Grains may become stressed from overcrowding, lack of nutrients or contamination. Under any of these conditions you may experience the following;
• Grains become very slimy (a mild sliminess is normal as the pro-biotic content is in the sliminess).
• Kefir smells unpleasant.
• White film forms on top of finished kefir.
• Grains diminish in volume.
In any of the above situations occur, the grains may benefit from a rinse, rest, and recovery period. Rinse the grains in filtered water; rest the grains in pasteurised, fresh, full cream milk in the refrigerator for a week or two; then get them back to work. It may be necessary to repeat the procedure a few times to completely recover the grains.
Each batch of kefir is unique and may not proceed exactly as the previous batch. Some common variations include but is not limited to;
Faster or slower culturing
The volume of milk cultured per batch and the culturing temperature may affect the rate of fermentation for each batch. Beware of drafts from doorways or heating vents, which may alter the culturing temperature and affect the finished product.
Floating or sinking of kefir grains
The position of the grains does not influence their effectiveness.
No growth or multiplication of grains
While kefir grains often do grow and multiply, they are sometimes reluctant to do so. Even if kefir grains do not grow or multiply, they should still make good kefir indefinitely. If a faster rate of multiplication is required, feed kefir nutrients to your kefir.
Rapid growth of grains
Under the right conditions, kefir grains may grow and multiply very quickly. Too many grains in a batch may crowd the bacteria and cause the milk to culture several hours faster than usual.
White film developing over the Kefir
White, green, orange, red or black spot formations on the surface of kefir does not generally occur however if it does immediately toss the entire batch, including the kefir grains. This may be dangerous to your health. Get a new batch of grains and start afresh.
If a white fuzzy film appears on the kefir’s culturing surface it is most probably yeast, this film is then non-pathogenic and regarded as generally safe.
Technically speaking it is yeast forming certain pseudo-mycelium which mimics the look of fuzzy mold (but it's not mold).
It usually happens as a result of one or a combination of the following: higher temperatures or tropical climates, too many grains in too little milk (which will increase the activity of the yeast), lack of regular milk changes and/or letting the kefir constantly over-ferment before changing it to new milk.
Sometimes it will form on ripening kefir. In this case, you can help discourage the mycodermia from forming by putting an airlock on the lid since the mycodermia thrives on oxygen.