Freezing Fruits and Vegetables at HomeCooperative Extension ServiceThe University of GeorgiaCollege of Family and Consumer Sciences教学课件.ppt

Freezing Fruits and Vegetables at Home Cooperative Extension Service The University of Georgia College of Family and Consumer Sciences Advantages of Freezing Many foods can be frozen. Good natural color, flavor and nutritive value can be retained. Texture usually better than for other methods of food preservation. But this is personal preference. Foods can be frozen in less time than they can be dried or canned. Advantages of Freezing Simple procedures. Adds convenience to food preparation. Proportions can be adapted to needs unlike other methods. Kitchen remains somewhat cool and comfortable. Disadvantages ofFreezing Foods Texture of some foods is undesirable because of changes due to the freezing process. Initial investment and cost of maintaining a freezer is high. Storage space is limited by how much the freezer will hold. How Freezing Affects Food Enzymes in Vegetables and Fruits To prevent color and flavor changes, as well as loss of some nutrients, enzymes should be controlled. Are slowed down but not destroyed during freezing. How Freezing Affects Food Enzymes in Vegetables Are destroyed by heat, called blanching, before packaging and freezing. Enzymes in Fruits Usually controlled by ascorbic acid (also called vitamin C) or some other additives. Fruits are usually not blanched, but can be. People like them raw and uncooked. How Freezing Affects Food Rancidity Another natural change that causes off-flavors, particularly in fatty foods. Not a common problem in fruits veggies. Will continue to happen at freezer temperatures, but slower than at warmer temps. Best control is to keep as much air out of the package as possible. How Freezing Affects Food Textural Changes The water in food freezes and expands. Ice crystals cause the cell walls of fruits and vegetables to rupture, making them softer when thawed. Some vegetables with very high water content do not freeze well: celery, lettuce, some tomatoes. How Freezing Affects Food Rate of Freezing is V