Phase behaviour of macromolecular components in biological and food systems

Abstract

Reasons for the greatly different phase behaviour of: (i) biological systems (cytoplasm of the cell), (ii) food systems and (iii) beverages are considered. The two phenomena: molecular mimicry and molecular symbiosis presumably control thermodynamic compatibility of biological macromolecules. The three interacting factors underlying molecular mimicry, are: (i) low excluded volume of densely packed protein globules, (ii) chemical resemblance of surfaces of the globules and (iii) the chemical information hidden in the hydrophobic interior of the globules. The symbiotic relationship presumably exists between rod-like macromolecules and protein globules, i.e. between macromolecules of the two extreme conformations typical of biopolymers. For instance, thermodynamic activity of an enzyme can be controlled by dissociation-association of rod-like macromolecules. Due to excluded volume effects, biopolymers behave as if they were in a solution of a higher concentration. Both molecular mimicry and molecular symbiosis could also be of importance for non-specific immune defence, digestion of proteins and formation of food structures. Unlike biological systems, thermodynamic incompatibility is typical of foods and still more of beverages. Denaturation, aggregation and complexing of food macromolecules decrease their mimicry and co-solubility. Due to their relatively low viscosity and high chemical and physical heterogeneity of macromolecules, the phase behaviour of beverages is similar to that of mixed solutions of synthetic polymers. Phase separation of biopolymer mixtures is of importance for controlling composition-property relationship in formulated food and drinks.

Plant protein interactions with polysaccharides and their influence on legume protein functionality A Review

“…The thermodynamic incompatibility manifests itself in the phase separation at concentrations exceeding the separation threshold with the predominance of one of the polymer components in each phase. The significance of this phenomenon for food and biological systems has been thoroughly analysed by Tolstoguzov [1].…”

Kinetics of Phase Separation of Oat β-Glucan/Whey Protein Isolate Binary Mixtures

“…However, in the absence of whey protein particles, as in the present investigation, the excluded volume approach seems to be more appropriate. Following this line of thought, as the β-glucan concentration increases and/or MW decreases, the excluded volume of the polysaccharide in the mixture decreases 42,43 . This is accompanied with an increase of phase-separation rate suggesting a relationship between the excluded volume of the polysaccharide and the rate of phase separation for the low and intermediate-molecular-weight samples.…”

Combination of Propylene Glycol Alginate and Lauric Acid on Water Retention and Mechanical Properties of Soy Protein Isolate-Based Films

“…The change of Tg is considered to be an effective index for the changes of compatibility between polymers. 30 There are common studies on the interaction between proteins and polysaccharides; however, there is only poor understanding about the dynamic interaction between polymer molecules. 31 The factors of Tg becomes more complex, especially after the addition of lipid, and forming of ternary co-blends.…”

“…The change of Tg is considered to be an effective index for the changes of compatibility between polymers. 30 There are common studies on the interaction between proteins and polysaccharides; however, there is only poor understanding about the dynamic interaction …”