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The phenomenon of milk kefir over fermenting.

Eek! Why is my milk kefir separating? What's the clear liquid at the bottom half of my glass jar? What should we do next and can i drink over cultured milk kefir?

We hear you and in this post we attempt to discuss;

1. Why over culturing happens? 
2. What we can do to prevent milk kefir from over fermenting?

3. How to remove milk kefir grains from over cultured milk kefir.
4. See: When is a good time to harvest post here.

Why over culturing happens? How can we prevent over fermenting?

Usually every 18 to 24 hours will make a batch of milk kefir and over fermenting happens when we leave the cultures for longer than the recommended period of time. But multiple factors come into play leading to over fermented milk kefir.

Milk kefir grains are known to propagate, meaning every time you make a fresh batch of milk kefir, your grains can grow between 5% to 10%, affecting milk to grains ratio. More grains = Faster Ferment. If you suspect this to be the case, remove extra milk kefir grains. A flat teaspoon of active grains is sufficient to ferment 500ml milk over 18 to 24 hours period. The extra kefir grains can be eaten or kept as spare in the fridge. To store, keep the extra grains submerged in fresh milk and refrigerate.
Temperature of the environment is also a factor to consider. Cold temperature can slow down the activeness of the grains, while higher temperature accelerates the process. Year round temperature in Singapore flautuate little and with an indoor temperature of 24 +-, is most favorable for fermentation. With this understanding as long as your ferment vessel is away from sunlight and any heat source (e.g., stove, kettle, hot and cold water dispenser.), temperature is a lesser influence overall.

Milk kefir can be made with any dairy milk, (eg., cow, goat.) but milk choice can influence the taste and texture of the outcome. Cow's milk produce a tangy thick milk kefir, and milk kefir made with lower lactose goat's milk has a distinctive taste and "thinner" texture. The richer the milk, the creamier, tastier, the milk kefir. Whenever possible aim for whole milk, AVOID reduced fat milk and lactose free milk. What about plant's milk? Some has success with non dairy milk, but the result is inconsistent. If you have extra milk kefir grains, we say give it a shot should it interest you. 

How to remove milk kefir grains from over cultured milk kefir?

Finished milk kefir when harvested at the appropriate time will be a thick but pourable consistency. It is fairly easy to pour through a strainer and remove the kefir grains.


Over cultured milk kefir will have separated into curds and whey. At this stage the grains are firmly lodged within the curds and can be challenging to differentiate grains from curds.


Here is an idea what you can do when you have in your hands over fermented milk kefir. And Yes!, over cultured milk kefir is still okay to drink, albeit extremely sour.

Step 1: Vigorously stir and mix over fermented milk kefir that has separated into whey and curds together.

sour milk kefir in a clear transparent glass jar on a table
mixing curds and whey

Step 2 : Run the mixture through your strainer as you would with "normal" milk kefir. This can take multiple rounds as we attempt to break down the curds and separate the kefir grains from the milk kefir.

pouring milk kefir into a strainer with bowl
wooden spoon mixing milk kefir in a strainer

Step 3 : Kefir grains and a small amount of curds might surround the grains still and that's okay. Culture as per normal, transfer the grains into a batch of fresh milk.

milk kefir grains in a sieve


In Conclusion..

Milk kefir grains are surprisingly resilient and can take a little "beating" here and there. They are truly workaholics and prefer to be churning out milk kefir on a consistent and regular basis. Take good care of them and they will produce a lifetime of milk kefir for you and your family.

over fermented milk kefir in a glass jar with flowers in the background
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