The Stability Of Juice Polyphenol In Storage And Processing And The Effect Of Interaction Between Juice Polyphenol And Protein On In Vitro Digestion

Phenolic compounds are hot spots of domestic functional factor and functional food development nowadays. It is popular to add fruit and vegetable juices rich in polyphenol into food system. Most researches on phenolic compounds at present are focused on their structures and functions, the researches on the interaction of phenolic compounds and other compounds in food system are very limited. In order to investigate the interaction of protein and phenolic compounds better, this project simplify the fruit-milk beverage system, investigating the simulation system which consists of whey protein (WP) and three phenolic compounds. This project investigates the change of phenolic compounds during the storage of fruit juice, the processing of fruit-milk beverage, and the in vitro digestion, in order to help people to comprehend the interaction between food protein and phenolic compounds, and provide basic information for the improved application of active ingredient in plants to food.Firstly, the thesis took freshly squeezed juice as object of study, and investigated its changes of phenolic components and antioxidant capacity. It has been found that the stability of phenolic compounds in fuits is influced by the species and temperature. The total phenolic contents and antioxidant capacities of bayberry/apple/pomelo juice decrease during the storage, but the total phenolic content of watermelon juice increases during the storage. Storage at 4oC is not suitable for anthocyanin abundant juice. Apple juice and pomelo juice can maintain their stability for a long time at -18oC, storage almost does not decrease its antioxidant capacity.Secondly, it investigated the effect of interaction between phenolic compounds and WP in fruit-milk processing on the antioxidant capacity of fruit-milk system. It has been found that the mixture of WP and naringin or chlorogenic acid does not result in the substantial reduction of total antioxidant capacity; However, the mixture of WP and catechin leads to the substantial reduction of total antioxidant capacity. The antioxidant capacity of the mixture of WP and naringin or chlorogenic acid increases after heated at 121oC for 10 min, while that of the mixture of WP and catechin decreases.Finally, the thesis investigated the effect of phenolic compounds in fruit-milk system on the digestibility of WP, and it researched on the effect of interaction between phenolic compounds and WP/ protease on the antioxidant capacity of phenolic compounds during in intro digestion. It has been found that, phenolic compounds can interact with WP and protease (pepsin and pancreatin), that leads to the decrease of digestibility of WP; Higher concentration of phenolic compounds, stronger influence on the digestibility of WP. The process of digestion has different effects on the antioxidant capacity of different mixed system consisting of phenolic compounds and WP, which depend on varied factors, such as phenolic components, phenolic concentration, and protease. Protease weakens antioxidant capacity of phenolic compounds during in vitro digestion.