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Food Sci
Addition of Thermal Energy
14
Science
Undergraduate 2
05/08/2010

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Cards

Term
Conduction
Definition
heat transfer between two molecules (direct contact with solid or non-moving liquid)
Term
Convection
Definition
Heat transfer occurs because of a moving liquid or gas. Natural or forced (mixing)
Term
Radiation
Definition
Heat transfer occurs because of light waves (electromagnetic energy)
Term
3 basic categories of heating techniques
Definition
Heating in air, Indirect contact heating, direct contact heating
Term
Heating in air examples
Definition
oven, cylindrical roaster
Term
Indirect contact heating examples
Definition
heat exchanger, pasteurizer, steam jacketed kettle
Term
Direct heating examples
Definition
retort/pressure cooker, fryer, direct steam injection, broiler/toaster, grill, microwave
Term
4 stages of frying
Definition
  1. initial heating
  2. Surface boiling (vap of water, forced convection of oil)
  3. Falling Rate: rate of evap decreases, chem changes inside of food, crust thickens
  4. bubble end point
Term
Broiling
Definition
  • Heating element emits infared energy
  • Broiling rapidly heats fodd surface, results in maillard browning
  • is distance dependent
Term
Microwave heating
Definition

Molecular friction of polar molecules

 

create fluctuating electrical field which changes direction 2.45 billion times per second

Term
factors affecting microwave heating
Definition
  • Chemical composition of the food

-dissociated ions affect heating rate

  • Product density, geometry...
  • Microwave frequency, wattage...
Term
Advantages of microwave heating
Definition
  • Energy efficient
  • can be nutritious
  • no burn-on to cooking surface
  • Desireable chemical changes still occur
Term
Disadvantages of microwave heating
Definition
  • no crisping or crusting
  • no maillard browning
  • Hot and Cold spots
  • Large quantities of food take longer to heat

 

Term
Microbiology and microwave heating
Definition
  • Non-homogeneous heating may lead to pathogens in cold spots
  • Temperature abuse is common with re-heating.

-Clostridium perfringens can survive if not adequately heated

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