KEFIR Kefir grain fermented dairy or "water"
Kefir is a cultured-milk beverage believed to have originated many centuries ago in the Northern Caucasus Mountains. Kefir milk has a uniform creamy consistency, a slightly sour taste somewhere between buttermilk and sour cream, and a mild yeasty aroma. Kefir may have small amounts of carbonation and alcohol. It can be enjoyed plain or sweetened to taste. Traditional kefir is prepared by combining fresh milk with the Kefir culture.
Water kefir is a newer derivative of traditional dairy kefir made from water and sugar or water and fruit juice instead of milk.
HACCP Category: Food Code 3-502.11 Special Process - Kefir is a symbiotic yeast/lactic acid bacterial culture fermented milk or fruit juice. With yeast present, it may contain alcohol and possibly ≥ 0.5 ABV if the starting level of sugar is high.
Ingredients: dairy milk (usually low fat or skim) or water with fruit juice, sugar (optional), and kefir grains (culture).
- Pasteurize all ingredients except the kefir culture.
- Cool to 64 - 72°F and add 2% to 5% kefir grains or culture.
- Ferment at 64 - 72°F for ~24 hours. After that time the pH ≤ 5.0. Fermentation can be continued to a lower pH.
- Sieve out the kefir grains and package the liquid kefir. The final kefir product can be flavored with fruits, fruit juices, or spices, but the flavoring cannot raise the pH > 5.0.
- Note: As kefir ferments the pH will continue to drop from 5 to 4. At approximately pH 4.5 the milk kefir will begin to set. Therefore, drinkable kefir should be pH 4.5 – 5 and kefir cheese would be ≤ 4.5 pH.
The kefir culture is more commonly referred to as “grains” since it forms grain-like casein-polysaccharide-microorganism particles during fermentation (photo at left). The exact combination of bacteria and yeasts vary between kefir cultures, and might include: Lactococcus lactis subspecies: lactis, cremoris, or diacetylactis, Leuconostoc mesenteroides subsp. Cremoris, Lactobacillus kefyr, Klyveromyces marxianus var. Marxianus, and Saccharomyces unisporus. To ensure consistency and absence of pathogens, use a commercial source for your kefir grains. Wild or natural cultures may contain pathogens.
Dairy kefir ingredients before fermentation are considered a Temperature Control for Safety Food (TCS food). Water kefir with sugar alone is TCS. The addition of fruit before fermentation may reduce the pH ≤ 4.2 resulting in it no longer being TCS.
Kefir is generally considered to be safe due to the lack of evidence of foodborne illness events related to it. Properly fermented kefir (pH ≤ 4.5) inhibits many pathogens, but not Escherichia coli, Listeria monocytogenes, and Salmonella spp. These pathogens may grow very slowly or just survive. Care therefore must be taken in the fermentation of kefir to prevent the access or growth of these microorganisms after the pasteurization or heating steps.
- Vegetative bacteria (e.g. E. coli O157, Listeria moncytogenes, Salmonella, and similar). Vibrio and Campylobacter are not expected in these types of foods.
- Vegetative bacteria that produce toxins (Staphylococcus aureus)
- Sporeforming bacteria that produce toxins (Clostridium botulinum, C. perfringens, and Bacillus cereus). B. cereus is associated with outbreaks in starches and grains.
The food safety of flavoring ingredients, fruits, fruit juices, or spices must be assessed when they are added after the fermentation step (generally right before bottling or packaging).
CCP1: Pasteurize all of the ingredients except for the fermentation culture ≥ 145°F for 30 minutes or ≥ 161°F immediately). This will destroy all of the vegetative pathogens that might be present.
CCP2: Ferment RAPIDLY with an active culture to get the Kefir pH ≤ 5 and optionally ≤ 4.2. At pH ≤ 5 with refrigeration, no pathogen can grow. At any temperature and pH ≤ 4.6 C. botulinum cannot grow and at pH ≤ 4.2 no foodborne illness bacteria can grow.
CCP3: Kefir that has a pH > 4.2 must be refrigerated ≤ 41F. SOP: Kefir with a pH ≤ 4.2 should be refrigerated to minimize continued fermentation (quality).