Sunday, May 2, 2010

Making yogurt at home is cheap and easy

I am testing D'Adamo's Genotype 3 Teacher Diet. One of his characteristics of Genotype 3 Teacher is the tendency to be "accepting" of the world including infections. Part of what he recommends to boost the immunity of Genotype 3 Teacher is including yogurt and certain cheeses in the diet as well as brewer's yeast and probiotic cultures that are often found in yogurt.

Though I have been avoiding dairy foods for about five years, I decided to include yogurt and cheese in my diet to help build healthy flora that might help fight my acne, gum disease, and middle ear infection. I researched healthy flora and learned probiotics are the bacteria you want; prebiotics are the foods that help good bacteria survive; legumes, veggies, and wholegrain feed them, and fermented foods like Kikkoman naturally brewed soy sauce, tempeh, yogurt, and miso contain them.

I found at Walmart for $0.50 a 6 oz. (180 ml) cup of Weight Watchers yogurt that says it has live and active L. Acidophilus and Bulgaricus, Bifidobacterium SP. and S. Thermophilus. D'Adamo recommends specifically Bifidobacterium as a supplement for Genotype 3 Teacher, so I have been eating a bit of that every day.

My budget Friday night was very tight when I went to the grocery store (I had $11 to spend) so when I picked up chips, crackers, 2 pizzas, and a gallon of milk for my son, I also just picked up one cup of any flavored Weight Watcher's Yogurt for myself and decided to make a pint of yogurt with some of my son's milk.

How I Made Yogurt

Fermentation Temperature

Ideal: 110-115 F / 44-46 C (Update per apparently this is a bit too hot if your goal is to digest the lactose for digestive tolerance; 100-110 F / 38-44 C is better)
Maximum: About 120 F / 49 C
Mine: 76 F / 25 C to 118 F / 48 C

I made yogurt 20 years ago, so I knew it could be done with very little fanfare or special equipment. But I was a bit shy anyway, and my biggest concern was keeping the right temperature. But as you will see, the bacteria were very forgiving, and the yogurt turned out just fine even with a very poor system and very poor monitoring.

My research before starting told me the bacteria liked to be at 110 F / 44 C. After I started, further research and my experience told me the bacteria survive up to 120 F / 49 C or more.

I figured that keeping closest to the ideal temperature would keep my target cultures dominant in the milk. But at the same time, the preparatory sterilization procedures and the limited duration of the fermentation would limit the growth of undesirable cultures in case my temperatures weren't ideal, just as long as I didn't kill off the target cultures with a high temperature.

I think that if you made yogurt every week of your life, you would not need a thermometer. You would intuitively follow something like this chart according partially to the Burn Safety: Hot Water Temperature chart below from
Temperature and Time to Cause
of Water a Bad Burn on Adult Skin
180°F (82°C) 0.25 second
160°F (71°C) 1 second
150°F (66°C) 2 seconds
140°F (60°C) 6 seconds
125°F (52°C) 2 minutes
120°F (49°C) 10 minutes
110°F (44°C) 10 hours
106°-108°F (41°-42° C) Pain threshold
I also think in college I made a single, lucky batch of stiff, delicious yogurt in a shallow metal dish in an oven with a light without a thermometer. But Friday I felt I needed one, and I have a bedroom alarm clock with a thermometer. So I used the alarm clock in our oven. To avoid the cooling effect of evaporation that would make my yogurt cooler than my thermometer reading, I covered my yogurt bowls with plastic wrap.

I was disappointed to discover our oven does not have a light. So through the night when I got up to use the bathroom, I looked at the alarm clock thermometer and turned on the bake and broil elements briefly or fanned the oven as needed.

My yogurt was fermenting at widely variable temperatures as cool as 76 F / 25 C and at least as hot as 118 F / 48 C through the night.

If I do this more, I will get a light to put in my oven.  (Update: after having made yogurt many times, I've settled on a lighted microwave oven with door slightly ajar and a winter coat or blanket wrap as needed.  I also have a cheap candy thermometer.  I also tried a crock pot, but it was too much trouble.)

Fermentation Duration

Constant ideal temperature for 4 to 7 hours (2012 update: often at 7 hours there is still no thickening, but with a few more hours everything is perfect) is enough to make yogurt. Once the milk stiffens into yogurt, all you have to do is wait for the yogurt to get to the level of acidity you like, then cool it down. I made mine overnight with a lot of temperature fluctuation down even to room temperature and put it finished (pretty mild tasting) into the refrigerator after about 10 or 12 hours. In retrospect I might have liked to let it ferment a little longer just to more thoroughly turn that nasty cow milk stuff into something healthy.


If the yogurt cultures don't have to compete with other cultures, it really makes things a lot more foolproof. So I tried to keep things sterile.

I thought I would use two containers in case something went wrong in one. So while my son baked a pizza, let a spoonful of yogurt sit out to warm up, and I microwave heated about 1/2 liter (2 cups) of milk to a painful temperature (target 180 degrees) in my two chosen plastic bowls. I knew I would barely be able to touch 180 F / 82 C degree milk without being burned, and that it wouldn't ruin the yogurt if the milk boiled, and that at that temperature milk gets frothy. One of them got probably a little too hot and developed scum I skimmed off with a reasonably washed spoon. No big deal. The heating would have gone better if I had identical volumes of milk in identical bowls.

I happened to have new unopened yogurt, which was also a nice added sterility touch, but not necessary. So when the milk had cooled down to where it felt just slightly warm (I didn't have a thermometer to measure it, but I just did my best to estimate barely above the pain threshold), I spooned half of the warmed yogurt into each bowl then put the bowls into the warm oven and monitored it through the night.

Starter Yogurt

It's of course easiest to start with good yogurt. Nearly all yogurt sold in the USA is labeled as having live and active cultures. I chose a yogurt that had on the label the name of the cultures I wanted. It was Weight Watchers yogurt. It says it has live and active L. Acidophilus and Bulgaricus, Bifidobacterium SP. and S. Thermophilus. I don't know if that was important, or if all yogurts typically have the cultures I chose.

I don't know how little starter yogurt it's wise to use. If I do this more, I will experiment again with several concurrent little bowls and varying amounts of starter yogurt.


Heather said...

You're working awfully hard at this. Google "crockpot yogurt recipe" for a super simple way to make yogurt. If you are happy with the yogurt you've made, you can use the last of your homemade yogurt to start your next batch. My kitchen tends to be cool, so I wrap my crockpot in a towel and put the whole works in a cooler to sit overnight while all those little yogurt bacteria do their thing. I have 3 kids, and they can easily use half a gallon of yogurt in a week. If I happen to need new starter for some reason, I've found that Brown Cow brand, while not the cheapest, seems to make the best yogurt.

Thomas Gail Haws said...

Hi, Heather. I tried using my crockpot. It was okay. But for me, the microwave with light on (door ajar) is simplest. I wrap it in coats and the temp stays at 110 F all night and gives me really stiff yogurt lately. Like you say, yogurt is pretty forgiving, and there's not much need to sweat it.

Odile said...

If you really want to get rid of the lactose, ferment your yogurt for 24 hours. It will taste the same, but it will have more pro-B's and no lactose. Got this tip from