Thermal Processing and Food Preservation Flashcards
4 reasons why we use heat as a preservation technique
- eliminate pathogens
- eliminates or reduces spoilage organisms
- extend the shelf life of the food
- improve palatability of the food
3 types of heat transfer
- conduction
- convection
- radiation
Define conduction
its 1 particle to another in a straight line, food does not move.
define what convection is
molecules begin to move apart and become less dense, passing up through cooler fluids which develops currents
*currents move through food
define what radiation is
head transferred directly from a radiant head force
what foods do conduction, convection, and radiation pertain to
- conduction: solid and semi solid foods (mashed potatoes, scrambled eggs)
- convection: liquid (frying hot oil, boiling water, oven hot air)
- radiation: solids (broiling, grilling
speed of conduction, convection, and radiation
conduction: relatively slow
convection: faster than conduction
radiation: fastest
frying>boiling>air
once surface of a solid is heated, what takes over
conduction
when will heat flow
anytime there is a difference in temperature
what way does heat flow
high temp to low temp
how do microwaves work
it excites the water molecules in the food, which then convert that energy into heat which cooks the food.
- Outside in
- non ionizing
thermal processing increases temperature is greater than
boiling point using pressure
how are thermal processing and pressure used
food retort
pressure cooking
canning
*produces safer shelf food
what is agitating retort
cans rotate causing the contents to move inside
*this means that the moving contents are indicative of CONVECTION heat transfer
in a can or container, what heat transfer happens to liquid and solid portion
- liquid portion: convection
2. solid: conduction
