Proteins Milk and Dairy

Proteins Most abundant molecule in cells making up 50% or more of their dry weight Every protein has a unique structure, or shape Allows it to perform a specific function Enzymes are proteins that function as catalysts for many reactions in foods Contains oxygen, hydrogen, carbon, nitrogen Most also contain sulfur May also contain: phosphorus, iron, copper, zinc Very important nutritionally and functionally in foods

Proteins Alanine Phenylalanine Glutamic acid https://www.youtube.com/watch?v=qBRFIMcxZNM Polymers of amino acids (set of 20) Some water soluble, some not Some charged, some not Sequence programmed by DNA for a purpose Alanine Phenylalanine Glutamic acid

Protein Folding Water hating (hydrophobic) amino acids The hydrophobic groups are concealed in the protein core by spontaneous, natural folding Peptide chain

Proteins Primary sequence of amino acids Secondary - local folding Tertiary - large scale folding Quaternary - association structures Computer model of b-lactoglobulin, an important milk serum protein

KVFGRCELAAAMKRHGLDNYRGYSLGNWVCAAKFESNFNTQATN RNTDGSTDYGILQIN Lysozyme www.lysozyme.co.uk KVFGRCELAAAMKRHGLDNYRGYSLGNWVCAAKFESNFNTQATN RNTDGSTDYGILQIN “Lysozyme reaction is hydrolysis of the beta (1-4) glycosidic bond between N-acetylglucosamine sugar (NAG) and N-acetylmuramic acid sugar (NAM).”

Protein Denaturation Abrupt change in protein structure on being moved from non- native conditions (heat, acid, intense mixing, solvents) Sometimes (rarely) reversible Enzymes no longer work Texture may change https://www.youtube.com/watch?v=3IL_Df5ouUc Image: Flickr user ClickFlashPhotos / Nicki Varkevisser

Enzymes http://www.youtube.com/watch?v=XTUm-75-PL4 Enzymes are proteins but catalyze reactions with protein and non-protein substances Each enzyme has a unique structure which enables it to attach to specific substrates and catalyze reactions When the reaction is complete the enzyme is released an able to act as a catalyst again How might enzymes help in food processing? How might they be a problem in food processing?

Isoelectric Point The pH at which a protein is electrically neutral Does not mean there are no charged groups It means the number of positive charges is equal to the number of negative charges The point at which the protein molecules precipitate Molecule that carry a like charge repel each other Removal of the charge allows them to interact with each other

General composition of milk Component COW GOAT SHEEP Water 87.3 87.6 60.7 Lactose 4.8 4.5 Fat 3.7 3.6 7.4 Protein (casein + whey) 3.4 3.5 Salts (minerals) 0.7 0.8 1.0

Mozzarella Heaven!

Cheese in the Sous Vide https://www.youtube.com/watch?v=3mSNJfl9kBE

NATURAL VS. PROCESSED CHEESE ...know what you're buying. Natural cheeses are made by the traditional methods. Processed cheese is natural cheese that has been ground, mixed, and pasteurized. The heat applied during this process halts the “aging” of the cheese, extending the shelf life and stabilizing flavor changes. Emulsifiers have been added to prevent the separation of fat, producing desirable slicing and melting qualities in the final product. The processed cheese has a slightly different taste and appearance than the natural cheese. For example, natural Swiss cheese has holes in it... processed Swiss cheese doesn’t. Natural cheese is usually more expensive than processed cheese. Natural vs. Processed Swiss