A team led by Prof LIU Shao Quan from the Food Science and Technology Program at the Department of Chemistry in NUS reported that Torulaspora delbrueckii fermented sugars and produced ethanol at the fastest rate, which was almost as fast as commercial grape wine yeasts such as Saccharomyces cerevisiae. The yeast T. delbrueckii generated high amounts of key odourants (isoamyl alcohol, 2-phenylethyl alcohol, ethyl octanoate, all of which impart fruity and floral aroma) and retained sufficient levels of cis-rose oxide and linalool (both are crucial lychee flavour character-impact volatile compounds). Therefore, this special yeast can be considered as a promising non-conventional yeast for industrial lychee wine fermentation. Two other yeasts, Williopsis saturnus and Kluyveromyces lactis, did not ferment sugars adequately and thus, producing only low quantities of ethanol, but they also retained significant concentrations of the original lychee aroma-impact compounds. The outcome of this work would help overcome the challenge of producing lychee wine with original flavour character.
Fruit wines are traditionally produced by simply adopting industrial grape wine vinification protocols via fermenting fruit juices with Saccharomyces wine yeasts. This practice may not be appropriate for tropical fruits, which usually possess delicate flavour that could be lost upon fermentation with these yeasts. The fruit wines produced as such are frequently deficient in the unique flavour characteristics of the original fruits. The results from this research demonstrate that tropical fruit wine production necessitates new protocols and novel yeasts may be a better option.
Scale-up and commercialization of lychee wine following this study will be carried out in partnership with Kosmode Biotechnology Ltd based at NUS Suzhou Research Institute, Suzhou Industrial Park, China.
Figure shows the changes in (a) sugars (indicated as oBrix), (b) ethyl hexanote, (c) 2-phenylethyl alcohol, and (d) linalool during the course of lychee wine fermentation by three unconventional yeasts Torulaspora delbrueckii Prelude (●); Williopsis saturnus NCYC 22 (▼); Kluyveromyces lactis KL 71 (■). [Image credit: Liu Shaoquan]
Reference
Chen D, Yap ZY, Liu SQ. “Evaluation of performance of Torulaspora delbrueckii, Williopsis saturnus and Kluyveromyces lactis in lychee wine fermentation.” International Journal of Food Microbiology 206 (2015) 45.
