Rehydrate yeast first, or not?

[Manimal]

I think that as long as you are careful to follow the instructions, it is preferable to rehydrate. The whole point of rehydration is to ensure that you inoculate the must with the optimal number of VIABLE yeast cells. If you don't rehydrate, and just toss them in some must, there will be osmotic stress put on the yeast as they try to take in water in a high sugar environment. So I'd say you should follow the instructions and rehydrate in water at the proper temperature. If you can get a yeast rehydration nutrient like GO-FERM, to add to the rehydration water, that's even better... just make sure it isn't a regular yeast nutrient since the DAP included is toxic to yeast at that concentration.

Sure, you will likely have little trouble with most fermentations just tossing the yeast in, but when you have difficult fermentation conditions such as low temperatures, low nutrient, etc. a properly prepared yeast inoculum can help get you to the end. Google Scott Labs and check out their website for more info on yeast rehyration.

[Mud]

What Manimal said.

[Tom]

Either way will work. I like to give the yeast a head start by making a starter or rehydrate the yeast

[summersolstice]

I use Lalvin dry yeast almost exclusively and I follow their reccomendations for hydrating their yeast.

[djrockinsteve]

I too use the Lalvin yeast packets. 15 minutes in warm water (@2 ounces) then into my juice. Several hours later I can see some bubbles and the next day it's fully underway. I also use pectin enzyme (20 drops per 6 gallon bucket) with the yeast. I have always had success this way.