how to fix your yogurt

I've been making yogurt for a couple of years now, I think.  I used El's method:  heat milk to 180 cool to 116, add a tablespoon of yogurt and stick in a cooler with a jar of hot water for 8 hours.  It worked.  Every once in a while I'd get a runny batch, and once in a while I'd pick up a fresh culture (ie, storebought yogurt).

For some reason, I had a string of bad batches lately.   Everything was the same--equipment, temps, milk, culture (though I did try a new brand to see if that was the issue).  Totally runny.  Even straining it with a coffee filter had dismal results.  

So after a bit of frustration (and one accidental batch of ricotta when I tried to experiment*),  I finally remembered to turn to Sandor Katz and the Wild Fermentation book.  Lots of good tips:

• Don't be tempted to add more culture to a batch thinking it will make it thicker. His explanation made sense to me from sourdough bread experience: You are aiming to achieve the perfect "population" of  organisms to get the culture to your desired product. Too many good bacteria, too little food, and they will peak and start to die off, leaving their end products behind (in both cases, a sour watery-ness). His rule of thumb is 1 tablespoon per quart of milk.  
• Longer is okay:  8 - 12 hours of culturing, even up to 18, is fine.  I always worried about going longer, but its a range, really.  You might get you some extra tang, but won't affect safety.
• Cooler is okay too--Katz's cooled temp (before adding the yogurt) is only 110 degrees.   Obviously there is some flexibility to different recipes.  So, like everything, find the method that works for you.
• Finally:  He had tips for failed yogurt.  One--let it go longer, after 8-12 hours, if not thick, add more hot water (to the cooler, or replace your jar of hot water with a fresh one) and let it sit another 4 hours or so.  Two--add a little more culture, stir it gently, and let it sit (again, check after 4 hours or so).

fresh raspberries for breakfast in nearly-November are a treat!

So what worked for me?   A little of everything. I started cooling my milk to 110.  My first new batch was still watery after 8 hours, I panicked and added more culture AND more hot water and let it go another 5-6 hours.  PERFECT.  The next batch, I checked after 8 hours (pretty watery), then replaced the hot jar of water and let it go another 4. Perfect.  This last bach:  I just let it go 12 hours without disturbing, and it came out just fine. Yay!

I don't know what changed for me, I am tempted to ask the smallish dairy that I get milk from if they had any changes--bad hay year, different feed, lots of young cows? (That's the nice thing about using a local producer, I know the milk I'm getting is only from 2 farms, not hundreds!).  But for whatever reason, a longer fermentation period seems to be what I need.


* Oh, and as for the ricotta, learn from my mistake and don't re-heat your failed yogurt thinking you can start again.  Reheated acidified milk is how you make cheese!  I'm not really a cheesemaker, but I've dabbled, and I realized once the curds formed what had happened.  I strained off the whey and voila!  Creamy ricotta!  Another good way to use up a failed batch of yogurt besides muffins and biscuits!