Ferments Kitchen Basics


You should be making yogurt: It’s easy, versatile, and great for your gut.

Yogurt is a fermented food — meaning a food that has been transformed through the hard work of beneficial bacteria. Here’s the basic science. Add a little bit of lactic acid bacteria to milk. The bacteria eat up the sugar (lactose) and convert it into more lactic acid. The bacteria reproduce and take over the milk this way. When the milk becomes acidic enough, the proteins (casein) coagulate into a jelly-like consistency, otherwise known as yogurt.

If you’re feeling intimidated, just remember humans have been making yogurt since the Stone Age, and that was long before we had recipes and food thermometers. Making yogurt is simple, but because I’m a geek I dove into all of the details about preparing one of humanity’s favorite kinds of nourishment for several millennia.

The role the gut microbiome plays in keeping us healthy is a fascinating area of research. However, don’t let the unregulated supplement industry take your money by selling probiotic pills that probably aren’t doing anything. Instead take your microbes the old fashioned way, in a spoonful of homemade yogurt.

Makes: 2 quarts


  • incubator (don't be scared, details below)
  • food thermometer (ideal but not mandatory)


  • 1/2 gallon nice milk

    Remember the No. 2 kitchen commandment? Quality ingredients will produce a better final product. Probably skip the gallon at the gas station

  • 1 tbsp yogurt (more on this below)


  • Gradually bring the milk to just shy of boil — at 180 °F or higher — over medium-low heat. Look for the surface of the milk to steam. Heating the milk to a high temperature denatures the whey protein known as lactoglobulin, joining it with the casein proteins to strengthen their structure and increase the yield. Doing it slowly keeps the final yogurt texture silky smooth. 
  • Remove milk from heat and cool to 110 °F on the counter, or if in a rush, nestled in an ice bath. This is the temperature that makes yogurt bacteria happiest. Add your starter culture (a tablespoon of yogurt from a previous batch or store-bought) and mix thoroughly. If you do not have a food thermometer, keep checking the temperature of the yogurt by placing a finger in the mixture and trying it to hold it there for 5 to 10 seconds. Once you can do so, you’re ready for the next step.
  • Place the cultured milk in a container, such as a wide-mouth quart jar. Loosely cover and incubate at 110 °F for 12 or so hours (this step is super easy and there’s a how-to below). When the yogurt has set, it will appear solid, perhaps with a bit of yellow whey pooling at the top. When you tilt the container, the yogurt will pull cleanly away from the side in a solid mass.
  • Refrigerate the yogurt for a minimum of two to three hours to firm it up further. Save a bit of the final product in order to culture your next batch.


Why do I need yogurt to make yogurt?
The live bacteria in the yogurt will inoculate (see definition 1B) a new batch. For your first attempts, save a bit of yogurt from the grocery store and use it for this recipe. Just be sure it’s plain yogurt. Anything with sugar will inhibit proper fermentation. Plus, you should probably avoid that stuff, as it’s just candy in sheep’s clothing. The strains of bacteria from commercially produced yogurts usually weaken after a few homemade batches and eventually stop thriving. Once you get the hang of it, buy yourself a yogurt starter culture, at a website like this, or this (or even Etsy). These starter yogurt cultures will last as long as you keep on using them.
Incubation 101:
While some varieties of yogurt can culture at room temperature (Finnish “Villi” is a popular one), most require you to incubate for several hours around 110F. There are several ways to do this. Here are a few:
  1. In an insulated cooler. Place yogurt container in the cooler. Pour 110 F water about ¾ of the way up the jars. Close lid tightly and wrap the cooler in a blanket. Check every couple of hours, and replace the water if it gets too cool.
  2. In a slow cooker. Program your slow cooker to around 110F. Place your container of yogurt inside. Wrap the slow cooker in a towel and let it incubate! Instant Pots also have a yogurt incubating function.
  3. In a gas oven with the pilot light lit. We are lucky enough to have a gas oven at the farm, which serves as our oven, incubator, and food dehydrator. A gas oven, turned off but with the pilot light lit, maintains a temperature of about 110F. Perfect for incubating yogurt! Also, if you have a fancy electric oven, you may be able to set the temperature to 110F. That would work too.