Don't worry if you can't find ultra-pasteurized half-and-half at your local grocery store. You can use regular pasteurized half-and-half, but you'll need to take one extra step to turn it into your homemade ultra-pasteurized half-and-half. Heat the pasteurized half-and-half to 180°F (82°C) in a saucepan on the stovetop and maintain that temperature for 20 minutes. Afterward, allow the half-and-half to cool and proceed with the culturing process.