39B-19

E. YILMAZ¹, R. L. Shewfelt¹, E. A. Baldwin², and J. W. Scott³. (1) Department of Food Science and Technology, The University of Georgia, Food Science Building, Athens, GA 30602, (2) USDA/ARS Citrus and Subtropical Products Laboratory, Winter Haven, FL 33883, (3) Gulf Coast Research Center, The University of Florida, Bradenton, FL 34203

Tomatoes are popular items at the supermarket, but they are also a source of consumer complaints due to a lack of 'home-grown' flavor. Genetic manipulation of tomato flavor seeks molecular markers. Important components in tomato flavor are compounds of oxylipin and alcohol pathways. Information is needed on the effects that key enzymes in these pathways have on volatile composition. Our objective was to determine the effect of added enzyme on key aromatic volatile compounds in homogenates prepared from red and green tomatoes. Fresh tomatoes were homogenized and then treated with lipoxygenase (LOX), alcohol dehydrogenase (ADH) or a combination of both enzymes. Aliquots were collected at 5, 10, 15 and 20 min denatured with calcium chloride, and frozen. Headspace gas chromatographic analysis was performed to evaluate effects on 15 key volatile compounds. In general, few changes were observed in untreated green homogenates, while marked increases in hexanal, cis-3-hexenal and trans-2-hexenal were observed in untreated red homogenates. Treatment with LOX lead to an initial accumulation of these three compounds followed by degredation in red homogenates with little change in green. ADH led to increased levels of ethanol and methanol in homogenates from both tissue types. Combination treatments in both types of homogenates tended to lead to degradation of volatile compounds rather than accumulation. Regression models were developed for each volatile compound as a function of ripeness stage, enzyme treatment, and duration. While an in vitro model cannot mimic enzyme activity in vivo, it can provide a perspective on the types of compounds that could be generated. These results confirm other studies in our laboratory that suggest development of volatile components in tomato flavor is not a simple process and modification of a single enzyme is unlikely to have a desired effect.