Lipoxygenase (EC 1.13.11.12) plays an important role in the genesis of flavour and aroma compounds in plant products as it catalyses the oxidation of polyunsaturated fatty acids containing cis,cis-1,4-pentadiene units. It is also important as it has the ability to form free radicals which can degrade such compounds as vitamins, proteins and lipids. Ripe intact cherry tomatoes were subjected to pressures of 200, 300, 400 and 600 MPa for 10 min at ambient temperature (ca. 20 deg C). The lipoxygenase acticity was determined by spectophotometry. The tomatoes were cut into small pieces, then blended for 1 min and the headspace volatile compounds were analysed by gas chromatography-mass spectrometry. Pressurisation at 200 and 300 MPa for 10 min did not significantly affect the lipoxygenase activity, while a pressure of 400 MPa for 10 min caused a significant decrease in its activity. Treatment at 600 MPa led to complete and irreversible loss of activity. Compared to unpressurised tomatoes, treatment at 600 MPa gave significantly reduced levels of hexanal, cis-3-hexenal and trans-2-hexenal, which are important contributors to 'fresh' flavour in tomato.
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