Dear Food Doc: I eat a lot of yogurt and recently purchased a yogurt-maker to make my own yogurt at home. Do you have any suggestions for making healthy, home-made yogurt?
Dear reader: It’s amazing how popular yogurt has become. Consumption has doubled in just the past 10 years. The grocery store dairy cases are full of different yogurt products.
Although consumers like the novel flavors and textures, the health properties of yogurt are also driving this demand. Yogurt is an excellent source of protein and calcium, and, of course, healthy bacteria. Indeed, for more than 100 years, scientists have studied how yogurt bacteria improve gastrointestinal health.
Yogurt is perhaps the first “health food." After all, according to the Bible, Abraham ate yogurt and he lived to 175.
Yogurt is also easy to make, even if you don’t have a yogurt machine. For ingredients, all you need is milk and a source of culture. Many store-bought yogurts have a long list of ingredients, including thickeners, sweeteners, and flavors. While they perform important functions, you can make a perfectly fine homemade yogurt without them.
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The milk can be skim, low-fat, or whole. The higher the fat, the richer and creamier the yogurt. Of course, a cup of whole milk yogurt will contain about 70 additional calories compared to skim milk yogurt.
Heat-treated milk makes the best yogurt. This involves raising the milk temperature to about 180 F and holding it there for 25 to 30 minutes. This is just below boiling so you need to stir constantly and not overcook. A double-boiler is ideal for this. Use a thermometer rather than guess.
Another suggestion is to add a half cup of nonfat dry milk powder per liter of milk. The milk powder and the heating step perform an essential function. Specifically, when the milk proteins are heated, their ability to bind water is significantly enhanced. Otherwise, your yogurt will be thin and watery.
After the heating step, cool the milk in the fridge or an ice bath. When the temperature reaches 105 to 115 F, it’s time to add the culture.
Yogurt cultures are available from online sources or from natural foods stores. Alternatively, a store-bought container of plain, unflavored and unsweetened yogurt can be used as the culture source. Most commercial yogurts contain live cultures, but to be sure, find one that has the “live and active” seal. Also, yogurt bacteria become sluggish during storage, so the fresher the better.
How much you need depends on the culture. The powder forms are very concentrated. A single teaspoon can make one liter of yogurt. In contrast, it takes about 10 teaspoons of fresh yogurt to make a liter of yogurt. To ensure even distribution, mix the culture with a small portion of milk, then add to the rest of the mix.
The yogurt can ferment directly in the container. The other option is to dispense and ferment in individual cups.
Incubating the inoculated milk is easy if you are using a machine. If not, you need to devise some means of maintaining the temperature at 105 to 115 F. While the August temperatures in Nebraska might be in that range, yogurt requires more consistent temperature control.
A gas oven with a pilot light or a lighted bulb in an electric oven might be warm enough. The low setting on your oven could also work, but if you get near 120 F, your yogurt will be kaput.
Other suggestions include crock pots or water baths. Whatever you decide, check ahead of time to make sure it holds at a suitable temperature.
Depending on how vigorous the culture, the fermentation may take four to six hours or as long as 12 to 16 hours. You can tell it’s done by noting the firmness of the yogurt. The longer you ferment and the higher the temperature, the firmer and more sour it will be. Once it’s done, place the yogurt in the refrigerator to stop the fermentation.
The most popular yogurts are now the Greek-style, which you can also make at home. Simply drain the yogurt through a colander lined with cheesecloth. About six hours in the fridge is sufficient.
Plain yogurt is what people consumed for thousands of years. The flavored versions are a more recent phenomenon. If plain is too plain, fresh fruit or high-fiber cereal is a great way to add some pizzazz.
Bob Hutkins is the Food Doc. He is a professor at the University of Nebraska-Lincoln, where he teaches and conducts research in food science and food microbiology. Send your questions on any topic related to food, food safety, food ingredients and food processing to the Food Doc at features@journalstar.com.