The aim of this study was to evaluate the effect of oxygen exposure of red wine, before (micro-oxygenation) and after (nano-oxygenation) bottling, on the phenolic composition and astringency of wine. The astringency was evaluated by sensory analysis and by a method based on the SDS-PAGE of salivary proteins after reaction of saliva with wine (SPI, saliva precipitation index). Micro-oxygenation caused a stabilization of color, but this effect disappeared after long aging. For the wine with the lower pH a decrease of wine astringency and SPI was observed 42 months after micro-oxygenation. Oxygen ingress through the closure postbottling was positively correlated with the decrease of SPI. Therefore, the astringency and reactivity of wines toward salivary proteins of a bottled red wine can be modulated by controlled oxygen exposure during aging. For both experiments the effect of oxygen exposure depended on wine composition.

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Aims: Little genetic information exists on the ability of wine lactic acid bacteria (LAB) to hydrolyse glycoconjugates during malolactic fermentation. We tried to fill this important gap by characterizing a gene codifying for a putative b-glucosidase enzyme from wine Lactobacillus plantarum and from a commercial strain of Oenococcus oeni. Methods and Results:The coding region of the putative b-glucosidase gene is 1400 nucleotides long and started with an ATG codon. The gene is widespread among LAB and the highest identity was observed between the nucleotide of L. plantarum, Lactobacillus pentosus, Lactobacillus paraplantarum and O. oeni b-glucosidase gene. The protein sequence deduced from the isolated genes has a calculated molecular mass of 61AE19 kDa. Furthermore, the expression of the b-glucosidase gene in L. plantarum strain was analysed, under several stress, by reverse transcriptase (RT)-PCR and Northern-blot analysis. The gene was apparently regulated by abiotic stresses such as temperature, ethanol and pH. Conclusions: The b-glucosidase gene is widespread among LAB and its expression is probably regulated by a wide range of abiotic stresses. Significance and Impact of the Study: The inhibitory effect of temperature and ethanol on the L. plantarum b-glucosidase gene may be useful to explain the differences found in b-glucosidase activity reported in wines by several authors.

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