FSN 204 Lecture Notes - Lecture 4: Viscosity, Evaporation, Freeze-Drying
11 Feb 2018
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Document Summary
Common unit operations in the food industry cont: heating, cooling, evaporating, drying/dehydrating, packaging, control. Goal to heat food as quickly as possible. Foods are heated by: conduction heat transfer through direct contact, convection heat transfer through a liquid (liquid/gas, radiation transfer of heat by electromagnetic waves (ir) Numerous types of heating equipment: selection depends on, type of product/package to be heated, desired/required temperature, types include, heat exchangers, kettles, retorts, roasters, steam injection, microwave. Plate heat exchangers: for liquid, low viscosity, no or very small particulate products (milk, juice) Scraped surface heat exchanger: caramel, candy syrups, chocolate. Blast freezers: rooms or spirals for solids. Scraped surface freezers: viscous liquids or liquids with suspended solids. Used to concentrate foods by removal of water. Also used to remove and recover volatiles. Atmospheric evaporation/concentration: used to boil water from sugar syrup (candy making, maple syrup, considerable energy and long times.
