Dehydration has been used as a method of food preservation since… well, nobody really knows. A long time, anyway – probably since shortly after our ancestors first discovered the big shiny yellow thing in the sky. It preserves food by removal of water – that is pretty much implied by the name – but how does removing water actually stop decay?
By removing the water, you remove any foothold for bacteria or other unfriendly microbes to start growing. All life needs water to start and maintain the metabolism – remove the water, remove the ability to live and multiply.
The process inevitably changes the flavour of whatever it is, which you can work to your advantage. I find that fruits which are heavily dehydrated but still have some water in them develop a pleasingly intense taste and chewy texture, making them more satisfying to eat – bananas and apples make particularly good “fruit chews”. Dehydrated tomatoes in a slow simmered pasta sauce or a stew will lend a very intense flavour, bursting with sweetness and concentrated “essence of tomato”.
Semi- or fully-dehydrated fruit can also make dynamite jams or preserves, with super intense flavours. The dehydration also concentrates all the sugars, making the “fruit chews” more hostile to unfriendly microbes, but they will still have a shorter shelf life than fully dehydrated foods. Vegetables also dehydrate nicely, as witnessed by the dried food on the shelves of your local supermarket and outdoors stores.
Incidentally, dehydration reduces the volume occupied by the food – dehydrated vegetables only require 1/15th of the amount of storage space required by non dehydrated food.
How do you dehydrate? There are many “do it yourself” methods listed online involving propping open oven doors, high speed fans, and whatnot, or you can buy an off-the-shelf dehydrator from amazon.com or a local store. They run from $40 in a closeout store like Big Lots, to $200 for a super shiny one which can almost make the coffee! At the end of the day, it doesn’t matter how much you spend, so long as it does the job – filling your pantry shelves with safely preserved food you can call on at a much, much, much later date. (Dehydrated foods have shelf lives measured in years so long as they are kept dry.)