Even though the milk kefir grains feeds on lactose resulting in a low-to-none lactose containing end product, milk kefir is not suitable for vegans. Thats why i want to train the milk kefir grains to ferment plant-based milk. Using plant-based milk is already possible, but because the plant-based milk doesn’t contain any lactose the kefir grains will starve and eventually die.

I want to research if it’s possible to slowly train the grains to eat other sources of sugar (forcing fast evolution). I’ll slowly introduce soy milk (because of its high protein).

Soy milk does contain sucrose and stachyose[^1] as the main sugar component. Because lactose breaks down into glucose and galactose (a sugar close to glucose) i’ll add glucose to the soy-milk. I make the soy-milk myself, using 1L of water with 100g (dried) soybeans.

To see how the kefir grains improve when slowly transitioning i will have 2 control groups; 100% soy-milk, and 100% milk.

Each day i’ll make a new batch, and examine the kefir grains based on their looks and reproduction/weight.

The schedule for training the grains is as follows:

Day % Soy % Milk
Day 1 10 % 90%
Day 2 20 % 80%
Day 3 30 % 70%
Day 4 40 % 60%
Day 5 50 % 50%
Day 6 60 % 40%
Day 7 70 % 30%
Day 8 80 % 20%
Day 9 90 % 10%


The results of the examination:

Weight Milk Soy & Milk Soy
Start (25-03) 20g 20g 20g
Batch 1 (26-03) 22g 26g 27g
Batch 2 (27-03) 25g 25g 22g
Batch 3 (28-03) 27g 33g 23g
Batch 4 (29-03) 32g 35g 22g
Batch 5* (30-03) 37g 41g 25g
Batch 6** (31-03) 47g 57g 22g
Batch 7 (01-04) 43g 58g 22g
Batch 8*** (04-04) 69g 92g 26g
Batch 9** (06-04) 35g 42g 17g
Looks Milk Soy & Milk Soy
Batch 1 Buttermilk-like structure Milk separated, yoghurt-like texture, slightly fizzy Milk separated a lot, fizzy taste
Batch 2 Buttermilk-like structure Milk separated, yoghurt-like texture, slightly fizzy Milk almost completely separated, strong fizzy taste
Batch 3 Buttermilk-like structure Strongly fermented and fizzy, jar almost exploding Very liquid, slightly fermented smell and taste
Batch 4 Fizzy/fermented. Thick buttermilk Very fizzy, nice slightly fermented smell, thick buttermilk texture Very liquid, minimal fermented taste and smell
Batch 5* Partly separated, less fizzy, curdled texture Heavily curdled texture, fizzy, pleasant sour yoghurt-like, slightly thicker, strong soy flavour, mild fermented smell
Batch 6** Fizzy, curdled. Fermented taste Thick structure, but more liquid than previous batch More fizzy than expected, slightly thicker texture, pleasant taste but still too soy-like
Batch 7 same steady result similar to batch slightly thickened. Too soy-like taste (not pleasant)
Batch 8 very curdled very fermented minimal fermented, very stinky
Batch 9 same results as previous batch same results as previous batch same results as previous batch
Batch 10 x x x

Looks of the first batch (after 24h of fermenting):

*Used other kind of soy milk (AH huismerk sojadrink) ** Shorter fermentation time (18h) * Didn’t take care of the kefir in the weekend, fermentation time for batch 8 is 62h ** To get a good result of how much the grains have grown i rinsed them with water to remove all the milk. The weight is lower compared to te results where i didn’t wash the grains


Looks of the second batch:


Looks of the grains at starting point:


Grains after batch 2:







31-03: I noticed the grains in 100% soy don’t reproduce and their effectiveness starts to decline. The grains in 100% milk have a steady consistency, but the mix-grains ferment crazy fast. Yeast and bacteria work more effective when submitted to manageable amounts of stress, but i also hope they react well to the glucose added. The soy-kefir has a very strong soy taste which is displeasing. Hopefully i can successfully make oatmilk-kefir in the future, which probably doesn’t have a strong by-taste.

I switched to store bought soy milk since it wasn’t doable to make soy-milk each morning, and the grains seem to react better on the store bought milk, probably due the higher sugar content.

07-04: The soy/milk grains are now completely converted to soymilk. Of all the batches, they’ve reproduces the most, going from 20g to 42g (where the milkgrains reached 35g and te soygrains shrunk to 17g). I hope the grains stay vital and don’t need lactose anymore. Further tests will get their own page ;)

[^1] Genetic Variability of Seed Sugar Content in Worldwide Soybean Germplasm Collections