Many forum members have lauded this yeast culture, but few have lauded the fact that it is a true top-cropping culture. If one watches the following YouTube, one learns that the standard practice at Timothy Taylor is to top crop. This fraction of the Timothy Taylor video explains their fermentation process: https://youtu.be/4Cak4stt9v4?t=620
With that said, here is what a Wyeast 1469 ferment looks like after the brown head has been skimmed and the second head has been allowed to form:
Here's what the head looks like top-cropped (there is still quite a bit of CO2
in the crop):
Here's a closeup photo:
The beauty of top-cropped yeast is that it is naturally purified, which is due to the fact that non-domesticated yeast and bacteria do not floc to the top. That is why top-cropping breweries can repitch hundreds to thousands of times. In a typical American craft brewery, bottom settling yeast cultures are preferred. That is a practical problem for amateur brewers because one cannot place selective pressure on the bottom-settling culture by cropping from the top. Yet, there is the constant threat from native microflora that sets an upper bound on the number of times a culture can be repitched without going back to a seed culture.
In a commercial brewery, the real threat to repitching is the cylindroconical fermentation vessel. Please do not get me wrong. Conicals were a major advancement in brewing technology from a production point of view. It is just that the hydrostatic pressure placed on a culture in the cone of a sizable conical more easily results in yeast cell oxidation via reactive oxygen species (ROS). ROS causes respiratory petites to be formed. That is not a problem for home brewers because the hydrostatic pressure to which yeast is subjected is trivial. That means little in the way of petite mutation at the home level. The bigger threat from home-based breweries is house is house microflora. What I have learned over the last 29 years is that if one manages a spot in one's home where fermentation takes place regularly well, the dominant microflora in that area tends to become domesticated brewing yeast. Cleaning and sanitizing usually results in native flora numbers being reduced to a point where they are not a threat. In essence, the longer a brewery remains in existence, the cleaner its products. By clean, I do not mean squeaky clean. I mean free of weird aromas and flavors, even if they are barely at threshold level.