Fusel alcohol

About: Fusel alcohol is a research topic. Over the lifetime, 735 publications have been published within this topic receiving 11902 citations. The topic is also known as: fuselol & fusel oil.

The Ehrlich Pathway for Fusel Alcohol Production : a Century of Research on Saccharomyces cerevisiae Metabolism

Abstract: Saccharomyces cerevisiae has been used for at least eight millennia in the production of alcoholic beverages (41). Along with ethanol and carbon dioxide, fermenting cultures of this yeast produce many low-molecular-weight flavor compounds. These alcohols, aldehydes, organic acids, esters, organic sulfides, and carbonyl compounds have a strong impact on product quality. Indeed, the subtle aroma balance of these compounds in fermented foods and beverages is often used as an organoleptic fingerprint for specific products and brands (42). Food fermentation by yeast and lactic acid bacteria is accompanied by the formation of the aliphatic and aromatic alcohols known as fusel alcohols. Fusel oil, which derives its name from the German word fusel (bad liquor), is obtained during the distillation of spirits and is enriched with these higher alcohols. While fusel alcohols at high concentrations impart off-flavors, low concentrations of these compounds and their esters make an essential contribution to the flavors and aromas of fermented foods and beverages. Fusel alcohols are derived from amino acid catabolism via a pathway that was first proposed a century ago by Ehrlich (13). Amino acids represent the major source of the assimilable nitrogen in wort and grape must, and these amino acids are taken up by yeast in a sequential manner (23, 32). Amino acids that are assimilated by the Ehrlich pathway (valine, leucine, isoleucine, methionine, and phenylalanine) are taken up slowly throughout the fermentation time (32). After the initial transamination reaction (Fig. ​(Fig.1),1), the resulting α-keto acid cannot be redirected into central carbon metabolism. Before α-keto acids are excreted into the growth medium, yeast cells convert them into fusel alcohols or acids via the Ehrlich pathway. FIG. 1. The Ehrlich pathway. Catabolism of branched-chain amino acids (leucine, valine, and isoleucine), aromatic amino acids (phenylalanine, tyrosine, and trytophan), and the sulfur-containing amino acid (methionine) leads to the formation of fusel acids and ... Current scientific interest in the Ehrlich pathway is supported by increased demands for natural flavor compounds such as isoamyl alcohol and 2-phenylethanol, which can be produced from amino acids in yeast-based bioconversion processes (14), as well as by the need to control flavor profiles of fermented food products. The goal of this paper is to present a concise centenary overview of the biochemistry, molecular biology, and physiology of this important pathway in S. cerevisiae.

Quantitative determination of the odorants of young red wines from different grape varieties

Abstract: Fifty-two young monovarietal red wines made with Grenache (17 samples), Tempranillo (11 samples), Cabernet Sauvignon (12 samples) and Merlot (12 samples) grapes have been analysed by HRGC–MS to obtain quantitative data on 47 odorants previously identified as potential aroma contributors by olfactometric techniques. Thirty-three odorants were present in the wines at concentrations higher than their corresponding odour thresholds. These include ethyl octanoate, β-damascenone, ethyl hexanoate, isovaleric acid and isoamyl acetate as the most important, which together with isoamyl and β-phenylethyl alcohols, fatty acids, 2,3-butanedione and ethyl butyrate are always found at concentrations higher than their odour thresholds. In some cases the ethyl esters of isobutyric and isovaleric acids, β-ionone, methionol, isobutyric acid, ethyl cinnamate, ethyl dihydrocinnamate, γ-nonalactone, eugenol, c-3-hexanol, geraniol, guaiacol, 3-isobutyl-2-methoxypyrazine, 4-ethylguaiacol, acetoin and t-whiskylactone were at a concentration high enough to be odour-active. There were 30 compounds that were found to differ significantly between varieties. These include 3-isobutyl-2-methoxypyrazine, isoamyl acetate, isovaleric acid, ethyl isobutyrate, ethyl isovalerate, fusel alcohols, c-3-hexenol, methionol, eugenol, guaiacol and γ-nonalactone. © 2000 Society of Chemical Industry

Formation and Occurrence of Flavor Compounds in Wine and Distilled Alcoholic Beverages

Abstract: The most probable mechanisms involved in the formation of carbonyl compounds, fusel alcohols, fatty acid esters, and free fatty acids by yeast in fermentation are discussed. Isopentyl alcohol, phenethyl alcohol, and their acetates in addition to the ethyl esters from hexanoate to laurate formed by different yeasts in sugar fermentation were determined. The bivariate distributions of the concentrations indicate that the mutual relationships of the compounds depend significantly on the yeast used and on the capacity of the yeast to produce alcohols and esters. The wine yeast used in this work produced smaller amounts of ethyl esters of fatty acids from acetic acid to octanoic acid under aerobic fermentation conditions than under strictly anaerobic conditions; on the other hand, ethyl laurate and ethyl 9-hexadecenoate were formed more abundantly in anaerobic conditions. Furthermore, qualitatively-similar flavor compositions were obtained in a Spanish sherry and a Finnish berry wine of sherry type. Hence, the formation of the most dominant compounds occurring in beverages depend more on the yeast selected than the raw materials used in fermentation.

Identification and Quantification of Impact Odorants of Aged Red Wines from Rioja. GC−Olfactometry, Quantitative GC-MS, and Odor Evaluation of HPLC Fractions

Abstract: An XAD-4 extract from a 5-year-old wine from Rioja (Spain) was analyzed by aroma extract dilution analysis. Most of the odorants were quantified by GC-MS. A second extract was fractionated in an HPLC system with a C-18 semipreparative column. Fifty fractions were recovered, their alcoholic degree and pH were further adjusted to those of the wine, and those fractions that showed strong odor characteristics were further re-extracted and analyzed by GC-O and GC-MS. Reconstitution experiments were carried out to confirm the role of the odorants detected in the fractions. Fifty-eight odorants were found in the Rioja wine, 52 of which could be identified. Methyl benzoate was found to be a wine aroma constituent for the first time. The most important odorants are 4-ethylguaiacol, (E)-whiskey lactone, 4-ethylphenol, beta-damascenone, fusel alcohols, isovaleric and hexanoic acids, eugenol, fatty acid ethyl esters, and ethyl esters of isoacids, Furaneol, phenylacetic acid, and (E)-2-hexenal. Comparison among the three techniques shows good agreement and demonstrates that they are complementary.