A yogurt starter contains bacteria that convert milk onto yogurt. Any plain (unflavored and unsweetened) yogurt can be used as a starter, as long as includes active cultures. Make sure to check the label before purchasing. You can also buy freeze-dried yogurt starter powder. Look for one that is thermophilic and will incubate at 110 degrees F / 43 degrees C, as yogurt cultures that incubate at lower temperatures won’t work in the Instant Pot. Chef's Tip ==> once you've made your first batch of Instant Pot yogurt, you can reserve 4 tablespoon tablespoons and use 2 as the starter for the next one (the other 2 for backup).