First, I assume that commercially produced yeast nutrient probably has FAN included in it, probably along with zinc and magnesium, etc.

Second, there has been previous discussion some time ago about adding quantities of dried yeast to the boil -- with the really cheap baker's yeast (2 pounds or almost a kilo for a bit more than $3.00 U.S.) being a very economical way to do that. [I realize there is special yeast made with extremely high zinc content, but I'm speaking now of just baker's yeast, or perhaps old packets of regular brewer's yeast.]

Questions:

1. Does boiling dried yeast provide FAN, or just minerals?

2. Assuming that boiling dried yeast does provide FAN and minerals that yeast need to grow, how much dried yeast would be the optimum amount to add to the boil when making a 5 U.S. Gallon batch (19 liters)?

3. Besides yeast nutrient, and perhaps dried yeast, is there any other source of FAN that is readily available as an adjunct?

Thanks.
Bill Velek

RESPONSE:

Bill, Yeast usually has a protein content of 35-50 % of its dry weight. But this is protein and not free amino nitrogen. FAN is around 1-3 % of the dry weight.

If you want to add 60 mg/L FAN (all malt wort has usually 150 – 220 mg/L FAN) you need to add 2-6 g of dry yeast per liter of wort to your boil. So for 19 L wort it would be 38-114 g of dry yeast. A side note... we tried in Weihenstephan to raise the FAN level in wort by adding yeast to the boil but the finished beer tasted awful.

The same for mineral addition by adding dry yeast to the boil. In regular brewer's yeast you have around 40-60 mg zinc per kg of dry yeast. To increase the zinc concentration by 0.2 mg/L you have to add around 5 g dry yeast per liter to the kettle.

Besides commercial yeast nutrients you could buy mono- or di-ammonium phosphate as a nitrogen source.

Regards,
Tobias & Forbes