Cultured foods are living foods and as such are rarely the same from one batch to the next. Culturing time, temperature, and microorganisms all play a part in determining what a particular batch of yogurt will be like.
WHAT MAKES LONG-CULTURED YOGURT DIFFERENT
Required culturing time varies between starter cultures. As the warmed milk is combined with the yogurt starter, the bacteria begin to feast on the lactose in the milk and produce lactic acid, and the culture proliferates and spreads throughout the milk.
The longer the culturing process goes on, the longer the culture has time to multiply, thereby increasing the amount of bacteria and acids in the yogurt while decreasing the lactose content of the milk.
Why Culture Yogurt for 24 Hours?
Certain diets such as GAPS or SCD promote a 24-hour culturing period for yogurt.
Some people want to reduce lactose content in the final product as much as possible.
CONCERNS WITH LONG-CULTURED YOGURT
Because the yogurt culture feeds off the lactose in the milk, a longer culturing time can stress the culture or even kill it, as the bacteria run out of food. As the bacteria begin to starve, it may affect a culture’s ability to perpetuate beyond a single batch.
If using a reusable heirloom starter culture, protect the health of the culture by removing enough yogurt to use as starter for the next batch within the required culturing time, or by maintaining a mother culture, prepared according to the instructions included with the starter. Always use the mother culture as starter for 24-hour batches and as starter for weekly fresh batches of mother culture. Avoid re-culturing using yogurt from a 24-hour batch as starter.