I made my own yogurt today and I feel so accomplished!! I was also totally astonished at how easy it was and how extremely inexpensive (I'll detail that later) it was.
I used my Super Baby Food book for guidance. In it the author, Ruth Yaron, explained in detail how she always made her own yogurt for her children - among all the other healthful things she did/does.
I bought a yogurt starter from Whole Foods rather than using premade, commercial, plain yogurt as my starter. The starter came with 6 packets of freeze dried live active cultures for $3.99. I used 2 packets in my first batch because it's one packet per quart and I used 2 quarts of milk. I will reuse my own yogurt as my starter for the next many batches (probably several months) so won't dip into my store bought supply for a while.
* Scald the milk (bring it to a boil (or 185 F) SLOWLY in a stainless pot) I just stuck my candy thermometer on the side and let it slowly heat to 185
* Removed from heat - left the thermometer inside and let it cool to 115 F
* Sat the thermometer on the rack in the oven and preheated my oven to the lowest temp. it would set for (it's all digital and 170 was the lowest it would go), then turned it off and cracked the door until the temp. dropped to 120 (ideal incubation temp. is between 100-115).
* Poured a little milk into one of the jars (I just used pint -16oz- mason jars) and mixed in the two packets of starter and stirred until the starter was dissolved.
* Returned that back to the pot and mixed it all in well
* Filled each jar appx. 3/4 full and put the lids on (pretty loosely)
* Placed all jars inside a rectangle cake pan for stability then sat the pan in the oven and turned the light on.
* The oven was cooled to around 115 and stayed there for the duration of the incubation -5.5 hours- the light being left on kept it just warm enough after the initial preheat to keep it at a perfect temperature for the bacteria cultures to activate.
I know all these steps seem really complicated but really it was super easy. The only thing it required was me planning to make the yogurt on a day I would be home all day and just keeping an eye on the temp. of the oven.
It's been in the fridge since about 4:30 this afternoon cooling and I have just now tasted it for the first time and it's pretty good for a first-timer! It's a little stronger than I would normally like (but a little honey mixed in will fix that), which means I kept it a little too warm. Next time I think I'll just turn the oven light on while I'm doing all the prep and by the time I get ready to put it all in, it should be just the right temp. - no preheating and then cooling the oven. Trial and error.....
Here's the best part of making your own yogurt: I get my milk for free thru a state program for low income families (US residents will know this as WIC) and since I'm pregnant now we get so much milk that we can hardly use it all (I get 5 gallons/month, Jacob gets 2 and Eli gets 3), so essentially all it cost me to make this yogurt was $1.33 (for 1/3 of the yogurt starter pack I bought). I would normally buy organic 6oz containers of yogurt and those are $.99 EACH. So I basically saved $7.60 for 2 weeks worth of yogurt. I know it doesn't seem like a lot to some of you, but trust me, it is a lot to us - that's $15 extra/month added back to my grocery/cleaning supply/diaper budget. And because it's so much cheaper we can actually use more than we normally would - this means extra parfaits and smoothies for us. YUM!