In my experience as a brewer, I have found that yeast washing is not necessary in most cases. When it comes to pitching yeast for a new batch of beer, there are a few options you can consider.
One option is to pitch fresh slurry directly from a yeast cake. This is when you take the yeast that has settled at the bottom of the fermentation vessel after a previous batch and use it to ferment a new batch of beer. Pitching fresh slurry can be done within a week of the previous fermentation, as the yeast is still healthy and active. This method is convenient and saves time, as you don't need to go through the process of yeast washing.
Another option is yeast washing, which involves separating the yeast from the trub and other unwanted materials that have settled at the bottom of the fermentation vessel. This can be done by collecting the yeast slurry, rinsing it with sterile water, and then collecting the clean yeast for future use. Some brewers prefer to wash yeast to remove any potential off-flavors or contaminants that may have accumulated during fermentation.
However, it's worth noting that yeast washing is not always necessary. Many brewers have reported no ill effects from pitching unwashed yeast, even after several months or up to a year later. I have personally pitched unwashed yeast that has been stored in the fridge for a few months without any issues. The yeast remained viable and produced a healthy fermentation.
If you choose to wash your yeast, there are a few important considerations to keep in mind. Firstly, cleanliness is crucial. Make sure all equipment and containers used in the yeast washing process are properly sanitized to prevent any contamination. Secondly, it's important to handle the yeast gently to avoid damaging or stressing the cells. Vigorous shaking or stirring can result in cell death and reduced fermentation performance.
While yeast washing can be an option for preserving and reusing yeast, it is not necessary in most cases. Pitching fresh slurry from a yeast cake is a convenient and effective method, and many brewers have successfully pitched unwashed yeast without any issues. Ultimately, the decision to wash or not to wash yeast depends on personal preference and brewing practices.