Ozonun polifenol oksidaz ve elma suyunun kalitesine etkisi

The aim of the thesis was to investigate the effect of ozone treatment on apple juice quality and changes that occur during the storage at different temperatures. The samples were treated with ozone for 15, 30, 45, and 60 minutes using the corona-discharge method. Effects of ozone treatment on color, polyphenol oxidase activity, protein content, and total phenolic content of apple juice were investigated. The apple juice color parameters (L*, a*, b*, and YI) were observed to be not significantly affected by ozonation, while total color difference values were affected. It was determined that ozone application did not affect the protein content of apple juice. On the other hand, the ozone inhibited the polyphenol oxidase (PPO) in the apple juice where PPO activity decreased as the ozone treatment time increased. Besides, the ozone treatment caused a marked decrease in the levels of the total phenolic content of apple juice. Ozonated samples were stored for 60 days at 4C, 25C, and 37C temperatures. The effects of storage temperature and time on the color and total phenolic content of the samples were evaluated. Change in L* values of apple juice versus storage time followed zero-order kinetics for all storage temperatures. The activation energy required to change the color of apple juice was found as 15.69 kJ/mol and increased by ozonation up to 36.89 kJ/mol. Total phenolic content in untreated apple juice was more affected by storage time than in ozonated samples.