PHYSICS OF FOOD

1
PHYSICS OF FOOD

• From foukeffa.org
• Written by Teri Micke
• Ag Student Texas AM
• GA Ag Ed Curriculum Office
• To accompany the Georgia Agriculture Education
  Curriculum Course 02431
• July 2002

2
OSMOSIS

• water molecules flow from a place of greater
  concentration to a place of lesser concentration
• example wilting lettuce (even more water than
  salad dressing --will wilt than)

3

• If we decrease the amount of water in a food, we
  will also decrease the amount of water in
  microbes. It may not kill them, but it wont
  allow them to reproduce.
• example brines in canned foods (pickles) or
  heavy syrups in fruit

4
WATER ACTIVITY

• written as aw
• degree of available water in food
• like the humidity of the food
• the more water, the more microbes
• this is why we can freeze food

5
aw of foods

• water 1.0
• fresh meat/veg .995
• marshmellow .750
• gum .700
• raisins .650

6

• Remember as we freeze food it creates ice
  crystals which puncture cells, so when we thaw
  food the cells cant hold water and it creates
  drip, which actually causes food to lose
  nutrients.

7

• Freezing food does not kill microbes or destroy
  proteins because they maintain a layer of water
  around them.
• By adjusting the pH it will affect the water
  layer around the protein --- salt has the same
  effect

8

• with pH protein leaves water
• with salt water leaves protein
• reverse is how gelatin is made
• collagen (a protein in connective tissue) is
  boiled until soluble in water, then dried to a
  powder, then sugar, color, and flavor is added
  ---JELLO

9
LIPIDS

• Emulsion - the dispersion of oil in water or
  water in oil aided by a detergent or protective
  colloid (particle too big to pass through a
  filter and settle out by gravity)
• example homogenized milk
• mayonnaise (oil, water, and egg whites)