The effects of co- and sequential inoculation of Torulaspora delbrueckii and Pichia kluyveri on chemical compositions of durian wine.

This is a first study on using two non-Saccharomyces yeasts, Torulaspora delbrueckii Biodiva and Pichia kluyveri FrootZen to produce durian wine via co-inoculation (Co-I) and sequential inoculation (Seq-I). T. delbrueckii inhibited the growth of P. kluyveri and P. kluyveri also partly retarded the growth of T. delbrueckii in Co-I and Seq-I treatments. Co-I and Seq-I produced similar levels of ethanol to T. delbrueckii Biodiva monoculture. In addition, Seq-I increased malic acid degradation and higher succinic acid production. Compared with T. delbrueckii Biodiva, Co-I produced similar amounts of ethyl esters, higher alcohols and moderately increased levels of ethyl acetate. Seq-I 2th (T. delbrueckii inoculated after 2 days fermentation with P. kluyveri) and Seq-I 5th produced excessive amounts of ethyl acetate (≥ 80 mg/L) but relatively lower levels of higher alcohols. This study suggested that Co-I could complete alcoholic fermentation with more complex aromas and might be novel way for wine making.

Combined effects of fermentation temperature and pH on kinetic changes of chemical constituents of durian wine fermented with Saccharomyces cerevisiae.

This study investigated the effects of temperature (20 and 30 °C) and pH (pH 3.1, 3.9) on kinetic changes of chemical constituents of the durian wine fermented with Saccharomyces cerevisiae. Temperature significantly affected growth of S. cerevisiae EC-1118 regardless of pH with a higher temperature leading to a faster cell death. The pH had a more significant effect on ethanol production than temperature with higher production at 20 °C (5.95%, v/v) and 30 °C (5.56%, v/v) at pH 3.9, relative to that at pH 3.1 (5.25 and 5.01%, v/v). However, relatively higher levels of isobutyl alcohol and isoamyl alcohol up to 64.52 ± 6.39 and 56.27 ± 3.00 mg/L, respectively, were produced at pH 3.1 than at pH 3.9 regardless of temperature. In contrast, production of esters was more affected by temperature than pH, where levels of ethyl esters (ethyl esters of octanoate, nonanoate, and decanoate) and acetate esters (ethyl acetate and isoamyl acetate) were significantly higher up to 2.13 ± 0.23 and 4.61 ± 0.22 mg/L, respectively, at 20 °C than at 30 °C. On the other hand, higher temperature improved the reduction of volatile sulfur compounds. This study illustrated that temperature control would be a more effective tool than pH in modulating the resulting aroma compound profile of durian wine.