Polygalacturonase, pectinesterase, and lipoxygenase activities in high-pressure-processed diced tomatoes

High-pressure processing (HPP) can inactivate pathogenic microorganisms and degradative enzymes without the use of heat, thereby minimizing the destru ction of flavors, nutrients, and other quality attributes. Lipoxygenase pla ys a role in the off-flavor production of tomatoes, whereas pectinesterase and polygalacturonase impact tomato texture. The purpose of this study was to determine HPP's ability to inactivate lipoxygenase, pectinesterase, and polygalacturonase in diced tomatoes. Processing conditions used were 400, 6 00, and 800 MPa for 1, 3, and 5 min at 25 and 45 degreesC. The magnitude of applied pressure had a significant effect on inactivating lipoxygenase and polygalacturonase (p < 0.05), with complete loss of activity occurring at 800 MPa. Pectinesterase was very resistant to pressure treatment. Percent s oluble solids, pH, titratable acidity, and color a/b values did not differ significantly among the high-pressure-processed samples as compared to the control, but color L values increased. This change in L values was not cons idered of practical importance. Apparent protein content decreased in the p ressure-processed samples, due possibly to protein denaturation, loss of so lubility, and/or a decrease in dye binding sites to assay protein content.