FNH 200 Lecture Notes - Lecture 8: Skimmed Milk, Instant Coffee, Photo-Oxidation Of Polymers
31 May 2019
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Document Summary
Dehydration as a food preservation method (part 2) Compare and contrast aspects of different dehydration methods (process, principles, effects on food quality) Describe the packaging requirements for foods dehydrated by different methods. Can only be done in dry, warm climates. Liquid foods and pur es are sprayed into a stream of heated air. Rapid, good rehydration due to small particle size. Examples : skim milk powder, instant coffee, tea, eggs. Dehydrating medium is dry, hot air , travelling at a set velocity. Results in shrunken , dense food with poor/moderate rehydration properties. Semi-solid foods are thinly layered onto a heated, rotating drum. Dried food is scraped off i. e. flakes. Frozen food is placed in a vacuum chamber with radiant heaters. Voids (space) from ice crystals act as channels when water sublimes. Appearance of final food quite resembles that of initial food. High nutrient and flavour retention; less colour change. Hot frying medium (i. e. oil, butter, lard) will evaporate the water.
