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LOW TEMP PRESERVATION, CHILLING EFFECT, GENERAL CHANGES DURING…
LOW TEMP PRESERVATION
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At high freezing rates, production of ice crystals (nucleation) more quickly (many seeds developed) than the growth process
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PROBLEMS
physical damage (formation of ice crystals)
-rupture cell walls, break emulsion
changes in texture & flavor caused by the increased solute concentration
-changes pH, denaturize proteins, increase enzyme activity
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Lower T, reduce respiration, transpiration & metabolic process of fruits & veg.
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CHILLING EFFECT
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biochemical reactions (drip loss in meat, reduce sweetness
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Chemical properties (taste, flavour)
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reduce or stops the growth and activity of microorganisms as well as retards many of the physical and chemical reactions that occur in foods
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postharvest physiological disorder caused by improper storage temperatures that result in sunken areas on the fruit (blemishes), disease susceptibility, and inhibition of color development and ripening.
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COOLED LIQUID
-immersion freezing
-IQF, carrot, peas, corn
COOLED SOLID
-plate freezing
-fish sticks, fillet, ice-cream
in carton
COOLED GAS
-cabinet freezing, air blast
-IQF, fruits, veges
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protective layer of ice
To:
-preserve taste, smell & texture
-minimize thaw drip loss
-avoid fat oxidation
-avoid dehydration