Data_Sheet_1_Pre-processing Cooling of Harvested Grapes Induces Changes in Berry Composition and Metabolism, and Affects Quality and Aroma Traits of the Resulting Wine.pdf

Due to the greenhouse gas increase, grapes are often exposed to high temperatures in several growing areas especially during the final developmental stages, and this is particularly true when early ripening cultivars are harvested. This may cause undesirable effects on berry metabolism and composition and wine quality, particularly concerning the aroma profile. Harvesting at night or keeping the harvested grapes in cold rooms before vinification are empirical protocols applied in specific viticultural areas. To study the effects of decreasing berry temperature after harvest, white-skinned berries (cv Vermentino) were maintained at 4 or 10°C for 24 or 48 h before processing (pre-cooling). Control grapes were kept at 22°C. Grapes cooled at 10°C for 24 and 48 h resulted richer in polyphenols and showed a significant up-regulation of genes involved in polyphenols biosynthesis (i.e., VvPAL, VvSTS2, and VvFLS1). Similar behavior was observed in samples kept at 4°C for 48 h. Pre-cooling induced specific changes in the volatile organic compound (VOC) profiles. In particular, higher amounts of a specific subcategory of terpenes, namely sesquiterpenes, were detected in cooled samples. The induction of the expression of key genes involved in terpenoids biosynthesis (VvHDR, VvDX3, VvTER, VvGT14) was detected in cooled grapes, with variable effects depending on temperature and treatment duration. In both cooled samples, the evolution of alcoholic fermentation followed a regular trend but ended earlier. Higher phenolic content was detected in wines obtained from the 10°C-treated grapes. Higher residual concentration of malic acid at the end of fermentation was detected in wine samples from grapes pre-cooled at 4°C. Sesquiterpenes also showed a general increase in wines from cooled grapes, especially after pre-cooling at 10°C for 48 h. Different sensory profiles characterized the wine samples, with the best scores in terms of general pleasantness obtained by the wine produced from grapes pre-cooled at 4°C for 24 h. These results demonstrate that pre-cooling harvested grapes induces specific effect on the VOC profile and other quality parameters of Vermentino wine, and this appears to be the result of specific metabolic and compositional changes occurring in the berries.

受温室气体排放增加影响，多个葡萄种植产区的葡萄常暴露于高温环境中，尤其在果实发育后期，早熟品种采收期的高温问题更为突出。这会对葡萄浆果的代谢、组分以及葡萄酒品质，尤其是香气特征，产生不利影响。夜间采收或在酿酒前将采收葡萄置于冷库暂存，是部分葡萄种植产区采用的经验性应对措施。
为探究采收后降低浆果温度的调控效果，本研究以白皮酿酒葡萄品种韦尔芒提诺（Vermentino）的浆果为实验材料，在加工前分别将其置于4℃或10℃环境下保存24小时或48小时（即预冷处理），对照组葡萄则维持在22℃环境中。
经10℃预冷24小时与48小时的葡萄浆果，其多酚类物质含量显著提升，且多酚生物合成相关基因（即VvPAL、VvSTS2及VvFLS1）的表达量显著上调；经4℃预冷48小时的样品也呈现出类似变化。预冷处理会使葡萄浆果的挥发性有机化合物（Volatile Organic Compound, VOC）谱发生特异性改变，具体而言，预冷样品中检测到更高含量的萜类化合物特定子类——倍半萜。同时，预冷处理可诱导萜类化合物生物合成相关关键基因（VvHDR、VvDX3、VvTER及VvGT14）的表达，且调控效果随处理温度与时长的不同而存在差异。
两组预冷处理的样品，其酒精发酵进程均呈现正常趋势，但发酵结束时间更早。经10℃预冷处理的葡萄所酿制的葡萄酒，酚类物质含量更高；而经4℃预冷处理的葡萄所酿制的葡萄酒，在发酵结束时残留的苹果酸浓度更高。预冷处理葡萄酿制的葡萄酒中，倍半萜类物质含量普遍升高，尤以10℃预冷48小时处理组最为显著。
各组葡萄酒均呈现独特的感官特征，其中经4℃预冷24小时处理的葡萄酿制的葡萄酒，在整体愉悦度评分中表现最优。
本研究结果表明，采收后预冷处理可对韦尔芒提诺葡萄酒的挥发性有机化合物谱及其他品质参数产生特异性调控效果，该效果源于葡萄浆果内部发生的特异性代谢与组分变化。