Susan, you ask some very good questions. I am a dairy person, not a microbiologist, but here are my thoughts. It's not just the microbial organisms that are important in this mix, but also the constituents in the grains. Polysaccharide sources from grains are complex, so one cannot simply use probiotics and expect the same outcome if the grains are absent. In terms of strains, there seems to be a competition among organisms for their place in the population, so one organism might replace another one, especially at the lower levels in the population. It is not predictable without some trial and error testing. Also, milk differs in composition, depending on whether one is using blended milk or milk from individual cows, buffalo, goats, sheep, camels or mares. So the problem is complex and does not lend itself to a simple answer. Trial and error got us here and that is probably what will answer your questions. Keep us informed.

As Jack points out, the kefir grains are complex mixtures of yeast and bacteria, bound together by extracellular polysaccharides that come mainly from the bacteria.  I will attach a paper we published a few years ago that describes the variety of bacteria responsible for both the acid and polysaccharide production.  These all came from water kefir or ginger beer, which differs significantly from dairy kefir, but the general idea is similar.  My advice would be to use an inoculum from a known sample of kefir, and not try creating a microbial mixture from scratch. As far as warming the milk prior to adding cultures, I would let it warm to the inoculation temperature.  Heating it might make it too warm, thus killing the microbes when they are added. And as Jack said, trial and error is your best bet when it comes to taste.

Please refere to the proceedings of OMICS 4th international conference and exhibition on probiotics and baby food. You will find some valuable articles on Kefir.

Dear Dr. Susan, Please note the basics in Kefir making. Kefir is the product obtained from milk with a acid-alcoholic fermentation. We do not add any starch nor sugars. The inoculum i.e. kefir grains are the accumulated clusters of the LAB and LFY, which are agglomerated due to formation of mucopolysaccharides by these organisms. The culture organisms including some probiotics grow and produce acid and synthesize some vitamins. As far as the ratio of kefir grains to milk is concerned, it may be maintained roughly at 5% of the milk. Milk should be pasteurized and after cooling to the incubation temperature the kefir grains are just passed through warm milk for 5-10 min and inoculated in the batch of milk.