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The primary purpose of blanching is to destroy enzyme activity in fruit and vegetables. It
is not intended as a sole method of preservation, but as a pre-treatment prior to
freezing, drying and canning.
Other functions of blanching include:
•Reducing surface microbial contamination
•Softening vegetable tissues to facilitate filling into containers
• Removing air from intercellular spaces prior to canning
Methods of blanching
Blanching is carried out at up to 100°C using hot water or steam at or near atmospheric
pressure. Some use of fluidised bed blanchers, utilising a mixture of air and steam, has
been reported. Advantages include faster, more uniform heating, good mixing of the
product, reduction in effluent, shorter
processing time and hence reduced loss of soluble and heat sensitive components.
There is also some use of microwaves for blanching. Advantages include rapid heating
and less loss of water soluble components. Disadvantages include high capital costs
and potential difficulties in uniformity of heating.
Steam Blanchers
This is the preferred method for foods with large cut surface areas as lower leaching
losses. Normally food material carried on a mesh belt or rotatory cylinder through a
steam atmosphere, residence time controlled by speed of the conveyor or rotation. Often
poor uniformity of heating in the multiple layers of food, so attaining the required time
temperature at the centre results in overheating of outside layers
Titany answered the question on November 5, 2021 at 05:15
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