High-pressure homogenization of orange juice to inactivate pectinmethylesterase

A homogenizer was used to treat orange juice at five pressures (0-250 MPa) and three initial temperatures (22, 35 and 45 degrees C). A maximum of five passes for the selected conditions were used to process orange juice. Pectinmethylesterase (PME) activity, microbial load, cloudy appearance, and vitamin C were evaluated in just squeezed and homogenized orange juices. A reduction of 50.4, 49.4 and 37.8% of PME activity was observed in juice homogenized by one pass at 250 MPa at the initial temperatures of 22, 35, and 45 degrees C, respectively. Pectinmethylesterase activity in orange juice was reduced as passes number was increased. The final temperature of the five times homogenized orange juice was not beyond 28 and 37 degrees C after being treated at 100 and 250 MPa, respectively. More than 30 and 80% of enzyme activity was reduced after five passes at 100 and 250 MPa, respectively. Less that 8.7 x 10(2) and 1.85 x 10(3) CFU/mL of mesophiles and yeasts plus molds, respectively, were counted in orangejuice treated five times at 100 MPa. The cloudy appearance of the homogenized orange juice was maintained for 12 days under low temperature conditions. Industrial relevance: "Cold pasteurization" of orange juice, using a homogenizer as a high-pressure procedure, could bean alternative to thermal processing to avoid sensory, nutritional and physiochemical changes in juice. This process may deliver a pasteurized orange juice with characteristics similar to just squeezed orange juice. In addition to reduce the microbial load, homogenization may reduce pectin methylesterase enzyme, which may cause phase-separation in juice and consequently give an unwanted appearance that consumers dislike. Additionally, homogenized orange juice appearance could be stable during several days before being brought to the consumers' daily eating table. (C) 2009 Elsevier Ltd. All rights reserved.