Dating back to Neolithic times

People have been making yogurt for thousands of years. The history of yogurt-making goes back to the early cultures of Central Asia, where nomads transported milk in goatskin sacks carried around their waists, and it fermented into yogurt using their own body heat. There are famous yogurt-making nations of Afghanistan, Eritrea, Turkey, India, Iran, Israel, Lebanon, Mongolia, Pakistan, and Serbia. They use milk from cows, camels, goats, sheep, and yaks.

Greek or Bulgarian Yogurt

Most of us are familiar with the famous Greek or Bulgarian yogurts. Greek yogurt is traditionally strained, making it thicker, creamier, and smoother. It also has double the protein of but reduced calcium. In both types of yogurts, bacteria cultures help break down lactose, so yogurt can be easier to digest for people who are lactose intolerant. Greek yogurt has even less lactose. Bulgarian yogurt is less creamy and more sour and tangy. Bulgarian yogurt has about three times as many probiotics as the Greek version.

Yogurt is a superfood

Yogurt is very nutritious. It is rich in protein, calcium, and vitamins, especially B. What makes yogurt especially healthy are the live cultures, called probiotics, which are excellent for maintaining a healthy digestive system, and they also boost our immune system.

It works like magic

Despite the lengthy instructions, making yogurt is not hard. Yogurt is created when certain safe, edible bacteria grow in warm milk. During the yogurt-making process, the lactose sugar in the milk is converted to lactic acid by the bacterial cultures. Your homemade yogurt will be pure with no thickeners, colors, or other added chemicals.

Start with good cultures

To make yogurt, you must choose the right starter culture that contains active live bacterial cultures. You can purchase various yogurt cultures commercially (Bulgarian or Greek types), but you can just start simply with the best quality yogurt you can find in a store. Carefully read the label to avoid any additives. Full fat yogurt works the best, but you can experiment. You will need only ¼ cup (or one tablespoon) for your first batch. Homemade yogurt keeps for up to two weeks in the fridge, but if you want to use it to make a new batch, you should do that within a week, when the bacteria is the most active. The culture can be frozen for up to three months—thaw in the refrigerator before using.

Reasons for failure

If the yogurt did not set or separated instead, the main causes could be that the milk was not at the right temperature when the starter was added, the incubation temperature was either too low or too high, or the wrong amount of starter was added. Either too much or too little will cause it to separate.

yogurt in a white bowl with a honey drizzler

Homemade Yogurt

Magda Born

There are many fancy ways to make yogurt, like using the Instant Pot or yogurt makers, which still does not eliminate the steps of heating and cooling the milk to an exact temperature, which is the most important step of the whole process. In this simple yogurt-making procedure, I am using my husband's old cooler, which in this instance is used as a "warmer." Despite the lengthy instructions, making yogurt is very easy. The precise temperatures and using good cultures are the most important steps. Happy yogurt-making!

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Equipment

Heavy bottomed pot
Candy thermometer or instant-read meter
A heatproof rubber spatula or wooden spoon
1-quart jar (or 2-pint jars)
Small insulated cooler

Ingredients

1 quart Milk Use whole milk for best results
1 Tbsp Yogurt (or 15 grams of yogurt)

Instructions

The Method:

Sterilize your jars by boiling them for a few minutes. Let the jar cool down before you fill it, but keep it still warm; but if it's too hot, it can kill the yogurt culture.
Heat your milk. Pour milk into a saucepan over medium heat. Clamp the candy thermometer on the side and gently heat the milk to around 180° F (82ºC). Watch it carefully and stir occasionally because it can quickly boil over if it gets too hot. (Cooking denatures the milk proteins so that they do not interfere with the incubation process.)
Cool it down. Turn off the heat and let cool to 110° F (43C) (stirring occasionally). When the heat is turned off, the temperature of the milk continues to rise from the residue heat of the pot or as the burner cools—often reaching a temperature of 200°F. This is actually a good thing. Holding the milk at (or slightly over) 180° F for a few moments will help firm up the milk proteins, which will in turn help produce a thicker yogurt.
Get your warm cooler ready. While waiting for the milk to cool down, fill the cooler with warm water (115° to 120°) and close the lid to keep the temperature constant.
Get the starter. Place the tablespoon of yogurt in a small bowl and set aside.
Inoculate your milk with your starter. When the milk has cooled down to 110-115° F (45ºC), ladle a small amount of warm milk into your yogurt starter and stir it to temper it. Add more milk until the yogurt starter is of a pourable consistency
Pour this mixture back into the warm milk and stir well. Pour the inoculated milk into the prepared jar and seal the jar.
Let it ferment. This is the step when the yogurt magic happens. Place the jar in the cooler filled with warm water, adding or removing water so that the level of the water is even with the level of the inoculated milk in the jar. Before placing the jar, double-check that the temperature is still between 115° to 120°. This is very important! Close the cooler fast and let the yogurt sit undisturbed for exactly six hours. The longer fermentation will yield a more tart yogurt, but it may kill the bacteria just after a few batches.
Finish it in the fridge. Remove the jar from the cooler. Dry the outside of the jar and the condensation on the inside of the lid. Check to see if the yogurt is set. The yogurt is ready when it looks thick, and it should be wobbly when you jiggle it. Place the yogurt in the refrigerator. Remember to keep the lid firmly on. Keeping the lid on tightly keeps the live bacteria in the yogurt. Chill the yogurt thoroughly, at least three hours (8-12 hours preferred). The yogurt will continue to thicken more up once cool.
Before tasting. Before eating, remove ¼ cup as the starter for your next batch and refrigerate with the lid tightly closed. Yogurt will develop its optimal flavor only after chilling. Most homemade yogurts are lumpy. This is the part I personally enjoy. To smooth it out, whisk gently before eating. If the top layer of whey bothers you, tip it into the sink. Consume within 7 to 10 days. The active cultures stay viable for around 7 days or frozen for 3 months. (It is a good idea to mark the lid with a date). For the batch in the picture above, I used a cup of cream, which rose to the top during the incubation process.
Happy yogurt-making!