Louisa Ling

Characterization of some volatile constituents of bell peppers

The steam volatile components of Californian green bell peppers (Capsicum annum aar. grossum, Sendt) have been qualitatively analyzed using conventional and capillary gas-liquid chromatographic separation with characterization by mass, infrared, and in some cases ultraviolet and proton magnetic resonance spectra. Major components identified in oil obtained by vacuum steam-distillation-continuous-extraction included 2-methoxy-3-isobutylpyrazine, trans-p-ocimene, limonene, methyl salicylate, linalool, nona-trans,cis-2,6-dienal, deca-trans,trans2,4-dienal, and hex-cis-3-enol. Additional components detected in small amounts in the vacuum isolated oil but in much larger amounts in oil isolated at atmospheric pressure were non-1 -en-4one, non-trans-2-en-4-one, nona-trans,trans-2,5-dien4-one, 2-pentylfuran, and benzaldehyde. The identities of 24 components were confirmed by direct comparison of their spectral and gas chromatographic retention data with those of authentic samples. Tentative identification was obtained for an additional 19 components from their mass spectral fragmentation patterns. Odor thresholds in water solution were determined for major components. 2-Methoxy-3-isobutylpyrazine was found to possess an extremely potent odor with an odor threshold of 2 parts per 1012 parts of water. Generally about 70 to 80% of untrained sensory panelists (40) indicated that the odor of dilute water solutions of this compound was similar to that of fresh green bell peppers.

Effect of storage and ripening on fresh tomato quality, Part I

Abstract Four varieties of fresh tomato were grown, stored and treated under commercial conditions to assess the effects of storage and ripening conditions on tomato taste and flavor. The qualitative and quantitative changes in values for volatiles, non-volatiles and physical characteristics were determined. The results are reported in two parts. This report discusses the effects of storage temperature and ethylene treatment on changes in the concentrations of 32 tomato volatiles with results expressed in terms of Odor Units (Uo) in order to best approximate human aroma effect. A second report discusses all other parameters along with general statistical analysis. The average Odor Unit value for each of the tracked analytes showed that only half the tracked volatiles were present in concentrations great enough to contribute to over-all aroma. Statistical analysis by Anova showed that the levels of all significant volatiles, except methyl salicylate, can be correlated to changes in storage conditions. The generation of volatiles decreases significantly with storage and ripening temperatures below 10° but the final ripening temperature is the most significant factor in determining levels of volatiles produced. If final ripening temperatures are raised to 20° for tomatoes initially stored at 10° or less, volatiles are produced at a level comparable to tomatoes stored above 10°. When final ripening takes place at temperatures below 10° volatile production is curtailed.