Effects of high hydrostatic pressure processing and of glucose oxidase-catalase addition on the color stability and sensorial score of grape juice

The effects of high hydrostatic pressure treatment (HHP) and the use of glucose oxidase-catalase enzymes on the color stability of a white grape juice were studied. The cold-prepared grape juice was stored for three weeks at 5 degrees C and evaluated for color and non-flavonoid phenolic content. The HHP treatments at 600 and 900 MPa slowed the degradation of non-flavonoid phenolics and reduced the rate of the browning during storage. No significant effect on the color was observed using 300 MPa. Further color stabilization was obtained using glucose oxidase-catalase enzymes and by setting the initial temperature of water inside the pressure vessel at 50 degrees C prior to HHP treatment. The sensory analyses indicated that enzymes and HHP improved the aroma and taste of juices; by contrast, operating the HHP process at an initial temperature of 50 degrees C showed no significant effect.