Title : Correlation between sensory attributes and volatile compounds produced during agave tequilana weber juice fermentation by native yeasts
Tequila is a Mexican alcoholic beverage distilled from the fermented juice of cooked Agave tequilana Weber (blue variety). Production is strictly regulated such that only beverages produced from A. tequilana Weber (blue variety) cultivated in a protected region of Mexico can be labeled with the guarantee of origin (Norma Oficial Mexicana, 2012). The tequila process involves multiple steps: cultivation and harvesting of the agave, hydrolysis of the agave carbohydrates into a mixture of fermentable sugars, especially fructose, and extraction of the agave juice to be fermented by yeast; the fermented juice is distilled twice to obtain silver tequila. The distillate can be optionally matured in white oak barrels for either 2 or 12 months to obtain rested or aged tequila, respectively. During alcoholic fermentation, the yeast cells produce primarily ethanol and CO2 as well as many flavor compounds as secondary products. The tequila aroma is represented by several classes of volatile compounds; many of these compounds are produced by the yeast during fermentation together with other substances derived from both raw and cooked agave. In some tequila distilleries, fermentation occurs spontaneously while in others, the agave juice is inoculated using commercial or indigenous yeast cultures, often Saccharomyces cerevisiae. The tequila industry, however, has very limited knowledge of the parameters that affect agave juice fermentation and yeast characterization. The purpose of this work was to analyze the fermentative and aromatic qualities of a group of selected yeast strains involved in the tequila process. The identification and quantification of volatile compounds in agave juice samples were performed by solid-phase microextraction coupled to GC–MS while the sensory profile was defined using a trained panel. The compounds analyzed included 47 volatile compounds classified into eight families. The agave juice fermented with S. cerevisiae strains had higher
levels of alcohols, acids, and methionol compounds than non-Saccharomyces strains. On the other hand, the highest concentration of terpenes, furans, aldehydes, esters, and acetoin was observed in the non- Saccharomyces strains (95% LSD). The attributes such as “fruit”, “solvent” and “vinegar” were associated with S. cerevisiae strains while “caramel”, “pumpkin candy” and “lemon blossom” were related to the non- Saccharomyces strains. Partial least-squares regression analysis of volatile compounds and sensory data indicated that mainly Maillard compounds were associated with “caramel” and “pumpkin candy” attributes.