Food Process Mechanisms Leading to Loss in Protein Quality

During the course of food product development, many formulators often experience loss in protein quality and bioavailability due to processing techniques and other parameters. Below are some of the mechanisms that lead to protein quality loss during food formulation. You are invited to post your comments!

Heat Destruction:
This is the destruction of amino acids contained in proteins by use of very high temperatures, leading to loss in functionality of the protein.

Non-Enzymatic Losses:
This is a loss in protein quality not requiring the action of enzymes. E.g. Maillard browning (formation of brown coloration in foods as a results of amine group of amino acids reacting with the aldose, ketose group of chemical compounds and/or reducing sugars, to give rise to complex products, which results in protein loss).

Protein-Protein Crosslinkage:
This is the formation of new linkages, or the modification of existing linkages between the amino acids of proteins, thereby causing a loss in bioavailability of these amino acids.

Protein Isomerization:
This is the formation of a protein isomer as a result of the processing conditions under which the food was subjected - leading to loss in bioavailability of amino acids in the protein. E.g. conversion of an L-Amino acid to the D-isomer.

Protein Oxidation:
This is the destruction of proteins by autolysis of fatty acids and fat compounds that are either in interaction with the protein or in close proximity to the protein, thereby leading to oxidation of the amino acid contained in the protein.

Alkali Treatment of Proteins:
The use of alkali in food treatment may lead to a loss in protein function, quality and bioavailability. E.g. Formation of hard curd from milk by alkali treatment which results in protein non-digestibility.

Losses by non-reducing mechanisms:
E.g. Caramelization (this is the formation of brown pigments on food surfaces when the amino group of certain amino acids reacts with carbonyl compounds under the influence of high temperatures, leading to losses in protein function and quality.