Fermentation activators adding yeast starter

The calculated amount of S02 is added and mixed thoroughly with the grapes, and the opening of the vessel is covered with a cloth to prevent the entry of insects. After 2-4 hrs the pure-yeast starter culture is added—again with stirring so that there is thorough mixing. The cloth cover is replaced. Active fermentation will be apparent within a day or so. 

Conduct of Fermentation. The ameliorating material normally is added to the sulfited juice prior to the onset of fermentation and thoroughly mixed in. An actively fermenting yeast starter is added. The large wineries maintain a yeast generator for the propagation of a continuous supply origi-... 

When the yeast starter is added, it is important to avoid antagonism with other strains naturally present in the must. Antagonistic reactions may reduce the fermentation rate and contribute to causing stuck fermentation (Section 3.8.1). For inoculation with DAY to be successful, the yeast starter must be more abundaut aud more active than the indigenous yeasts, which must be inhibited by proper hygiene, sufficiently low temperatures, and appropriate use of sulfite. 

Inoculation of the juice is strongly recommended. The chosen yeast strain should be highly ethanol tolerant and should produce little volatile acidity in difficult fermentation conditions. The dry yeasts should not be introduced directly into the juice to start the fermentation for this type of winemaking. A yeast starter should be prepared in diluted must, supplemented with NH4+ and yeast hulls, then seeded with dried active yeast at a dose of 2.5 g/hl of the total volume to be inoculated. The starter is added to the must on the second day of fermentation, at a rate of 2% of the total volume. This increases the maximum yeast population, which controls fermentation rate and volatile acidity production (Section 2.3.4). In one experiment, adding yeast in this way reduced the final volatile acidity content by 20%. 

An active yeast starter, consisting of selected sfiains of Saccharomyces cerevisiae, is added at the same time to ensure that the second fermentation ( prise de mousse ) will be successfully completed... 

White wines are normally fermented in containers that can be partially closed so that the surface of the fermenting wine is protected from the air by a blanket of carbon dioxide. For the home winemaker, 5-gallon carboys serve admirably. An hour or so after adding S02, one adds approximately 3% of an actively fermenting pure-culture starter yeast. 

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