Ferments - Dairy Kefir
In a nutshell
Dairy kefir is fermented milk containing healthy nutrients, prebiotics and probiotics
Those with lactose-intolerance or following a FODMAP diet should proceed carefully
Dairy kefir is easy to make at home
Figure 1: Dairy kefir showing kefir grains on non-metallic spoon
What is Kefir
Kefir comes in two forms, dairy and non-dairy. This post is about dairy kefir which is fermented milk made using kefir grains. It is thicker than milk but not as thick as yogurt, it’s taste can range from mildly to very tart and it has a bubbly mouth-feel [1,2].
Dairy kefir is thought to have originated in the Caucusus region of eastern Europe [3] and can be made from cow, goat and sheep milk.
Kefir is often compared to yogurt. The two can taste similar but they are quite different. Kefir is produced differently and has a very different composition. Kefir is made by adding bacteria and fungi (yeasts) to milk whereas yogurt is produced by bacteria only. Kefir, therefore, contains more potentially beneficial components. Kefir also tends to have a less viscous (runnier) consistency.
“…complexity and ingredient synergy are the keys to the health benefits of dairy kefir.”
Is Kefir healthy, and how much can be consumed?
Kefir contains a mixture of macro- and micronutrients, metabolites, prebiotics, and probiotics which originate from the combination and interaction between the milk used, and the microorganisms in the kefir grains [4].
The reported health benefits of dairy kefir may be caused by the presence of probiotic microorganisms, the broad range of bioactive metabolites formed during fermentation, or the interaction of those two with our body or our gut microbiome. My own view on this matter is that complexity and ingredient synergy are the keys to the health benefits of dairy kefir.
There is evidence that dairy kefir may benefit many types of human ill-health [4]:
Bacterial and fungal infections
Chronic inflammation
Excessive oxidation
Chronic high insulin
Cancer
High blood pressure
Type II diabetes
Mental health
Gut health - irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD)
Lactose intolerance
Dairy kefir is generally considered low FODMAP because the fermentable carbohydrate in milk (lactose), which gives raw milk a high FODMAP rating, is mostly fermented by the microorganisms in the kefir grains.
I’ve read recommendations that range around one to two cups of dairy kefir per day. I consume in the order of two to three cups per day sometimes on its own, sometimes with berries, and sometimes with berries and added supplements as a post-exercise drink.
“...most of the lactose in milk is fermented and does not appear in dairy kefir. However, small amounts can persist and anyone intolerant of lactose should proceed with caution.”
Can dairy kefir be harmful?
Any natural food type can have deleterious effects which is why each of us should decide for ourselves what to eat. The consumption of fermented food is no exception. It is especially important to test the waters by taking a small amount initially to ensure no ill effects and proceed from there.
Dairy kefir presents potential challenges for anyone who may be lactose intolerant or not used to dairy kefir, or any fermented food for that matter.
As described above, most of the lactose in milk is fermented and does not appear in dairy kefir. However, small amounts can persist and anyone intolerant of lactose should proceed with caution. Lactose can be reduced to a minimum during the fermentation process described below.
Those suffering from things like IBS and IBD, should also be careful. Kefir is often described as low FODMAP and can also be made so as much as possible in the fermentation process described below.
How is dairy kefir made?
This is a simple, straight forward process that, once started, is very easy to perpetuate. I’ve found that the greatest challenge is taking the time every couple of days to remove the grains from a mature batch and start a new one.
Equipment and ingredients
Kefir grains – I get mine from Happy Kombucha in the UK
Milk – I use unpasteurized whole fat but pasteurized and reduced fat works too
Glass or plastic fermentation jar – I use glass Kilner jars
Lid, cloth or paper to keep dust out of the jar
Plastic sieve or strainer – never metal
Plastic spatula – never metal
Glass or plastic storage jar – I use a bowl to collect and store the ferment in the fridge
Scale capable of weighing gram amounts – for weighing kefir grains
Kefir Grains
Kefir grains look like small, irregularly lobe-shaped cauliflower-like florets (Figure 1), range in colour from white to slightly yellow, and have a gelatinous texture. They are composed of a mixture of bacteria and fungi (yeast) living symbiotically within a matrix of complex carbohydrates [4].
Fermentation method
The process described below is pretty generic. The best thing to do is follow the instructions that come with bought kefir grains.
Activate the grains according to the suppliers instructions. The ones I use come with mixing and temperature recommendations
5g of grains to 250mL of milk
Fermented at a temperature between 18oC (64oF) and 20oC (68oF)
Ferment until the milk looks like it’s beginning to separate (Figure 2)
This typically takes between 24-h and 48-h depending on the grains: milk ratio and the temperature used (see 1 above)
The extent of the fermentation is a matter of choice. The milder taste I prefer comes from kefir that shows incomplete milk separation (Figure 2)
Stronger (tangier) tasting comes from kefir in which the milk is more completely separated
Strain the finished kefir through a sieve into a collection bowl
Use spatula to carefully work kefir through the sieve and ensure grains are collected in sieve
Transfer grains to scale for weighing
Once kefir is separated from grains, refrigerate for future consumption
Weigh collected grains and start a new fermentation as described starting above at 1
Figure 2: Partially separated milk at end of my kefir fermentation
A few principles apply as follows:
• Keep the ferment away from direct sunlight. It can disrupt the fermentation and may encourage production of harmful microorganisms
Ensure that all equipment is always clean
Once grains are activated and established, they will multiply. The main thing to remember is the ratio of grains:milk (e.g., 5g:250mL) ratio. Once I reach the volume I want for each fermentation (1,750 mL) I remove excess grains and eat them. Alternatives may include starting an additional ferment, giving to a friend or disposal
For anyone interested in a tangier taste or who wants to reduce the lactose as much as possible (e.g., for lactose intolerance or FODMAP reasons), the fermentation process described can be adjusted as follows:
Increase the fermentation temperature – the supplier should provide a not-to-exceed for the grains
Increase the fermentation time
Conduct a secondary fermentation – once the grains are removed, keep the ferment going with the small amount of microorganisms dispersed outside the grains in the kefir
Grain storage
If for any reason, it’s not possible to maintain a 24-h to 48-h fermentation process, the grains can be removed and safely stored. The grains I used can be stored in the refrigerator at the same 5g:250mL, grain:milk ratio used in the ferment. I’ve done this successfully for one to two weeks and I’ve read that it can be used for up to a month.
Once I want to start the fermentation again, I just take the jar out of the fridge and ferment as usual.
References
The Art of Fermentation: An In-Depth Exploration of Essential Concepts and Processes from Around the World. Sandor Elix Katz (2012)
Fermentation: How to Make Your Own Sauerkraut, Kimchi, Brine Pickles, Kefir, Kombucha, Vegan Dairy, and More. Asa Simonsson (2019)
Gänzle M. The periodic table of fermented foods: limitations and opportunities. Appl Microbiol Biotechnol. 2022 Apr;106(8):2815-2826. doi: 10.1007/s00253-022-11909-y. Epub 2022 Apr 12. PMID: 35412130
Azizi NF, Kumar MR, Yeap SK, Abdullah JO, Khalid M, Omar AR, Osman MA, Mortadza SAS, Alitheen NB. Kefir and Its Biological Activities. Foods. 2021 May 27;10(6):1210. doi: 10.3390/foods10061210. PMID: 34071977; PMCID: PMC8226494