Why re-pitch your brewing yeast? 

It won’t come as a surprise that at Bluestone we’re big advocates for liquid yeast. Compared to dried yeast, it can provide enhanced esters, higher flocculation, purer flavours and aromas, as well as numerous other benefits. Not least of these is that you can re-pitch it multiple times. While the process of re-pitching does offer some challenges, and a little extra work, when done correctly, the juice is definitely worth the squeeze.

So, why skill yourself in the art of re-pitching?

  1. You can save money

The main reason brewers choose to re-pitch yeast is financial. We’ve calculated that a brewer re-pitching yeast over the course of seven 1000L brews would save around $2500 compared to using two bricks of dried yeast for each brew (our calculations are in the chart below). For probrewers these savings over the course of a year are significant.

table showing relative yeast prices

  1. It’s kinder on the environment

If you’re looking to burnish your green credentials and reduce your impact on the environment, re-pitching yeast makes a lot of sense. Reusing the yeast you’ve already got reduces transport emissions as well as cutting back on packaging waste. Choosing a local yeast supplier also reduces your carbon footprint as you’re not transporting yeast from Europe or North America.

  1. It makes you more self-sufficient

As we’ve learned from the pandemic, external forces, which are out of our control, can really disrupt supply chains and your brewing processes. Having your own source of yeast means you’re less dependent on others and more resilient to external events. Choosing a local yeast supplier also eliminates the risk of international shipping disruptions.

 

Re-pitching 101

 

The act of reusing yeast for brewing is almost as old as the process of brewing itself. While not properly understood at the time, early brewers saved yeast from one brew and used it to inoculate another. While we now have more sophisticated methods, and advancements like the microscope and refrigeration mean we’re less reliant on luck and guesswork, the fundamentals of the process remain the same. If you’re interested in diving a little deeper into the process, we’ve put together a step-by-step guide on how to re-pitch brewing yeast (add link here).

 

Navigating potential pitfalls

 

Yeast Health

Brewing can be a stressful process, and not just for the brewer. As alcohol levels rise, and sugar and pH levels drop, beer becomes an inhospitable environment for yeast cells. Once yeast has played its part in the brewing process, it’s living on borrowed time.

For this reason, we advise harvesting the yeast from your brew as early as possible – usually around day five or six. You want to get it before it starts to run out of food and die off.

It is also important to harvest the yeast before dry hopping or the use of additives as these can introduce infections that can be passed from one brew to the next via the collected yeast.

Once the yeast has been extracted it should be stored at 2C. This slows the yeast’s metabolism and helps delay death until the yeast can be re-pitched in a happy environment of fresh wort. Please also note, the yeast should be re-pitched within one week of refrigeration.

It’s vital that anything coming into contact with the yeast while it’s being harvested and transferred to a storage vessel is sterilised – including the storage vessel. Any contamination during harvesting, transfer and storage will be passed on to your next batch of beer and potentially compromise it.

 

Quality control 

The first test you should undertake before re-pitching a batch of yeast is on the beer it has just brewed. If this brew is showing any signs of faults, or it’s not hitting the sensory notes you’re expecting, it’s not advisable to re-pitch the yeast.

The second test you should undertake is to check yeast viability – or the percentage of living cells in a cell population. For more information on how this is done, you can read this article on checking yeast viability. If your cell count shows viability is low, then it’s not advisable to re-pitch the yeast.

 

In summary

Part of the appeal of brewing beer resides in its many traditions. Brewing different styles of beer and employing different brewing techniques creates a link between now and then, here and there. The act of re-pitching yeast has been around for centuries and has helped in the development of most well-known styles and breweries. So, when we re-pitch our yeast, we’re creating a link between one brew and the next as well as a link to many long-standing brewing processes.

Happy brewing!

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