1. Define or describe:

• M-G ratio
• M block
• G block
• propylene glycol alginate (PGA)
• egg-box model

2.  Give the source of algins/alginates.

3.  Explain the difference between alginic acid and an alginate.

4.  a) Describe the impact of the D-mannuronic acid:L-guluronic acid ratio on the gelling ability and gel strength of alginates, and b) give the molecular explanation for the phenomenon.

5.  a) Describe the effect of lowering the pH of sodium alginate solutions from 6.5 to 3.5 and b) give the molecular explanation for the phenomenon.

6.  Explain the behavior of solutions of sodium alginate upon addition of calcium ions.  Explain why this phenomenon occurs.

7.  Describe the differences between diffusion setting, internal setting, and setting by cooling for the preparation of calcium alginate gels.

8.  Describe the preparation of PGA.

9.  Describe in molecular terms why PGA a) are, in contrast to unmodified alginates, compatible with low-pH systems, b) can be used in milk systems, and c) have the ability to stabilize emulsions and foams.

Web Authors: James R. Daniel, Ph. D. and James N. BeMiller, Ph. D.
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