Summary: Food Ingredient Functionality: Physical Aspects

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• 1 Bulk rheology

• 1.1 Viscosity of biopolymer solutions

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• The viscosity is dependent on 3 parameters

  1. Concentration
     
  2. Conformation (shape)
  3. Molecular weight, M

• What kind of conformation does xanthan have?

  Rigid rod, helical polysaccharide

• What kind of conformation does alginate have?

  Semi flexible

• How are the stiffness and hydrodynamic radius related?

  The stiffer the polymer, the higher the hydrodynamic radius

• How are pH and viscosity related?

  An increase in the charge density, provides more electrostatic repulsion and stretches the backbone. This increases the stiffness and thereby increases the radius and the viscosity. 
  
  
  The pH only has an effect on anionic polysaccharides (e.g. Pectin, alginate) but non on non-ionic polysaccharides.

• How are ionic strength and viscosity related?

  The ionic strength screens the charges. When charges are screened, the electrostatic repulsion decreases and the stiffness parameter decreases.

• How is the intrinsic viscosity of proteins compared to polysaccharides?

  The viscosity of proteins is much lower. This is due to the much lower molecular weight and more compact shape. The global shape does not contribute much to the viscosity. When proteins aggregate, they can increase the viscosity.

• What is the overlap concentration?

  Where the concentration changes from dilute to semi-dilute. The single polymers do not act as single molecules anymore, they start to overlap.

• 1.2 Viscosity of suspension

• How are pH, the flexibility and the viscosity of a suspension related?

  An increase in pH will increase the internal electrostatic repulsion between the group on the polysaccharide backbone. Therefore, the polysaccharide chain will take more space, and the volume fraction will increase. The particles get closer and may form a network.
  
  In addition, the flexibility of the chains will change, because the repulsion can result in less mobile particles. As a result the viscosity will increase. 

• 2 Interactions in food

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• How are the macroscopic properties of a food product determined?

  By their physical properties and the interaction forces between these different ingredients