Optional Equipment Sterilization: Place 2 cups of cold water and trivet in Instant Pot. Place silicone spatula, Pyrex glass measuring cup, and measuring spoon in Instant Pot. Close the lid and move the Venting Knob to Sealing Position. Sterilize (Pressure Cook or Manual button) everything at High Pressure for 3 minutes + Natural Release. Or Sterilize on Stovetop: sterilize the equipment (including food thermometer) on stovetop by boiling them for 10 minutes.After sterilization, air dries the equipment on a clean rack.
Heat Milk to 180°F - 200°F to Denature the Protein: Pour 2L (½ gallon) of whole milk in inner pot. Close lid. Use the Yogurt More function to boil the milk to at least 180°F (it will say “BOIL” on the screen). This takes roughly 35 minutes – 40 minutes. The Instant Pot screen will change to “YOGT” when the boiling is done.
Check Milk Temperature: Open the lid. Check the milk temperature immediately in a few spots to make sure the milk is over 180°F. Stir with a silicone spatula and check the temperature again to ensure the milk is over 180°F. *Pro Tip: If the milk is not over 180°F, close the lid and heat the milk with the "Slow Cook Less" function for another 15 minutes. DON'T bother straining yet! Do this after it's cooled for Step 5.
Prepare Yogurt Starter: After the milk is heated over 180°F, place 32g (a little more than 2 tbsp) Plain Greek Yogurt with Active Bacterial Cultures into the Pyrex glass measuring cup. Do not add the yogurt starter to the hot milk, as it will kill the bacterial cultures. *Pro Tip: If you sterilized the measuring cup, make sure it has cooled to the touch.
Cool Milk to 111°F: Leave the pot on counter-top and wait until the milk cools to 111°F. Or alternative method to quickly cool down the milk temperature: Fill a larger pot or kitchen sink with cold tap water. Partially submerge the inner pot with heated milk into the cold tap water. Stir the milk in a circular motion with a silicone spatula and frequently measure the temperature. It will take 2 minutes – 4 minutes to cool the milk to 111°F. Remove the pot from cold water immediately. *Pro Tip: Try not to touch the bottom of the pot with the spatula as it may have some milk solid stuck to the bottom of the pot.
Add Yogurt Starter: Add ½ cup of 111°F milk to the Pyrex glass filled with yogurt starter. Gently mix it with the measuring spoon. Pour the yogurt milk mixture in the inner pot and give it a few gentle stirs with a silicone spatula.
Yogurt Incubation: Place inner pot back in the Instant Pot. Close lid. Use the Yogurt Normal Function to incubate the yogurt. Adjust the time to 8:00 hours – 12:00 hours depending on how tangy you like your yogurt (longer time = tangier). *Pro Tip: Don’t disrupt the fermentation process by moving the Instant Pot or opening the lid. You can open the lid for a taste test once the yogurt is set (after roughly 6 hours).
Stop Incubating Process: Once the yogurt has reached your desired tangy level, remove the inner pot of yogurt and place it in the fridge for a few hours to stop the incubating process. The yogurt will also thicken a little.
Serve: Plain yogurt is done. Serve by adding sweeteners such as honey or maple syrup. Add fruits, granola or your favorite toppings. The sky is limit! Enjoy~*Pro Tip: If the yogurt is too runny, you can strain the yogurt with a yogurt strainer.