March 04, 2020

What is the optimal ratio of milk kefir grains to milk?

What is the optimal ratio of milk kefir grains to milk?

There is a huge difference in opinion in the culturing world and the scientific world on the ratio of milk kefir grains to milk.

Just to give you an idea of the different opinions:

  • Dom from ( - 1.6 tablespoons of grains per 1 cup of milk
  • - 1 teaspoon of grains to 1 cup of milk
  • Kombucha kamp – .5 tablespoons to 1 cup of milk
  • - 1 tablespoon to 1 cup or less
  • Cultures for health –.25 teaspoons per 1 cup of milk

The consensus among home fermenters is from about .25 teaspoons per cup to 1.6 tablespoons per cup.

That’s a huge difference.

What we recommend:

For the first batch or two we tend to recommend using 1 tablespoon to 1 cup of milk just to help adjust to the new environment.

From there they can really take off and usually .5 to 1 teaspoon is enough for 1 cup depending on the environment.

That ratio gives the best flavor and texture in our opinion.

What ratio does the science think is ideal?

Peer reviewed journals measure what can be quantified.

Instead of flavor, taste and what feels right, they measure microorganism counts, grain growth, ph level, lactose level, alcohol level etc.

Those measurements are optimized with more grains and less milk. So in the scientific community, they usually deal with more grains per milk. Ratios such as 3%, 5%, 7%, 10% or even higher is common. That is basically .5 tablespoons per cup of milk to 1.6 tablespoons per cup or more. 

More grains tend to create better growth, a lower ph, less lactose and more alcohol. Basically, a stronger ferment.

From a scientific standpoint, that’s optimized, but is it really?

Best Ratio for Growing Grains

For example, according to a study, a 10% ratio helps grains grow the best. It was compared against a 5%, 15% and a 20% ratio. That is 1.6 tablespoons per cup. Hardly anyone recommends that kind of ratio as it will usually taste horrible with a over-fermented texture.

Even if you wanted to grow more grains, I’m not sure if that’s ideal either. Fast grain growth through over-fermenting is never ideal for the long-term health of the grains.

Best Ratio for Probiotics

There are only two studies I can find that discusses ratio and probiotic count.

The first study tested a ratio of 3%, 5% or 7% per milk. Basically, that means .5 tablespoons of milk kefir grains per 1 cup of milk, .8 tablespoons of milk kefir grains per 1 cup of milk and 1.1 tablespoons of milk kefir grains per 1 cup of milk.

The .5 tablespoons of milk kefir grains had the highest LAC (Lactic Acid Bacteria) probiotic count and the 1.1 tablespoons of grains had the lowest!

The second study completely contradicts the first study. When the ratio increased from from 2% to 5% (more grains), the count went from 450 million CFU to 4.1 billion CFU.

Why the difference?

One reason might be that the first study only tested Lactic Acid Bacteria, while the 2nd study did a total plate count. So perhaps the LAB decreases while the total count increases.

In any case, diversity of microorganisms is better than total count. 

When grains are fermented in a cool slow environment, there is a greater diversity of microorganisms. 

I would suspect the same is true when you ferment with fewer grains. Less grains per milk likely means greater diversity but an overall lower count.

Bottom line

There is a great difference of opinion on what is the ideal ratio of grains to milk.

On the one hand, growth and total probiotic count seem to increase with more grains per milk. However, you may be sacrificing flavor, texture, diversity and health of the grains with too many grains per milk.

Our recommended ideal range falls somewhere in the middle of those advocating for the health of the grains and ferment. 

Our recommendation for optimal flavor, texture and health (once the grains are fully active) is .5 to 1 teaspoon per cup of milk.

What is your favorite ratio of grains to milk?