How long will a sourdough starter last in the fridge without being fed? We will be out of town for 3 weeks and I don't want to loose this starter. Should I freeze it?
Freezing your starter is one choice. Another would be to lower the hydration down to 60%. After you return home, you should feed your starter at least twice to be sure it's active. The final choice is to dry some of your starter, which everybody should do regularly anyways, and rebuild the starter upon return. If you haven't dried your starter before, there are plenty of archived threads available through the search button that will describe the process far better than I can.
True, all what PG said, except for freezing the starter as is. Freezing will kill the wild yeasts and many bacteria, and will render the starter useless.
If you dry it out, it should freeze OK. I like this write-up on drying and freezing your starter: Drying Your Starter
There's a link on how to revive it on there. I used a similar procedure to revive a dried starter the other day, except I used even smaller amounts. Using a quarter teaspoon of dried starter I had a very active starter in three days.
My starter was neglected for 25 days. It remained in the fridge all the time. After 25 days, when I fed it (1:3:4) , it was sluggish. After the 2nd and the 3rd feed, it was back on track, tripling in 5hrs. When I baked with it the bread tasted as good as before.
You can probably leave your starter in the refrigerator, but when you return there will be a lot of "hooch" (brownish liquid) on top. You can either mix that in and re-feed a few times or pour the hooch off. (It's basically the by-product of your starter.) I'd probably pour it off. Re-feed your starter every two hours for the first four hours; then after another 4 hours. Refrigerate overnight again and next morning feed it every 4 hours until you see it has fully revived.
Thanks folks for all the suggestions. I now have options to ensure my starter survives.
Just one more to add to your collection although it has been mentioned by postal grunt....all that I will add is that I do long term storage at 50% hydration without a problem.
Be sure to make sure it is really strong before you store it. When you know it is ready to go 'dormant' feed it at the hydration level you choose and put it into the refrig. immediately so it has a lot of fresh food rather than letting it sit at room temp and feed. One way - you will be storing a hungry starter and it will be unhappy; other way - you will be storing a well fed starter that has plenty of food to eat.
I also cut down the amount of starter I start my batch with. The ratio I use came from a member here who got it from his teacher at SFBI. The recommendation was to store no less than 350g of starter. Ratio being 50:100:200. Starter has ample food to keep it busy while you are away.
Upon return do the refreshing/building piece that others have mentioned.