Rehydrating Dried Yeast
TroubleShooting
Justin Cooke - Yuma, Arizona asks,
The rehydrate/don’t rehydrate dried yeast debate has got me confused. So far I’ve only used SAFALE US-05 and pitched it dry in the wort for both of my batches. The beer was good in the first batch, and the jury is still out on the second since it’s still fermenting. Is there a final verdict you can offer me? Or should I just start strictly using liquid yeast? I prefer hoppy IPAs and beers with a good hop character and plan to brew those exclusively very soon.
It has been a while since I have used dried yeast and did a little reading before answering this question. All good references I found on this topic did not leave any doubt in my mind about what is best for the yeast cell, and that is to rehydrate dried yeast with water prior to pitching into wort (or must for any winemakers out there in the audience).
The basic reason behind this practice is that cell membranes serve a variety of important functions for the cell and these functions all require membranes that are fluid. And when dried yeast cells are hydrated in a liquid other than water, like brewer’s wort, there is a short timeframe when compounds that ordinarily do not pass across the cell wall do indeed cross the cell wall. This leads to a reduction in cell viability in comparison to yeast that has been hydrated in warm water. While the optimum rehydration temperature seems to be strain-dependent, the range cited is usually 95–105 °F (35–41 °C). As the rehydration temperature decreases, viability following rehydration also decreases; rehydrating in water warmer than 105 °F (41 °C) also decreases viability.
The likely cause for this on-going debate is that rehydrating in wort does not result in total failure. So the argument follows that rehydrating in wort works, therefore arguments about rehydration in water and improved viability are simply textbook. In practice, commercial breweries place yeast viability and vitality towards the top of yeast topics that clearly influence beer quality. I believe in the “put your money where your mouth is” gauge. Based on what is said and done vis-à-vis equipment investments in pursuit of yeast
viability and vitality, the logical con-clusion is that this is indeed a worthwhile pursuit.
My recommendation to new homebrewers is to add different techniques as the basics are mastered and when new and more advanced brewing methods are an avenue to either better beer or something of practical interest. I certainly would not suggest jumping from dried yeast to liquid yeast simply because there are two arguments about yeast hydration. You can certainly brew excellent tasting beer using dried yeast and the basic science suggests that hydrating in warm water prior to pitching is the best way to handle this type of yeast.
