Source: Refs. 10 and 17.
Source: Refs. 10 and 17.
countries and is considered to have health benefits. Among all the fermented dairy products, only this and similar product contain small amount of alcohol. Also, among all the fermented dairy products, pure cultures of bacteria, yeasts, and/or mold are used, but in kefir, the kefir grains are used and recycled. Kefir grains are masses of bacteria, yeasts, polysaccharides, and other products of bacterial metabolism, together with curds of milk protein. Production of kefir is a two-step process: first, the production of mother kefir, followed by the production of the kefir drink. Table 25 lists the basic steps in kefir manufacturing (1-9,18).
Acidophilus milk is considered to have probiotic benefits. Like yogurt, it is advertised as having live cultures of Lactobacillus acidophilus and Bifidobacterium bifidum. These live cultures are claimed to provide the benefit of maintaining a healthy intestinal microflora. Traditional acidophilus milk has a considerable amount of lactic acid and is considered too sour for consumers in some locations. Therefore, a small amount of sugar is added to the final product to make it more palatable. This later product is called sweet acidophilus milk. Table 26 lists the basic steps in the manufacture of acidophilus milk (1-9).
Table 24 Basic Steps in Sour Milk Processing Standardization of milk
Heating of milk to 85-95°C followed by homogenization
Cooling of milk to 19-25 °C and transfer of milk to fermentation tank
Addition of 1-2% start culture (inoculation)
Shock-free fermentation to pH 4.65-4.55
Homogenization of gel
Filling into bottles, jars, or one-way packs or wholesale packs
Table 25 Basic Steps in Kefir Processing
Preparation of''mother'' kefir
Standardization of milk for preparation of mother kefir Pasteurize milk at 90-95°°C for 15 min and cool to 18-22°°C Spread kefir grains at the bottom of a container (5-10 cm thick)
and add pasteurized milk (20-30 times the amount of kefir grains) Ferment for 18-24 hr with mixing 2-3 times. Kefir grains float to the surface Filter out the kefir grains with a fine sieve; wash the grains with water, and save for the next fermentation Save the fermented milk for the next-step inoculation
Blend fermented milk from above with 8-10 times fresh, pasteurized, and untreated milk Fill into bottles, closed and fermented for 1-3 days at 18-22°C [Another option is to mix the fermented milk with fresh milk at 1-5%; ferment at 20-25°C for 12-15 hr until pH 4.4-4.5 followed by ripening in storage tanks 1-3 days at 10°C. Product is not as traditional but acceptable.] Cool to refrigerated temperature Store and distribute
Table 26 Basic Steps for Sweet Acidophilus Milk Processing
Procedure #1 Standardization of milk
Heating milk to 95°C for 60 min, cooling to 37°C, and holding for 3-4 hr, reheating to 95°C for 10-15 min, cooling to 37°C Inoculation with 2-5% bulk starter Incubation for up to 24 hr or to 1% lactic acid Cooling to 5°C Packing and distribution
Procedure #2 Standardization of milk Homogenization of milk at 14.5 MPa Heating to 95°C for 60 min Cooling to 37°C
Inoculation with Direct Vat Inoculation (DVI) starter Incubation for 12-16 hr or to about 0.65% lactic acid Ultra High Temperature (UHT) of 140-145 °C
for 2-3 sec to eliminate undesirable contaminants Cooling to 10°C or lower Packaging and distribution
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