Effect of blanching on foods

 

As we know that blanching is the most common and easiest way to preserve the fruits and vegetables for short shelf life and also it is done prior to any processing. Throughout college, it is one of my favorite topics. But do we know that what are the after-effects of blanching on foods? Let me explain about it further - 

In general, the time-temperature combination used for blanching is a compromise which ensures adequate enzyme inactivation but prevents excessive softening and loss of flavor in the food.

Nutrients

Some minerals, water-soluble vitamins, and other water-soluble components are lost during blanching. Losses of vitamins are mostly due to leaching, thermal destruction, and, to a lesser extent, oxidation. The extent of vitamin loss depends on a number of factors including: 

• the maturity of the food and variety 

• methods used in the preparation of the food, particularly the extent of cutting, slicing or dicing

the surface-area-to-volume ratio of the pieces of food 

• method of blanching 

• time and temperature of blanching (lower vitamin losses at higher temperatures for shorter times)

• the method of cooling • the ratio of water to food (in both water blanching and cooling).  

Colour and flavor

Blanching brightens the color of some foods by removing air and dust on the surface and thus altering the wavelength of reflected light. The time and temperature of blanching also influence the change in food pigments according to their D value. Sodium carbonate (0.125% w/w) or calcium oxide are often added to blancher water to protect chlorophyll and to retain the color of green vegetables, although the increase in pH may increase the losses of ascorbic acid. Enzymic browning of cut apples and potatoes is prevented by holding the food in dilute (2% w/w) brine prior to blanching. When correctly blanched, most foods have no significant changes to flavor or aroma, but under-blanching can lead to the development of off-flavors during the storage of dried or frozen foods. Changes in color and flavor are described in more detail by Selman (1987).

Texture

One of the purposes of blanching is to soften the texture of vegetables to facilitate filling into containers prior to canning. However, when used for freezing or drying, the time– temperature conditions needed to achieve enzyme inactivation cause an excessive loss of texture in some types of food (for example certain varieties of potato) and in large pieces of food. Calcium chloride (1–2%) is therefore added to blancher water to form insoluble calcium pectate complexes and thus to maintain firmness in the tissues.

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