Expression of terroir: A case study of innovative vineyard fermentation at Greystone Winery

Abstract

Greystone has been innovatively working on a new type of wild fermentation of Pinot noir wine that is fermented in vineyard. This study aimed to comprehensively analyse the Greystone Pinot noir wines spontaneously fermented both in vineyard and in winery, by investigating the fermentation dynamics, microbial diversity, and chemical composition across two vintages. Fermentation dynamics showed that the initiation of alcoholic fermentation generally takes about four to five days, concluding roughly within two weeks, irrespective of whether it is a vineyard or winery ferment. However, while fermentation dynamics were observed to vary, the 2020 winery ferments displayed a generally faster fermentation than their vineyard counterparts did. This inconsistency across vintages might be attributed to certain external factors, like the ambient temperature that affects yeast diversity and activities. Yeast diversity analysed by next-generation sequencing showed that the 2019 vintage exhibited a broader yeast diversity compared to the 2020 vintage. Notably, several non-Saccharomyces yeast genera, including Hanseniaspora, Metschnikowia, Pichia, Torulaspora, and Lachancea, which were consistent across two vintages, showed potential in enhancing wine aroma and structure. Moreover, when considering the combined effects of the vintage and fermentation environment, it was evident that they significantly influence the fungal community composition. Between these two factors, the vintage played a more crucial role than the fermentation environment. Analysed by UPLC, phenolic compounds were gradually extracted as fermentation progresses. Interestingly, the winery ferments displayed slightly faster phenolic extraction rates, which aligned with their observed fermentation dynamics. In terms of colour properties, while there were no significant differences between fermentation types, the 2019 vintage stood out by presenting higher levels of anthocyanins and total phenolics than the 2020 vintage. Aroma profiling of bottled wines by GC-MS revealed that the impact of fermentation location on wine aroma seemed minimal, although there were a few ester compounds that displayed significant variations. Most notably, the vintage emerged as a significant factor influencing the aroma compounds in Pinot noir wines, with both vintages presenting distinct aromatic profiles.