What Are the Two Main Ingredients You Use to Make Yogurt?

A yogurt-making machine is helpful, but not necessary, for making yogurt.

Although some yogurt that you buy in the store may have a long list of ingredients, all that is needed to make yogurt is two things -- milk and a "starter" containing live yogurt bacteria cultures. The other ingredients in commercially made yogurt are usually stabilizers, preservatives and extra ingredients added for flavor.

Milk

The first main ingredient used to make yogurt is milk. Whole milk gives the yogurt a richer taste, but low-fat or nonfat milk works for people who prefer to reduce the fat in their diets. Most yogurt-makers in the United States use cow's milk, but people in other cultures use milk from goats, sheep, yaks, water buffalo and even horses. Raw milk should be pasteurized to remove bacteria that may interfere with the fermentation process. Some yogurt makers also add nonfat dry milk or evaporated milk to the regular milk.

Starter

The second main ingredient used to make yogurt is starter. Starter is a culture containing the live bacteria Streptococcus thermophilus and L. bulgaricus or L. acidophilus. For homemade yogurt, you can use yogurt from a previous batch as a starter to make the next. You can also use store-bought yogurt. Make sure the yogurt is very fresh and that it contains active cultures. David B. Fankhauser, a professor of biology and chemistry at U.C. Clermont College, recommends using plain Dannon brand yogurt as a starter, but any brand with active cultures should work.

Considerations

Use more milk than starter, at a ratio of approximately one gallon of milk per cup of starter. The milk should be heated to approximately 180 degrees, then cooled to about 115 degrees before adding the starter. The combination should be poured into sterilized jars and kept warm while the yogurt sets, which will take about four hours. The longer the yogurt sets, the stronger the flavor will be. When the yogurt is done, put it in the refrigerator.

How It Works

Making yogurt is a controlled fermentation process. The bacteria in the starter multiply while the yogurt is incubating. They break down the sugar in the milk, converting it into lactic acid. The lactic acid gives yogurt its tart flavor. The lactic acid is also what makes the protein in the milk solidify. Yogurt can be easier for people to digest than milk because the bacteria have already partially digested it.

References

• University of Cincinnati Clermont College: Yogurt Making Illustrated
• University of California Davis Dairy Research and Information Center: Make Yogurt at Home
• "New York Times"; The Curious Cook: They Do the Work, You Reap the Yogurt; Harold McGee; April 14, 2009

Resources

• "New York Times"; Well: Make York Own Yogurt; Tara Parker-Pope; April 16, 2009