Effect Of Tea On The Quality And Digestion Of Marinated Egg During Processing

Egg was taken as a carrier to study the changes of egg quality with additive of tea, inorder to provide theoretical guidance for the industrial production of tea-leaf egg and othertea-marinated products, and laid an significant theoretical basis for widely use of tea inmarinated liquid. Meanwhile, the effect and impact mechanism of gastrointestinal digestion oftea towards egg white was also examined. It not only could puzzle out customers’ confusingabout whether tea would affect the gastronintestinal digestion of protein, but also providetheoretical reference for the study of protein gastrointestinal digestion affected by tea. Themain contents and results of testing are as follows:Firstly, the changes of egg quality during marinating process affected by green tea andblack tea were ananlyzed. The results showed that these two kinds of tea could lead to thecolor change of egg, but the influence degrees were different. These two kinds of tea couldalso effectively reduce the TBA values of egg yolk, and inhibit the oxidation ofpolyunsaturated fatty acids (PUFA) into monounsaturated fatty acids (MUFA). Sensoryevaluation results showed that the tea-leaf egg was with best taste when the additive of teawas1g/100mL, the marinating temperature was100oC and marinating time was2h.Correlation analysis showed that tea polyphenol (TP) had a correlation with thephysicochemical and sensory properties of egg.Secondly, the feasibility of tea-leaf egg curing at room temperature was investigated, andthe effect of tea on egg quality during curing process was also studied. The results showedthat when the addition of green tea and black tea were1g/100mL, there was no microbialgrowth in curing process for48h and36h, respectively. This result suggested that it wasfeasible for curing at room temperature of tea-leaf egg. Moreover, tea showed stronginhibition of three kinds of typical microorganism of egg when the dose of contaminatedbacteria was less than3lgCFU/mL, which further demonstrated the feasibility for curing atroom temperature of tea-leaf egg. During curing process at room temperature, the L*, a*andb*values of both tea-leaf eggs were all decreased with the extension of curing time. The twokinds of tea also showed strong antioxidant ability during curing process. Sensory evaluationresults showed that both tea-leaf egg had the highest mark when curing12h.Thirdly, the effect of tea on the gastrointestinal digestion of egg white was studied.Results showed that tea could promote egg white digestion in simulated gastric fluid andinhibited egg white digestion in simulated intestinal fluid. It also showed that tea promotedthe whole gastrointestinal digestion of egg white and the effects of TP on proteins were in adose-dependent manner.Finally, the impact mechanisms of gastrointestinal digestion of TP towards two kinds oftypical egg white protein (ovabulmin (OVA) and lysozyme (LYZ)) were investigated,respectively. The results showed that with the presence of TP, OVA/LYZ was easier to bedigested in the pepsin solution at pH1.2and and was harder to be digested in pancreatinsolution at pH7.5. The results of binding affnity between TP and OVA/LYZ, and thesecondary structure of OVA/LYZ affected by TP at pH1.2and pH7.5suggested that TP-protein (TP-substrate) was another mechanism of TP affecting digestion. Different degreesof conformational change occurred to OVA/LYZ at pH1.2and pH7.5with the addition of TP,which might lead to different degrees of unfolding of OVA/LYZ and then affected theirdigestibilities. Different changes of second structure of proteins (substrate) affected by TP atpH1.2and pH7.5might also resulted in the difference of digestibilities between pH1.2andpH7.5.