In the recent "Very liquid sd" post, there was a lot of information on yeast vs. bacteria. One thing that I found confusing is this: I have heard from other sources (including at a class at SFBI, assuming my notes are correct) that w.r.t temperature, lower temperatures restrict yeast activity *more* than bacteria activity. This also seems to match with my (naive?) experience: if I leave a starter in the fridge, it takes forever to double, but the sourness is there in 12-24 hours easily. But, but, in the earlier thread Debra Wink says:
"Dan gave us a good overview of how dough is affected by hydration (some cereal chemistry as well as metabolic effects), but now let's take a look at how the culture is affected---the population dynamics---because that will determine the magnitude of the metabolic effects. Lowering hydration will slow all the microorganisms, yes, but yeasts are not quite as sensitive to it as the lactobacilli. In other words, the growth rate of the bacteria declines more sharply than that of the yeasts. Sourdough LAB thrive in warmth at high hydrations; low hydration and cool temperatures really slow them down. Yeast benefit from this, because they have less competition from the bacteria, so they have more space, and the resources to expand. They aren't quite as hindered by low hydration, low temperature, low pH, salinity, etc., as lactobacilli are, so even if they do slow some, they gain an edge because the bacteria are slowed more."
i.,e, the exact opposite of what I heard at SFBI, read elsewhere, and my experience, w.r.t the effect of temperature on yeast vs. bacteria. Can someone (Debra?:)) clarify the effect of temperature on acidity and bacteria, please? Thanks.