Google has failed me and I have some peppers and onions to freeze. It seems that every time that I freeze them, no matter what I do, a lot of ice crystals form in the bag. Does anyone have any suggestions or methods they use to mitigate ice crystals?
You need to get as much air out as possible.
If you have a vacuum sealer… you probably wouldn’t be asking this question, so I’ll assume you don’t have one.
Try this: put it in a plastic bag, then put the bag in water as you seal it. The water pressure should “mold” the bag fairly tightly around the contents. Then dry the bag off, wrap it tightly in plastic wrap, and stick it in the freezer.
Faster freezing. High-moisture fruits and veggies (which most are) will “exhale” moisture if they freeze at normal rates. AFAIK, the reason commercial producers can do it is the same reason they’re so successful in general at producing high-quality thawed-fresh veggies: speed of freezing. Not sure how you can do this in a home freezer.
Zero air in the bag. If you don’t have a vacuum sealer, use the trick I learned a long time ago and suck the last of the air out of the bag before you zip it. I’ve found that you can often press, roll and fold the bag around the contents to exclude most air, but around lumpy things like fruit, I zip the bag down to the last half inch, pouch that gap open, and suck the air down to a tight crinkle. Quickly zip shut. Reduces icing and frost a huge amount on all frozen stuff.
I flash freeze veggies. Spread them out on a baking sheet, freeze, and then bag/vacuum seal.
This is the trick. The food freezes quicker, and any “exhaled” moisture doesn’t remain in the bag to form crystals. Freeze, then bag.
In the food industry that’s called individually quick freezing or IQF (Individually Quick Frozen). Anytime you see a bag of things that are frozen but still loose, that’s how they do it. Think frozen strawberries, frozen shrimp (in a bag, not box), frozen peas etc. If they just put them in the bag and froze them they would be one big chunk of stuff since they would all freeze together.
The flash freeze works.
Thanks everyone, I’m trying the flash freeze process as we speak.
Wouldn’t home-freezing of onions or peppers just turn them into limp mush when they thaw?
WAG, but I’d bet the OP is sauteing them first, in which case it doesn’t matter and I know for a fact they’ll be fine. I friend of mine runs a restaurant and cooks then freezes peppers and onions ahead of time as a matter of course. It’s the only way he can stay caught up, especially during his busy season.
It’s been three and a half hours since the “flash freezing” process and I just bagged the onions and peppers and so far there are no ice crystals.
I won’t know if they turn out soggy until I thaw them out and use them in another recipe, so I’ll just wait and see.
Depending on your subsequent usage, but you could also try freezing them (intentionally) in a water bath. Then they won’t get freezer burned. I’ve done this for chopped herbs with good results.
I assume you are trying to preserve summer gardening produce. Try blanching the peppers as you would use them (sliced, chopped, whatever) and then freezing in baggies with equal amt of water.
Onions can keep for months (even up to a year) stored in a cellar environment. If I recall correctly from my vintage housekeeping books–not available ATM–I believe the best way is to bury them, not touching each other as much as possible, in hay or sawdust in the cool dark. If I run across a good source, I’ll post an update.
Just FYI–never store whole onions or potatoes in the fridge.
Mother Earth News has thisto say about onion storage:
Pull when at least half of the tops are dead or have
fallen over. Avoid harvesting in wet weather.
Cure in a warm (80 degrees or warmer), shady,
well-ventilated place for a week. Trim back tops,
and then cure two weeks more. Trim again before
storing. Store in boxes or mesh bags in a cool place with moderate
humidity.
Other sources confirm that you can keep onions up to a year in a cellar-type environment, as I thought. Ixnay to the sawdust, that’s for apples and turnips and such (sorry). They need cold and air circulation.
I haven’t seen the episode of Good Eats in a while, but Alton Brown used a technique involving dry ice in order to freeze fruits quickly, thereby minimizing the size of the ice crystals IN the fruit and the resulting mushiness when thawing.
I envy those of you who have a freezer you can put a baking sheet in. 
I’ve never expected frozen onions or peppers to have great texture after freezing. If you can keep the ice crystals down you can stir fry them frozen and get something not awful. But they’ll be find for dropping in soups and stews. They won’t have all their flavor left after freezing though.
I believe he actually used liquid nitrogen in that episode, but I could be wrong.
I only use frozen peppers and onions in stir fry dishes and sometimes chili and they always seemed okay (not fresh obviously). It’s just me and my son so I usually end up with a lot of left over food and I always feel bad if I waste it so I was just looking for a way to freeze without ice crystals caking up.
I prefer the pepper texture after freezing. With the tough Melrose peppers, you can scrape the pulp off the outer skin, and use it instead of tomato paste. With bell peppers, it depends what you’re using them for.
What do you make that onion texture is an issue?
Freezing delicate fruits like strawberries so that they did not turn into mush was a major breakthrough in frozen food tech about 30 years ago. Some forms involved something a lot like edible antifreeze, but others were purely fancy freezing techniques - maybe under moderate vacuum or pressure coupled with very fast freezing. But for the most part these are like KFC - you can know the trick, but won’t have the equipment to duplicate it.