High Gravity Brewing…I Like Big Beers and I Cannot Lie!
What is High Gravity Brewing?
High gravity brewing (HGB) refers to the process of fermenting with a high sugar content when making high alcohol content beer. In the last decade, craft brewers have undoubtedly increased the popularity of certain beer styles that are accompanied by a high alcohol content. Some common styles of big beers using HGB are Barleywine, Imperial Stouts, Belgian Style Golden Strong Ale, Scotch Ale/Wee Heavy, Imperial IPAs, etc. When making beer using wort within the range of 14-17°P, expect an above average alcohol content in the final product, 6-8% ABV. In general, we recommend the industry standard of 1 million cells/ml/°P for ales less than 16°P, 1.5 million cells/ml/°P for lagers less than 16°P, and an additional 0.5 million cells/ml/°P for high gravity ales or lagers over 16°P. However, these are generalizations only and may not apply to all situations. If you prefer a different pitch rate or are unsure how much to pitch, please call our excellent Technical Support Team (719) 482-4895 ext. 3.
Fermentation Issues in HGB
Using concentrated wort is only one element to consider when making a HGB. The yeast you choose needs to tolerate high levels of ethanol. The HGB environment is very stressful on yeast cells for a multitude of reasons. One is high ethanol content, which increases permeability of the yeast cell’s membrane. Due to the increased permeability, the cell membrane is less stable, and leaks amino acids, proteases, and other important components to cellular vitality. The mitochondrial membrane may also be targeted by ethanol toxicity, which could damage the DNA of the yeast cell.
Another reason for cell stress is the increased amount of time it takes to finish fermentation. The more time it takes, the more likely you will run into nutrient deficiencies for the yeast. Thus, it is crucial to select a yeast strain that is tolerant to a high ethanol content and to supplement the wort with additional yeast nutrient. Yeast nutrient deficiencies are one of the primary limitations in HGB. BSI sells a proprietary yeast nutrient that would be highly beneficial to brewers wanting to brew a big beer to replenish some of the nutrients during fermentation.
High Gravity Brewing Techniques
While choosing the right yeast strain is essential for producing a big beer, there are other techniques that will assist in healthy fermentation. The most important is the use of healthy yeast cells at a higher pitch rate as described above. High gravity beers typically contain more complex sugars that can be more challenging for yeast to ferment. Fresh liquid yeast strains are often known for their ability to ferment a broader range of sugars, leading to better attenuation and fermentation performance in high gravity beers. Additionally, liquid yeast often contains a higher cell count and viability compared to dry yeast. Having a sufficient and healthy yeast population is crucial for fermentation in high gravity conditions. Another specific benefit to using fresh liquid yeast from BSI is the great variety of strains to choose from, a benefit you do not have if using dry yeast.
As mentioned, nutrient deficiencies are one of the primary limiting factors in producing a good HGB. So, the next technique for HGB is supplementing with enzymes such as glucoamylase and a nitrogen source, such as glutamine or asparagine, to keep your yeast chugging along. Additionally, adding a fatty acid source such as oleic acid may help the yeast cell membrane from becoming too permeable.
BSI has a long list of high alcohol tolerant yeast strains as well as high gravity specific strains, such as BSI-99 / Tom Hardy Ale, an English strain which is one of our top sellers for HGB beers and Barleywine. With proper techniques, Tom Hardy Ale can ferment up to 20%+ ABV. More suggested BSI strains include:
High Alcohol Tolerant
|BSI-715 / Champagne (Ale)
|BSI-530 / Trappist Ale 3
|BSI-540 / Trappist Ale 4
|BSI-570 / Belgian Ale 4
|B-87 / Trappist Ale
|B-88 / Breendonk Belgian Ale
|S-11 / French Saison
|S-24 / Saison
High Gravity Specific
|BSI-510 / Trappist Ale
|BSI-565 / Saison
|BSI-7 / English Ale 4
|B-62 / Belgian Ale II
|B-87 / Trappist Ale
|A-78 / Scotch Ale
By: Austin Snow & Kyle McMichael, Micro Technologists
Gregory, Casey P., et al. (1984). “High Gravity Brewing: Effects of Nutrition on Yeast Composition, Fermentative Ability, and Alcohol Production.” Applied and Environmental Microbiology, 48(3), 639-646. https://europepmc.org/backend/ptpmcrender.fcgi?accid=PMC241579&blobtype=pdf
Puligundla, P., et al. (2020) “Recent Developments in High Gravity Brewing.” Innovative Food Science and Emerging Technologies, 64, 102399. https://www.sciencedirect.com/science/article/abs/pii/S1466856420303453