11 - Proteins

11 - Proteins - Proteins March 10-22, 2010 Contribute...

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Proteins March 10-22, 2010 Contribute towards ~20% of total caloric intake Presence of proteins + amino acids are helpful in flavour + texture development Phenolalanine & lysine give more (chemical) browning than glycine Proteins can vary in structure and function: o Structural proteins: Keratin – chicken feathers Actin/myosin complex – muscle structure Rigomortis + meat muscle products o Enzymes Ex. Meat tenderizer Ex. Lysozyme (found in egg whites) – has anti-microbial properties Hormones Ex. insuluin Growth factors Tyrosine inhibitors In soy beans This is why you need to soak or heat treat because soybeans naturally contain tyrosine inhibitors Trypsin is a digestive enzyme Peptides Casein phosphopeptides o Formed upon digestion of casein milk proteins o Helpful in Ca 2= absorption Proteins can vary in composition and sequences: o Simple proteins: Basic polypeptide Just consists of linked amino acids Ex. Ovalbumin – egg protein, H 2 O soluble protein o Conjugated proteins: Undergone post-translational modification in rough ER to Golgi apparatus (where post-translational occurs Takes polypeptide and adds other groups Glycosylated Ex. ovomucin (important protein in thick albumin) Phosphorylated Ex. Casein Addition of PO 4 - groups PO 4 - interact with Ca 2+ help keep Ca 2+ soluble (needed in order to be absorbed in diet) Not a pure keylation Protein-rich sources in the diet include: o Dairy products 36% protein in milk 80% is caseius Colloidal in milk (this is why skim milk is bluish-grey in colour – fat removed but protein is still present b/c they’re not fully soluble 20% is whey Water-soluble in milk, in comparison in caseius Yogurt uses acid to change pH, causing coagulation of primarily caseins Cheese uses enzymes which act on particular casein protein to coagulate
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Proteins March 10-22, 2010 o Egg protein High biological value b/c it has excellent complement of quality protein High quality, complete protein (good array of essential amino acids) o Meats Connective tissue --- collagen Too much connective tissue adds toughness b/c of fibrous collagen Softening would be from high moisture heat treatment Provide iron from myoglobin in tissue o Cereals -- Limiting in lys, trp, thr Soybean -- Limiting in lys (less than desirable amount) Structure of proteins 1° structure o ~20 amino acids o o Chemistry that can affect protein: acids, alkaline, hydrophobic
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This note was uploaded on 12/26/2011 for the course FND 100 taught by Professor Y.yuan during the Winter '10 term at Ryerson.

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11 - Proteins - Proteins March 10-22, 2010 Contribute...

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