Wednesday, March 9, 2011

Dehydrated or Freeze Dried...Whats best for you? Home Store 101 #3

Dehydration and Freeze Drying - Two Preservation Methods, Compared and Defined

submitted by Denis Korn


"Dehydrated" is a general designation for all foods that have had water removed. It includes a number of different products and dehydrating techniques. Methods of drying include:
          o Air drying
          o Spray drying
          o Drum drying
          o Belt drying
    * Most commonly, “dehydrated” is a term applied to vegetables, fruits, spices, and beans.
    * Spray dried items include milk powder, dairy and cheese powders, fruit powders, vegetable powders, egg powders, and oil powders.
    * Most dehydrated vegetables and fruits are dried at high temperatures for short periods of time.
    * Advantages of dehydration:
          o Reduced weight
          o Longer shelf life
          o Lower cost
          o No waste and compact
          o A large, easy-to-use variety of foods
    * Disadvantages of dehydration:
          o Many products - such as corn, peas, and green beans - have to be cooked to reconstitute, resulting in increased time and loss of nutritional value.
          o High temperature drying of some items reduces nutritional value and taste.
          o Texture of some products is altered from original.
Freeze drying is a specific technology that refers to foods which have been frozen and then dried at low temperatures in a vacuum chamber.  The moisture is drawn from the chamber, leaving foods with a very low moisture content.  This process is known as sublimation.
    * Advantages of freeze drying:
          o Foods retain the highest nutritional value, taste, texture and appearance.
          o Foods do not “shrivel up,” therefore retaining their original shape.
          o Foods reconstitute easily in hot or cold water and can be eaten dry if necessary; no cooking is required in preparation.
          o The only method used to dry meat products for long term shelf life.
          o The chosen method of drying by the military, pharmaceutical companies, supplement manufacturers, and those concerned with nutrition and flavor.
          o The lowest moisture content obtainable, resulting in long shelf stability.
          o Excellent for fruits, vegetables, and meats.
          o Very lightweight.
    * Disadvantages:
          o Energy intensive- requires special equipment.
          o Higher cost.
          o Limited number of processors.

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