ENZYME INACTIVATION ON APPLE JUICE TREATED BY ULTRAPASTEURIZATION AND PULSED ELECTRIC FIELDS TECHNOLOGY

Apple juice was pasteurized by an ultra-high temperature treatment (UHT) at 115, 125 and 135C for 3 and 5 s, and compared with a high-voltage pulsed electric field treatment (PEF) at ranges between 33 and 42 kV/cm with frequencies of 150, 200, 250 and 300 pulses per second (pps). Enzyme inactivation and physicochemical properties of the treated juices were compared using a nontreated sample as control. The UHT treatment was more efficient in enzyme inactivation, reducing 95% the residual activity of polyphenoloxidase at the maximum temperature and time. However, a PEF treatment at 38.5 kV/cm and 300 pps combined with a temperature of 50C achieved a 70% reduction of residual PFO activity. In terms of quality characteristics as a function of physicochemical properties, color, pH, acidity and soluble solids were all less affected by PEF than by UHT when compared with the untreated juice. Apple juice is a popular beverage worldwide and it is consumed nearly as much as orange juice. Consumers prefer fresh-squeezed fruit juices with high nutrient value and fresh-like sensory attributes. Enzymatic browning negatively impacts appearance, nutritive value and flavor of fruit juices. The use of ultra-high temperature processing is efficient in microbial control, as well as in enzyme inactivation. Any thermal processing may, however, decrease the overall quality of the treated juices. Pulsed electric field processing provides a potential alternative to thermal pasteurization of fruit juices.