Which factors influence extraction during skin contact?

• A. Grape variety
• B. Ambient humidity
• C. Time and temperature
• D. Fermentation vessel color

Answer: (C)

Extraction during skin contact is governed mainly by how long the juice stays in contact with the skins and how warm the must is. The compounds in the skins—color pigments, tannins, and other phenolics—diffuse into the juice over time, so longer contact increases the total amount extracted. Temperature drives the rate of that extraction: higher temperatures speed diffusion and solubility, giving more extraction in a shorter period. But pushing either duration or warmth too far can bring out harsh tannins, excessive color, or off flavors, so balance is key.

Ambient humidity doesn’t directly change how much dissolves from the skins, and the color of the fermentation vessel doesn’t influence the chemistry of what’s extracted—what matters is controlling time and temperature. Grape variety can affect the potential amount and character of compounds available for extraction (thicker skins, different phenolics), but the immediate factors determining how much is pulled into the juice during skin contact are time and temperature.