hydrolysis in the early of secongary fermentation, the formation of melanin and proteolytic have certain relations.(2) It is suggests that by pure breed fermentation four kinds mucor choosed: soluble protein, soluble protein, free amino acid molecules, peptides, proteins hydrolysate with douchi color variation has a significant correlation (p<0.01).By watching all pure fermented douchi samples color changes, fermentation time, microbial strains of multiple comparison found that the Mucor racemosus and Actinomucor elegans for deepening douchi color plays an important role and ascertained the douchi’s color rapid changes in the early stage of secondary fermentation stage.(3) Testing the samples of douchi melanin rapid fermentation involves by SDS-PAGE found that the later of starter propagation and the early of secongary fermentation (namely melanin rapid growth),7s protein components in douchi samples all have different levels of consumption.Especially the Mucor racemosus douchi and Actinomucor elegans douchi with larger variations in color, soy protein degradation basic already all below37kDa, Wutongqiao mucor compared with former fermented eight days of douchi samples, also have part of the7s protein degradation. That7s protein is the source of melanin.(4) Through the study of the correlation of all samples with douche fermented black bean color analysis and curvilinear regression found that polypeptide and douchi color change the formation of melanin has the highest correlation (Pearson coefficient is0.865**)and curve fitting degree y=1.4834×x0342(R2=0.716).(5) By the HPLC test results found that in the process of rapid formation of melanin, the peaks of the sample liquid time backwards, according to the principle of reverse phase liquid chromatography, this stage is the main consumption of fermented black bean hydrophilic peptide. Further found through the analysis of the amino acids and free amino acid test, participation of melanin of hydrophilic peptide, mainly contains aspartic acid, glutamic acid, glycine, lysine, arginine of hydrophilic peptides.