Formation of Aroma Compounds During Longan Juice Fermentation by Williopsis Saturnus Var. Saturnus With the Addition of Selected Amino Acids

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 APPLICATIONSTropical 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.

Evaluation ofWilliopsis saturnusInoculum Level on Fermentation and Flavor Compounds of White Wines Made from Emir (Vitis viniferaL.) Grown in Anatolia

“…However, in trial A, levels of glucose, fructose, sucrose and total sugar were determined as 29.7, 32.2, 1.01 and 62.89 g/L, respectively. Similar results were obtained byTrinh et al (2011) …”

“…All sugars in all fermentations except in trial A (W. saturnus monoculture) were utilized with a density below 1.000 and with <1.12 g/L levels of glucose, fructose and sucrose. A similar behavior was reported bySoden et al (2000),Jolly et al (2003),Kapsopoulou et al (2007),Erten and Tanguler (2010),Trinh et al (2011), andLee et al (2012b), who studied the effects of non-Saccharomyces yeasts on wine fermentation in mixed cultures with S. cerevisiae. However, in trial A, levels of glucose, fructose, sucrose and total sugar were determined as 29.7, 32.2, 1.01 and 62.89 g/L, respectively.…”

“…They are quantitatively the largest group of volatile compounds and are characterized by their strong and pungent Downloaded by [UQ Library] at 10:04 19 November 2014 smell and taste, which can significantly influence wine taste and character (Trinh et al, 2011;Manzanares et al, 2011). Among all the trials, while the highest total alcohol (249.02 mg/L) was produced in trial C, the lowest (135.42 mg/L) was found in trial F. A total concentration of higher alcohols below 300 mg/L contributes positively to wine quality, but amounts higher than 400 mg/L may detract from the quality (Erten et al, 2006;Manzanares et al, 2011).…”

“…Williopsis saturnus, formerly known as Hansenula saturnus, synthesizes important levels of volatile esters, especially isoamyl acetate and ethyl acetate (Yilmaztekin et al, 2008;Erten and Tanguler, 2010;Trinh et al, 2011). Generally, it is not found in the natural environment grape surfaces and winery equipments, but with the production of desirable flavour, W. saturnus can potentially enhance the fruity flavor in wines obtained from neutral cultivar characteristics (Erten and Tanguler, 2010).…”

Effects of Saccharomyces cerevisiae in association with Torulaspora delbrueckii on the aroma and amino acids in longan wines

“…Longan ( Dimocarpus longan Lour) is one of the main commercial fruits of Thailand, which can be consumed as fresh or processed, such as canned longan and dried longan. Fresh longan has high polyphenols, rich amount of sugar, potassium, copper, ascorbic acid, and other vitamins, and also has a relatively high content of amino acids, which favor its use as a raw material for wine production (Trinh, Yu, Curran, & Liu, ), while dried longan essentially consists of glucose, sucrose, fructose, and free amino acids as well as various vitamins and minerals. Various compounds have been found during the drying process of longan, such as ocimenes, furfural, isoamyl alcohol, linalool oxide, benzenemethanol, ethyl hexadecanoate, and 2‐furancarboxylic acid.…”