Metabolic and Molecular Rearrangements of Sauvignon Blanc (Vitis vinifera L.) Berries in Response to Foliar Applications of Specific Dry Yeast.

Dry yeast extracts (DYE) are applied to vineyards to improve aromatic and secondary metabolic compound content and wine quality; however, systematic information on the underpinning molecular mechanisms is lacking. This work aimed to unravel, through a systematic approach, the metabolic and molecular responses of Sauvignon Blanc berries to DYE treatments. To accomplish this, DYE spraying was performed in a commercial vineyard for two consecutive years. Berries were sampled at several time points after the treatment, and grapes were analyzed for sugars, acidity, free and bound aroma precursors, amino acids, and targeted and untargeted RNA-Seq transcriptional profiles. The results obtained indicated that the DYE treatment did not interfere with the technological ripening parameters of sugars and acidity. Some aroma precursors, including cys-3MH and GSH-3MH, responsible for the typical aromatic nuances of Sauvignon Blanc, were stimulated by the treatment during both vintages. The levels of amino acids and the global RNA-seq transcriptional profiles indicated that DYE spraying upregulated ROS homeostatic and thermotolerance genes, as well as ethylene and jasmonic acid biosynthetic genes, and activated abiotic and biotic stress responses. Overall, the data suggested that the DYE reduced berry oxidative stress through the regulation of specific subsets of metabolic and hormonal pathways.

Effect of pre-harvest inactivated yeast treatment on the anthocyanin content and quality of table grapes.

Due to the global warming, more and more often the red-pink grape varieties grown in the Mediterranean basin reveal an insufficient accumulation of anthocyanins and thus a scarce coloration. Nowadays, this is becoming an important technological issue, which may result in the reduction of the fresh market value of table grape. This study aimed at assessing the effect of the pre-harvest treatment by specific inactivated yeasts (YE) on the qualitative parameters and anthocyanin pattern of three red table grape varieties, which typically present poor and/or incomplete coloration during warm years. An increment of anthocyanins level up to almost seven folds corresponding to an improvement of red skin appearance was observed in all the treated table grapes, which was preserved after cold storage, too. While, no significant influence on chemical composition and berry texture and dimensions was found, meaning that YE did not cause appreciable taste changes in grapes.

Effect of pre-bloom leaf removal on grape aroma composition and wine sensory profile of Semillon cultivar.

BACKGROUND: Early leaf removal at pre-bloom is an innovative viticultural practice for regulating yield components and improving grape quality. The effects of this technique on vine performance, grape composition and wine sensory profile of Semillon variety were assessed. RESULTS: Pre-bloom leaf removal enhanced canopy porosity, total soluble solids in musts and reduced cluster compactness. This practice had a strong effect on glycoside aroma precursors, in particular by increasing glycoside terpenols and norisoprenoids. Metabolites of linalool were the most responsive to leaf removal. Wine produced from defoliated vines was preferred in tasting trials for its more intense fruity notes and mouthfeel attributes. CONCLUSION: Pre-bloom leaf removal is a powerful technique for modifying canopy microclimate, vine yield, grape composition and wine quality. The increase of glycoside aroma compounds in treated grapes has potential positive effect in improving the sensory profile of the resulting wines. © 2017 Society of Chemical Industry.