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Foam and emulsion properties

4 important questions on Foam and emulsion properties

What is the critical protein concentration?

When increasing the protein concentration, the droplet size gets smaller, as the droplets coalesce less if there is more protein to stabilise the interface. At the critical protein concentration, the droplet size will not decrease further anymore, as the interface is stabilised completely.

In which 2 ways can creaming occur and how can you distinguish the difference?

Due to large droplets (coalescence)
Due to larger clusters of droplets (flocculates)

Using microscopy you can distinguish the difference.
Adding SDS, leads to dissociation of the flocculates

Flocculation the reason, the droplet size gets smaller

Particle size due to coalescence not affected

How are the droplet size and the zeta-potential (charge) related?

The lower the zeta potential (charge), the less electrostatic repulsion, so the larger the droplet size.

How are protein purity and emulsion stability related?

A pure protein, without polysaccharides, has a clear pI, where flocculation occurs and a larger droplet size can be found.

A protein with added polysaccharides, does not have a clear pI or a point where flocculation occurs. The stability at a low pH is the result of protein(+)-polysaccharide(-) complex that absorbs at the interface, and therefore gives steric repulsion and stability against flocculation.

The question on the page originate from the summary of the following study material:

Food Ingredient Functionality: Proteins

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