I've been making my own yogurt for a few years now and I don't think I'll ever go back. Not only does it actually save me some grocery money, but this homemade yogurt is seriously good. I'm eating more yogurt now than ever before.
The method I've adopted is very basic — no special heirloom yogurt cultures or fancy incubating equipment required. You could even make a batch tonight and have homemade yogurt for breakfast by tomorrow morning!
What Do I Need to Make Yogurt?
All you need to make homemade yogurt is a half gallon of milk and about a half cup of yogurt. Whole or 2% milk will make the thickest, creamiest yogurt, but you can also use skim milk if you like. For the yogurt, either Greek or regular yogurt is fine, but avoid any flavorings; stick to plain, unflavored yogurts.
When you're buying yogurt, also check that it lists "Live Active Yogurt Cultures" in the ingredients — we need those! The live cultures are what actually turn the milk into yogurt. The number of cultures doesn't really matter; as long as there is at least one, you can make yogurt. This said, different strains of bacteria have different health benefits, so I personally look for the yogurt with the most number of cultures lists. Some common ones are L. Bulgaricus, S. Thermophilus, L. Acidophilus, Bifidus, L. Casei.
What Equipment Do I Need?
All you need to make yogurt is a heavy pot with a lid. I like to use a 3-quart Dutch oven. Once the lid is on, a heavy pot like this does an admirable job of keeping the milk cozy and at a fairly steady temperature (ideally around 110°F) while the bacteria go to work turning the milk into yogurt. It also helps to put the pot somewhere insulated and warm while this is happening, like an oven with the light turned on or a picnic cooler with a hot water bottle.
You can certainly use a yogurt maker or even a dehydrator if you have one — these are great for holding the yogurt at a very steady temperature as it incubates — but can make great yogurt without them.
Once you have this basic method for making yogurt down pat, there are all sorts of tweaks and changes you can make. Some people like to add dry milk powder or gelatin for extra thickness, others like to strain off the liquid whey for a dense Greek-style yogurt. Using different brands of commercial yogurt to culture the milk can also give you subtly different flavors and nutritional benefits.
You can also try purchasing a special starter from a health food store, food co-op or online. My favorite resource for interesting starters is Cultures for Health:
Do you make your own yogurt? What's your favorite method?
Warm the milk to right below boiling, about 200°F.
How To Make Yogurt at Home
Makes about 2 quarts yogurt
What You Need
1/2 gallon milk — whole or 2% are best, but skim can also be used
1/2 cup commercial yogurt containing active cultures
3 quart or larger Dutch oven or heavy saucepan with a lid
Instant-read or candy thermometer (one that can clip to the side of the pan)
Small measuring cup or small bowl
Heat the milk. Pour the milk into the Dutch oven and set over medium to medium-high heat. Warm the milk to right below boiling, about 200°F. Stir the milk gently as it heats to make sure the bottom doesn't scorch and the milk doesn't boil over. According to the National Center for Home Food Preservation, this heating step is necessary to change the protein structure in the milk so it sets as a solid instead of separating.
Cool the milk. Let the milk cool until it is just warm to the touch, 112°F to 115°F. Stir occasionally to prevent a skin from forming. (Though if one does form, you can either stir it back in or pull it out for a snack!) You can help this step go faster by placing the Dutch oven in an ice water bath and gently stirring the milk.
Thin the yogurt with milk. Scoop out about a cup of warm milk with a measuring cup and add the yogurt. Whisk until smooth and the yogurt is dissolved in the milk.
Whisk the thinned yogurt into the milk. Pour the thinned yogurt into the warm milk while whisking gently. This inoculates the milk with the yogurt culture.
Transfer the pot to the (turned-off) oven. Cover the Dutch oven with the lid and place the whole pot in a turned-off oven — turn on the oven light or wrap the pot in towels to keep the milk warm as it sets (ideally around 110°F, though some variance is fine). You can also make the yogurt in a dehydrator left at 110°F or using a yogurt maker.
Wait for the yogurt to set. Let the yogurt set for at least 4 hours or as long as overnight — the exact time will depend on the cultures used, the temperature of the yogurt, and your yogurt preferences. The longer yogurt sits, the thicker and more tart it becomes. If this is your first time making yogurt, start checking it after 4 hours and stop when it reaches a flavor and consistency you like. Avoid jostling or stirring the yogurt until it has fully set.
Cool the yogurt. Once the yogurt has set to your liking, remove it from the oven. If you see any watery whey on the surface of the yogurt, you can either drain this off or whisk it back into the yogurt before transferring to containers. Whisking also gives the yogurt a more consistent creamy texture. Transfer the to storage containers, cover, and refrigerate. Homemade yogurt will keep for about 2 weeks in the refrigerator.
Your next batch of homemade yogurt. Once you start making your own yogurt, you can use some of each batch to culture your next batch. Just save 1/2 cup to use for this purpose. If after a few batches, you notice some odd flavors in your yogurt or that it's not culturing quite as quickly, that means that either some outside bacteria has taken up residence in your yogurt or that this strain is becoming weak. As long as this batch still tastes good to you, it will be safe to eat, but go back to using some store-bought commercial yogurt in your next batch.
• Cost Breakdown: We eat about a quart of yogurt a week in our house, which was costing roughly $2.60 a week. A half gallon of milk makes a little less than two quarts of yogurt, which has been just enough to last us two weeks. We buy a local brand of milk that costs $3.70 per half gallon ($1.85 per quart), so we end up saving about 75-cents per week on yogurt. Nice.
• Holding the Temperature: If your milk drops below 110° while it's incubating, that's fine. It will take a little longer to set and might end up a little looser, but the bacteria in the yogurt culture will keep the milk from spoiling. By the way, even after 8 hours in the oven (overnight), our yogurt made in the Dutch oven still usually registers about 100° when I take it out of the oven!