Hi all ! So, now that I have a bunch of new yeast strains available to brew (frozen from a starter, top cropped and bottom cropped) I would like to hear your opinions regarding them. The point is I don`t know wich one is healthier, sounds like frozen from a starter would be in first place, is it?. Neither frozen nor top cropped have performed a fermentation or a complete fermentation, so they would be less stressed. Could it be that yeasts that have fermented a 1050 or less gravity beer at the correct fermentation temp were healthier than the formers?. I would appreciate your opinions. Tebu
I don't freeze yeast often, so no comment. I will say that I reuse yeast often, always bottom cropped (washed), and for most strains I have no issue reusing 4 or 5 times
The frozen from a starter should be the most viable if you used a glycerol solution to freeze them. If you just used a wort or buffer solution and no glycol, all that yeast is dead. Also, when unfreezing, make sure you do it very slowly. I would recommend putting the vials in a glass or bowl of cold water in a refrigerator for a couple of days. All that being said, since the top/bottom cropped yeast has already been used, I would use that first and save the fresh frozen yeasts for later batches that will also make more top/bottom crops to really sustain your yeast bank for as long as possible.
Yes i have used glycerol, i thought top cropped yeast was very close to the frozen one in regards of health.
True, the top cropped yeast will be very close, especially this time. But the more times you use it, the more mutant yeast cells will grow. You should reuse top cropped yeast only 3-4 times (5 max if you use VERY tight fermentation conditions) to prevent mutant off flavors. Bottom cropped yeast get a little tricky because you only really want the middle layer of yeast. The reason is the bottom layer is the cells that flocculated too fast and propagating these ones could cause future premature flocculation and under attenuation. The top layer are the cells that flocculated too slowly and will cause future over attenuation; these also are the most likely to have developed mutant off flavors. So you should only use washed bottom crop yeast 1-3 more times.
