Mezcal, a traditional beverage that originated in Mexico, is produced from species of the Agavaceae family. The esters associated with the yeasts utilized during fermentation are important for improving the organoleptic properties of the beverage. We improved the ester contents in a mezcal beverage by using the yeast Kluyveromyces marxianus, which was engineered with the ATF1 gene. ATF1 expression in the recombinant yeast significantly increased compared with that in the parental yeast, but its fermentative parameters were unchanged. Volatile-organic-compound-content analysis showed that esters had significantly increased in the mezcal produced with the engineered yeast. In a sensory-panel test, 48% of the panelists preferred the mezcal produced from the engineered yeast, 30% preferred the mezcal produced from the wild type, and 15 and 7% preferred the two mezcal types produced following the routine procedure. Correlation analysis showed that the fruitiness/sweetness description of the mezcal produced using the ATF1-engineered K. marxianus yeast correlated with the content of the esters, whose presence improved the organoleptic properties of the craft mezcal beverage.
We studied the fatty acid composition of musts obtained from Pedro Ximénez Vitis vinifera grapes at two ripening stages (unripe and ripe). The overall fatty acid content was found to increase with ripening while the proportion of unsaturated acids decreased. Linoleic acid underwent the most marked decrease in this respect, which reveals that grapes lose some of their potential herbaceous aroma on ripening. Unsaturated fatty acids C16:l, C18:l and C18:2 prevailed in the neutral lipid fraction and their proportions increased with ripening. On the other hand, palmitic acid (C16:0) was preferentially encountered in the polar lipid fraction and its proportion increased with ripening.
IntroductionFatty acids in grapes play a major role in wine making, insofar as they are growth and survival factors for yeasts during alcoholic fermentation of musts and a source of aroma compounds for the resulting wine. In fact, they are responsible for the formation of a number of volatile compounds such as aliphatic aldehydes, ketones, alcohols and short-chain fatty acids.The role of fatty acids as growth and survival factors was shown by Stier (1953, 1954), who observed how yeasts under anaerobic conditions multiplied actively on adding certain sterols, oleanolic acid (a triterpene) and long-chain fatty acids to the medium. Bréchot et al. (1971;Bréchot, 1974) showed the stimulating effect of oleic and oleanolic acid on the anaerobic growth of yeasts, and Watson (1982) found that unsaturated fatty acids in yeast membranes rather than ergosterol were responsible for the tolerance of these cells to ethanol. However, Youings and Rose (1989) found that Saccharomyces cerevisiae Y185 requires the presence of sterols
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.