“Yeast cells need 100% of their essential vitamins and minerals (nutrients) to make it through a fermentation properly nourished and to be ready to work again another day, much the same way humans do.”
At White Labs, we do countless experiments on nutrient levels, especially FAN (Free Amino Nitrogen). Yeast needs sufficient nitrogen to carry out fermentation efficiently, and lower than the optimal levels can inhibit this process. The presence of FAN in a beer affects vital aspects such as the fermentation rate, attenuation, aroma, and yeast vitality. Yeast uses FAN as a key source of nutrients during fermentation, particularly in the initial stages. FAN also plays a role in yeast vitality, which ensures complete fermentation and that the beer is free of off-flavors and aromas. Inadequate FAN levels can lead to stressed yeast, producing undesirable flavors and aromas such as diacetyl, acetaldehyde, and sulfur compounds.
FAN requirements are more critical with propagation and yeast growth, as cells need enough nutrients to reproduce. In our latest White Labs experiment, we wanted to assess the minimum nitrogen requirement for some of our core strains to optimize the propagation wort supplementation.
All strains were grown on wort from the Brewhouse, with the standard strength and nutrient supplementation.
Propagation Scale:
48 Well Plates
The Propagation Standard Conditions:
Pitch Rate: 5 million cells/mL
Temperature: 86 °F/30 °C
FAN levels were determined using analytical techniques such as spectrophotometry, enzymatic assays, and chromatography. These techniques measured different aspects of amino acid levels, with results reported in units such as mg/L (ppm) or g/L. Generally, a level of at least 150 mg/L of FAN is ideal for standard beer fermentation.
The following graphs show the calculated requirements per strain in wort with 180ppm FAN, roughly grouped by yeast categories:
The studies gave us some interesting and conclusive results regarding the general requirements of FAN in particular strain groupings. Lager strains seemed to require the least amount of FAN, ranging from 85 - 100ppm. Like the Belgian strains, the more wild-like yeast strains required more FAN, up to 155ppm. With this ongoing knowledge and research, brewers have more information for creating optimal conditions for yeast in any beer style.
Most strains evolved with certain beer styles, making them compatible with the nutrient requirements and wort recipes. But we’re all for experimenting with new strains in different styles. Knowledge of starting gravity and nutrient requirements for different strains can make brewing easier!
For example, if brewing a Belgian lager with a high FAN-requiring Belgian strain, an extra dosage of nutrients could go a long way in flavor development and attenuation for the beer. Another key consideration would be the type of malt being used in the brewing process. Undermodified malts and roasted specialty malts can have low amounts of FAN, so be sure to check your certificate of analysis for FAN levels on some of these malt varieties.
If you’re not brewing with malt, nitrogen is a whole different ball game as nitrogen is often not readily available. Seltzers, ciders, meads, wines, and other alternative beverages need a boost of either organic or inorganic nitrogen for optimal fermentation. Check out our mead research with Lost Cause Meadery!
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