Yogurt didn't set up, Troubleshooting help

[ctrygirlatheart]

What went wrong here?  I tried to make my first batch of yogurt a couple of days ago, I've made cheeses before without any issues so yogurt seemed easy enough, but it never set up.  I scalded the milk (is this even needed?), added the cultures and transfered everything to a quart jar that I put in a pan of water and put in the oven.  I turned the oven on warm on and off through out the day when the temp felt too low and twelve hours later still  milk.  What did I do wrong?

[rush2ady]

Was the milk too hot when you added the culture?  Maybe you killed the culture.  Other than that, seems like your process is a little complicated, but it should've worked!

And technically, it's not necessary to boil the milk before adding the culture.  If I am using pasteurized milk from the grocery store, I will boil it first, then let it cool just enough before adding the culture.  If I'm using my fresh raw milk, I won't boil it, but warm it up enough to then add the culture. 

If you boil the milk, it kills any bacteria (good or bad) in the milk... this will maintain the purity of your yogurt culture. 

I don't boil the raw milk first because I want to preserve the naturally present good bacteria and enzymes.  But this will effect the yogurt culture, and can change taste over time as the bacterial composition changes.

[Llyra]

The most likely thing is that at some point the milk was too hot, and you killed the culture-- either when adding the culture, or during the incubation. Most of my yogurt failures have been related to too much heat. If you're going to make it in the oven, you may need a thermometer, to be sure your oven isn't getting too hot. The ideal temp for yogurt is between about 108 and 112 F. If it's hotter than that at any point during the process, even for a short time, the culture may not survive. I know my oven on "warm" is about 180 F, which would be too hot.

I would highly recommend using a reliable thermometer, to check the milk temp before you add the culture (you have to let it cool after scalding) and also to check the temp of your oven. I myself use a yogurt-maker that plugs in-- to me, it's just simpler. We make a LOT of yogurt-- a quart every second day-- and I'd drive myself nuts trying to do it in the oven or on a heating pad.

[ctrygirlatheart]

Definetly killed the culture then, the instructions on the culture didn't say anything about letting it cool after the scald!  Will try again today.  Thanks!!

[MyLittleWarrior]

Yep, after the scald cool it down to about 110* before adding the culture.  Also, I have a gas oven and range, and the pilot light in my oven keeps it at the perfect temp, so I just culture my yogurt in the off oven with the door closed.  I've heard of people with electric ovens leaving the oven light on for warmth and culturing yogurt that way.  Some people use a water bath in the crock pot, but this also requires frequent temp checks.  I've had good luck wrapping my yogurt jar in a heating pad set on low and covering with a dish towel too.  Good luck with your next batch!