Milk kefir is well-protected by its acidity, so mold is rare. Mold appears as dry, fuzzy, colored spots (green, blue, black, pink) floating on top of the milk surface.

Solution: Discard the entire contents of the jar, including the grains, immediately. It is not salvageable. Sanitize everything thoroughly before starting over with fresh grains.

This is often not mold, but rather dried cream/fat or a harmless yeast (like Kahm) that has discolored.

Solution: If it’s not fuzzy, you can usually just skim it off. Does the kefir underneath still smell good (fresh and sour)? Then it’s likely safe. If in doubt, throw it out and start over.

This is the most common ‘problem’. You see thick white curds floating on top of a clear yellow liquid (whey). This is normal, but it means your kefir is “over-fermented.” The grains have consumed all the food. It is safe, but will taste very sour.

Solution:

• Stir or shake the jar vigorously to mix the layers back together before straining.
• For next time: Shorten the fermentation time (harvest sooner) OR use more milk for the amount of grains you have.

See above regarding “separating.” It has fermented too long, or the grain-to-milk ratio is unbalanced (too many grains for too little milk). This happens faster in summer.

Solution: Harvest sooner or use more milk.

Possible causes:

• Too cold: Below 18°C (65°F) fermentation is very slow. Move to a warmer spot.
• New grains: Grains fresh from the mail sometimes need a week (several cycles) to wake up fully. Keep changing the milk every 24 hours, even if it’s thin.
• Too much milk: The ratio is off. Use less milk until your grains have grown.
• Wrong milk: Lactose-free milk does not work well. Skim/low-fat milk will always be thinner than whole milk.

This often happens in warm weather. The yeasts in the culture become more active than the bacteria, causing a yeasty taste and sometimes carbonation (fizz). This is not dangerous.

Solution: Find a cooler spot for your jar (preferably below 25°C/77°F). You can also give the grains a “reset” by placing them in fresh milk in the fridge for 24 hours to calm the yeasts down.

Milk kefir grains sometimes grow slowly, or take a ‘pause’, especially in winter.

Tips to encourage growth:

• Temperature: Ensure a constant temperature between 20-25°C (68-77°F).
• Food: Use organic whole milk. Change the milk every 24 hours, even if it hasn’t thickened fully. They need fresh lactose to grow.
• Patience: Sometimes it takes a few weeks before they get a growth spurt.

Good news! This is not a problem. That slimy substance is called Kefiran. It is produced by the bacteria and is a sign of a healthy, active culture. Kefiran is actually very beneficial for your gut. Do not rinse it off!