How to Make Milk Kefir

Milk kefir is not only easy to make, it is a delicious, probiotic-rich, versatile beverage your whole family will enjoy.

Direct-set style powdered Kefir Starter Culture is a great option for people interested in making their own kefir but who do not want to maintain a set of milk kefir grains

Start by gathering your equipment and choosing a variety of milk to use:

Equipment. 

• One glass jar (pint, quart, or half-gallon)
• A plastic, wood, or stainless steel stirring utensil 
• A breathable cover for the jar such as a tight-weave dish towel or paper coffee filter
• A rubber band to secure the cover
• Fine mesh strainer, plastic or stainless steel (optional)

Ingredients. 

• 1/2 to 1 teaspoons milk kefir grains. 
• 1 to 4 cups of milk 

Milk Considerations. Milk kefir grains can be used with pasteurized or raw milk, homogenized or non-homogenized milk, cow or goat milk. We do not recommend using ultra-high temperature (UHT) milk or ultra-pasteurized (UP) milk. UHT/UP milk will yield inconsistent results. If using raw milk, use milk that is fairly fresh to avoid issues with rising bacteria levels. Click here for more information on choosing a milk variety. Alternative milk varieties such as soy milk or coconut milk may be used. Click here for more information on the importance of revitalization periods for the kefir grains when using alternative varieties of milk.

A note about hygiene. When working with kefir, it is important not to introduce competing bacteria to the process. Be sure to wash and rinse your hands well prior to working with the milk. Also be sure to thoroughly clean and rinse the container and all utensils that will come in contact with the milk or the kefir grains. Beware soap and food residue the dishwasher may have missed. When in doubt, give everything an extra rinse. The culturing container can be cleaned with regular soap and hot water (rinse very well) or with vinegar. Never use bleach on any item that will come in contact with the milk or kefir grains.

The Basic Process

1. Place the kefir grains in the milk. Stir the milk and kefir grains briefly. We recommend using a wooden or plastic utensil. If metal must be used, be sure it is stainless steel and not a reactive variety of metal.
2. Cover the jar with a towel or coffee filter and secure with a rubber band. Alternatively a loose lid may be used. (Be sure the lid isn't air-tight).

Culturing the Kefir

Choose a safe spot. An ideal culturing spot should be relatively warm but not excessively so. Temperatures between 70° and 80°F are ideal (see below). The best fermenting spot for kefir is out of direct sunlight. Indirect light or darkness is neither favorable nor problematic. Be sure the kefir is not fermenting near any other cultured foods such as kombucha, yogurt, sourdough, sauerkraut, etc. In addition, do not culture your kefir near a garbage can. Cross contamination of stray yeasts and bacteria can be problematic for the kefir grains and any other fermented foods you are working with.

Stir occasionally. While not required, it can be helpful to occasionally stir or gently shake the culturing mixture. Agitation allows the kefir grains access to fresh milk during the process and will generally speed fermentation.

Allow the kefir to ferment. Check the kefir every 6 to 12 hours or so. Unless it is particularly warm in your home, kefir normally takes at least 24 hours to form. The length of the fermentation period is dependent on ambient temperature. Ambient temperatures that are too hot or too cold can disrupt the process: too cold and the process slows down, too hot and fermentation proceeds too quickly and results in a less desirable flavor pattern. We recommend choosing a culturing spot with an ambient temperature between 70° and 80°F for ideal results.

Remember: Faster fermentation isn’t necessarily better. Slow and steady fermentation results in a more desirable taste profile.

How to Know It Worked

The primary sign that the process worked properly is that the milk will thicken and coagulate. Dairy milk cultured with kefir grains will initially thicken, then coagulate, then separate into curds and whey (solid portion with a clear liquid portion). Ideally, kefir should only culture to the point where it thickens or coagulates. Which particular point is best depends on the taste profile you prefer. Some experimentation may be necessary to find the best point at which to stop the process. We do not recommend culturing the kefir to the point it separates into curds and whey. While it is safe to consume (provided the kefir has not been sitting longer than 48 hours and it smells, looks, and tastes okay), the taste isn't generally considered pleasant and the acidic level of the kefir can be hard on the kefir grains. If you accidentally allow your kefir to over-culture, the kefir can be used for cooking in place of milk in recipes.Please note, alternative milks such as soy and coconut milk may not thicken significantly during the culturing process.

Normal Variations vs. Signs of Problems

Normal Variations. Each batch of kefir is unique and therefore may not proceed exactly as the previous batch. Some common variations include:

• The batch may culture more or less quickly than a previous batch. This is generally a function of the ratio of milk to kefir grains as well as ambient temperature. Beware of drafts that may decrease the temperature in the place your kefir is sitting.
• The kefir grains may sink or float in the milk. The position of the kefir grains does not influence their effectiveness.

Signs of Potential Problems  

Milk Does Not Thicken. If the milk does not thicken after being allowed to culture for 48 hours, discard the milk and place the kefir grains in fresh milk. Do not try to culture kefir grains in the same milk for longer than 48 hours. While the milk and kefir grains were sitting, the bacteria level in the milk has risen which can make the milk unsafe to consume and present a considerable level of competition to the bacteria and yeast that comprise the kefir grains. Competing bacteria can cause damage to the kefir grains. Once the kefir grains have been placed in new milk, move the culture to a new warmer spot (lack of culturing is almost always a temperature issue) and check the kefir every 12 hours to determine at what point the kefir has thickened. If the warmer location does not resolve the issue, it may be that your kefir grains have died. While it is very unusual it does occasionally happen and the kefir grains should be replaced. Please note: alternative milks such as soy and coconut milk may not thicken significantly during the culturing process.

Mold. It is very uncommon to find mold developing on a batch of kefir.  However unlikely, mold can and does occasionally develop and can generally be seen by the formation of white, green, orange, red, or black spots on the surface of the kefir, or a pink discoloration of the milk. Potential causes of mold include:

• Contamination from soap or food residue in the jar or on the utensils used to prepare the kefir.
• Transient yeasts and bacteria in the air or poor hygiene practices when preparing the kefir.  
• Allowing the kefir to ferment too close to a garbage can which can be a source of transient bacteria.
• Allowing the kefir to ferment too close to other fermented foods (yogurt, sourdough, kefir, sauerkraut, etc.) or rising bread made with commercial baking yeast.
• Mold spores in the air from a humid environment such as a kitchen or bathroom or in the air ducts. (High humidity levels in general can make it more difficult to prevent mold.)
• If mold does develop, immediately toss the entire batch including the kefir grains. Do not try to salvage a moldy batch or moldy kefir grains even if you do not see mold on the kefir grains themselves. Doing so may be dangerous to your health. Obtain a new set of kefir grains, clean the jar thoroughly, and try again another day.  

Pests.  Fermenting kefir is very attractive to ants and fruit flies which is why we recommend using a tight-weave cover and securing the cover with a tight rubber band to keep the invaders out. If you find worms (maggots) have infested your kefir, this is a sign that fruit flies or house flies have invaded and laid their eggs. If this happens, immediately toss the entire batch including the kefir grains. Do not try to salvage an infested batch or infested kefir grains. Doing so can be dangerous to your health. Obtain a new set of kefir grains, clean the jar thoroughly, and try again another day.  

Colorful Kefir Grains. Kefir Grains that turn pink, orange, or green may be contaminated. It is best to play it safe and toss colorful kefir grains. Please note: yellow kefir grains are not a bad sign but rather a normal variation.

Safety First! Please note, all this information is presented as suggestion only and does not substitute for using good judgment. No matter what ingredients or ratios you choose to use, regardless of whether visible mold is present or not, we implore you to always use your best judgment when making and consuming kefir and to never consume any kefir that looks, tastes, or smells unpleasant.

Harvesting the Kefir

Congratulations! You’ve brewed your first batch of kefir. Now comes the fun part: harvesting and enjoying your beverage. Prior to harvesting your batch, you will need to prepare a clean jar with fresh milk to transfer the kefir grains into.   

Removing the Kefir Grains. There are several ways to remove kefir grains from finished kefir. Some people simply use their fingers. Be sure your hands are very clean before attempting this! Many people though find that using a fine mesh strainer is more efficient. Simply place the strainer over a bowl or storage container and pour the finished kefir through the strainer. You may need to use your (very clean!) fingers to gently work the kefir through the strainer to locate the kefir grains. Please note: if your kefir has coagulated or separated into curds and whey, it is often helpful to first stir the kefir well to homogenize the liquid prior to pouring it through the strainer.

Flavoring. If desired, kefir can be flavored using flavor extract, fruit, or even flavor syrups. An additional option is to use a secondary fermentation period to infuse the kefir with flavor and allow the kefir yeast and bacteria to develop further. 

Storage Tips. Unless a secondary fermentation period is used, kefir should be immediately stored in the refrigerator. While estimates vary, we recommend consuming kefir within two weeks.