ABSTRACT
The wide diversity of the intramolecular and intermolecular interactions of food biopolymers is determined by the variety of different monomer units making up their polymeric chains. Table 4.1 reviews the chemical structures of the main monomer units comprising food proteins and polysaccharides. It is well known that proteins are built from a basic menu of 20 amino acids. In addition some food proteins contain extra amino-acid residues, e.g., phosphoserine in casein and hydroxyproline in gelatin. Using their constituent carboxyl and amino groups, the amino acids are joined together by peptide bonds into a unique linear sequence (the polypeptide chain) which is the distinguishing characteristic of each individual protein. The composition and sequence of the amino-acid side chains, possessing non-polar (hydrophobic), polar, or charged functional groups, determines the overall amphiphilic nature of each protein molecule. In contrast, the polysaccharides are made from chains of monomeric sugar units. The carbohydrate groups are mainly polar or charged, which gives the polysaccharides a predominantly hydrophilic character (Cantor and Schimmel, 1980; Lehninger, 1982).
