I forgot to refrigerate my liquid yeast, and its been out of the fridge for _______ hours/days/weeks; should I pitch it anyway or buy new?
Liquid yeast should stay refrigerated until a few hours before it is pitched (added) into wort. The goal is to activate the yeast from dormancy by bringing it to fermentation temperatures before pitching it into the wort. This will reduce unnecessary stress incurred by the yeast from rapidly changing conditions (both temperature and the presence of fermentable sugars). Generally, the longer liquid yeast is left at higher temperatures the more viable yeast begins to die because of lack of oxygen and lack of energy (food and nutrients). While forgetting to refrigerate yeast for 24-48 hours is not a huge concern, just remember that healthier yeast cultures will lead to better fermentations and result in better tasting beer. However, it only takes a single cell of yeast to produce enough yeast to ferment a batch of beer, though it is best to make a starter before fermentation begins to ensure an adequate pitch rate. If the yeast has been out of refrigeration for over 72 hours (3 days), or
