Yogurt

I've been eating store-bought yogurt for many years. Some have suggested that my original attempt to make kefir from store-bought kefir was actually yogurt. Considering how easily it thickened, that may be right. Now, seemed to be the time to try making yogurt on purpose.

One motivation is economics. I pay $1.29 for a container of yogurt that is about 3/4 of a cup. A gallon of milk is $2.59. If I can turn that gallon of milk into twenty-one 3/4 cup servings of yogurt, the cost of one serving comes down to 12 cents. OK, saving $1.17 per day on yogurt is not going to fund my retirement.

Another good reason to make yogurt myself is that I know what is in it. The whole theme of this blog is to nurture the microbes that have taken residence in my gut. The yogurt container says it has live cultures. I believe it, but making new yogurt from the store-bought is proof.

The other issue is fat versus sugar. Many of my favorite yogurt flavors proudly proclaim that they have 0 grams of fat. Unfortunately, they make up for the lack of fat by adding sugar. There isn't too much fat in my diet, but there is too much sugar. So, that settles it. I'm going to make my own yogurt.

I found instructions in a book titled fermented foods at every meal (yeah, they didn't use capital letters) by Hayley Barisa Ryczek.

The process starts with a confusing step to heat the milk to 185°F and then letting it cool to 110°F. Why not just heat the milk to 110°F and be done with it? I guess the answer has to do with a change in the protein structure that happens when the milk is heated. I dutifully followed directions. This process took quite a bit of tending and it left a film on the bottom of the pan that was difficult to clean. I might try a Pyrex measuring cup in the microwave next time. Once I figure out the heating time, that process should be repeatable.

Update: Next time I tried the microwave. I started with 12 oz of milk from the fridge. I nuked it for 2 minutes, and that brought the temperature to 100 degrees. Then, another 30 seconds for another 20 degrees. Another minute brought it to 160 degrees. I stopped it after an additional 40 seconds when it started to boil. My thermometer read 200 degrees. Next time, I am going to try 3:30 and see where that leaves me.

The milk took much longer to cool to 110 degrees in the Pyrex measuring cup, than in the pan. I had to wait about 40 minutes. Still, I like this method better. I can just toss the measuring cup in the dishwasher. The pan was a little troublesome to clean.

My recipe called for a quart of milk and 1/4 cup of yogurt used as a starter. I was just experimenting, so I used 1 cup of milk and 1 tablespoon of yogurt. I wanted to test two brands of commercial yogurt for live cultures, so there were 2 cups of milk total.

Another confusing step in the recipe asks me to combine the yogurt with an equal quantity of milk before adding it to the rest of the milk. Why? I don't see any reason for this. I just put a tablespoon of yogurt into a mason jar, added a cup of milk, and shook the contents.

Incubation

The next step in the process is to incubate the yogurt for 8 to 24 hours. There were many ideas suggested for keeping the developing yogurt near 100°C during the incubation. I have an electric thermal storage heating system in my house. The night before my yogurt trial, I put a mason jar filled with water on top of the heater. In the morning, the water was around 90°F. That seemed close enough for me. I'll need to explore some other options after the heating season is over.

I incubated my yogurt for about 20 hours. 

Results

My starter cultures came from a carton of Chobani yogurt and from a carton of Stonyfield Farm yogurt. Both claim to have live cultures, and both yielded successful homemade yogurt. Hence, there are live cultures in both brands, as advertised.

I tilted the jars here to show that the yogurt thickened properly. The yellowish color is just a remnant of the lighting. The yogurt was the expected off-white color and it tasted like unsweetened yogurt. Chalk up another success.

I've read that the incubation time will affect the sweetness of the yogurt. The longer that it incubates, the more lactose (milk sugar) that the bacteria eats, and the more lactic acid it produces. Thus, shorter incubation periods yield sweeter yogurt. I'll experiment with that in the future.