| The overall objectives of this project were to determine the volatiles in strawberries that are important to fresh fruit aroma or contribute to aroma changes during heating. Solid-phase microextraction was compared with two common methods of volatile isolation, batch solvent extraction and dynamic headspace, and was found to be more efficient and less variable than the other two traditional methods. Volatiles were extracted from strawberry puree and evaluated using gas chromatography/olfactometry. Of the compounds identified, the ten most aroma-active volatiles were: diacetyl, methyl butyrate, ethyl butyrate, methyl-2-methyl butyrate, hexanal, E-2 hexenal, 1-octen-3-one, 2,5-dimethyl-4-hydroxy-3(2H)-furanone, linalool, and γ-decalactone. However, many additional aroma-active volatiles could not be identified because of their extremely low concentration in strawberry puree.; A sensory panel was trained using descriptive analysis to evaluate differences between strawberry cultivars based on the aroma attributes: fruity, green, floral, caramel, peach, and strawberry flavor intensity. Significant differences between cultivars were found for all of the aroma descriptors. Correlations were made between sensory analysis, gas chromatography/ofactometry analysis, and the measured concentration of certain volatiles. The ratings for peach were highly correlated with the presence of two compounds with peach-like aroma, γ-decalactone and γ-dodecalactone. The ratings for fruity were weakly correlated with the sum of the esters: ethyl butyrate, methyl butyrate, methyl-2-methyl butyrate, ethyl hexanoate, and methyl hexanote. The other aroma descriptors were not well correlated with the aroma-active volatiles that could be measured in the strawberry puree.; Solid-phase microextraction coupled with gas chromatography/pulsed flame photometric detection was used to monitor sulfur volatiles during the heating of strawberry puree. Carbon disulfide, dimethyl sulfide, dimethyl disulfide, dimethyl disulfide, methyl thioacetate, and methyl thiobutyrate were identified and quantified in the strawberry puree. Sulfur dioxide, hydrogen sulfide, methanethiol, and methional were also identified but could not be quantified. The compounds dimethyl disulfide, methyl thiobutyrate, and methyl thioacetate, did not change significantly during heating, while dimethyl disulfide decreased by over 70%. The most important change was in dimethyl sulfide, which increased from an undetectable amount to a level over 100 times its aroma detection threshold. |
