FORMATION OF AROMA COMPOUNDS DURING LONGAN JUICE FERMENTATION BY WILLIOPSIS SATURNUS VAR. SATURNUS WITH THE ADDITION OF SELECTED AMINO ACIDS

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ABSTRACT Longan (Dimocarpus longan Lour.) is a type of tropical fruit. This study investigated the impact of L-leucine and L-phenylalanine on the volatile profiles of longan wine fermented with a non-Saccharomyces yeast Williopsis saturnus ssp. saturnus CBS254 with a view to enhancing longan wine aroma. The results revealed the ability of this yeast to enhance isoamyl alcohol and its ester isoamyl acetate (banana-like aroma), and 2-phenylethanol and its ester 2-phenylethyl acetate (rose-like aroma) with the addition of L-leucine and L-phenylalanine, respectively. The increased production of the targeted acetate esters appeared to be at the expense of other acetate esters except for methyl acetate, whereas the effects on the biotransformation of other volatiles were minimal. Therefore, these findings suggest that the combination(s) of an amino acid and yeast can be employed as a tool to manipulate the level of the targeted aroma compounds so as to impart a specific aroma or to add flavor complexity to longan wine. PRACTICAL APPLICATIONS Tropical fruits such as longan are often in oversupply during the peak season and some are wasted because of lack of adequate processing technologies. Thus, there is a need to add value to longan fruit via processing. Although drying as a form of processing is commonly applied to longan fruit, fermentation is not widely practiced to process and preserve this fruit because of lack of research and information. Longan wine fermentation using the conventional grape wine fermentation technology results in longan wine with inferior flavor. The aim of this study is to investigate the fermentation of longan juice using a non-Saccharomyces yeast Williopsis saturnus var. saturnus with addition of L-leucine and L-phenylalanine so as to modulate the formation of aroma compounds.