I've read that you can leave an ale to secondary for months and enough yeast will remain in suspension that you won't need to pitch additional yeast when bottling. But are there times when you do need to pitch more yeast before bottling to ensure you get carbonated beer? For instance...
What if you crash-cool your ale? Will the yeast fall out of suspension such that there won't be any left to carbonate your brew in the bottle?
What if you started with a high gravity beer and the yeast gave all they had? Will they be too tired to eat the priming sugar?
Are there any other factors that would make it a good idea to pitch more yeast before bottling?
Rich:Unwanted banana flavor is unusual with a yeast like Safale S-5, but can happen if the temperature got too high. I agree it can be a variable that's easy to eliminate. I really only offered it as an option if you didn't save yeast or it went bad. Some commercial brewers use a different strain for carbonation as well, that's why cultivating from the bottle can be such a crapshoot.
– TinCoyote Feb 19 '10 at 01:23