Hyperspectral imaging and machine learning for monitoring grapevine physiology

The implementation of food safety assurance systems in wineries involves ensuring that the wines produced do not pose a risk to consumer health and are therefore free from harmful substances, such as those that may be incorporated during the production process (pesticides, additives, etc.), allergens or mycotoxins.

Red grapes contain significant amounts of phenolic compounds, known to contribute to wine quality and to provide important health benefits. Berry skin phenolics can be elicited by plant hormones. The aim of this work was to increase the content of anthocyanins and trans-resveratrol in five red varieties cultured in Argentina: Malbec (M), Bonarda (B), Syrah (S), Cabernet Sauvignon (CS), and Pinot Noir (PN), in two different growing regions: Santa Rosa (SR) and Valle de Uco (VU), by applying a post-veraison hormonal treatment with abscisic acid (ABA) and methyl jasmonate (MeJA).

Global warming is accelerating grape ripening, leading to unbalanced wines from fruit with high sugar content but poor aroma and colour development. Reducing the size of the photosynthetic apparatus after veraison has been shown to delay technological ripeness in cool climates, but methods have not been tested in areas with high irradiance and temperature where fruit exposure could have disastrous effects on berry composition. In this Cabernet-Sauvignon trial, we compared the application of an antitranspirant (pinolene), to severe canopy topping and above bunch zone leaf removal, all performed at mid-ripening, with an untouched control. We monitored the vines weekly by measuring stem water potential, gas exchange, fruit zone light exposure. We sampled berries to measure berry weight, total soluble solids, pH, titratable acidity, and the anthocyanin profile. At harvest, we assessed yield components, measured carbon isotope discrimination, rated sunburn on clusters, and produced experimental wines. We submitted harvest samples to metabolomic profiling through PFP-Q Exactive MS/MS and wines to sensory analysis. Application of the antitranspirant significantly reduced stomatal conductance and assimilation rate but did not affect the stem water potential. Inversely, leaf removal and topping increased water potential but did not affect leaf gas exchange. The late topping was the only treatment able to decrease sugar content (up to 2Bx), increase titratable acidity and pH, and improve anthocyanin content because of lower degradation of di-hydroxylated forms. Late leaf removal above the bunch zone increased lightning conditions in the canopy and produced the most significant damage on fruits. Yield components were not affected. This work suggests that late-season canopy management can effectively control ripening speeds and improve grapes and wines. Still, the effect on grape exposure in a critical time must be well balanced to avoid problems with the appropriate technique.

The fresh mushroom off-flavour (FMOff) has been appearing in wines since the 2000s. Some C8 compounds such as 1-octen-3-one, 1-octen-3-ol, 1-hydroxyoctan-3-one, 3-octanol and others are involved in this specific off-flavour [1-3]. At the same time, glycosidic precursors of some FMOff compounds have been identified in musts contaminated by Crustomyces subabruptus [4], highlighting the role of aroma precursors in this specific taint. However, the fate of these volatile molecules and glycosidic fractions during fermentation is not well known.

French lawmakers have chosen the family-type winegrowing business as the benchmark for drafting the legal framework for winegrowing businesses and winegrowers. In france (source: msa), in 2022, there were 1,444 new winegrowers, an increase of 3% compared with 2021, representing 10% of new farm managers. The retention rate for winegrowers is 75% (up 13% on 2021), compared with 77% for all agricultural sectors (stable).