The impact of Saccharomyces and non-Saccharomyces yeasts on wine colour: A laboratory study of vinylphenolic pyranoanthocyanin formation and anthocyanin cell wall adsorption

Wine fermentation is a complex process driven by yeasts, which influence the key properties of wine quality: aroma, flavour and colour. We investigated 95 different Saccharomyces and non-Saccharomyces strains for their impact on wine colour through the synthesis of the stable pigments, pyranoanthocyanins. All strains were screened for their hydroxycinnamate decarboxylase (HCDC) activity that varied from 0.0% to 91.1%. Eight strains that showed more than 40% HCDC activity were further studied for vinylphenolic pyranoanthocyanin formation. Fermentations were carried out in deep well microtiter plates using synthetic grape must containing Pinot Noir skin extract supplemented with p-coumaric acid. Two strains Pichia guilliermondii ZIM624 and Wickerhamomyces anomalus S138 synthesized vinylphenolic pyranoanthocyanins in the highest concentration in single culture fermentations, 40.2 and 38.5 mg L−1, respectively. The highest produced concentration of vinylphenolic pyranoanthocyanins in co-inoculation experiments was 16.4 mg L−1 compared to 29.8 mg L−1 in sequential fermentations. For the first time, S. paradoxus strains were assessed for pyranoanthocyanin formation. Selected strains were also tested as mono-cultures for adsorption of anthocyanins on yeast cell walls and all strains showed anthocyanin and pyranoanthocyanin adsorption to their cell wall with Metschnikowia reukafii ZIM2019 showing the highest adsorbing capability (9.1%).