Yogurt fermentation time and temperature impact the bacterial quality of homemade yogurt. At the right temperature, milk turns to yogurt in 6 - 8 hours. But yogurt is not a food to rush along or be impatient with. Yogurt is a living food, full of active, beneficial bacteria that have a vital job to do. GAPS and 'specific carbohydrate diet' yogurt recommend yogurt with a long fermentation.
Within milk there is a type of sugar called lactose. Sugar is not permitted on GAPS & SCD. The bacteria that make up a Yogurt Starter Culture consume and thrive on the lactose in milk. The longer the fermentation the more the bacteria have time to eat - the more they eat, the less lactose there is! The important thing to get is, even after a a standard 8 hour fermentation, the milk still has plenty of lactose. 24 hours is an ideal fermentation time which produces a yogurt with minimal sugar.
Homemade 'specific carbohydrate diet' yogurt may be fermented for even up to 30 hours, however beyond that, you risk starving the bacteria and spoiling the yogurt.
Just as good bacteria (in the starter culture) consume the sugar in milk, bad bacteria (living inside our digestive system) also like to consume sugar. Inside the gut, lactose is a source of food for these guys. THEY LOVE IT! Bad bacteria in our digestive system are the dudes that are a big nuisance to our health. So a yogurt that has been left to ferment for 24 hours is not only wildly abundant with healthy bacteria, it starves the bad bacteria of their favourite food source. Being almost lactose free, means, it’s almost sugar free!
This is the basis of the SCD diet; to remove all sugars and heal the gut by depriving bad bacteria of the food they love. Learn why SCD yogurt should be your first, go to healing food.
Natural, unsweetened, Greek yogurt is the nearest thing in the supermarket to homemade 24 hour yogurt, however, even this remains full of lactose. I doubt many commercial yogurts are left to ferment longer than 6 hours. It's pretty simple: all store-bought yogurt feeds bad bacteria and 24 hour yogurt feeds good bacteria.
"These friendly creatures and their by-products keep pathogens at bay, guard against infectious illness and aid in the fullest possible digestion of all food we consume." Nourishing Traditions, page 81
A bowl of fresh, chilled, homemade, 24 hour yogurt has an abundance of good bacteria set in the environment they grew in. By contrast, store bought yogurt has been transported from factory to supermarket and then to your fridge. No wonder preservatives and stabilisers are often added to ensure longevity and shelf life.
Many people worry about casein; the protein found in milk that is well known for causing allergic symptoms and digestive upset. People who have problems digesting casein can often tolerate 24 hour fermented raw milk yogurt and goat milk yogurt. Coconut cream yogurt, easy coconut cream yogurt and homemade almond milk yogurt, vegan, date sweetened, coconut and cashew yogurt are other great alternatives if you prefer to avoid casein altogether.
Higher heat will speed up the fermentation process. But that’s not such a good thing if you are aiming for a probiotic rich yogurt. Too much heat will damage or kill off your starter culture. Conversely, if the temperature is too cool, the culture will become dormant and fermentation will not occur.
Homemade 24 hour SCD yogurt requires a stable, continuous heat between 36 – 42 degrees Celsius for (obviously) 24 hours. A Luvele yoghurt maker will ensure your yogurt remains at the ideal fermentation temperature for perfect homemade yoghurt goodness, every time, in every season! The recipe and instructions for cow's milk yogurt can be found here or view an easy, step by step infographic here.
Fermentation time will also effect the taste of homemade yogurt. A short fermentation will result in a milder tasting yogurt while a tub that has been left to incubate for 24 hours (or up to 30 hours) will taste tart and full of flavour. Additionally, it is the combination of bacteria that determine the flavour. Some yogurt starter cultures specify 'mild' or 'tart'.