Impact of press fractioning on current and phenolic compositions of Pinot noir and Pinot meunier wines

Abstract

In the Champagne’s region, a complete press cycle is a series of pressure increases (squeezes) and decreases (returns). After alcoholic fermentation, the two wines (the “cuvee” and the “tailles”) obtained from grape juice fractions exhibit strong differences for numerous characteristics. Nevertheless, there is no study of the impact of the press cycle, followed after each pressure increase (22-28 steps), on wine colour, current analyses and phenolic composition. So, the aim of this study (vintage 2020) was to investigate the composition changes of Pinot noir and Pinot meunier wines, produced from 22-28 grape juices isolated for each complete pressing cycle. The studied parameters were: colour (L*a*b*), pH, TA, malic and tartaric acids, alcohol, a-NH2, Ca2+ and K+, as well as anthocyanins (peonidin and malvidin), phenolic acids (protocatechuic acid, caftaric acid, cis-coutaric acid, trans-coutaric acid, fertaric acid, GRP) and flavanols (catechin and epicatechin). Previously published studies on wine characteristics obtained with juice fractions were based on 4-5 samples per pressing, i.e. one sample from each of the 4-5 squeezes. Most of the parameters showed fully mathematically modelable evolutions, with polynomial curves of order 2 (Vrigneau et al., 2019). When we study the wines from the musts taken after each change in pressure of 200 mBars, i.e. 22 to 28 samples for the entire pressing cycle, we observe that there is in fact a relative stability of the parameters throughout the squeeze and that the most marked changes are essentially observed after a stage of depressurisation and pomace reworking. These observations, never published to our knowledge, show the interest of juice separation after a significant change in grape juice quality instead of juice separation based solely on volumetric rules. These results lead us to reconsider how to separate the “Cuvée” and the “Tailles”. For catechins/epicatechins and GRP, the concentrations increase considerably at the beginning of each squeeze before decreasing, once the juices that have undergone the oxidative shock linked to the decompaction of the pomace are extracted. Other compounds such as protocatechuic or cis-coutaric acids increase throughout the pressing process, in a rather regular way. Finally, compounds such as trans-coutaric and caftatir acids show maximum levels well before the end of pressing. We can therefore see that the content and composition of the phenolic compounds evolve quite differently from those observed in the usual oenological analyses.
As a conclusion, this study brings a greater understanding of Pinot noir and Pinot meunier wine on their phenolic compositions and colour changes all along the press cycle. These results could be a good tool for winemakers to decide how to separate the grape juice
fractions during the pressing cycle to produce different styles of wines with different sensory qualities and aging potential.

References

Vrigneau C., Salmon T., Soufyani Y., Robillard B., Bécard B., Liu P-H., Heredia Mira F. J., Trosset J-Y., Marchal R. Impact of press fractioning on Pinot noir and Pinot meunier grape juice and wine compositions and colour. 11th International symposium of Enology (Œno2019) – 11th edition of In Vino Analytica Scientia symposium (IVAS 2019), June 25-28, 2019, Bordeaux, France.