Detecting the interaction between phytochemicals and casein in milk with microplate reader

• Main Authors: Chiao-Chen Yu, 余巧甄
• Other Authors: Pei-Fen Liu
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/cgi-bin/gs32/gsweb.cgi/login?o=dnclcdr&s=id=%22107NCHU5253051%22.&searchmode=basic

碩士 === 國立中興大學 === 食品暨應用生物科技學系所 === 107 === In our daily diet, milk usually mixes with other food materials to generate conventional products like milk tea, latte, or fruit flavor yogurt. These food materials often contain functional small molecules, phytochemicals, existed in the mixed milk products. Because casein is the most abundant (~80%) protein in milk, chances are high that casein may interact with phytochemicals during the mixing and leading to unexpected effects. Identifying the interaction between phytochemical and casein in the milk is then becoming important for applications like food processing and new product development. However, the current techniques have limitations that hamper the detecting of interactions between phytochemicals and casein proteins in milk. To overcome these limitations, we developed a new strategy for detecting the interaction between phytochemicals and casein in the milk sample. In this study, we successfully combined “pulse proteolysis”, “Bradford protein assay”, and “microplate reader” to detect the interaction between phytochemicals and casein in milk. The consistent results between SDS-PAGE and microplate reader demonstrate the possibility of using Bradford assay with microplate reader to determine the interaction between phytochemicals and caseins in milk. However, we also found that urea and organic solvent may complicate the conditions of sample and result in misjudgments from the plate reader. Dose-dependent experiments were then selected to avoid the addition of urea. We then successfully detected the interaction between tea polyphenols and caseins in milk. Subsequent testes showed that the binding of casein with the larger gallate esters containing polyphenols epigallocatechin gallate (EGCG) or epicatechingallate (ECG) were more effective than with smaller polyphenols epicatechin (EC) or catechins (C). According to our result, this new method is applicable for quantitatively detecting the interaction of phytochemicals and caseins in the food environment. It is then possible for high-throughput screening to provide information like guidance for mixing foods during the food processing, or awareness for taking drugs with regular diet.