How To Make Kefir

Introduction

Kefir is simple to make, as the kefir grain microbes work at room temperature and no heat is required. The basic method is the same, whether using dairy milk or a substitute. In a nutshell, bacteria and yeasts in the kefir grains ferment milk to make kefir at room temperature. When enough acid is produced to make the milk curdle, usually at about pH 4.6, it is done. The grains are strained out and put in fresh milk to make another batch, and the kefir product can be eaten or drunk, or put in the fridge for later.

Just as its composition can be an unknown quantity, almost every aspect of the production of kefir is also variable: the quantity of grains used, the type of milk, the fermenting vessel, when you stop fermenting, what you flavour it with and how you eat it. To make kefir that tastes delicious and is mild enough for all to enjoy, follow the basic method below.

Finding Your Kefir Grains

Strainer with fresh kefir grains separating from kefir water

First, you will need some kefir grains. If you know someone who makes their own kefir, ask them for some – you will only need half a teaspoon to get started. Alternatively, they can be purchased online. Fresh grains are preferable; dried ones are available, but they require prior reconstitution, following the given instructions.

When you get your grains, take a moment to contemplate that these fascinating structures, containing billions of microscopic creatures, are direct descendants of those original kefir grains from thousands of years ago. If you gently prod them with a teaspoon, you will find that they are extremely gelatinous and cannot be easily damaged or destroyed.

If you are using some kefir grains for the first time, it is best to follow the acclimatization instructions below, to ensure that the grains are working before you waste a whole pint of milk. Be sure to follow the basic hygiene principles.

The Fermenting Set-Up

The set-up you use will have a significant effect upon your kefir – indeed, it is one of the easiest ways to influence the flavour. The two set-ups below will result in subtly different kefirs. You might prefer one over the other (the flavour from the anaerobic/closed method is a good starting point for most people), but there are no rights or wrongs. Remember, kefir was originally made in a goatskin bag!

An anaerobic system with a small head of oxygen in the jar provides a microaerophilic environment that favours growth of LAB. While it supports the growth of carbon dioxide- and alcohol-producing yeasts, they grow less efficiently without oxygen, as do oxygen-requiring Acetobacter sp. This means that lactic acid will be a more dominant source of flavour in this type of kefir than yeasty or vinegary flavours. Another advantage of this anaerobic set-up is that the low oxygen conditions make it very difficult for any contaminating moulds to grow, although this is quite unlikely in the 24-hour fermentation time.

Open/aerobic system on the left; closed/anaerobic system on the right.

The aerobic/open system has a cloth cap to keep out contaminants and to allow easy movement of gases in and out. The lactobacilli will be content with the low levels of oxygen at the bottom of the jar, which they like. The yeasts will have greater access to oxygen and will create energy through a much more efficient pathway, enhancing their growth. This will taste yeasty but will contain relatively little alcohol. It may be slightly fizzy, but some of the carbon dioxide produced will escape. If Acetobacter sp. are present, which require oxygen to convert alcohol to acetic acid, your kefir might gain some vinegary flavours.

Vessels for Fermenting

For a closed system, you need to use a vessel that will keep oxygen and airborne contaminants out but will allow a little expansion for carbon dioxide production. Good quality clip-top jars with rubber gaskets are perfect for this. Kilner or IKEA jars, for example, have dishwasher-safe metalwork and are extremely sturdy. Similar-looking jars that have been sold with sweets inside are not designed for kitchen use and may not be robust enough. It is not essential to use glass (ceramic containers can be suitable), but glass is non-porous, non-reactive and allows you to see what is going on.

If you do not have a clip-top jar, or are making a smaller quantity of kefir, use an ordinary jam jar. The lid should be left a turn undone, to prevent too great a build-up of pressure. Always make sure that you clean the lid (especially metal lids, which have a lip) as well as the jar. If you do not have a suitable jar, you can just use a bowl with a beeswax or silicone cover, or a plate over the top.

To make an aerobic system, you need a jar of larger capacity than the amount of kefir you want to make. You could use a litre clip-top jar and just fold the lid back, or unclip it all together. You’ll also need a rubber band and some sturdy kitchen roll or a piece of linen.

Technically, there is nothing wrong with using plastic containers, although they can make the milk smell slightly odd. If that does not bother you, go ahead; you could even simply put the grains straight into a plastic pint milk bottle (as long as you do not mix up milk and kefir). Before knowing the Vessels for fermenting you have to know about the details of how to dehydrate.

CHOOSING YOUR MILK

Animal Milks

Use fresh milk that is not near to being on the turn – pasteurized cow’s milk contains Paenibacilli, non-harmful psychrotrophic bacteria that survive pasteurization and eventually cause milk spoilage. If you use milk when it is about to go off, they can compete with the kefir grain microbes and the milk will turn before it has a chance to make kefir.

Organic milk is a good option as the cow’s natural diet contributes to a product with a superior nutritional composition. The higher the fat and protein content, the more luxurious-tasting and thicker the kefir. In recent years there has been a tendency to opt for ‘low fat’ products in the belief that these are healthier, but in this context, using ‘whole’ milk is fine. At least some of the fats will be broken down into free fatty acid components that could be useful for your own commensal gut bacteria. Any fresh animal milk works, from skimmed cow’s to full fat Jersey, goat, sheep or even camel if you can find it.

You can use either homogenized or unhomogenized milk. There is some debate about homogenized milk having a reduced nutrient content, but it certainly makes smoother kefir. Given the ability of kefir microbes to break down fats, this may not be as important a consideration. Goat’s and sheep’s milk have a different structure and are naturally more homogenized.

Raw (unpasteurized) milk can be used, but sometimes people find that it is hard to make kefir from it. This is because there are so many other bacteria, including LAB, already in the raw milk, competing with the kefir bacteria for food. However, turning it into kefir could be a safer way of consuming raw milk: there are so many ‘good’ microbes in the kefir grains that they can usually inhibit the growth of small numbers of pathogenic (harmful) bacteria that could be present in the unpasteurized milk. On the other hand, studies have also shown that the very nastiest pathogens can survive and even proliferate in kefir cultures. If you are keeping raw milk at room temperature for 24 hours to make kefir, you would have to accept the risk that, if there are pathogens in the starting milk, there could be more of them in the finished kefir. This kefir should not be fed to children, the elderly or those who are immunocompromised. If using raw milk, divide your grains and freeze half, just in case an issue arises.

UHT milk gets a rather bad press, as it is felt to be comparatively poor in terms of nutrients. However, it may be the only milk available, and kefir made from UHT milk is better than no kefir at all. The proteins are denatured by the treatment and it does not seem to make a particularly unctuous kefir, but there will still be some nutritive value from the action of all those microbes.

Fresh milk can also be baked, in order to produce a Russian type of kefir called ryazhenka, which is delicious. Simply bake the milk for 6 hours first in a very low oven. Firstly you may learn about rehydrating.

Plant-Based Milks

Milk kefir grains can be used to make kefir from soya, oat, rice or any nut milk, but it is true to say that some are an acquired taste! The key to success is to use a nutrient-rich substrate. Many plant-based milks have as few as 12 calories per 100 millilitres, which is not enough to support a greedy population of kefir grains. Ideally, you are looking for a product that has a good distribution of protein, fat and carbohydrate, providing a variety of nutrients to match the variety of nutritional requirements of the kefir grains. Home-made nut milks can be a fantastic choice, as they are additive free. Alternatively, you can mix some different types together.

Soya milk kefir thickens nicely.

Wooden spoon over jar with kefir milk, kefir grains on top

Soya milk has been well studied in the scientific literature and has a reasonable protein content: soya kefir contains several bioactive peptides that are proposed to be beneficial.35 It also contains all the essential amino acids needed by the human body. A home-made plant-based milk would be an ideal substrate. Additive-free tinned coconut milk (Aroy-D or Biona) can result in a thick, almost yoghurty kefir.

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