30G-16 |
Changes in volatile sulfur compounds in strawberries during heating |
K. SCHULBACH1, C. A. Sims, and R. L. Rouseff. (1) Department of Food Science and Human Nutrition, University of Florida, 359 FSHN Bldg., Newell Drive, Gainesville, FL 32611-0370 Volatile sulfur compounds are significant aroma components in the flavor of some varieties of strawberries. Many of these compounds are unstable and concentrations change rapidly during heating. Previously published heating studies of strawberry products did not include analysis of these important compounds possibly due to their low concentrations and/or high volatilities. Our objective was to determine the major sulfur compounds in strawberries and to quantify their changes during heating. Aliquots of strawberry puree were placed in small diameter thin-wall glass tubes and heated for time periods ranging from 20 sec. to 15 min. at 75, 85, or 95 degrees C. Each tube was cooled in an ice water bath and then 5.0 mL of the puree was transferred to a 40 mL vial and stabilized with 5.0 mL of saturated calcium chloride. The vial was placed in a 35 degrees C water bath and allowed to equilibrate for 5 min. after which time a SPME fiber (PDMS/Divinylbenzene) was exposed to the headspace for 10 min. The fiber was desorbed in the injector of a HP 5890 Series II at 200 degrees C for 5 min. and separations were performed on both a polar and a non-polar phase column. Compounds were detected using a pulsed flame photometric detector and identified by comparing retention times with authentic standards on the two columns. Our results showed 11 major sulfur compounds in the strawberry puree. Some compounds, especially dimethyl sulfide, increased rapidly during heating. Other compounds such as methylthiol butyrate and methylthiol acetate did not change significantly while methanethiol decreased. A more complete understanding of the changes in aroma active compounds during heating can result in a reduction in the formation of compounds that produce off flavors.
Session 30G, Fruit & Vegetable Product: Processed Fruits and Vegetables
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