I have two runny jars of yogurt in my fridge. One is actually being strained right now…and has the right texture of yogurt, but isn’t sour at all. I’m perplexed by this – I used the same milk (Grass Point Farms whole milk) and cultures (Fage Total) as last time, and all three batches taste and smell completely different. Time for a little research…
And so I find, in Fundamental Food Microbiology by Bibek Ray (2004), that this creaminess and sweetness is likely due to this batch of yogurt having a higher ratio of Streptococcus thermophilus to Lactobacillus bulgaricus, resulting from fermentation (incubation) happening at a lower temperature:
“If the temperature is raised above 110°F, the Lactobacillus sp. dominates, causing more acid and less flavor production; at temperatures below 110°F, growth of Streptococcus sp. is favored, forming a product containing less acid and more flavor.”
These experiments were a further development of my tea light method. I decided to experiment with whether the material of my yogurt jar made a difference in the solidification of the yogurt – I’m thinking a lot about heat dissipation these days, through ceramic vs. glass. So, bringing the experiment another step toward what it will be like on the road, I also set the containers outside in the cooler. (The air was cooler, so when I woke up in the morning I closed the lid a little bit, propping it open with my tent poles. I think I’ll do this from the beginning from now on.)
So, the method works well enough. I still want my yogurt firmer throughout, however, instead of just thick at the bottom and all watery at the top, and I suspect this may contribute to the slightly bland and watery taste of the final yogurt (in addition to my not-favorite Fage cultures being somewhat bland, in my opinion), so tonight I’m going to try a couple more tea light methods on a ceramic tile to encourage more regular and even heat dissipation, like a pilot light, which (I discovered in lifting up the top of my stove) is certainly hotter than a tea light but whose heat is deflected from the stovetop by a metal tab and a heavy enameled metal stovetop.