Fermentation times are recommended between 12 and 72 hours. Some instructions from the tropical North Queensland recommend a fermentation time of only 6 hours.
The fermentation time has to be longer with a lower average fermentation temperature and shorter with a higher average fermenation temperature.
Shorter fermentation results in a milder, sweeter aroma and a lively sparkling product. Longer fermentation makes a stronger Kefir aroma, sparkling and slightly sour.
Brigitta Cadisch-Umbricht found that Kefir fermented for 24 hours has a mild laxative effect, fermented for 48 hours is balancing and longer fermentation of about 70 hours has a very mild constipating effect.
The Right Temperature
The best fermentation temperature for Kefir is between 22oC and 30o C (72 - 86o F).
Researchers have found nearly 30 different bacteria and 25 different yeasts in Kefir cultures. Every bacteria and culture has specific temperature requirements, this is why a constant low temperature can't be compensated with a longer fermentation time, or a constant high temperature with a shorter fermentation time. Your Kefir brewing needs some balance like hatching an egg. A fertilised egg, for example, kept under a temperature of 37.4o C (99o F) for 21 days will bring forth a healthy chick, a higher temperature and quicker breeding time will result in no new living chicken but only in a terrible smell.
It does not matter if your temperature varies during fermentation time between 18o C and 30o C which gives a wider spectrum of bacterial and yeast growth. A fermentation of a constant 18o C or constant 30o C is not recommended.
The temperature requirements of the bacteria Leu. citrovorum has a temperature requirement of 20o C (68o F), Lactobacillus acidophilus a requirement of 38o C (100o C) but some literature recommends 43.3 - 44.5o C (110o - 112o F). Lactobacillus bulgaricus likes temperatures between 43.3 - 46.6o C (110o - 116o F).
In winter and in cooler ares a heating device is recommended. A special designed heating panel for Kefir home production is available.
The Fermentation Pot
The most suitable fermentation pots are glass, glazed pottery, or porcelain. When using pottery please make sure that non lead glaze is used.
Copper is not recommended either and I think everyone knows that aluminium should not be used for food processing at all and in any case, aluminium is not suitable for lactic acid fermentation. In the country of origin, leather bags have been used for Kefir fermentation too.
Problems Associated with Kefir Fermentation
There is no doubt that you should ferment Kefir hygienically, as with any food processing. Contaminated bread, meat or fish is unhealthy and Kefir is no exception. Kefir is fermented in a covered container, and is not likely to be contaminated.
Don't make a science out of simplicity and believe scare tactic campaigns from people who don't really know about Kefir and/or do not want you to be healthy. Kefir was with us for a very long time and was produced in Russian farm kitchens where modern hygiene was not much known.
In my opinion if the Kefir grains or plants are left in natural balance, then brewed in a home environment as before, then you are on the safe side.
If manufacturers extract a single strain of a bacteria and culture that, as it is done with acidophilus or the Yakult Strain then laboratory cleanliness is the only solution. Both products are a blessing and so is your own product.
Kefir, an alcoholic beverage?
Depending on the fermentation process, fermentation temperature, time and type of culture used, the alcohol content of Kefir will vary from 0.06 % (Marshall 1984), up to a maximum of 3% alcohol. The average alcohol content in home brewing is around 0.5% with a loose lid and 1% in an airtight jar. Shaking the fermentation container during the fermentation time also results in higher alcohol content.
Can I eat the grains?
Yes, you can. The stories about Kombucha which are now starting with Kefir, that cultures can grow in your brain, stomach and so on, have never been proven. I received thousands of phone calls in this regard and offered in broadcast interviews $1000 for the first person who has a culture grown inside the body. The $1000 has not been claimed. If you hear fairy tales like that, ask for the address of the person, and talk to the person or the doctor personally, and let me know only if you have proof. Please don't waste your money for a phone call or letter and my time with nonsense like that.
How long does the culture live?
The grains or plant live, with proper care as long as their owners. Kefir cultures reproduce themselves and do not know a physical death.
Storage and Care for the Kefir Culture
There are many brief information sheets given to friends along with the Kefir culture and the recommendations of care for the culture and storage vary dramatically. Most recommendations advise to wash the culture before every use. Some say with cold water, some with water around 20o C. Washing is recommended to clean up unwanted or unfriendly bacteria which may settle on the sibiotic system. The advice to wash a culture, you only find in Western literature. The people I know from Russia, Poland, Romania and Hungary who have known about Kefir fermenting from childhood do not recommend washing. They say that the beneficial micro flora around the culture will be disturbed or destroyed - definitely with chlorinated water and fluoridated water - and don't wash the culture except for drying purposes or if fermentation is paused for a short term.
I personally agree with the natural way in not washing the culture.
For a short break of Kefir fermenting, like going on a holiday for a fortnight, the grains are placed in fresh milk, and then stored in the refrigerator at 4o C.
The Kefir grains are tougher than most people think. To compare different cultures, I asked a friend in north Queensland (and it's really hot up there) to send me a culture. I live 3000 km south and the parcel was 12 days on the road by Australia Post. The fresh grains, bottled together with a 1/4 litre milk arrived absolutely active and the first brew was perfect. Not only that, the long fermentation and 3000 km truck shaking, produced a very pleasant tasting Kefir.
If you are not sure in the handling of Kefir then try to think a few hundred years back in a simple farm kitchen in the Caucasus mountains and make your own mind up. Like the Australian saying- "use the KISS method" Keep It Simple Silly.
For long storage it is recommended to change the milk every few weeks to feed the grains and keep them fully active.
Some say that deep freezing may kill the culture and others had no problem to reactivating the culture after a long storage in a deep freezer.