Blanching is a unit operation prior to freezing, canning, or
drying 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. Hot water and steam are the most
commonly used heating media for blanching in industry,
but microwave and hot gas blanching have also been
studied. Different hot water and steam blanchers have
been designed to improve product quality, increase yield,
and facilitate processing of products with different
thermal properties and geometries. More recently, energy
conservation and waste reduction have driven further
improvement of equipment design. Although blanching
seems a simple operation, heat transfer to a conveyed bed
of product and its effects on product properties are very
difficult to accurately model with predictive mathematics.
Processing conditions are usually set up to inactivate
enzymes, but other quality parameters, such as color and
texture, are commonly monitored. For a given product,
typically mass flow rate is fixed, temperature is measured,
and heating media flow rate is adjusted to ensure that the
temperature is kept at the set point.
Blanching is a unit operation prior to freezing, canning, ordrying in which fruits or vegetables are heated for thepurpose of inactivating enzymes; modifying texture;preserving color, flavor, and nutritional value; andremoving trapped air. Hot water and steam are the mostcommonly used heating media for blanching in industry,but microwave and hot gas blanching have also beenstudied. Different hot water and steam blanchers havebeen designed to improve product quality, increase yield,and facilitate processing of products with differentthermal properties and geometries. More recently, energyconservation and waste reduction have driven furtherimprovement of equipment design. Although blanchingseems a simple operation, heat transfer to a conveyed bedof product and its effects on product properties are verydifficult to accurately model with predictive mathematics.Processing conditions are usually set up to inactivateenzymes, but other quality parameters, such as color andtexture, are commonly monitored. For a given product,typically mass flow rate is fixed, temperature is measured,and heating media flow rate is adjusted to ensure that thetemperature is kept at the set point.
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