How kefir is made: The basic principles.
Quite simply, when our kefir culture is added to milk, juice or water with added natural sugars, the culture starts to eat the lactose or any other available sugar and makes acid, which brings the pH down. This happens best between 25° and 37° C.
We target 30° C in our instructions to allow for thermometer error etc., as the culture suffers at 38°C and will start dying at 40°C.
For food safety, high probiotic content and the best flavour a pH below 4.6 is recommended. We have found that a sugar content around 4%, or 4 grams per 100 ml, is required. Check the nutrition panel and add some sugar if needed.
12 to 24 hours at the desired temperature should be enough time to make a wonderful kefir. The longer the kefir is kept in the ideal temperature range for culture growth, the more lactose, which is a dairy sugar, or other sugars available, get eaten. As more sugar is eaten, more acid is produced and the tangier the kefir becomes.
You can also add an optional second fermentation step by capping the jar and fermenting another 12 to 24 hours. This will add natural carbonation to the kefir. Be careful not to let too much pressure build up inside the jar as it may cause weaker glass jars to explode if left to over pressurise. It is recommended that this extra fermentation step only be done with high-quality flip top glass jars or flexible plastic jars.
How kefir is made: The basic methodology.
Milk, juice or water (coconut water, mineral water with added natural sugars, etc) is warmed to 30°C and then inoculated with kefir culture. This can be done in a jar, thermos or any container. Place a tight weave cheesecloth over the top of the jar so that it is covered but can breathe and place in a warm location for 12 to 24 hours. The temperature should be maintained between 25° C and 35° C for the duration of the fermentation period. You can place the jar into an esky with warm water or wrap in a blanket and place on top of the water heater.
As with making any fermented milk products, cleanliness is vital in kefir making. Make sure that you thoroughly clean and sterilise all your utensils before using them. By heating milk to 30° C and then keeping it at that temperature you are deliberately creating the perfect environment to grow bacteria. Just be sure that you are only growing the bacteria (starter culture) that you have introduced and not some other bacteria that blew in on the wind (cross-contamination).
Shelf Life of Cultures:
When stored correctly freeze-dried lactic cultures are typically viable long after any date on the pack.