Chapter 13: Food Engineering

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Food engineering
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is dedicated to the engineering processes related to food production
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Genetic engineering
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is not normally the work of a food engineer
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conservation of mass
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the mass that enters a facility (raw materials) equals the mass that leaves a facility (product plus waste)
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law of conservation of energy
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states that energy cannot be created or destroyed; it can only be changed from one form to another
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Calorie
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unit used to measure heat, 1 is the amount of heat to raise 1 gram of water 1°C
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kilo Joule
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another measure, 1 is 239 calories
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BTU
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another measure, 1 is 252 calories
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Kinetic energy
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is associated with motion and is one of the two basic forms of energy
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Potential energy
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is associated with position or proximity to other systems
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Heat transfer
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is the transmission of energy from a higher temperature object to a lower temperature object
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Pasteurization and _________ are common examples of processes that use heat transfer
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freezing
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Conduction
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heat transfer from molecule to molecule
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Convection
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transfer of heat between liquid or gas and solid surfaces
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Radiation
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transfer by electromagnetic radiation (sunlight or microwaves)
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Thermal conductivity
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refers to the rate of heat transfer through a unit of thickness
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Insulators
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are materials that resist heat transfer
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Thermal resistivity
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is the opposite of thermal conductivity (related to the insulation value or R-value of materials)
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Heat capacity
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is the amount of heat energy necessary to speed up a material’s molecules enough to raise the temperature of a unit mass of a material by 1°C (measured in calories)
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Specific heat
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is the ratio of the heat capacity of a food to that of water
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heat exchanger
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is equipment used to either add or remove heat from food
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Boundary layer
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the dividing line between dissimilar materials
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The field of psychrometrics…
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…is concerned with evaluating thermodynamic properties of mixed gases present in air
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Mass transfer involves the transport of _____ ___ _________ within physical systems
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atoms and molecules
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Examples of Mass Transfer
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Separation of components by distillation Diffusion of salt *WATER EVAPORATION* Membrane filtration
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Latent heat
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is the heat input that results in a change of state (freezing/melting and boiling/condensing)
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Sensible heat
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is change that can be detected by touch
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Rheology
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is the study of flow and deformation characteristics of foods
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Viscosity
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is related to the friction within a fluid that prevents it from flowing freely
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Newtonian foods
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homogeneous mixtures that show no change in viscosity as shear rate is increased (linear) Water, juice, soda, oils
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Non-Newtonian foods
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heterogeneous mixtures that change (thinning or thickening) as shear rate is increased Mayonnaise, applesauce, chocolate syrup
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Laminar flow
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occurs when flow rate or velocity is low
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Turbulent flow
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occurs when flow velocity increases to mixing and eddy currents in the fluid
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Viscosity is measured using instruments called ___________
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viscometers
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About ____ the energy is used for converting raw materials into products
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half
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Compost
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solid wastes unsuitable for feeding

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