Blanching is the process whereby food is briefly cooked in boiling water, steam, or syrup, such that it destroys enzymes that catalyze the reactions of food spoilage. When drying food, blanching also serves to weaken the fibers on the surface of the fruit or vegetables, allowing dehydration (and rehydration) to occur more efficiently. It also helps to prevent discoloration and completely kills any microbes on or near the surface of the produce, slowing spoilage during dehydration.
Steam blanching is typically the preferred blanching method when dehydrating vegetables, though water blanching also will suffice if you don't have a blanching basket. The biggest downside to water blanching is that more nutrients will be lost when the vegetables or fruit is fully submerged in the water.
Steam blanching can be done on the stove or in the microwave.
Steam blanching on the stove:
Stainless steel or bamboo steaming baskets can be found at most department stores or thrift stores. These are highly recommended. Steamer pans will also work.
- Choose a sauce pan that comfortably fits your steaming basket with the lid on.
- Place an inch or two of water in the bottom of the pan and bring to a full boil.
- Add the steamer basket containing your prepared vegetables or fruit and cover the pan tightly with the lid.
- Carefully time your blanching per recipe so as not to over-cook your produce. As a rule of thumb, this will be about half of the cooking time as you would normally use to fully cook the vegetables.
- As soon as the food has been steamed for the recommended time, immediately remove it from the heat, and run cool water over it to stop it from cooking any further.
Steam blanching in the microwave:
Steam blanching in the microwave is quick and easy. You will just need a microwave-safe dish with a lid (a bowl with a plate over the top will usually do the trick).
- Wash, peel, and slice the vegetables or fruit as desired for drying.
- Place the vegetables in a microwave-safe bowl and add a splash of water.
- Cover the bowl with a microwave-safe lid or plate, and microwave on high for half the time it would take to fully cook the vegetables in the microwave. You may need to try fully cooking a batch of the vegetables to get a feel for how long this will take in your microwave.
- Pause the microwave once or twice to stir the vegetables or fruit to ensure even cooking.
- When cooking is finished, immediately rinse the vegetables or fruit under cool running water to halt the cooking.