What is Flash Freezing?
Flash freezing is a process in which food is very quickly frozen at extremely cold temperatures. In commercial processing, foods are flash frozen so that as many nutrients are retained as possible, and to make sure that the food is as fresh and flavorful as it can be. Some home cooks also practice a form of freezing to preserve foods like fruits and vegetables. This concept is also used in scientific and medical research to rapidly preserve specimens.
The concept of flash freezing was developed by Clarence Birdseye, who wanted to find a way to eat fresh vegetables in the winter and to move produce around without the risk of damage. He realized that freezing food at extremely cold temperatures well below the freezing point could be an excellent preservation method, and he turned the concept into a massive frozen foods company, inspiring other pioneers to do likewise.
On the industrial scale, this process is done in large freezers that get well below the freezing point. Foods are ideally frozen as soon as they are prepared or picked, and they freeze within only a few hours because the temperatures are so cold. Once flash frozen, the foods can be moved to a conventional freezer with a temperature closer to the freezing point, and they should stay frozen solid.
Fishing boats often use flash freezing to keep their catch as fresh as possible, especially if they are working in remote areas and will not be reaching port for days or weeks. In these cases, the fish are cleaned and then frozen as they are caught, and when the hold is full, the fish are offloaded for sale. This method is also used to preserve fruit and vegetable crops, and to preserve frozen meals that consumers can re-heat as needed.
Home cooks generally lack the equipment needed for real flash freezing, but they can fake it by freezing foods on a tray. By laying the food out to maximize exposure to the freezing temperatures in a home freezer, the cooks can encourage the food to freeze solid overnight. Keeping the freezer relatively empty to ensure that the air flows evenly over the food, and packing the food with ice, can help to ensure that it freezes properly. Once flash frozen, the individual pieces of food will also not be prone to sticking to each other, because they have been frozen independently, which can be extremely useful.
I didn't know that TV dinners were flash frozen. Are they frozen inside the divided trays, or is all the food laid out separately and then transferred to the trays?
I had never heard of this technique before! Flash freezing meat would make it a lot easier to separate the pieces when it comes time to cook them.
I freeze several pieces of thin steak together to save on freezer bags. However, if I don't have time to thaw them out completely, it is nearly impossible to separate them and take out what I need. I wind up having to take a sharp knife and risk injuring myself while chopping through the frozen block.
@giddion – Fruits that have been flash frozen retain their shape and their texture better than those that have been frozen slowly in bags. I had a big patch of strawberries last summer, and after I learned how to flash freeze at home, I was able to eat them later without having to use a spoon.
If you buy frozen strawberries at the supermarket and slowly thaw them out, you usually wind up with a mushy mess. My flash frozen strawberries were a lot like the fresh ones. Sure, they were a little softer than they had been, but they were not reduced to goo.
After I thawed them out, I kept them in the refrigerator and snacked on them. They were good by themselves and sliced up in salads.
I am considering doing some flash freezing at home next summer. I have these wonderful blackberry bushes growing on my property, and they produce far too many berries for me to eat before they go bad.
I do have one question about flash freezing, though. I know that many frozen fruits are super mushy when they thaw out. Will flash frozen fruit by mushy, too, or will it hold its shape better?
I do flash freezing before I put away my strawberries and raspberries in the freezer because they tend to stick together the most. I also do this with beans.
I've heard that cans have dangerous substances in them. So instead of buying canned beans, I boil them at home and flash freeze. If you don't lay them out on a sheet and freeze it that way first, it sticks together and breaks apart and becomes mushy later when it thaws. Flash freezing lets it come undone real easily. Especially if you like to make chilli and bean salad.
We do use flash freezing for specimens in our lab. It is the same idea as flash freezing food but we don't use a freezer to freeze the specimens initially. We use cold gas that comes in cans. All we need to do is spray it on the specimen and it freezes right away. Then we place the sample in a freezer.
Some labs also use liquid nitrogen. That process is a bit longer and more expensive though because it requires additional flash freezing equipment. That's why we prefer cold gas in our lab.
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