Protein Denaturation and Consequence

DENATURATION - Loss of native structure

Protein denaturation denotes the loss of the native protein structure due to a change of the physiological conditions to other conditions. Protein structure can be seen on four different levels: primary (amino acid sequence), secondary (presence of alfa helices or beta sheets substructures), tertiary (three dimensionally folded protein) and quaternary structure (protein clusters, dimers etc). Apart from the primary structure these structures originate from the following interactions between amino acids: SS bounds, electrostatic interactions, H-bounding, hydrophobic interactions and Vanderwaals forces (figures could be added to explain this better). If these interactions change due to a change in the environment of the protein (e.g. pH change will induce charge change in protein and thus may influence electrostatic interactions), this may have an effect on these structural elements. As long as the primary structure of the protein does not change (= changes on amino acid level), these changes are considered as protein denaturation. Denaturation can be induced by heat, Insostatic pressure (physically disrupting the structure), pH change, addition of salts (playing with salt concentration), removal of water (e.g. sublimation during freezing), physical shear, etc. (proteins have a isoelectric character, neutral charge). The protein structure is affected by the hydrogen bonds, the more water, the morw hydrogen bonds.

 Heat denaturation though is considered to occur mostly in the food industry. Each protein is characterised by a particular denaturation time and temperature, but this may be affected by the water activity of your product. Protein could also undergo denaturation during cooled storage due to a change in hydrophobic interactions at low temperatures. Since all the above mentioned interactions are not broken at once, denaturation is a step wise process and as such can be reversible or unreversible (figures could be added explaining this).

Denaturation is important because

-           It changes drastically the functionality of proteins (good or bad).

-          Solubility may be affected (coagulation of egg white) (other examples could be given).

-          It may also affect the biological activity of proteins, such as enzymes.

-          It may have a positive impact on the digestibility of proteins, since they become more accessible for digestive proteases.

-          As no changes on amino acids are involved, no negative impact on nutritional value is expected, on the contrary bio-availability increases.

Summary of consequences: 1. Inactivate antimicrobial factors; 2. Digestibility of proteins is higher (proteases can reach the protein in a better way when it is denatured); 3. Nutritional value increases; 4. Changes on functionality which could be good or bad (activation of enzymes, gelatinization, change of physical characteristics - cooked egg). Denaturation is important because it changes drastically the functionality of proteins (good or bad). Solubitlity e.g. may be affected (coagulation of egg white) (other examples could be given). It may also affect the biological activity of proteins, such as enzymes. It may have a positive impact on the digestibility of proteins, sine they become more accessible for digestive proteases. As no changes on amino acids are involved, no negative impact on nutritional value is expected, on the contrary even since bio-availability increases.