1. PHYSICS OF FOOD From foukeffa.org Written by Teri Micke
Ag Student Texas A&M
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 won’t 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

6. Remember as we freeze food it creates ice crystals which puncture cells, so when we thaw food the cells can’t 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)