I’ve been steadily using my new yogurt maker. It’s like a microscope: I can see things I never saw before. I started with the recommended fermentation time: 12 hours. Then I did batches at 16, 20, 24, and 28 hours. The yogurt grew steadily more sour. The increase was remarkably clear. I am unable to find this crucial info anywhere on the web — that 28 hours produces more sour yogurt than 24 hours, etc. By making my yogurt much more sour than commercial yogurt I’m getting a lot more of the crucial ingredient (bacteria).
The results are so clear, I think, because I’m starting with a hyper-pasteurized product (which can be stored at room temperature) and the yogurt maker holds the fermentation temperature very constant. Constancy of temperature means constancy of selection means greater population. (The theory behind the Shangri-La Diet says the main reason for the obesity epidemic is that we’re eating food with exactly the same flavor from one instance to the next — from one can of Coke to the next, for example.) If the temperature is 120 there is selection for bacteria that grow best at 120; if the temperature goes down to 110 many of those bacteria die and are replaced by bacteria that grow best at 110. If the temperature goes back up to 120, those bacteria die . . . and so on. More temperature variation means more diversity of bacteria but less number of bacteria. I’ll get my diversity of bacteria elsewhere — from kombucha, say.
I suspect that commercial yogurt makers are time-limited. If they fermented twice as long they could only make half as much. The average yogurt buyer has no idea that more sour = more healthy, so they couldn’t charge more.
Although the yogurt maker’s box shows the machine set to 32 hours, the actual maximum time is 24 hours. To get 28 hours I reset it during the process.
The official website of the National Yogurt Association, aboutyogurt.com, contains nothing about how to make yogurt.
The Salton Yogurt Maker might be the best yogurt maker available in America. I can’t tell if you have to preheat the milk — the worst part.
More Does more sour = more healthy? I agree with the two commenters who suggest that the number of live bacteria probably goes down after a certain point as the mixture becomes more acidic. The number of live+dead bacteria, however, probably continues to increase. My guess is that the total live+dead is maximized when the yogurt is most sour; the number of live bacteria is maximum around the tme that the acidity is most quickly increasing, somewhere in the middle. I think the digestive benefits come only from live bacteria but that the immunostimulatory benefits come from both live and dead bacteria. I find it hard to believe that the immune system can tell whether bacteria it encounters are alive or dead.