- Pasteurization, homogenization, and fat content
- Quantity of milk for yogurt
- Yogurt culturing temperature
- Culturing time for yogurt
- Potential contamination sources
Are you using regular pasteurized, homogenized, whole milk?
Regular pasteurized, homogenized milk is most reliable for making yogurt. However, the direct-set yogurts are much more tolerant of different types of milk.
For tips on making raw milk yogurt with your starter see http://www.culturesforhealth.com/learn/yogurt/make-direct-set-raw-milk-yogurt/
The lower fat milks, and raw milk, will set much thinner than whole, homogenized milk. Even if it’s thin, as long as the yogurt smells and tastes pleasant, it’s still cultured and is finished yogurt
Filtered milk which has had the lactose removed will not culture. Lactose is the food source for yogurt bacteria
Powdered milk can be used with direct set yogurts. Follow manufacturers directions for mixing amounts. Add an additional ⅓-½ cup powdered milk per quart for a thicker yogurt.
Evaporated milk (not sweetened-condensed) will also work provided it does not have added ingredients such as stabilizers or preservatives.
How much milk are you using?
Use 1 packet for 1-2 quarts of milk. Use 2 packets for up to 4 gallons of milk. Do not try to make less than 1 quart of yogurt
If using Kosher Yogurt Starter, use ⅛ teaspoon with 1-2 quarts of milk. (For larger batches, use ¼ teaspoon with 1-4 gallons milk.)
What is the temperature in the space you are culturing? Have you verified that the temperature is being maintained?
Thermophilic yogurts simply cannot tolerate temperatures higher than 118ºF.
To test the temperature in the yogurt maker, pour 110ºF water into the container and take temperature readings at various time intervals, to ensure that the container is holding the correct temperature range. For more details: http://www.culturesforhealth.com/learn/yogurt/testing-yogurt-maker/
How long are you culturing?
Yogurt may set at any point between 4-8 hours. If you like a tangier yogurt, it’s fine to leave it to culture for as long as 24 hours.
Is there anything culturing near your yogurt?
While pretty tolerant, it’s best to keep yogurt at least 4’ from other cultures. If you’re worried about contamination from another source, it’s a good idea to use a solid lid instead of the breathable cover. If you are using jars with an alternate heat source, we love these! http://www.culturesforhealth.com/plastic-lids-wide-mouth-jars.html