EFFECT of PASTEURIZATION ON MICROBIOLOGICAL and SENSORY QUALITY of WHITE GRAPE JUICE and WINE

The effect of pasteurization on the microbiological and sensory quality of white grape juice and wine was investigated. Heat treatment of less than 3 Pasteurization Units (PUs = minutes at 60°C or equivalent) was sufficient to reduce 106 cells/mL of Saccharomyces cerevisiae and Hansenula anomala added to Chenin blanc juice to an undetectable level. In contrast, heat treatment exceeding 105 PUs was required to have a measurable browning effect on juice, as measured by absorbance at 420 nm and by formation of 5-hydroxymethyl-furfural. Furthermore, up to 50,000 PUs did not significantly affect flavor, as determined by duo-trio tests with 18 trained judges. Pasteurized (23 PUs) and nonpasteurized juice fermented at the same rate, although not as rapidly as pasteurized, thiamine-supplemented juice. Tunnel pasteurization (13.7 PUs) reduced 5 × 106 yeast cells/mL added to grape juice to an undetectable level and did not significantly affect juice or wine flavor.