Does yogurt "wear out"??

[ccrow]

OK, so I used Stonyfield Farms yogurt as a starter for a batch of yogurt that came out fine. Then I used some of that batch to make the next one; it came out not smooth, but leaning toward ricotta texture, & was a bit more tangy. Then I tried to use some of *that* batch to make more... nothing happened. I scalded & cooled the milk as usual, stirred in the starter, left it in a warm oven as usual, but after 5 hours all I had was warm milk with a slight yogurt flavor. Anybody know what went wrong?

[RosemaryHoney]

I've had similar trouble making yogurt from my own homemade yogurt. Sometimes it works fine, other times I have poor results. Now I buy a tub of yogurt (I've been using Siggi's), divide it into ice cube trays, freeze it, and store the cubes in a freezer bag, using each one as my starter. That way it's a fresh starter each time. It works really well, and I haven't had any trouble.

[nofunlatte]

That's a great tip, RH! I didn't know you could freeze yogurt. Do you just take out a couple of cubes and thaw them before putting them into the scalded milk?

[RosemaryHoney]

Yes, completely thaw the yogurt cubes in the fridge, and proceed as you normally would.

[ccrow]

Thanks for the replies! I don't think time would have been a factor, it was about the same each time- definitely less than 2 weeks. I asked my son(microbiology major) about it & I think I may have inadvertently selected for more heat-loving bacteria while making it. Time to experiment a bit I think. Or just buy it; I do like that cream on top, lol.

[Sam Fujisaka]

I buy and use "fresh" starter every fourth batch. Each successive culturing gives me a slightly more tangy flavor; and the third batch is not quite as vigorous in that the yogurt thickens just a bit less.

[scubadoo97]

I've noted the increase in tang from successive batches

[kerosundae]

hmm... I've always used yogurt that I make as starter for the next batch unless I don't have any on hand (I finished the last bit because it had been too long since I last made it); so as zeldog suggests, it may be because there was too much time in between? I would've thought the contrary--the longer you leave it the more dense the yogurt population, until you cross the threshold where they all die out; but if it tastes fine, it should me that it's still alive.

[Zeldog]

I've seen one or two recipes where they say not to re-use a starter more than twice, but they never said why. I just made my third consecutive batch (which is 2 re-uses) with what was originally Fage yogurt and it is every bit as good as the first one. But I've gone no more than 2 weeks between batches. If you go longer the bugs might be less energetic.

There are lots of yogurt makers out there. I'm sure they will comment.