High Gravity Page-An introduction to High Gravity Fermentations for Mead, Wine, and Distilling.
Making beer at moderate starting gravity is pretty routine and simple. Just mash in grain, sterilize mash by boiling, cool, add some oxygen, pitch any old beer yeast, and voila, ~10% dissolved solids turns into ~3% dissolved solids in final beer.
Making wines for drinking or distilling, and making high gravity beer with added simple sugars or sake, is more difficult. Here’s a few tips that will help in fermenting high gravity musts and worts containing up to 20-30% dissolved solids and more.
- Use the right yeast strain for the right job. Yeast vary widely in the ability to produce alcohol. In general, wine yeasts and some distillation yeasts are very alcohol tolerant, require less nutrient, and are more tolerant of stress conditions. Some bourbon and distillation yeasts are cross-overs from brewing, but still retain some higher alcohol tolerance.
- Ensure pitching rate is high. Most wine yeast seem to do ok at lower pitching rates (<15 million/ml). For gravities higher than 20P, use a pitching rate of 20-75 million/ml.
- Use nutrient. Yeast need pretty similar things to plants, and need fertilizer with added nitrogen. Yeast Assimilable Nitrogen is found in pretty high supply in wort (YAN). Learn how to calculate YAN, and add a yeast nutrient, and supplemental organic or diammonium phosphate. Wort has ~150-300 ppm. Honey and sugar washes have nearly zero.
1g/L of DAP = 210 ppm
1g/L of Fermaid K = 155 ppm
The key is to adjust the YAN to above that of wort (300 ppm-1000 ppm), and for production of 15-24% alcohol. Staggered additions (1/2 of nutrients added at pitching, an the second at 75% sugar depletion.
Zinc is sometimes in limiting supply. Supplement to 6 ppb.
4. Use oxygen to saturation after pitching. Additional oxygen boosts can be performed.
5. Control temperature. Keep within the low end of temperature range in the beginning of fermentation. Letting temperature climb at the end of fermentation helps get rid of sulfur and diacetyl.
High gravity brewing is not as hard as some people say. Yeast can do heroics if they are given the right niche.