Foods that have defrosted have no remaining ice crystals. If defrosted foods have warmed above refrigerator temperature (40 F) they should not be refrozen, except for very high acid foods, such as fruits.
Many thawed foods, i.e. those still containing many ice crystals or a firm-to-hard core of ice in the center, may be safely refrozen.
Any signs of spoilage, off-odors or color in any food indicate you should dispose of the food without tasting.
Remember, however, that you can't rely on appearance and odor. Some foods may look and smell fine, but if they've been at room temperature too long, food poisoning bacteria may have multiplied enough to cause illness.
Meats, such as beef, pork, veal, lamb and poultry can be refrozen when they are still firm with ice crystals. Meat still safe to eat can be cooked and refrozen. Discard meats if they have any signs of spoilage such as an off-color or off-odor.
Fruits usually ferment when they start to spoil, which will not make them dangerous to eat but will spoil the flavor. Defrosted fruits that smell and taste good can be refrozen.
Vegetables should be refrozen only if they contain plenty of ice crystals.
Shellfish, prepared foods or leftovers should not be refrozen if defrosted. If the condition of the food is poor or even questionable, get rid of it. It may be dangerous.
Never refreeze melted ice cream, cream pies, eclairs or similar foods.
Unfrosted cakes, uncooked fruit pies, breads and rolls can be refrozen.
The investment in the foods in the freezer may be significant, but so are the benefits of serving safe foods.
Foods That Do Not Freeze Well
Pepper, cloves, imitation vanilla, garlic (especially uncooked), sage and celery seasonings may become strong and/or bitter.
Curry may develop a musty off-flavor.
Onion changes flavor during freezing.
Salt loses flavor and has the tendency to increase rancidity of any item containing fat.
Add artificial sweeteners and salt substitutes at serving time to be on the safe side.
Cooked egg whites become tough and rubbery.
Soft meringues toughen and shrink.
Mayonnaise and cooked egg or cream-based salad dressings seperate when frozen alone.
Milk sauces or wheat-flour thickened gravies may separate or curdle.
Half-and-half, sour cream and cottage cheese separate and may become grainy and watery when frozen alone. Buttermilk and yogurt react similarly, but can be used for baking.
Custard or cream fillings tend to separate and become lumpy and watery.
Boiled or fluffy frostings made with egg whites become sticky and weep.
Cooked pasta products lose texture and tend to taste rewarmed when frozen alone.
Most gelatin dishes tend to weep when thawed.
Cheese or crumb toppings become soggy.
Fried foods, except french-fried potatoes and onion rings, lose crispness and become soggy.
Lettuce, tomatoes, celery, cucumbers, parsley, radishes and similar high-water-content vegetables become limp and watery.
Potatoes might darken and have a texture change when included in frozen soups and stews. New potatoes freeze better than older ones.