Temperature Shock for Wine Yeast

What is temperature shock?

I have been using Lavalin EC-1118 Wine Yeast for all of my wine production. The technical data sheet from Lavalin indicates that “The difference in temperature between the must to be inoculated and the rehydration medium should not be higher than 10°C (if necessary, acclimatize the temperature of the medium by slowly adding must)”. I have been rehydrating the yeast at a temperature between 32’C - 35’C. During the summer the temperature of my processing area is about 21’C -25’C. This is a difference of about 10’C. I have not had any problems getting the wine to ferment, until now. The temperature has decreased to as low as 16’C. That is a significant difference from 35’C, and has resulted in temperature shock to the yeast. I have noticed that fermentation was not starting in a reasonable time after addition of the yeast.

I store the Yeast packets in the same room as the Must and at the same temperature. Going forward I will pitch the dry yeast directly onto the surface of the Must.