Frozen food

Freezing has been known to be an extremely effective means of preserving food for extended periods since Paleolithic and Neolithic times, when man used ice and snow to cool food.

One of the main advantages of freezing preservation is the convenience and ease of food preservation with minimal impact on food quality compared to other preservation techniques (e.g., thermal processing or drying).

Better sensory quality is obtained in frozen foods but at a cost if increased energy requirement to maintain them, in a frozen state.

Successful freezing can now preserve food almost in its original form. This makes it possible to preserve and transport food worldwide. As freezing prevents growth of microbes, frozen food can be stored for long periods; there is no need to use preservatives or additives to extend shelf life.

However, it should be recognized that a number of physical and biochemical reactions can still occur and many of these will be accentuated when recommended conditions of handling, production and storage are not maintained.

Freezing allows flexibility in manufacture and supply and means that food can be preserved at near its optimum quality for distribution and transportation.

Frozen foods are always packaged before being displayed and in the majority of cases the packaging obscures, and protects, the food on display. If packed in transparent film the surface of many frozen foods will discolor rapidly when illuminated.
Frozen food

Shelf life of a product

The perception of quality of a product also depends on its form-fresh, frozen, canned or dried. Processing of fruits and vegetables extends the season of a perishable crop. Heat preservation (canning) provides a shelf-stable product, but usually at the cost of color, flavor, and texture. 

Better sensory quality is obtained in frozen foods but at a cost if increased energy requirement to maintain them, in a frozen state. Dried fruit products such as raisins and prunes offer very different attributes than their fresh counterparts. The consumer judges canned products with a different set of criteria than frozen or fresh items of the same commodity. 

Fresh fruits and vegetables are perishable, i.e., they have limited shelf life. They are living, respiring tissue that is also senescing and dying. Certain fruits such as bananas and tomatoes will ripen after harvest, developing desirable color, texture, and flavor during handling and storage. All other fruits and vegetables such as oranges, grapes, cucumbers, and carrots will show little or no improvement in quality within the postharvest system. 

Packing and handling systems have been developed to move the product from farm to consumer expeditiously to minimize quality degradation. Techniques used to extend shelf life of fresh products include 

Lowering the temperature to slow respiration and senescence 

Maintaining an optimal relative humidity to slow water loss without accelerating decay 

Adding chemical preservatives to halt physiological and microbial losses 

Maintaining an optimal gaseous environment to slow respiration and senescence

Longer shelf life can also be obtained by selecting cultivars that are more able to withstand the rigors of the handling system and by harvesting a crop at optimal maturity for storage and handling. 

Shelf life of a product