Name: Sous Vide Yogurt
Total time: 1 d 1 h
Ingredients: 3¾ cups whole milk; ¼ cup plain yogurt with live and active cultures

Why This Recipe Works

For this recipe we used a small amount of store-bought yogurt with live cultures. The live cultures—namely Lactobacillus bulgaricus and Streptococcus thermophilus—are beneficial bacteria that give yogurt the flavor (tangy) and texture (thick) that we love. It doesn't hurt that these cultures are purportedly very good for you, too. First, we heated milk to 185°F/85°C to kill unwanted microorganisms and denature the proteins in the milk. This protein reconfiguration allowed the cultured milk to transform into creamy yogurt rather than separate into curds and whey. We learned that it was important to resist the urge to stir the milk during this heating process. As the proteins denature, they become loose strands eager to tangle with each other; stirring led to small lumps in the end product. We then cooled the milk to 110°F/43.5°C to create a friendly environment for the starter culture and to prevent curdling. We stirred in the yogurt starter, put the mixture into jars, and finally placed the jars in a water bath to incubate. The beauty of using a sous vide circulator for this process was that we could precisely hold our yogurt in the culturing temperature sweet spot without any babysitting. Five hours later, we were rewarded with delicious, tangy homemade yogurt. We found we could leave it for as long as 24 hours; the longer the incubation time, the greater the pucker.

Before You Begin

The success of this recipe hinges on using yogurt that contains live and active cultures. You will need two 16-ounce Mason jars for this recipe. Be careful not to overtighten the jars before placing them in the prepared water bath; that can cause the glass to crack. This recipe can be doubled. To make Greek yogurt transfer completely cooled yogurt to fine-mesh strainer lined with double layer of coffee filters. Cover and refrigerate until 2 cups of liquid have drained into bowl, 7 to 8 hours (discard drained liquid). For more about sous vide cooking, refer to our sous vide guide.

Instructions

Using sous vide circulator, bring water to 110°F/43.5°C in 7-quart container. Heat milk in large saucepan over medium-low heat, without stirring, until milk registers 185°F/85°C. Strain milk through fine-mesh strainer into 8-cup liquid measuring cup. Let cool until milk registers 110°F/43.5°C, stirring occasionally to prevent skin from forming, about 30 minutes.

Combine yogurt and ½ cup cooled milk in small bowl. Gently stir yogurt mixture into remaining cooled milk, and then transfer to two 16-ounce Mason jars and seal; do not overtighten lid. Place jars in prepared water bath, cover, and cook for at least 5 hours or up to 24 hours. Let yogurt cool at room temperature for 15 minutes. Transfer to refrigerator and let sit until fully chilled, about 3 hours. Stir yogurt to recombine before serving.

to make ahead

Yogurt can be refrigerated for up to 1 week; stir to recombine before serving.