In Alcoholic Fermentation and Yeast

You may have noticed on wine yeast packets and in the literature that there are mainly two different ways to rehydrate active dried wine yeast. The one procedure is a water only procedure and the other a water juice mixture. The existence of two different procedures on different companies’ yeasts can be quite confusing to winemakers if they would like to standardize their cellar practices. Well the good news is you can. Just pick one that suits you best. The reason why one company – say Lallemand – has the water only rehydration and another company – say Anchor Yeast – has a water/juice rehydration is simply legacy. In the seventies when both companies started to produce and sell wine yeast they just happen to choose different methods and then stuck to it. What is very important is that you follow the method you choose exactly and not take short cuts. Yeast rehydration is extremely important for optimal yeast functionality.

So you might ask why two methods exist in the first place. Well, the best way for me to explain this is that water is what was taken out of the yeast when dried after production, so water is all that’s needed to restore the original cell form. However, water has no osmotic strength, which means that if you do not follow the exact protocol and add juice to the rehydration mixture after 30 minutes, then cell constituents (very small, but very important stuff on the inside of the yeast) can leak out from the high (inside the yeast) to the low (water) osmotic pressure. Simple chemistry. The yeast will lose some or all of its functionality, which could result in fermentation problems. So by adding one third juice to your rehydration mix you add some osmotic pressure – making rehydration more idiot proof. You also provide something for the yeast to start fermenting on right away.

In big co-operative wineries the yeasts for several tanks are rehydrated at the same time. So by the time the winemaker returns to the first tank’s mix – 30 minutes could have passed. In this case the water/juice rehydration would be the safer option.

I don’t have any evidence that one method is more effective that the other if both are followed exactly as prescribed. If anyone out there has experience of one being better than the other then please let me know.

This was a rather boring blog to write. Will have to bring in more humor and opinion in my next attempt. Its useful information though…

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