linoleic-acid and 1-hexanol

The composition of volatile compounds in Korla fragrant pears was determined using headspace solid-phase microextraction followed by a gas chromatography-mass spectrometry analysis using fruits at 30, 90, and 150 days after bloom. Hexanal, (E)-2-hexenal, 1-hexanol, (E)-2-hexen-1-ol, (Z)-3-hexen-1-ol, and hexyl acetate were identified as the major compounds. The composition of volatile compounds was associated with fatty acid concentrations and key enzyme activity in the lipoxygenase pathway. In vitro linoleic and linolenic acid feeding experiments conducted using cubes of fruit flesh demonstrated that the concentrations of volatile esters, such as hexyl acetate, in the treated fruits increased significantly after incubation for 12 h compared with those in the control fruits, which was accompanied by a reduction in aldehyde and alcohol concentrations (p < 0.05 or p < 0.01). However, the treatments did not significantly influence the enzyme activity and expression of genes encoding the enzymes.

Topics: Aldehydes; alpha-Linolenic Acid; Esters; Fatty Acids; Food Analysis; Fruit; Gas Chromatography-Mass Spectrometry; Gene Expression Regulation, Plant; Hexanols; Linoleic Acid; Odorants; Pyrus; Solid Phase Microextraction; Volatile Organic Compounds

Ten different varieties of tomatoes were separated into peel and flesh and each portion was measured separately. Headspace volatiles were measured in real time using selected ion flow tube mass spectrometry. Lipoxygenase activity was measured using the adsorption of conjugated dienes formed by lipoxygenase. Lipid was extracted and fatty acids were quantified using a gas chromatograph. Volatiles were significantly greater in the peel than flesh when there was a significant difference. The lipoxygenase activity of flesh and peel correlated with the volatiles produced by the lipoxygenase pathway. There was no correlation with other volatiles, which are not dependent on lipid oxidation by lipoxygenase. The lipoxygenase activity, total fatty acid content, and linolenic acid of the peel were greater than the flesh, which is directly related to an increase in fresh, green volatiles. Addition of exogenous lipoxygenase had no effect on lipoxygenase-derived volatiles formed. The addition of linoleic acid caused an increase in hexanal, 1-hexanol, and (E)-2-heptenal in the flesh and (E)-2-heptenal in the peel. Stored unrefrigerated peel had higher volatile concentrations, whereas refrigerated peel had significantly lower concentration than day 0. Storage decreased lipoxygenase activity in the unrefrigerated and refrigerated peel, but had no effect on the fatty acid content. Overall, linolenic acid was the most important to the formation of headspace volatiles, but lipoxygenase activity and unknown factors are also important.. The peel of a tomato is most beneficial to the production of volatiles associated with the fresh aroma of tomatoes; therefore, it should be used in the processing of tomato products to produce a fresh, green aroma rather than being removed. Knowledge of the effects of lipoxygenase activity, total fatty acid content, and fatty acid profile on flavor volatiles will allow for better selection of a variety for raw consumption.

Topics: Aldehydes; Fatty Acids; Food Storage; Fruit; Hexanols; Linoleic Acid; Lipoxygenase; Odorants; Solanum lycopersicum; Taste; Temperature; Volatile Organic Compounds