Food Chemistry Previous Exam I
University of Kentucky, Department of Animal & Food Sciences, FSC 434
1. True (T) or False (F) (2 pts. Each)
Syneresis often is the result of starch retrogradation
Water is an ionic molecule.
Constitutional water will not freeze at -40EC.
At a given moisture content chocolate will have a higher water activity than crackers.
The conversion of glucose into sorbitol is a reduction reaction
A dipole-ion interaction is not as strong as a dipole-dipole interaction.
Ketoses can not form glycosylamines.
Maltose has two free hemiacetals.
Aldehydes are produced from the Strecker degradation reactions.
Amylopectin can form gels with divalent ions.
Sweet corn syrups will have a low dextrose equivalency.
Changing temperatures has little effect on the viscosity of kappa carrageenan.
2. Explain how the structure of water relates to interactions between water and:
Neutral groups with hydrogen-bonding capabilities
Give specific examples (e.g., a diagram) of each type of the above interactions showing the orientation of the molecules with water. (10 pts.)
3. List, and describe, each component in the two equations used to define water activity (6 pts).
4. List three (3) characteristics of a food that can be affected by changes in water activity and explain why and how these effects occur. (6 pts).
5. Draw a typical Brabender Visoamylograph (with the appropriate axis labels) for a starch and describe what is happening at each stage (8 pts).
6. Define a reducing sugar (5 pts).
7. Describe three (3) ways to minimize Maillard browning in foods and explain why each method or treatment is effective. (8 pts).
8. Draw and label an example (the entire reaction) of the formation of a glycosylamine in the initial stages of Maillard browning. (8 pts).
9. List three (3) examples of structures containing a glycosidic bonds (two must involve non-carbohydrate materials) (6 pts).
10. Describe the structure of low methoxy pectin. What two requirements does low methoxy pectin have in order to form a gel? Briefly explain how each of these requirements assists in gel formation (8 pts).
11. What property(s) does xanthan gum, carboxymethyl cellulose and starch phosphate monoesters have in common that contributes to their ability to increase viscosity? (6 pts).
12. Show how the structure of glucose differs from gluconic acid. (5 pts.)