Gel - Improving gel characteristics
3 important questions on Gel - Improving gel characteristics
How does the pH influence the gel strength at a high concentration of biopolymers?
Change in pH --> increased repulsion
- Flexibility is decreased, chains more straight and stiff --> increased gel hardness (higher fracture stress) and increased brittleness (decreased fracture strain).
- Repulsion between junction zones or within helices --> more difficult for chains to come together and interact. Especially for small distance interactions (hydrogen bonds). Too much repulsion, less junction zones are formed --> decreased gel hardness (lower fracture stress)
What is the effect of salt addition on the gel strength?
Charged polymers (because of pH) --> adding salt will screen charges, reduce electrostatic repulsion
- Helix formation enhanced --> stronger network
- Distance between the chains is reduced, flexibility enhanced --> chains more mobile and network becomes weaker --> gel strength decreases
How does the interaction of proteins and polysaccharides effect the gel strength?
- (-)polymers + (-)proteins --> (-)proteins requires space, less space for polymer network to form. Electrostatic repulsion --> less mobile network, stronger network
- (-)polymers + (+)particles --> attractive interactions between polymers and particles. Interactions stronger than between polymers themselves, particles withdraw the polymers from the network. Gel network is disrupted. Aggregation can occur and aggregates can sediment.
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