Abstract
The name "yeast-derived products" (YDPs) refers to different preparations obtained from yeast cells through various processes. These YDPs have different characteristics and applications in oenology, one being the improvement of the sensory properties of wines. This work aimed to identify the impact of YDPs obtained from different yeast strains and through different downstream inactivation processes on polyphenols in a red wine at different aging times. At an oenological dosage of 40 mg/L in a young wine, the addition of YDPs resulted in a variable decrease in total polyphenol index (TPI) (2 to 9 % depending on the YDPs) and a significant decrease in the precipitation of tannins (15 to 50 %) and high molecular weight (HMW) pigments (19 to 85 %) were obtained in the BSA assay, thus demonstrating the involvement of tannins and HMW pigments in interactions with the studied yeast-derived products. Pigment involvement led to a change in colour indices (L*a*b* and colour intensity), but in most cases this change was not visible to the human eye at the oenological dosage tested (40 mg/L). Experiments conducted on both the young wine and the same wine aged for three months using the same yeast-derived products, dosages and aging conditions revealed the influence of the chemical evolution of polyphenols on their interactions with YDPs. The significant variation observed in this study highlights the critical role of yeast selection and the yeast fragmentation downstream process on YDP efficiency. The high-pressure homogenisation (HPH) yeast fractions were shown to be more efficient than the corresponding whole yeast cells. Increasing the contact surface area between yeast cell constituents and wine matrix enabled by the HPH process may be a key strategy for enhancing the effectiveness of yeast derivatives in red wines, and in aged wines in particular, in which the phenolic compounds underwent changes and exhibited less interaction with the studied yeast-derived products. This research has contributed to increasing our understanding of and the potential for apply these processing aids in oenology.