Peter J. Costello

Occurrence of 2-Acetyl-1-Pyrroline in Mousy Wines

Abstract The potent flavour compound 2-acetyl-1-pyrroline (1) was identified for the first time in wines spoiled by mousy taint. Identification was verified by comparison of GC and GC-MS data with those of authentic reference material. GC-SNEFF analysis of (1) further confirmed its intense mousy aroma.

Not all wine yeast are equal

It may come as a surprise to learn that there are over 200 commercial strains of Saccharomyces cerevisiae available for winemakers to work their magic on grape juice. Why so many? Surely one or two reliable workhorse strains should suffice; after all, don?t they just make ethanol from sugar? The answer to this is an emphatic no; the more we look at the role(s) of yeast in winemaking, the more we are learning about their influences on appearance, aroma, flavour, mouthfeel and final ethanol concentration. And different yeast are more or less robust and efficient in converting the hostile environment of grape juice into wine. Indeed, not all wine yeasts are equal.

Whole transcriptome RNAseq analysis of Oenococcus oeni reveals distinct intra-specific expression patterns during malolactic fermentation, including genes involved in diacetyl metabolism

We report the first whole transcriptome RNAseq analysis of the wine-associated lactic acid bacterium Oenococcus oeni using a combination of reference-based mapping and de novo transcript assembly in three distinct strains during malolactic fermentation in Cabernet Sauvignon wine. Two of the strains (AWRIB551 and AWRIB552) exhibited similar transcriptomes relative to the third strain (AWRIB419) which was dissimilar by comparison. Significant intra-specific variation for genes related to glycolysis/gluconeogenesis, purine metabolism, aminoacyl-tRNA biosynthesis, ABC transporters and phosphotransferase systems was observed. Importantly, thirteen genes associated with the production of diacetyl, a commercially valuable aroma and flavour compound, were also found to be differentially expressed between the strains in a manner that correlated positively with total diacetyl production. This included a key strain-specific gene that is predicted to encode a l-lactate dehydrogenase that may enable l-lactic acid to be utilised as a precursor for the production of diacetyl. In conjunction with previous comparative genomic studies of O. oeni, this study progresses the understanding of genetic variations which contribute to the phenotypes of this industrially-important bacterium.