Lecture 13 Protein denaturation

What are some denaturing agents?

-Heat -Alcohol -Enzyme -Acid -Mechanical energy

What are the stages of Protein Denaturation?

1) Unfolding 2)Aggregation 3)Flocculation 4)Precipitation

What is stage 2 of denaturation of a protein?

Aggregation: Increase the interactions between adjacent denatured protein molecules

Describe alcohol as a denaturing agent

Alcohol is hydrophilic and will compete for the water binding sites on a protein molecule, dehydrating the protein therefore denaturing it.

Describe mechanical energy as a denaturing agent

Applying human forces disrupts protein structure like whipping egg whites to form foamy structure and kneading dough which forms an elastic structure that traps gases.

Describe enzymes as a denaturing agent

Enzymes hydrolyzes peptide bonds of the casein proteins which alters the form of the casein that keeps the milk proteins in a solution therefore curds are formed.

What happens in stage 3 of protein denaturation?

Flocculation: Aggregates and becomes larger in size where they flocculate.

Describe the heating of meat

Heat denatures muscle fibre proteins at 40-50 degrees C but connective tissue proteins surrounding the muscle cells are denatured until around 60-75 and this is when water losses and shrinkage only become apparent.

What is denaturation by unfolding of a protein?

Hydrogen bonds and other bonds that stabilise the structure are broken. This results in the solubility decreasing.

What happens in stage 4 of protein denaturation?

Precipitation: become visually apparent e.g. curdled milk (paneer)

What is the Definition for protein Denaturation?

Process in which the native structure of protein is disrupted, or when the protein loses its function

How does heat cause denaturing of proteins?

Proteins are heat sensitive thus it disrupts the weaker intermolecular linkages (ie. hydrogen bonds). Temperature required for denaturation depends on the protein.

Describe acid as a denaturing agent

Proteins are sensitive to pH, therefore adding acid to milk has a neutralising effect therefore precipitation occurs because the proteins are attracted to each other. eg. yogurt

Definition Coagulation

The precipitation of a denatured protein into a semi-solid structure.