The Influence of PEF, Pulsed Light, Microwave and Conventional Heat Treatments on Quality Parameters of Berry Fruit Juice Blends

Due to the degradative effect of the traditional pasteurization process related to the long exposure of high temperatures to the food matrix, alternative methods of food preservation are being investigated. In the case of liquid fruit products, unconventional thermal and non-thermal methods can be used for this purpose. The aim of the study was to evaluate the effect of various preservation methods: conventional pasteurization (PT), microwave pasteurization (MP), hot bottling (HB), pulsed electric field (PEF) and pulsed light (PL) on selected quality parameters of mixed juices. In the studied samples, extract (TTS), active acidity (pH), titratable acidity (TTA), nephelometric turbidity (NT), total polyphenol content (TPC), color parameters and antioxidant activity (AA) were determined. Qualitative and quantitative chromatographic analysis of anthocyanins was also performed. The different influence of the preservation methods and the raw materials used on the individual characteristics was demonstrated. The TTS and TTA changes did not exceed 4%, while no changes in pH were observed. Thermal methods increased turbidity significantly, with HB increasing it to the greatest extent. Non-thermal methods caused greater degradation of TPC, anthocyanins, and AA, while they caused significantly less color change. The microwave pasteurization resulted in an increase in TPC in two out of three studied juice blends. Based on the obtained results, it can be concluded that thermal methods allowed for the preservation of a greater amount of bioactive compounds, which translates into a potentially greater health-promoting value of the produced juice blends.