Effects of Polyphenols in Different Teas on Physicochemical Characteristics of Egg White Protein Gel During Tea Eggs Making

Tea egg is a Chinese traditional snack and leisure food, fresh chicken eggs and tea are the main ingredients. The influence of tea is the most important one, because the polyphenols in different teas can affect the egg white gel (EGL) and will impact the quality and flavour of tea eggs. To investigate the effects of tea on the physicochemical characteristics of EGL during tea egg making, the common used tea (green and black tea), and their usual physical form (in leaf and powder) were selected, respectively. The results indicated that the physicochemical characteristics of EGL were more susceptible to green tea than black tea. EGL also had different results on the physical form of tea. When the tea concentration ranged from 1 to 12 g/100 mL (per gram dry tea in 100 mL of water), the soluble protein content and surface hydrophobicity in the EGL were both direct proportional to the tea concentration, whereas the pH exhibited an inverse relationship. The water holding capacity in green tea groups was like an inverted “U”, but it was kept increased in black tea groups. The content of free sulfhydryl groups in tea leaf groups was like an asymmetric inverted “V”, but it was positive correlation with the amount of tea in powder groups. Considering only the physicochemical properties of protein gel in egg white, green tea in leaf form of 6 g/100mL could make eggs with the best gel quality and stronger tea flavour. This study will standardize tea eggs making, and promote the sharing of traditional Chinese cuisine with the global community.