Harvest and Pre-Fermentation Treatments

Grape proteases are acidic, with an optimum pH near 2.0. In the pH range of must, 40-60% of the potential proteasic activity exists. Protein hydrolysis activity during the pre-fermentation phase varies greatly, depending on grape maturity and harvest treatments. This certainly affects fermentation kinetics but the relationship has never been established. A slight sulfur dioxide additiou (around 25 mg/1), however, has been confirmed to stimulate proteasic activity. This explains, at least partially, its activation effect on fermentation (Section 8.7.3). 

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