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Foam - Decision tree foam

5 important questions on Foam - Decision tree foam

A foam (single system) is stable, how come?

The air-water interface is densely packed with proteins.

A foam (single system) is unstable, how come?

Not sufficient proteins on interface

Turbid --> aggregate formation
Fast formation but unstable --> too small
Strong charge? --> too much repulsion

A foam (mixed system) has repulsion between the proteins and polysaccharides and forms less easy and/or is less stable, how come?

There are less proteins on the interface

Due to increased viscosity, proteins more slower to the interface and foam formation is inhibited
Polymer prevents proteins to move to the interface

Increase disproportionation and coalescence

A foam (mixed system) has attraction between the proteins and polysaccharides and is more stable, how come?

Thicker interface --> all PS are attached to the proteins --> Prevents disproportionation and coalescence
Thicker interface and interfacial film --> PS are attached to the proteins and excess PS in water film

A foam (mixed system) has attraction between the proteins and polysaccharides and is not more stable, how come?

Less proteins and PS on the interface --> due to coacervate formation, limited diffusion to interface --> increase disproportionation and coalescence (possible sedimentation of the coacervates