Since 1963, wine active dry yeasts have been used in the wine industry successfully to the benefit of wine quality. Their use has been one of the positive revolutions for the industry and has led to selection programs with research institutes in the different wine regions of the world, as well as further understanding of the wine microbial ecosystem. Nowadays, over 300 different strains are available to winemakers, from Saccharomyces but also non-Saccharomyces, and their economic, technical and qualitative advantages are proven.

The rehydration of wine active dry yeast (WADY) was extensively studied for 40 years, and was shown to be of the utmost importance in relation to the successful outcome of the alcoholic fermentation. Krauss et al (1981) were already showing the importance of temperature and the type of rehydration media on fermentative activity to have a healthy cell membrane and retain the constituents of the cells and allow the nutrients to enter. It was shown even then, that the fermentation activity benefited from rehydration compared to direct inoculation. Later, Soubeyrand et al. (2006) confirmed the importance of the rehydration procedure on not only the viability, but also on the fermentation behavior. They showed that CO2 release, correlated to sugar consumption and was a good indicator of yeast vitality. Rinaldo et al. (2017) described this concept of yeast vitality as a broad term encompassing the overall health/fitness of a cell including its metabolic activity, membrane function and integrity, and overall capability to function in the current environment. A wine yeast with increased vitality has a better chance of surviving the challenging conditions during wine fermentation, minimize the risk of stuck fermentations occurring and develop the full sensory potential of the grapes. When fermentation conditions become too challenging or yeast become stressed, vitality decreases, and fermentation problems are more likely to occur and there is less volatile aroma compounds.

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