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HNSC 1200 (29)
Snehil Dua (29)
Lecture 28

HNSC 1200 Lecture 28: Unit 5.5

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Human Nutritional Sciences
HNSC 1200
Snehil Dua

Functional Properties of Proteins Learning Objectives: Explain the functional properties of protein Discuss the role of enzymes and non-enzymatic browning Course Notes: Proteins play important roles in food as well: water binding, gel formation, thickening, emulsion, foam formation (e.g., egg whites, whip cream) and the Maillard reaction Protein Hydration: o The water binding (hydration) capacity or proteins is relate to the amino acid composition o The more charged amino acids, the greater the hydration capacity. o Protein molecules can entrap water because of their hydrophilic characteristics (food system – sausages, cakes and breads) o Gelatin can thicken products and increase viscosity by forming gel matrixes (food system – soups, gelatin desserts and dairy products) Protein-Surface Properties: o Proteins are amphiphilic, so they can act as a water-oil interface because they exhibit both hydrophobic and hydrophilic characteristics, helping to stabilize emulsions (food system – salad dressings, bologna, sausages, ice cream, soups, cheese and sauces). o They are also involved in the production of food forms: forms are unique in that the dispersed phase is a gas within a liquid phase (food system – sponge cakes, whipped toppings, beer froth and ice cream) Flavour Binding o Proteins bind to flavour molecules o They can also beused to enhance the flavour of processed food (food system – simulated meats e.g., textured soy protein, tofu). Denaturation and Coagulation o Protein denaturation involves unfolding of protein structure without breakage of peptide bonds o Denaturation is caused by cooking, freezing, changes in pH, salts enzymes and mechanical action o Denaturation changes the original properties of the protein o In most cases, denatured proteins are less soluble o If it is an enzyme, function ability will be lost o Continuous denaturation (unfolding) can lead to recombination of the protein molecules in different way s to produce a new molecular shape o The newly shaped molecules may bond together to form a continuous network referred to as coagulation (e.g., coagulation of egg white when heated) o SEE FIGURE 24 OSDP Proteins as Enzymes Enzymes act as catalysts that speed up chemical reactions without being sued in the reaction itself SEE FIGURE 25 Enzymes do not stop functioning when an animal is slaughtered or when a plant is harvested; therefore, we must consider enzyme acidity when dealing with foods o Names of enzymes often include the substrate or substa
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