How much yeast to pitch? 0.6 to 1.8 grams per litre
Few brewing variables are discussed as categorically as pitching rate: underpitching gives esters and fusel alcohols, overpitching gives a flat beer. A review by Jacques Bertens on Hobbybrouwen.nl shows the picture is more nuanced, and converts everything into grams of dry yeast per litre, which is far more practical for homebrewers than counting cells.
The conversion is simple: one gram of dry yeast holds roughly 10 billion living cells, so 0.1 g per litre corresponds to about 1 million cells per millilitre. For a 1.048 beer the working range runs from a low 0.6 g/L, through 0.9 (standard top-fermenting pitch) and 1.2 (generous), up to 1.8 g/L, the classic norm for lager yeast. At a different gravity you scale accordingly.
The article explains what happens in the fermenter. With too little yeast, cells must divide more often, stay longer in the growth phase and produce more esters and higher alcohols. He also notes that oxygen and unsaturated fatty acids suppress ester formation, and that a low pitch raises the demand for amino acids, which can lead to more fusel alcohols. Diacetyl is linked to the yeast's valine synthesis and disappears again when the beer gets enough conditioning time.
He looks at eleven dry yeasts available in the Netherlands, in five categories: neutral American top-fermenting strains, Belgian and spicy strains, wheat-beer strains, lager strains and kveik. He adds a fair caveat: strain-specific research is scarce, and many studies use industrial lager yeasts. I read it mainly as a good reason to experiment with your own pitching rates.
Source: Hobbybrouwen.nl
The conversion is simple: one gram of dry yeast holds roughly 10 billion living cells, so 0.1 g per litre corresponds to about 1 million cells per millilitre. For a 1.048 beer the working range runs from a low 0.6 g/L, through 0.9 (standard top-fermenting pitch) and 1.2 (generous), up to 1.8 g/L, the classic norm for lager yeast. At a different gravity you scale accordingly.
The article explains what happens in the fermenter. With too little yeast, cells must divide more often, stay longer in the growth phase and produce more esters and higher alcohols. He also notes that oxygen and unsaturated fatty acids suppress ester formation, and that a low pitch raises the demand for amino acids, which can lead to more fusel alcohols. Diacetyl is linked to the yeast's valine synthesis and disappears again when the beer gets enough conditioning time.
He looks at eleven dry yeasts available in the Netherlands, in five categories: neutral American top-fermenting strains, Belgian and spicy strains, wheat-beer strains, lager strains and kveik. He adds a fair caveat: strain-specific research is scarce, and many studies use industrial lager yeasts. I read it mainly as a good reason to experiment with your own pitching rates.
Source: Hobbybrouwen.nl
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