Food Analysis Previous Exam II

University of Kentucky, Department of Animal & Food Sciences, FSC 535

 1. True (T) or False (F) (30 pts.)

Ketoses can act as reducing sugars.

Aldoses are polyhydroxyl-ketones.

The anthrone method is specific for ketones.

Producing an antibody specific for a simple sugar requires a hapten.

Simple sugars are generally insoluble in 80% ethanol.

The Bligh and Dyer method of extraction lipids (chloroform/methanol/water) is effective for extracting polar lipids.

Pectin is generally insoluble in 80% ethanol.

The smoke point of an oil is directly related to its’ iodine value.

Total soluble fiber is soluble in 78% ethanol.

Solid Fat Index is actually the measurement of the contraction of oil as it melts.

Hexane is generally a good solvent for phospholipids

Cloud point measures the temperature at which fat crystallization begins.

The color indicator for peroxide value is phenolphthalein.

Thiobarbituric acid assays measures the level of peroxides in an oil sample.

Using thin layer chromatography on silica and a non-polar solvent, phospholipids migrate slower than triglycerides.


2. Briefly describe the theory behind the analysis of reducing sugars using Fehling’s reagent (6 pts.)

3. Briefly describe the theory behind an analysis of for total carbohydrate. (5 pts.)

4. Describe the principle means of separation for simple sugars (e.g., mono- and di-saccharides) on one type of HPLC column (5 pts.)

5. Describe the general principles involved in the analysis of pectin by HPLC. (5 pts.)

6. Define dextrose equivalence and describe why this analysis is useful in the corn syrup industry. (5 pts.)

7. Describe three (3) methods for the analysis of fructose and briefly describe how they work and their limitations for the analysis of fructose. (6 pts.)

8. Describe the principles involved in the analysis of total dietary fiber. (4 pts.)

9. List 5 important attributes for a solvent used for extracting lipids. What is a common lipid extraction solvent and describe how the five attributes you listed relate to it. (5 pts.)

10. Describe how the moisture content of a sample (e.g., ranging from 1 to 10%) can effect the amount and type of lipids extracted using petroleum ether. (4 pts.)

11. How would you determine if an oil had been winterized properly? (5 pts.)

12. Describe the method for determining the Lovibond color of an oil sample. (4 pts.)

13. Briefly write down the differences between the following items. (20 pts.)

a. Total soluble fiber vs. Total insoluble fiber

b. Copper (II) vs. Copper (I)

c. Specific gravity vs. Refractometry

d. Soxhlet extraction vs. Bligh and Dyer extraction

e. Wiley melting point vs iodine value

f. Smoke point vs fire point

g. Active oxygen method vs. Rancimat

h. Aldoses vs. Ketoses

I. Soxtec vs. Goldfish extraction

j. Free fatty acids vs. Peroxide value

14. You are the quality assurance director at a major snack food processor. During the last month the companies cheese puff product has exhibited a significant increase in customer complaints about off-flavors due to rancidity. You have been using two different supplies for the same partially hydrogenated soybean oil (approximately 20% of the cheese puff) during the month in question. How would you go about investigation the cause of the oil’s instability. Note. Your laboratory has maintained adequate retained samples of each shipment of oil received and the code dates of cheese puffs during this period. Describe the sample preparation and types of analyses you would do to attempt to determine the cause of the product deterioration. Explain why you think each analysis you listed will help solve the mystery. (15 pts.)