Ch. 13 Food Engineering – Flashcards
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What is the equation for mass balance?
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Mass In = Mass Out + Accumulation
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What essentially means that the mass that enters a facility (raw materials) equals the mass that leaves a facility (product plus waste)?*
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The conservation of mass
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What is the equation for energy balance?
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Energy In = Energy Out + Accumulation
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What states that energy cannot be created or destroyed; it can only be changed from one form to another?*
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The law of conservation of energy
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What are the units of measure for energy?
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British Thermal Unit (BTU) or kilo Joules (kJ)
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What are the temperature scales?
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Fahrenheit, Celsius, Kelvin
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What is the unit used to measure heat, 1 is the amount of heat to raise 1 gram of water 1°C?*
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Calorie
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What is another measure that represents 1 is 239 calories?*
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kilo Joule
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What is another measure that represents 1 is 252 calories?*
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BTU
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What is associated with motion and is one of the two basic forms of energy?*
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Kinetic energy
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What is the other form of energy and is associated with position or proximity to other systems Total energy is the sum of kinetic and potential energy in a system?*
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Potential energy
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What is the transmission of energy from a higher temperature object to a lower temperature object?**
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Heat transfer
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What are common examples of processes that use heat transfer?**
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Pasteurization and freezing
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What refers to heat transfer from molecule to molecule (frying pan to eggs) where the temperature gradient is from high to low (think of it as key transfer in a solid—ex. spam and canned ham)?**
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Conduction
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What refers to the transfer of heat between liquid or gas and solid surfaces (fire to frying pan)?**
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Convection
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What does force convection use to move fluid?**
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A fan or pump.
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What refers to transfer by electromagnetic radiation (sunlight or microwaves)?
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Radiation
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What refers to the rate of heat transfer through a unit of thickness?*
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Thermal conductivity
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Foods with more ______ have more conductivity.
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water
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What are materials that transmit heat readily?
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Conductors
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What are materials that resist heat transfer?*
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Insulators
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What is the opposite of thermal conductivity (related to the insulation value or R-value of materials)?*
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Thermal resistivity
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What 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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Heat capacity
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What is the ratio of the heat capacity of a food to that of water?*
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Specific heat
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T/F: Lower values heat more quickly
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True
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What is the specific heat for air?
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.25
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Protein?
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.4
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Fat?
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.5
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Water?
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1
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What is equipment used to either add or remove heat from food?*
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A heat exchanger
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What are the common designs of a heat exchanger?
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A double pipe for parallel or counterflow Scraped surface heat exchanger for chocolate Plate heat exchanger for milk and beverages
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What is it called when conduction occurs within a solid food while convection occurs between the food and cooking oil?
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Deep Fat Frying
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What is the dividing line between dissimilar materials?*
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Boundary layer
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What involves the transport of atoms and molecules within physical systems?*
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Mass Transfer
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What are some examples of mass transfer?*
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Separation of components by distillation Diffusion of salt Water evaporation Membrane filtration
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What field is concerned with evaluating thermodynamic properties of mixed gases present in air?*
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psychrometrics
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What is an application of Psychometrics?
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the evaporation of water from food where the wet bulb temperature is useful for calculating drying rate.
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What properties are represented by Psychometrics?
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Dry bulb temperature Wet bulb temperature Relative humidity Moisture content Dew point Total heat content (enthalpy) Specific volume Vapor pressure
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What is the heat input that results in a change of state (freezing/melting and boiling/condensing)?*
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Latent heat
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What is change that can be detected by touch?*
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Sensible heat
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What are the food engineering applications?
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Rheology Water management Energy use Handling processing wastes
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What is the study of flow and deformation characteristics of foods?*
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Rheology
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What are some applications of Rheology?
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Altering food structure Designing processing equipment Stabilizing suspensions Product development
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What is related to the friction within a fluid that prevents it from flowing freely?*
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Viscosity
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What are homogeneous mixtures that show no change in viscosity as shear rate is increased (linear)?*
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Newtonian foods
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What are some examples of Newtonian foods?*
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Water, juice, soda, oils
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What are heterogeneous mixtures that change (thinning or thickening) as shear rate is increased?*
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Non-Newtonian foods
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What are some examples of Non-Newtonian foods?*
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Mayonnaise, applesauce, chocolate syrup
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When does Laminar flow occur?*
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when flow rate or velocity is low
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When does Turbulent flow occur?*
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when flow velocity increases to mixing and eddy currents in the fluid
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How is Viscosity measured?*
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viscometers
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What is water used for?
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Cleaning Cooling/heating Food component
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What are some different treatment options?
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Filtration Chlorination Boiling UV or ozone treatment
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What are some energy purposes?
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Food preservation Packaging Storage
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About ____ the energy is used for converting raw materials into products *
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half
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What are some food processors that generate waste?
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Canneries Wineries Meat packing companies Cheese manufacturers
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What are some waste uses? *
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Animal feed - solid or dried wastes from plant or animal processing Compost - solid wastes unsuitable for feeding Lactose and whey products - liquid waste from cheese making
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