How to Store Your Amish Friendship Bread Starter in the Refrigerator
Minimize hassle by storing an active Amish Friendship Bread sourdough starter in the fridge.
Reduce your starter to 1 cup and give it a good feeding. Stir well and leave on the counter for 12 hours before placing in the fridge (if you have to put it in before then, you can. I just like to give the yeast a chance to start metabolizing the sugars). Mix well before putting it into the fridge.
Store your starter in a jar or a container with a lid. Leave the lid cracked open--some people seal their jars and claim to have no issues, but I don't recommend this because the starter does release CO2, acids, and ethanol. If you left a sealed container of starter on the counter at room temperature, it could explode if air isn't regularly released. While this is unlikely in the fridge due to the slow fermentation, you always risk forgetting about your starter, and then this could be a problem. So play it safe and leave it cracked open. Note: you can store your starter in a Ziploc bag in the fridge, but be vigilant ... you will have to seal the bag so it doesn't spill, which means you'll want to make sure you don't forget about it as you may need to remove air from the bag from time to time. You could also prop it in a bowl to keep it upright.
Date it. Either write on the glass container or jar with a dry erase pen, or put a note on your fridge with the date you put your starter in. You can also circle the dates on your calendar. Be clear when you're going to feed your starter. Don't forget!
You don't need to stir it while it's in the fridge unless you see it separating. To understand why separating happening, read this tutorial post.
Feed your starter regularly. For ideal results, remove it once a week to feed. Otherwise, you can feed every 10 days or (risky but possible) up to two weeks.
Remove your starter at least 12-24 hours prior to baking with it. I remove mine 48 hours prior as I usually don't see activity until the second day. When it's ready, feed it and remove one (or more) cups for baking.
Keep your containers clean. If you end up storing your starter in the fridge for more than a month, be sure to clean and/or swap your storage containers regularly.
Give your starter another 12 hours after feeding it before you return it to the fridge. This gives your starter a chance to begin metabolizing the ingredients before it goes into slo-mo at the colder temperatures. You'll want to see bubbles (the more, the better) to make sure it's still healthy and active.
Refrigerated starters still have to be fed regularly at the proper ratios. If you are not baking with your starter regularly, discard some of it before feeding.
Make sure your starter is fed (and fed at the proper ratio of 1 cup flour, 1 cup sugar, and 1 cup milk for every 1 cup of starter in your container) before popping it into the fridge.
When in doubt, throw it out. Toss it, and make a new starter (or pull a bag from the freezer).