1. I recently brewed an English IPA with an OG of 1.065 using WLP002. I made a proper starter, oxygenated from about 1 minute, and fermented at 65ºF rising to 67ºF at the end of fermentation. The beer ended up fairly fruity (cherry and almost a little fruity/tart), which was the opposite of what I was trying to accomplish. The only irregularity was that I over chilled the wort to 58ºF, pitched, and then brought the temp to 65ºF over about 3 hours. Can you offer some tips for reducing fruity esters with English yeasts? How cool could you go for the first couple days?
2. I brew a yearly Belgian Strong Golden that is one of my most successful beers. I use and love WLP570 for it, but It's always a hassle to get it to clear. I usually keg, fine with gelatin and then bottle later. This year the yeast made more sulfur than it has in the past. What factors influence sulfur production in beer yeast? I have been "burping" the kegs for the last couple months and the aroma is greatly reduced but not gone. With wine one must be cautious with H2S because it can form mercaptans and disulfides that are harder to get rid of than H2S. I have used CuSO4 at work for such problems. Is there a risk to allowing beer to have some sulfur for extended periods? Once bottled, it will never go away right?
Chris and Jamil answer:
You want to avoid stressing the yeast, causing them to express heat shock proteins with large temperature changes. It would have been better to change the wort temperature before pitching the yeast.
As for fruitiness, it is a complex question that depends on the pitching rates, oxygen levels, yeast health, nutrients, wort gravity, temperature, etc. Keep in mind that in general low cell counts + heat + oxygen will result in more ester production. Stress will cause yeast to produce more sulfur. Stress comes in many forms, but the most common causes would be temperature changes, high gravity worts, or a lack of certain nutrients. H2S is related to yeast growth, but normally the evolution of CO2 from fermentation will drive the sulfur off. Capping fermentation early or dropping the temperature early can trap more sulfur in the beer. Wort spoilage organisms can also create H2S.
It is important to taste your beer before kegging. If you notice that a flavor needs correcting, it is often easier to keep it in the fermenter and let the yeast help by raising the temp a little. H2S is quite volatile and mostly blows off, while SO2 can combine with aldehydes, forming compounds that persist.