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Processing of Foods

Exposure to Heat

Fried Foods:  The longer the food is fried and the higher the temperature, the more vitamin and mineral potency is lost. Frying temperatures usually reach 375 degrees. Corn and safflower oils are best due to their higher smoke points of 450 to 500 degrees.

Canned Foods:  Nutrient losses occur from blanching and sterilization, which utilizes temperatures of 240 degrees or higher for 25 to 40 minutes. See also: Canned Food Convenience and/or Cooking with Canned Tuna.

Frozen Foods:  Many are cooked before they are frozen. Higher quality foods are usually sold as fresh. Lower quality foods are used in frozen foods due to their poor appearance. See also: Frozen Food Facts.

Dehydrated Foods:  Very dependent on the quality of the initial product. Some methods of commercial dehydration may use temperatures of 300 degrees.

Dairy Products:  Many vitamins lose their potency or maybe totally destroyed by the pasteurization process. The homogenization process breaks down the normal-size fat particles, thus allowing the formation of the enzyme, "Xanthene Oxidase". A Canadian study has shown that this enzyme may enter the bloodstream and destroy a vital body chemical that ordinarily provides protection for the coronary arteries. See also: Dairy Food Facts.

Note:  Various nutrients have different degrees of stability under the conditions of processing and preparation. Vitamin A is easily destroyed by heat and light. Vitamin C is not only affected by heat, but also by contact with a variety of metals, such as bronze, brass, copper, cold rolled steel or black iron, found in some types of food processing equipment.

Exposure to Cold

Frozen Food:  Freezing may have only minimal effects on vitamin and mineral potency, depending on he methods used and how soon they were frozen in relation to the time they were picked. Remember, the highest quality of foods are sold to restaurants or are sold fresh.

Fresh Fruits and Vegetables:  Fresh fruits and vegetables are sometimes harvested before they are ripe, then allowed to ripen on their way to market, either naturally or with a bit of ethylene gas. This may cause a reduction of some of the trace minerals.

Note: There are four methods of commercially freezing foods:

  1. Air Blast Freezing:  Products are frozen by high velocity cold air. This method is the most widely used on all kinds of products.
  2. Plate Freezing:  The product is placed in contact with a cold metal surface.
  3. Cryogenic Freezing:  Freezing at very low temperatures (below 100 degrees) in direct contact with liquid nitrogen or carbon dioxide. Use for freezing meat patties and other meat products.
  4. Freon Immersion Freezing:  Utilizes Freon to freeze the product instantaneously, thus allowing the product to retain its total weight. Presently, Freon immersion freezing is being used to freeze hard-boiled eggs, scrambled egg patties and shrimp. Some foods may retain more nutrients when they are frozen shortly after harvesting. A Stanford University study showed that frozen spinach had 212 percent more vitamin C than fresh. Frozen Brussels sprouts had 27 percent more vitamin C than fresh.

Quality of Food Processed

Fruits and Vegetables:  May be affected by genetic differences, climatic conditions, maturity at harvest or soil variances.

Meat and Poultry:   The lowest quality is used for canned goods, frozen foods and TV dinners.

Enrichment and Fortification:   Refining/Replacement Nutrients: bread and milk are the two most abused products in this area.

Fortification:   Vitamin D is added to milk, almost all breakfast cereals are fortified and vitamin C is added to hundreds of products.

Note:   During processing more vitamin E is lost than any other vitamins. Wheat flour (except the 100 percent varieties) lose up to 90 percent of its vitamin E value. Rice cereal products may lose up to 70 percent of their vitamin E.

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