Mixtures of proteins and polysaccharides

Question 1

Example number 3. Mixture of polysaccharides and proteins. pI of the protein is 5 (have both negatively and positively charges= neutral). For the polysaccharides at high pH very negative charge, but at low pH negative charge or almost neutral.

Answer 1

1. High pH: charges both negative, electrostatic repulsion.
2. Proteins positive and polysaccharides negative, electrostatic attraction. They will aggregate or cluster–>complex (small, soluble), coacervates ( larger, insoluble).

Question 2

Addition of polysaccharides after the emulsion leads to (2):

Answer 2

1. Low concentration: bridging interaction.
2. Intermediate concentration: additional layer, steric repulsion, stable
3. High concentration: additional polysaccharides will stay in the continuous phase. Depletion interaction, limited space, unstable–>phase separation. Electrostatic repulsion.