Denaturation of Proteins Continued… Changes many of the physical characteristics of a protein. Alter the ability to bind to water causing proteins to shrink when cooked Reduce water solubility causing precipitates (solids) to form and later separated.

Methods of Denaturing a Protein Temperature Changes: Adding heat is the most common method in food production. Heat: rate of increase for protein denaturation is 600 times the rate for every 100C increase in temperature. This rate increases if the protein is wet. Cold: milk that is frozen then thawed will have a curdled look because of denaturation.

Methods of Denaturing a Protein Continued… Mechanical Actions – beating, rolling, kneading. Elastic protein strands that give bread dough its structure – gluten. During the kneading process gluten changes shape & strengthens, enabling the bread to rise without tearing.

Methods of Denaturing a Protein Continued… Change in pH – helps food scientist develop new food products. Ex) Denaturing soy in a base, then running it through an acid bath to coagulate creates simulated meat products. Ex) Sour cream, buttermilk, & yogurt are made by denaturing milk proteins with acids.

Methods of Denaturing a Protein Continued… Exposing protein to minerals or salts Ex) Adding salt early in cooking high protein legumes will cause them to toughen

Functions of Protein in Food Proteins have varying degrees of water absorption, solubility, and viscosity that food scientist consider when analyzing food products.

Functions of Protein in Food Continued… Form Gels – a protein gel is of mostly fluids locked in a tangled 3 dimensional mesh. Liquid keeps the protein from collapsing, and the protein keeps the liquid from flowing away. Strengthened by adding more gelatin or mineral salts Weakened by adding acids, fruit, or vegetable pieces Ex) Jello, chicken hot dogs, bologna type sausages

Functions of Protein in Food Continued… Texturize – used in meat substitutes to give protein consistency, and developing cheeses with a smoother texture. Emulsify – emulsions require an emulsifier, which can be a denatured protein. Ex) Egg yolk: used in ice cream & mayo to keep mixtures stable. Emulsion – stable mixture of fat in a water based liquid. Require a nonpolar substance (fat), polar substance (water), and emulsifier (can be a denatured protein).

Functions of Protein in Food Continued… Form Foams – gas usually surrounded by a film of protein suspended in a liquid or semisolid. Made in 3 ways Bubbling gas through a mixture: The elasticity of the protein in milk makes the foaming action possible. Ex) blowing bubbles in milk. Whipping or beating: most common method & more stable. Ex) beating egg whites. Depressurization: Release in pressure causing dissolved air and liquid to release as foam. Ex) whipped cream cans.

Functions of Protein in Food Continued… Develop Gluten – formed when wheat flour is combined with moisture and kneaded. During baking, gluten coagulates, making the baked product light and airy.