The influence of pasteurization methods on the phenolic profiles of cloudy apple juices

Two types of preservation methods based on the ultra high temperature (UHT) and microwave (MW) technologies were used for pasteurisation of cloudy juices prepared from different varieties of apples. The technological trials using Vaculiq press for juice production under anaerobic conditions and EnbioJet microwave flow pasteurizer or UHT system were performed in order to evaluate the effect of preservation method on the stability of phenolic compounds in apple juice. The chemical properties verified embraced determinations of polyphenols by HPLC-DAD-MS, total antioxidant activity, as well as chromatographic profiling of antioxidants by HPLC post-column derivatization. The obtained results indicate that the degradation of phenolic compounds during MW and UHT preservation processes was in the range 20-32% and 7-18%, respectively. As a consequence, the reduction of antioxidant activity at the level of 12-39% and 10-28% for MW and UHT technologies was observed. The results also revealed a significant effect of apple variety on the changes in polyphenolic profile due to the pasteurization process. Our studies could be of use while selecting the proper technology of preservation to maximize stability of apple phytochemicals and thereby to enhance the healthiness of diet for human populations.