| Summary: | 碩士 === 國立臺灣海洋大學 === 食品科學系 === 94 === Abstract
Kefir is the famous traditional alcohol containing fermented milk, and it is also called champagne yogurt or the angry wine of milk.
The microflora of kefirs were composed different obviously in different areas, mainly are Lactobacillus spp., Lactococcus spp., Leuconostoc spp., Streptococcus spp., Candida spp., Kluyveromyces spp., and Saccharomyces spp., and the predominant genus is Lactobacillus spp. The kefir collected from Belgium, Irish, and Spain of European area also had Acetobacter spp., Pediococcus spp., and Hansenula yalbensis.
The mainly maunfacturing product of marketing kefir was fermented with starters such as kefir grains and freeze dry powder of certain kefir grains. Those starters were inoculated about 1%-10% after activation, and propagating in manufacturing process, then fermenting 12-18 h at 20oC-25oC and refrigerating to yield kefir.
Immobilized kefir grain showed to promote glucose utilization and alcohol production in kefir fermented. After inoculation and fermentation, the microflora of kefir showed that the counts of Lactococcus spp. is increased by about 26-30% and the Lactobacillus spp. is reduced by about 13-23%. While continuous inocubating two times and fermented in succession, the microflora of kefir indicated that the count of lactose not using yeast was obvious reduced. Kefir that inoculate the lactic acid bacteria and ferment in advance, and then Sac. cerevisiae was inoculated and fermented, the Lactobacillus spp. grows better than the Lactococcus spp. in kefir products. While milk or soymilk used as substrate and the kefir grains were inoculated and fermented, the alcohol and diacetyl productions (2,291 ppm and 253 ppm) of milk kefir were higher than soymilk did. Kefir grains was employed as starters for kefir and the inoculation rate is mostly about 5%. As the inoculation rate increased to 10%, the recovered kefir present higher sour and lower stickiness. And more foams were obtained while 1% kefir grains was used for inoculation.
The main flavor components of kefir are alcohol, carbon dioxide, and lactic acid, and the range of their contents in different areas are between 0.184-1.6%, 0.07-3.5%, and 0.036-1%, respectively. Other minor flavor components of kefir are diacetyl, acetic aldehyde, and acetic acid.
The microflora in kefir grains were used to produce extracellular polysaccharides after metabolizing called kefiran, its molecular weight above for 1.0 × 106 dal, and form with the same ratio of lactose and glucose, can make kefir for the emulsification stabilizer.
Several kinds of physiology functions were observed on kefir such as improvement on intestinal flora, antitumor, and antioxidant. After consumed kefir, the lactic acid bacteria was increased in the small intestine of rats, and promotion of inhibition function of Gram-negative anaerobic bacteria in the large intestine was monitored simultaneously. The thymine dimmer can be up to 50% with repair the activation when the kefir extract (1,800 �慊/mL) added to the melanoma HMV-1 cell before has not been injured by UV. The ability of removed DPPH free radical in kefir that ferment to the 32nd hour were 1.5 times higher up than have not fermented milk.
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