How Many Times Can We Re-Pitch the Same Yeast?
The re-pitching of yeast is a frequent topic of discussion among brewers, both commercial and amateur.
Re-pitching is a practice of recovering the yeast cake after fermentation and re-culturing or re-pitching it directly. This is a common practice in most breweries. Harvesting and re-pitching allows a brewer to spread the cost of the culture over several brews. Brewers typically can re-use yeast for seven to ten generations, provided they follow sound harvesting and storage practices.
Although there are many “rules of thumb” and anecdotal guidelines about how frequently re-pitching can be done before the yeast profile changes (mutation), no one has arrived at a solution to know precisely the composition of a yeast culture (all microbes) and how they might change from pitch to pitch.
Theoretically speaking, barring any outside influence in a totally sterile environment, a yeast strain should be able to used time and time again. However, it’s nearly impossible to maintain a 100% sterile environment free from any outside contamination. With every harvest, there’s a chance of outside contamination. Because of this, it’s been extremely difficult to pinpoint an exact number times yeast can be successfully re-pitched.
Yeast Harvesting Guidlines
Experts say that all yeast in the brew house can’t always be successfully re-pitched. However, they offer some general guidelines, such as:
- Opt for the youngest generation of yeast available for harvest because using fewer generations will minimize opportunities for mutation or contamination;
- Harvest from a low gravity and low hopped beer, as high gravity and/or highly hopped beers can stress the yeast and have detrimental effects on future fermentations;
- Don’t harvest yeast from beers with alcohol contents greater than 6.5%- ABV; and
- Harvest yeast from fermentations with normal fermentation characteristics.
The amount of yeast harvested also depends on many factors, such as the number of batches the brewer needs to inoculate and the amount of time between brews. The variables also include whether the culture is void of sterols, enzymes, and glycogen, and whether there’s poor cell membrane health.
The solution to all this guesswork and to controlling all the variables is FlavorDNA.
FlavorDNA is microbial analysis that will uncover your brew’s flavor DNA. This next generation sequencing (NGS) provides rapid turn-around and complete profiling for brewing consistency.
Brewers who use FlavorDNA profiling know precisely the composition of a yeast culture (all microbes) and any change in that composition from pitch to pitch in rapid and comprehensive fashion.
FlavorDNA also provides cost savings of requiring new yeast or preventing significant changes because of off flavor profile variation.
FlavorDNA Market Study
We are currently conducting a market study open to brewers who qualify. Approved brewers will receive up to three FlavorDNA analysis at no charge. For more information, or to see if you qualify for this study, please contact us at (424) 247-6203 or firstname.lastname@example.org.