What are the purposes of blanching?

Blanching is a thermal treatment in unit operation that is usually performed prior to food processes such as drying, freezing, frying, and canning, in which fruits or vegetables are heated for the purpose of inactivating enzymes; modifying texture; preserving color, flavor, and nutritional value; and removing trapped air.

Blanching is a must for most vegetables to be frozen. It slows or stops the enzyme action which can cause loss of flavor, color and texture.

It is essential to preserve the product quality during the long-term storage because it inactivates the enzymes and destroys microorganisms that might contaminate raw vegetables and fruits during production, harvesting and transportation.

Blanching reduces the numbers of contaminating microorganisms on the surface of foods and hence assists in subsequent preservation operations. This is particularly important in heat sterilization, as the time and temperature of processing are designed to achieve a specified reduction in cell numbers.

Blanching cleans the surface from dirt and organisms, brightens the color and prevents loss of vitamins. It softens vegetables and makes them easier to pack.

The blanching time is very important and varies with the vegetable and size. Under-blanching stimulates the activity of enzymes and is worse than no blanching. Over-blanching causes loss of color, vitamins and minerals. Over-blanching also can cause excessive softening and loss of flavor in the food.

In order to avoid the side effects of blanching, a low temperature condition is generally employed in order to mitigate the quality problem. However, a low temperature condition results in a longer process time than a high temperature condition, thus leading to reduced productivity in the food industry.

Objective of blanching including:
*Inactivation of quality-deterioration enzymes
*Enhancing dehydration rates and product quality
*Removing pesticide residues and toxic constituents
*Expelling air entrapped inside plant tissues
*Minimizing non-enzymatic browning reactions
*Decreasing microbial load
*Peeling of products
*Increasing extraction efficiency of bioactive compounds
What are the purposes of blanching?


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