Research On Characteristic Differences Between Tibetan Kefir And Artificial Microorganism Carriers

With the development of our economy, consumption of dairy products areincreasing sharply. Tibetan kefir grains, a kind of traditional Chinese diary starter,are getting more attention of people. Tibetan kefir grains have many kinds ofmicroorganisms growing in it. Under proper conditions, Tibetan kefir grains cangrow in milk, and form new grains. The cultured milk is called Tibetan kefir.Tibetan kefir grains from different areas have differences in flora and components.Now, people still cannot have new Tibetan kefir grains without original one.Therefore, researches on how to get new Tibetan kefir grains are imperative.This study was based on Tibetan kefir grains from the northeast area. Usingscanning electron microscopy to observe the microstructure, we found that shortbacillus arranged compactly on the outer surface of Tibetan kefir grains, and theinner surface had both bacillus and yeast. However, no coccus was found on bothsurfaces of Tibetan kefir grains. This kind of Tibetan kefir grains, about0.5~3.5cmin diameter, have7%protein,12%polysaccharide and76%water.The flora of Tibetan kefir grains was analyzed by PCR-DGGE. There werenumerous kinds of microorganisms, including5kinds of bacterium and5kinds ofyeasts. Six different bacillus (Lactobacillus helveticus、 Lactobacillus buchneri、Lactobacillus sunkii、Lactobacillus kefiri、Enterobacteriaceae bacterium and Enterobacterhormaechei), two different coccus(Lactococcus lactis and Enterococcus sp.) and twokinds of yeasts(Saccharomyces cerevisiae and Kazachstania unispora) were isolatedwith the traditional separation method. The appropriate incubation conditions forTibetan kefir grains were28℃with agitation (110r/min), no rinse when changingculture milk, and adding0.25%Tyrone and0.1%MnSO4·H2O to the culture milk. Inaddition, the change of culture conditions and medium composition did notinfluence the composition and fermentability of Tibetan kefir grains, showing thatTibetan kefir grains are stable starters.Two kinds of artificial carriers were made in this study. The microcapsulecarriers have water98%, protein1.2%, and no polysaccharide. The cheeselikecarriers have water59%, protein26%, and polysaccharide8%. There are somedifferences between artificial carriers and Tibetan kefir grains: more Lactobacillushelveticus and less Lactobacillus kefiranofaciens in artificial carriers. After ferment,microstructure and compositions of these two carriers changed greatly, and thenumber of microorganism increased. However, no polysaccharide connectingmicroorganism was observed. During ferment, their mass decreased, and theircompositions had some trend being close to that of Tibetan kefir grains.