I froze some grains 5 years ago. I removed them from the freezer 6 months ago and have been making kefir with them every day. It took about 3 or 4 days for the little beasts to wake-up from their cryogenic sleep. The 1st batch wasn't very good. The 2nd batch was better. By the 3rd batch everything seemed back to normal. I'm amazed they lasted so long in the freezer. I rinsed the grains in distilled water, then strained out the excess water. Then I wrapped them in 2 layers of plastic wrap and a baggie. I did not add any milk or water to the grains before freezing them. Maybe there's a better way, I don't know. All I know is, it worked for me. Good luck.