linoleic-acid and phenylacetaldehyde

The volatile oil from Boletopsis leucomelas (Pers.) Fayod was extracted by hydrodistillation with diethylether, and the volatile components of the oil were analyzed by gas chromatography-mass spectrometry. The oil contained 86 components, representing 87.5% of the total oil. The main components of the oil were linoleic acid (15.0%), phenylacetaldehyde (11.2%), and palmitic acid (9.4%). Furthermore, sulfur-containing compounds including 3-thiophenecarboxaldehyde, 2-acetylthiazole, S-methyl methanethiosulfonate, and benzothiazole were detected using gas chromatography-pulsed flame photometric detection. The odor components were evaluated by the odor activity value, and aroma extract dilution analysis was performed through gas chromatography-olfactometry analysis. The oil had a mushroom-like, fatty, and burnt odor. The main components contributing to the mushroom-like and fatty odor were hexanal, nonanal, 1-octen-3-ol, and (2E)-nonenal, while the burnt odor was due to furfuryl alcohol, benzaldehyde, 5-methyl furfural, 2,3,5-trimethylpyrazine, 2-acethylthiazole, and indole.

Topics: Acetaldehyde; Agaricales; Aldehydes; Benzaldehydes; Chromatography, Gas; Furans; Gas Chromatography-Mass Spectrometry; Indoles; Linoleic Acid; Octanols; Odorants; Oils, Volatile; Olfactometry; Palmitic Acid; Photometry; Plant Oils; Plants, Edible; Sulfur Compounds; Volatile Organic Compounds

The effect of lipids on the formation of the Strecker aldehyde phenylacetaldehyde during wort boiling was studied to determine the role that small changes in the lipid content of the wort have in the production of significant flavor compounds in beer. Wort was treated with 0-2.77 mmol per liter of glucose, linoleic acid, or 2,4-decadienal and heated at 60-98 degrees C for 1 h. After this time, the amount of the Strecker aldehyde phenylacetaldehyde increased in the samples treated with linoleic acid or decadienal but not in the samples treated with glucose. Thus, the amount of phenylacetaldehyde produced in the presence of linoleic acid was 1.1-2.5 times the amount of the Strecker aldehyde produced in the control wort, and this amount increased to 3.6-4.6 times when decadienal was employed. The higher reactivity of decadienal than linoleic acid for this reaction decreased with temperature and was related to the oxidation of linoleic acid that occurred to a higher extent at higher temperatures. The above results suggest that lipids can contribute to the formation of Strecker aldehydes during wort boiling and that changes in the lipid content of the wort will produce significant changes in the formation of Strecker aldehydes in addition to other well-known consequences in beer quality and yeast metabolism. On the other hand, because of the high glucose content in wort, small changes in its content are not expected to affect the amount of Strecker aldehydes produced.

Topics: Acetaldehyde; Aldehydes; Beer; Edible Grain; Glucose; Hot Temperature; Linoleic Acid; Lipid Peroxidation; Lipids; Taste