I recently found a partially empty 16 oz package of Fleischmann's active dry yeast in my garage fridge. I was thinking it was 5 or 6 years old and decided to see if it had any viability left. I used the standard proofing method( 1/2 cup hot water, sugar and 2 tsp yeast). It doubled to 1 cup in 12 minutes which was pretty close to fresh yeast. Afterwards I checked the package. I had marked it as being open on 03/2009. That was 11 years and 1 month earlier. It was sealed from exposure to air and held at refrigerator temps and was still good to go.

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