Forum: cooking.stackexchange.com
Tags: <freezing><milk><fermentation><kefir>
Title: How to properly freeze kefir grains
Question: I have been making kefir regularly for a couple years. Lately, however, my family's interest in it has waned and I have been using it less often and so feeding it less often.  I want to store some kefir grains so I don't lose them due to my own negligence. I've heard that grains can be frozen but I'm scared to kill some in the experiment.  What is a proven procedure for freezing (and subsequently rethawing) my kefir grains such that they stay viable?

Answers:
sents: text: Less complicated than the other method, but similar steps at the beginning.
text: I have used two methods and both worked.
text: I have heard success stories for grains in the freezer for over a year.
text: No milk powder involved.
text: Wash the grains in both cases.
text: Methods: Put in fresh milk (the same you used before to make the kefir) and then freeze in a plastic container or so (I used a plastic bag)
text: Let the grains dry.
text: Not just with kitchen tissue, but actually leave it dry for an hour or two.
text: Finally put it into kitchen tissue and wrap that in a plastic bag or so for freezing.
text: For thawing I left the grains in the fridge for half a day and then gave them directly into milk.
text: I tested both methods, as stated.
text: Both worked just fine.
text: In my case the max.
text: time was more than 2 months.
text: However, when "reactivating" the grains it took both some time and the results of the first two or three batches were not consumable (well, I guess they were, but just not pleasurable as kefir proper).
answer_details: author: cooking.stackexchange.com/users/5092/0xC0000022L
score: 13
sents: text: One method for storing kefir grains for periods of up to 2 months, is by freezing spare grains.
text: To freeze effectively, wash the grains with pre-boiled COOLED water.
text: Pat-dry the grains between pre-ironed cooled white toweling to remove excess moisture.
text: Place the grains in a jar or in a plastic bag, seal and put in the freezer.
text: With milk grains, first add some dry milk powder, [DMP] adding enough to completely cover the grains with the DMP, seal jar or bag and then freeze.
text: DMP is mixed with the milk kefir-grains as a cryoprotectant agent to prevent freezer burn.
text: Although I've found that kefir grains are viable for up to one year with this method, this length of time may completely remove the yeast component found in healthy kefir grains [if frozen for longer than 2 months, but not specifically].
text: Because of this potential, freezing kefir grains as explained above, is best performed for a period of no longer than 2 months.
text: If DMP is omitted for freezing milk kefir-grains, then a period of no longer than 1 month is recommended.
text: Otherwise the yeast component of kefir grains may become damaged, especially if continual partial thawing and freezing due to poor freezer mechanism is involved.
text: To reactivate frozen kefir grains, thaw by placing the grains in a glass filled with cold water for a few minutes.
text: Place the grains into a strainer and wash off any powdered milk that's adhered to the grains with cold water.
text: http://users.sa.chariot.net.au/~dna/Makekefir.html#Storing_kefir-grains
answer_details: author: cooking.stackexchange.com/users/51/Janelle
score: 7
sents: text: I've successfully frozen and defrosted milk kefir grains.
text: The defrosted kefir grains worked the first time culturing in fresh milk.
text: I washed the kefir grains in filtered water till water was clear.
text: Packed the washed kefir grains into zip lock snack bags with some plain filtered water and heat sealed the bag.
text: I double bagged and heat sealed each bag.
text: After 5 months I took the bag of frozen kefir grains and defrosted at room temperature overnight.
text: In the morning I fed the kefir grains with some warm fresh milk and left to culture for 24 hours.
text: They haven't looked back.
text: Making beautiful kefir every day.
answer_details: author: cooking.stackexchange.com/users/10373/Marg Black
score: 4
sents: text: I have been making kefir for many years now.
text: I always freeze grains using the dry milk powder mentioned above.
text: Four days ago I cleaned our freezer of expired foods and found grains frozen 5 years ago.
text: I was curious it
text: they might be revived after so long since I've never left them for over one year.
text: I rinsed them with tapwater (I admit to being abusive to my grains) then left them in milk at room temperature.
text: I was certain they were dead, but my husband bet they were still viable.
text: Less than 48 hours later, they cultured the milk.
text: After being frozen 5 years they are alive and working well.
text: I'm really surprised.
text: Since I've read frozen viability is much shorter, I wanted to share my experience.
text: Good luck culturing!
answer_details: author: cooking.stackexchange.com/users/76780/Mars
score: 3
sents: text: To freeze milk kefir grains, I place the unwashed grains in a pint glass bottle and fill the jar 3/4 full with fresh milk, put on the lid and place in the freezer compartment.
text: To freeze water kefir grains, I do the same thing only I fill the jar 3/4 full with sugar water, (the same type as I use to make water kefir), put on the lid and place in the freezer.
text: Leaving enouh room for the ice to expand safely in the jar.
text: When I want to reuse either of them, I take the jar out of the freezer and sit it on the refrigerator top until thoroughly thawed and then use as normal.
text: When I first reuse them, they always work immediately as if they had not been frozen at all.
answer_details: author: cooking.stackexchange.com/users/68342/Rick Evans
score: 2
sents: text: I have frozen dairy kefir grains in a 1/2 c canning jar with no rinsing, adding in a little kefir to surround grains.
text: When I was ready to use, I left jar in refrigerator overnight and added to fresh milk in the morning.
text: My grains have been frozen several times and reused in this manner.
text: So far so good.
answer_details: author: cooking.stackexchange.com/users/58534/Catherine Dobbins
score: 1

Summary of the answers:
Milk kefir grains can be froze for several months or even a year before being defrosted.
It is possible to freeze kefir grains for up to a year.