2.  Denaturation changes the shape of a protein molecule without breaking its peptide bonds.  The result is a looser, less compact structure.

3.  http://www.youtube.com/watch?v=v2-iY7ZoDOc http://www.youtube.com/watch?v=v2-iY7ZoDOc

4.  Denaturation is the first step in the process of coagulation.  Coagulation changes a liquid into a soft, semi- solid mass (polypeptides unfold during denaturation, then collide and clump together to from a solid).

5.  http://www.youtube.com/watch?v=y77dNgSbrQI http://www.youtube.com/watch?v=y77dNgSbrQI

6.  Example: Beating an egg denatures its proteins. The protein coagulates as the egg cooks.

7.  Heat is the most common agent in denaturing protein.  Other means of denaturation include freezing, mechanical treatment (i.e. beating eggs or kneading dough) and very high or low pH (i.e. adding lemon juice to sour milk lowers pH and milk proteins denature).

8.  Before coagulation occurs, denaturation is sometimes reversible. That’s why whipped egg whites left to stand can turn to liquid again.

9.  Eggs contain every vitamin and mineral for calcium and vitamin C.  The yolk contains all of the fat, along with most of the other nutrients.

10.  Proteins can act as emulsifiers.  An emulsifier stabilizes oil and water mixtures.  Certain proteins contain polar amino acids; one end is attracted to water and one end is attracted to oil (i.e. the proteins in eggs keep mayonnaise blended).

11.  http://www.youtube.com/watch?v=R7sYROUNO7g http://www.youtube.com/watch?v=R7sYROUNO7g

12.  Meringue is a foam.  Air bubbles are incorporated and trapped in a protein film by whipping.  Foams add volume and lightness to products.  Foam begins with a protein-containing liquid (i.e. egg whites).

13.  Remember, whipping denatures the protein molecule; the protein molecule coagulates to form a film around the air pockets.  The large protein molecules in egg whites make them ideal for foams.  Cream of tartar lowers pH and is often added to stabilize the protein and produce a higher quality foam.

14.  Fat (i.e. in egg yolks) can drastically reduce a foam’s volume, or prevent foaming entirely.  Cooks must be very careful to keep the yolks out when separating whites to whip.  Fats tend to cling to plastic so recipes often specify using glass or metal bowls for whipping egg whites.

15.  http://www.youtube.com/watch?v=iAp8pEaWB1Y http://www.youtube.com/watch?v=iAp8pEaWB1Y

16.  Over-whipping can also be a problem.  A foam is most stable just before reaching its maximum volume.  Past that point, the proteins unfold to the point that they lose elasticity.

17.  http://www.youtube.com/watch?v=2xJwoz5FRbg http://www.youtube.com/watch?v=2xJwoz5FRbg

18.  http://www.youtube.com/watch?v=3ok5LHMP-R4 http://www.youtube.com/watch?v=3ok5LHMP-R4

19.  http://www.youtube.com/watch?v=OQyRuOEKfVk http://www.youtube.com/watch?v=OQyRuOEKfVk

20.  http://www.youtube.com/watch?v=k4jZdQm1yHc http://www.youtube.com/watch?v=k4jZdQm1yHc