Onions have been grown as a food source for about 5,000 years. While there are many varieties they can basically be divided into three main types found in the grocery store: yellow, red and white onion. Onion flakes and onion powder are derived from pure onion that has been dehydrated. Both have many culinary uses.
Onion flakes are simply onions that have been finely chopped and allowed to dry. The drying process is greatly accelerated by a dehydrator machine that removes the moisture from the onions without cooking them. Onion powder is produced by extending the process used to make onion flakes. After they are dehydrated, the onion flakes are finely ground into a powder. Onion flakes and onion powder can be made using yellow, white or red onions.
Anyone who has ever chopped an onion knows they can irritate the eyes and cause tearing This will not happen when using either onion flakes or onion powder, because the dehydration process has removed about 94 percent of the moisture from the onion. However, there is a big difference between the strength of onion flakes and that of onion powder, due to the concentration of onion. For example, 1 tablespoon .of onion flakes is equivalent to a whole onion, whereas 1 teaspoon .of onion powder equals about one onion.
You can use a fresh onion in a variety of ways: Eat it raw in salads, or cook it in a variety of ways. However, onion flakes and particularly onion powder need to be cooked before they are suitable for consumption, although you can sprinkle onions flakes over some dishes as a garnish. Onion flakes are best when re-hydrated, at which point they can be use as you would freshly chopped onions. Onion powder is best in recipes that call for the flavor of onions.There is, however, an aesthetic difference in the finished dish: the powder adds flavor, but it can not be seen once mixed into other ingredients.
Onion flakes and onion powder are each more expensive than buying a couple of fresh onions. However, a tub of onion flakes will last a fairly long time. Onion powder is more concentrated than onion flakes and takes up less space in your cupboard. But it is more expensive than onion flakes. This reflects the extra processing cost, but it is also because the powder equates to about three or four times more onion than the flakes.