Chapter 5
1. Describe and discuss the relationship of polysaccharide structure to solubility, solution stability, and viscosity.
2. Give the molecular explanation for the differences in solution viscosity of linear and branch-on-branch polysaccharides of the same molecular weight at the same concentration.
3. Discuss the factors involved in, and a general procedure for, making a gum solution.
4. Define or identify
| food gum hydrocolloid body bulk glass transition temperature, Tg sol "fish eyes" hydrodynamic volume rheology stress strain viscoelastic behavior |
viscosity shear modulus elastic modulus (G') storage modulus (G') viscous modulus (G") loss modulus (G") yield stress (yield value) Bingham plastic Newtonian flow pseudoplastic flow, pseudoplasticity long flow short flow |
thixotropic flow, thixotropy hysteresis gels (two definitions) junction zone syneresis hydrogel xerogel emulsifier emulsion stabilizer amphoteric steric stabilization |
5. Describe and give a molecular explanation for the effects of the following on polysaccharide solution viscosity:
| chemical structure molecular shape temperature concentration |
pH ionic strength* concentration of solution* |
*Explain why it increases solution viscosity of some polysaccharides and decreases solution viscosity of others.
6. Describe the relationship of molecular weight to solution viscosity of a linear polysaccharide.
7. Describe and compare the two general kinds of shear-thinning rheology.
8. Describe, with examples of applications, how use can be made of pseudoplastic rheology in processing and formulating food products.
9. Discuss the molecular basis for pseudoplasticity and for thixotropy.
10. Discuss the effects of concentration and molecular weight on the pseudoplasticity of solutions of a specific gum.
11. Discuss the relationship of the degree of pseudoplasticity to mouthfeel.
12. Discuss the molecular basis for a yield value (yield stress).
13. Discuss how polysaccharides that produce solutions with yield values can be applied (using examples).
14. Identify applications of yield value.
15. Describe the concept of overlap concentration (c*).
16. Describe the molecular basis for gel formation.
17. List the five types of junction zones related to food gum use.
18. Describe the molecular basis for syneresis and a means to control it (with an explanation).
19. Describe the molecular basis of gel textural properties.
20. Given the chemical structure of a polysaccharide,
predict the properties of that polysaccharide. Such properties
should include a) solubility, b) viscosity, c) the effect of pH on
viscosity and solubility, and/or d) the effect of added salts on
viscosity.
Web Authors: James R. Daniel, Ph. D. and James N. BeMiller, Ph. D.
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