Title: Final Exam
Course: Food Analysis Labs > Section: Course Content

The final exam will cover experiments E5-E7.

The focus will be on the main objective of understanding why food analysis is important, what kinds of methods are available, how to select them, and how to interpret the data. Start by reviewing the Powerpoint slides first, then the Glossary and BlackBoard Quizzes. Use the textbook for those topics you need to review deeper.

The exam will be in-class with mostly open-ended questions.

Q: Give an example of why proteins are an important part of foods. What do they do for your body, or for foods?
Feedback: Correct answers could include: Proteins are important as building blocks for your body. Proteins have important effects on the physical properties of foods. The identity of proteins present in foods can be critical for example, to people with food allergies.

Q: Which two things usually need to be performed to prepare a food sample for protein analysis. For example, starting with fish muscle, describe the two main steps needed to prepare the sample for analysis.
Feedback: Homogenization, by grinding, blending, or crushing, followed by extraction into buffer.

Q: Give three examples of methods of protein separation, = for example, describing three different properties you could use to separate a mixture of proteins.
Feedback: Separation by differences in solubility, adsorption properties, size.

Q: In our experiment, we discussed four different sources of interference in protein analysis. Describe at least two of these, providing concrete examples as needed for clarity.
Feedback: Food processing methods such as heating the sample could reduce extractability of proteins. Selection of standards that are unlike the sample could interfere in interpretation. Non-protein nitrogen present in foods could interfere. For colorimetric assays, the measurements must be within the linear range of the assay.

Q: In developing a protein separation strategy, it is best to start with a step that can easily be used with large quantities of material.
- True
- False
A: True

Q: During electrophoresis, proteins migrate towards which electrode? Why?
Feedback: The proteins will migrate towards the positive, or red, electrode wire, because they are negatively charged, having bound SDS (Sodium dodecyl sulfate).

Q: During electrophoresis, proteins will migrate such that which proteins go the farthest? And which travel the least?
Feedback: The smallest proteins will travel the farthest, with the largest traveling the least.

Q: Three types of chemical components in foods are contaminants, residues, and constituents. In Experiment 6 on caffeine content, we discussed several ways that these components enter the food supply. Give three examples of ways these chemicals get into food.
Feedback: Pesticide use in farming, veterinary drugs in livestock, food processing, food additives, choice of packaging materials.

Q: Give three examples of general analytical approaches for the analysis of chemical constituents of foods. In other words, name the instruments or methods that are used in their analysis.
Feedback: Gas Chromatography (GC), High Pressure (or Performance) Liquid Chromatography (HPLC), Immunoassays, Thin Layer Chromatography (TLC)

Q: Describe two potential sources of interference in analyzing your soft drinks for caffeine.
Feedback: Other components with similar chemical properties in the drink. Solids or bubbles present in the sample.

Q: Chemical constituents of food are often present in very dilute concentration and therefore significant sample preparation is typically required.
- True
- False
A: True

Q: After measuring caffeine in soft drinks, and participating in the discussion board exercise on powdered caffeine, now perform the following calculation:

Given that 1 teaspoon = 5600 mg, and if one 12oz (0.355L) can of mountain dew contains only 54 mg of caffeine, - drinking a beverage with a teaspoon of powdered caffeine would be an equivalent amount of caffeine to consuming how many 12oz cans of mountain dew?

If the average adult has 5 liters of blood, and absorbs the entire teaspoon of caffeine, what would you estimate the quantity of caffeine in their blood to be (in mg/L)? Is it more or less than a can of mountain dew itself?
Feedback: About 103 or 104 cans of mountain dew. The mountain dew would have 54mg/0.355L or 152 mg/L. The person's blood would have 5600mg/5L or 1120mg/L. They would have a higher concentration of caffeine in their blood than a can of mountain dew does.

Q: Describe a reason that it is important to identify and quantify some of the chemical components of foods.
Feedback: Correct answers include: Food safety (microbial and chemical), regulation requirements, fair trade, food quality analysis

Q: Flavor is caused by receptors in the mouth and nose detecting chemicals found within food. These receptors respond by producing signals that are interpreted by the brain as sensations of taste and aroma.
- True
- False
A: True

Q: The chemicals that produce a single flavor can contain hundreds or thousands of component substances.
- True
- False
A: True

Q: Describe one of the three major reasons that we need to identify and quantify the components of flavors?
Feedback: Correct answers include: Identifying the chemical profile allows us to develop processes that preserve food flavor, it enables us to synthesize artificial flavor compounds. And it may be regulated, such as in countries where there may be minimum or maximum amounts of total higher alcohols in certain alcoholic beverages.

Q: What is the method / instrument of choice in analyzing flavor components?
Feedback: Gas Chromatography (GC)

Q: Generally speaking, some sample preparation is required prior to GC analysis of flavor samples. How did you prepare the sample of wine prior to GC analysis in your lab?
Feedback: Distillation, or distillation of volatile components.

Q: Leaving your wine open to air could result in a change in its volatile component profile.
- True
- False
A: True

Q: For flavor components that are thermally unstable, too low in volatility, or yield poor chromatographic separation due to poor polarity, a derivatization step may be required prior to GC analysis.
- True
- False
A: True