Kefir is a bubbly fermented drink similar to yogurt, made when probiotic bacterial cultures called kefir grains interact with and ferment milk. If you have bulk kefir, you can freeze the drink for later consumption. Freezing does not kill the beneficial probiotics in kefir; they simply go dormant until thawed and consumed. Similar to freezing milk, the solids and whey in kefir will separate in the freezing process, but you simply shake the thawed kefir to reincorporate.

Pour the kefir in moisture-vapor resistant containers, such as freezer bags or plastic freezer storage containers, leaving one-half-inch of head space at the top for a pint of kefir, 1 inch for a quart of kefir or 1 1/2 inches for a gallon container. If the container has a narrow opening, provide 1 1/2 inches of head space at the top regardless of the amount of kefir.

Remove as much air from the containers as possible and seal the containers or bags tightly to prevent air from damaging the kefir. Label the containers with the date of freezer storage and the freezer expiration date, about 3 months after freezing. Write directly on the container or bag with a permanent marker or make a label using a piece of freezer tape.

Place the kefir containers against the walls of the freezer, where the temperature is coldest, so the kefir freezes as quickly as possible. Damage from moisture and vapor is less likely to occur when the kefir is frozen fast. Leave them against the walls for about 24 hours or until frozen solid, then move the containers anywhere in the freezer if you wish.

Remove the kefir container from the freezer and place it in the refrigerator to thaw at least 24 hours before you plan to drink it. Thawing time depends on the type of packaging; a gallon of kefir frozen in a solid block inside a plastic storage container takes considerably longer to thaw than a pint of kefir stored flat in a freezer bag.