Effect of L-isoleucine and L-phenylalanine Addition on Aroma Compound Formation During Longan Juice Fermentation by a Co-culture of Saccharomyces cerevisiae and Williopsis saturnus

Abstract

Some amino acids are known to be precursors of aroma-active compounds produced by yeast metabolism. This study examined the effect of the addition of L-isoleucine and L-phenylalanine on the volatile profiles of longan wine fermented by a co-culture of Saccharomyces cerevisiae var. bayanus EC-1118 and Williopsis saturnus var. saturnus CBS254 inoculated at a ratio of 1:1 000 cfu/mL with the aim of enhancing longan wine aroma. Significantly higher concentrations of active amyl alcohol (2-methyl-1-butanol), 2-phenylethyl alcohol and their corresponding acetate esters were found in the longan wine with added L-isoleucine and L-phenylalanine respectively, compared with the control (without added amino acids). The biosynthesis of other volatile compounds was either similar or minimally different, although the formation of some acetate esters, such as isoamyl acetate, hexyl acetate and ethyl acetate, was decreased. These results suggest that the added amino acids play an important role in enhancing the production of targeted aroma compounds in longan wine fermented with mixed yeasts, and that the addition of selected amino acids can be a valuable tool to modulate the formation of aroma compounds in longan wine.

Synergistic Effects of Branched-chain Amino Acids and Phenylalanine Addition on Major Volatile Compounds in Wine during Alcoholic Fermentation

“…Generally, the formation of higher alcohols and their corresponding acetate esters is directly proportional to the quantity of amino acids added to the juice (Trinh et al, 2010;Lee et al, 2013). As reported by Chen et al (2014), supplementation of lychee juice with Phe resulted in significantly higher amounts of 2-phenylethyl alcohol, 2-phenylethyl acetate, 2-phenylethyl isobutyrate and 2-phenylethyl hexanoate.…”

Chemical and Volatile Composition of Mango Wines Fermented with Different Saccharomyces cerevisiae Yeast Strains

“…Major volatiles (high RPA in the FID chromatogram; which are important for wine quality) were quantified using individual external standards dissolved in 10% v/v mango juice diluted with water, except for ethanol dissolved in 100% v/v mango juice (Lee et al, 2010b;Trinh et al, 2010). Good linearity was obtained for all standard curves (R 2 >0.97).…”

“…The method was based on that described elsewhere (Lee et al, 2010a;Trinh et al, 2010) with some modifications. Volatile compounds of fresh juice and final fermented juice (samples after 14-day fermentation) were measured using headspace (HS) solid-phase microextraction (SPME) method coupled with gas chromatography (GC)-mass spectrometer (MS) and flame ionization detector (FID) (HS-SPME-GC-MS⁄ FID).…”

“…The FID temperature was set at 250°C, and the MSD was operated in the electron impact mode at 70 eV. The volatile compounds were identified by using Wiley mass spectrum library and comparison of linear retention index (LRI) of each volatile with the LRI in other reports (Tairu et al, 1999;Lee et al, 2010a;Trinh et al, 2010). LRI was determined by using a series of alkanes (C5-C40) run under the same HS-SPME-GC-MS⁄ FID condition as sample o for all three mango wines during the fermentation.…”

“…The volatile composition of the three mango wines is almost the same, but the concentration of each volatile may be different. To compare the volatile compounds in the three wines, FID peak area and RPA were used and they can semi-quantitatively represent the concentration of different volatiles (Alves et al, 2010;Lee et al, 2010ab;Trinh et al, 2010). For further accuracy, 12 major volatile compounds, which are generally considered as important factors influencing fruit or grape wine quality (Gürbüz et al, 2006;Alves et al, 2010;Lee et al, 2010ab;Trinh et al, 2010), were quantified with external standards (Table 4).…”