FNH 200 Chapter Notes -Maillard Reaction, Case-Hardening, Instant Soup
6 Aug 2013
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Document Summary
Water activity (aw) = defines proportion of water in food in free, unbound form. Dehydration = removal of as much water from food as possible to increase storage life. Concentration = some water removed to concentrate food constituents; no shelf-stable, require other forms of preseravtion. Case hardening = sugars from hard case around food during rapid dehydration. Sublimation = from frozen state directly to gas phase, without transition through liquid. Reasons for dehydrating food preservation retention of size and shape while preserving reduce weight and bulk for easy storage, transportation. Convenience items (instant coffee, instant soup preps) * dehydration does not kill microorganisms; once rehydrated => resume growth under favorable conditions. As water removed cell tissue shrinks and loses elasticity. Water migrates from interior of food to surface and evaporates, carried away by dehydrating medium. Loss of water soluble substances => poor rehydration properties. Rapid drying causes sugars to form hard, impermeable cases around food.
