CHAPTER 8: Protein Modifications and the Food Matrix: Consequences, Chemistry and Characterization

Proteins are one of the macronutrients present in foods. During the manufacturing process, they undergo modifications induced by physical (e.g. heat, irradiation, pressure) and chemical methods or by the action of an enzyme. The understanding of these modifications is important for assessing their effects on the quality of foods and the digestibility and nutritional values. Proteins can be modified by reaction with carbohydrates via the well-known Maillard reaction. They can also be modified by primary and secondary lipid oxidation products, metals, polyphenols, reactive oxygen species or free radicals. Some of the modifications involve changes in secondary and primary structures, crosslinking and reduction of molecular size. This chapter covers various modifications that can occur during storage, processing and cooking or by the use of chemicals and enzymes. The chapter is completed with spectroscopic and chemical methods used for the characterization and determination of the functionalities of the modified proteins.