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COMPONENTS	/100 gm	COMPONENTS	/100 gm
Energy Fat [%] Protein [%] Lactose [%] Water [%]	61 KCal *a 3.5 *a 3.3 2 ~ 3.5 *a 87.5	Minerals Calcium Phosphor Magnesium Potassium Sodium Chloride	mg 120 100 12 150 50 100
Milk acid Pyruvic acid Hippuric acid Orotic acid Citric acid Lactic acid Ethyl alcohol Butyric acid Palmiitic acid Palmitoleic acid Oleic acid Cholesterol [mg] Phosphates [mg]	gm 0.8 *b *b *c *c 1 *d 0.9 *e *h *h *h *h 5 ~ 13 *i 40	Vitamins A Carotene Thiamin B2 B6 B12 [μg] Folic acid [μg] Niacin C D E	mg 0.06 0.02 0.02 0.17 0.05 0.5 4.3 ~ 9.3 *f 0.09 1 0.08 0.11
Essential Amino Acids Tryptophan Phenylalanin+tyrosin Leucine Isoleusine Threonine Methionine+cystine Lycine Valine	gm 0.05 0.35 0.34 0.21 0.17 0.12 0.27 0.22	Trace Elements Iron Copper [μg] Molybdenum [μg] Magnesium [μg] Zinc	mg 0.05 12 5.5 5 0.36
Aromatic Compounds Acetaldehyde *g Diacetyl *g Acetoin *g

*a There is room for debate regarding energy value of kefir, which is derived not only from fat content of kefir [which is slightly changed and reduced especially if kefir is ripened], but also from protein and the carbohydrate of ready-to-consume kefir. The majority of digestible carbohydrate of kefir is milk-sugar [lactose], of which at 24 hour fermentation followed by 24 hour storage seems to be approximately 3.5%, going by the figures available. This is about 50% of the original lactose content of fresh milk. We need to consider that the figures given in the table above were assessed from kefir prepared with commercial starter-cultures [and not prepared with kefir grains].

This needs clarification, for we also need to consider that kefir prepared with kefir grains, the grain is synthesized from lactose by specific encapsulated organisms. Any portion of lactose synthesized into kefiran, which becomes part of the ever increasing grains, remains unavailable as energy, for the kefir grains are separated from the kefir before consumption. Remaining with the grains is the kefiran synthesized from a portion of lactose found in the milk. Also, any synthesized kefiran found in the actual kefir, may have no energy value, for kefiran is not readily digestible. This is because the variety of linkage types of the kefiran molecule accounts for the rather poor accessibility of kefiran to enzyme attack. The length of fermentation, and kefir grain-to-milk ratio for preparing kefir, including the growth rate of the actual kefir grains, may play an important role in determining the amount of, and the value of carbohydrate of kefir prepared with kefir grains. More research is needed in regards to carbohydrate of kefir prepared with kefir grains.

*b Although Pyruvic and Hippuric acids are produced during fermentation, neither was detected during storage [kefir stored for 21 days @ 4°C]. [1]

*c Orotic and citric acids increase slightly during storage [kefir stored for 21 days @ 4°C]. [1]

*d The form of lactic acid in kefir is almost 100% L-Lactic acid, as apposed to yogurt, which contains almost equal proportions of D-Lactic acid and L-Lactic acid through fermentation of lactose. For this reason kefir is quite suitable as infant food. D-Lactic acid can cause Lactic acidosis, of which infants are especially susceptible. It has been noted that Lactic acid concentration increases during storage, reaching a maximum of 7739 parts per million [ppm] by day 21 with kefir stored at 4°C. [1]

*e Initial Ethanol content of fresh kefir varies, although Ethanol concentration increases during storage. [1] Ethanol may reach a maximum of 2% to 3% alcohol by volume, depending on the initial lactose content of the fresh milk, including culture and ripening conditions and length of fermentation including the amount of culture used to inocluate milk.

*f Under parallel culture-conditions, kefir prepared with traditional kefir grains [Vs commercial starter-cultures ] has the lowest folacin content in the fresh product [day 0], however, it exhibits the highest rate of folacin biosynthesis during storage [over culturing fresh milk with commercially prepared starter-cultures]. Kefir prepared with traditional kefir grains, folacin increased by 116.2% during storage for 48 h @ 4°C. [2]

*g Amounts of acetaldehyde and acetoin increased during fermentation. Acetaldehyde content in kefir samples doubled from day 0 to day 21, reaching a final concentration of 1.1g/100g. During storage, the concentration of acetoin decreased from 25 ppm on day 0 to 16 ppm on day 21. Although diacetyl was not detected during fermentation or storage,[1] other research explaines kefir does contain diacetyl[5]. The nature of the mother-culture, medium, culture conditions including storage play an important roll regarding biosynthesis of compounds of kefir.

*h Three isomers determined by a two-step methylation method followed by gas chromatography was used to identify conjugated linoleic acids [CLA] isomers of (c9, t11; t10, c12; t9, t11), butyric, palmitic, palmitoleic, oleic acids, which have been proven as antimutagenic components [protects damage to DNA of body cells] of milk fat, were in higher concentrations in kefir, than that found in fresh milk and yogurt. [3]

*i Research in 1993 in Yugoslavia explains that the organisms of kefir grains assimilate cholesterol in milk by some 84 to 41% during a 24 hour culture-cycle with the kefir grains in milk followed by 48 hour storage. Out of 6 batches of kefir grains, some were more effective at assimilating cholesterol than other batches. A smaller amount of cholesterol is reduced during storage compared to the incubation period with the kefir grains.[4]

END NOTES Raw unpasteurized milk contains greater quantities of heat sensitive vitamins such as some 30% more vitamin B12 than pasteurized milk, which will reflect the content of those vitamins in kefir. Milk exposed to direct sunlight will have a reduction in Riboflavin content, because of the sensitivity to Ultra Violet radiation of this particular vitamin. For this reason among others, culturing kefir in clear, glass containers should not be exposed to direct sunlight. The table of contents above does not explain the vitamin content of raw milk kefir, for figures were not available to the author at the time of writing.

 

References

1. Guzel-Seydim Z, Seydim AC, Greene AK. 2000. Organic acids and volatile flavor components evolved during refrigerated storage of kefir. J of Dairy Science. Dep. of Animal & Vet. Sci., Clemson University, SC 29634-0361, USA.

2. Drewek Z, Czarnocka-Roczniokowa B. 1986. Microbiological processes in folacin synthesis in kefir. Acta Alimentaria Polonica 12[1]:39-45. Dep. of food Eng. & Biotch., Argric. & Tch. Uni., Olsztyn Poland.

3. GuzelL-Seydim ZB, Seydim AC, Greene AK, Tas T. 2006. Determination of antimutagenic properties of acetone extracted fermented milks and changes in their total fatty acid profiles including conjugated linoleic acids. International Journal of Dairy Technology; 59[3]:209-215

4. Vujicic IF, Vulic M, Könyves T. 1992. Activity of kefir cultures in the assimilation of cholesterol in milk. Biotechnol. Letters.;14[8]:47–850

5. Zourari A & Anifantakis EM. [1988]: Le kéfir: Caractères physico-chimiques, microbiologiques et nutritionnels. Technologie de production. Une revue. Lait.;68:373-392.

References to some of the figures represented in the Table Above

Hallé C, Leroi X, Dousset & M. Pidoux 1994. Les Kéfirs : des associations bactéries lactiques-levures. In Roissart De H, Luquet FM. [Eds], Bactéries lactiques: Aspects fondamentaux et Technilogiques; 2:169-182 Uriange, France, lorica,

Rener E, Renz-Schaven. 1986. Nahrwerttabellen für milch und milchprodukte. Verlag B. Renner. Köhner KG. Gieben, Germany

Akalin AS, Gönç S, Dinkçi N. 2004. Liquid Chromatographic Determination of Thiamin in Dairy Products. International J of Food Sci. and Nutrition.; 55[4]:345-349

 

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Characteristics of Kefir During Storage

Changes in microbiological, physicochemical, including sensory parameters of kefir were studied during cold storage. Batches were prepared with 1% and 5% added kefir grains. Samples for analysis were taken 24 hours after inoculation, followed by 2, 7, 14, 21, and 28 days of the liquid kefir stored at 4 to 6°C. After fermentation for 24 hours with kefir grains [inoculation], lactobacilli and lactococci were found at levels of 100,000,000 colony forming units per millilitre [cfu/ml], and yeasts and acetic acid bacteria were present at levels of 100,000 and 1,000,000 cfu/ml, respectively.

Lactic acid producing microflora decreased by approximately 1.5 log units between days 7 and 14, and stabilized at that level. Yeast and acetic acid bacterial counts, lactose, and pH remained constant over the storage period. However, the total fat content and dry matter decreased. The percentage of kefir-grains did exert an influence, and the sample batches made using 1% added kefir-grains had higher lactic acid bacterial counts, lactose, and pH. The sample batches prepared with 5% added kefir-grains had higher yeast and acetic acid bacterial counts and viscosity. The total fat and dry matter contents were similar in both sample batches. Sensory profile of the kefir samples revealed maximum acceptability levels in the first 48 hours of storage.

Reference

Irigoyen A, Arana I, Castiella M, Torre P, and Ibáñez FC. 2005. Microbiological, physicochemical, and sensory characteristics of kefir during storage. Food Chemistry;90[4]:613-620

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