NDFS 355 exam 3

Dew

Exposed surface cools by radiating heat, atmospheric moisture condenses at a rate greater than it can evaporate

Frost

A solid surface is chilled below the dew point of the surrounding air

Adiabatic

no net gain or loss of heat energy/enthalpy

drying capacity of air

the amount of moisture that air can hold before it becomes saturated

Heat load

sensible heat of the product + heat of respiration of the product

permeate

material that passes through membrane

retentate

material that does not pass through the membrane

flux

flow rate per unit area per unit time

osmosis vs reverse osmosis

osmosis = no pressure, reverse osmosis = pressure

electrodialysis

selective passage of anions or cations depending on membrane, no water passage

What are microwaves?

oscillating electromagnetic field, 1m to 1mm

2 ways microwaves heat food

dipolar heating, ionic induction

penetration depth

depends on food, 1 to 1.5 inches

heating rate

related directly to water content, influenced by ion content

susceptors

metalized film (crisping, browning, heating)