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Success at last! Yogurt after 20 years of trying...

The other day Julius and Sara were talking about their goat cheese making adventures, and the conversation quickly turned to lyophillized lactic acid bacteria and how easy it made the whole process. From there it was a short segue into talking about yogurt, which requires a bunch of fancy named bacteria (Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus to name a couple, there are other Eurasian exotics... that don't figure in this story) who spend their time eating the milk sugars, excreting lactic acid and forming denatured protein webs until the milk has set.

I remember my mom making yogurt in the oven when I was little. She seemed to have a pretty good success rate, producing tangy yogurt that was too strong for my juvenile taste buds and only a couple times ending up with sad goopy sour milk. I've been experimenting with making yogurt every couple of years or so for the last 20 years. Scalding the milk, adding "live" starter yogurt purchased at the supermarket, putting it in the oven, waiting over night only to find slimy stringy goopy nonyogurt-like product that to my dismay tasted too incredibly sour to eat.

Then Julius generously offered to give me their packet of yogurt starter culture since they weren't using it. I took them up on their kind offer and went home entrusted with the "special stuff" determined to make a go of it. This time I used whole milk, and rigged up 2 thermometers for a water bath in my rice pot. I heated the milk to 80oC and waited for the temp to drop adding the culture at 40oC, then floated the glass jars in the water bath, whereupon they sank to the bottom mixing the milk with water :{ I tried again with my last 12 oz of milk and another spoonful of starter culture. Sealing it into the insulated rice pot for 7 hours.

SUCCESS! A Firm solid set but still with an ethereal melting mouth feel and a tangy but not bitter taste.
The only sad thing was the very small amount I managed to make.

Next day I got some non-fat milk and milk powder and tried again, this time using the larger crock pot. I mixed in the milk powder, 3 heaping Tbs to 1 quart of milk, then heated the milk to 180oF, whisking to dissolve the lumps. Once the milk had attained the upper temp I cooled the milk in the water bath until it equilibrated at 110oF, mixing in the starter culture. Then left it to sit in the water bath (aka crock pot- I switched it on every so often to maintain temp- it was not as well insulated as the rice cooker) for 6 hours by which time it had set firmly. A comparison between the two versions revealed that I prefer the higher protein content texture of the milk solid fortified yogurt but the creamier taste of the whole milk- the finish is better on the back of the tongue. They tasted the same, but had a slightly different mouth feel. I think for everyday eating the non-fat milk is fine, altho for a dessert option I would use whole milk. Both times I took a small vertical section of the jar (to ensure complete sampling of various layers of bacteria- apparently sometimes they stratify?) for starter next time I make yogurt. You can freeze it for months, thaw and use just like the powdered culture. I won't feel confident until I've managed to do this multiple times, but at least I recognize now that I need a thermometer in my arsenal to truly attempt yogurt.
Good luck with your efforts!

http://caloriecount.about.com/calories-yogurt-plain-whole-milk-8-i1116

Update: The longer you hold your milk at 80oC the firmer the set is. I've also started putting a teaspoon of yogurt in the bottom of each jar and this helps too. Now I use fat free milk, milk powder & starter culture and maintain heat in the crockpot at 40oC for the first 30 minutes, then I allow it to cool normally over the course of 6-12 hours.

A friend turned me onto this sous vide controller, which essentially makes it so you don't have to watch as closely

http://auberins.com/index.php?main_page=product_info&cPath=8&products_id=44
or just get a more modern slow cooker...