Colloidal dispersions, emulsions and mayonnaise

1. What is a colloid?

• a) A mixture with two immiscible liquids dispersed throughout each other.
• b) A mixture where one substance is evenly dispersed throughout another.
• c) A pure substance made up of only one element.
• d) A mixture with two immiscible solids dissolved in each other.

What type of colloid is mayonnaise?

• a) Oil-in-water emulsion
• b) Water-in-oil emulsion
• c) Solid sol
• d) Gas sol

What is the role of the egg yolk in the mayonnaise preparation?

• To act as a thickening agent.
• b) To provide flavor.
• c) To emulsify the oil and water.
• d) All of the above.

Why is it important to use fresh ingredients, especially the eggs, when making mayonnaise?

• a) To ensure the mayonnaise will taste good.
• b) To prevent the growth of harmful bacteria.
• c) To achieve the desired texture and consistency.
• d) All of the above.

5. What makes mayonnaise a colloidal dispersion?

• a) The small oil droplets are dispersed throughout the water-based continuous phase.
• b) The mixture has a cloudy appearance due to the scattering of light.
• c) The components do not settle out over time due to Brownian motion.
• d) All of the above.

6. How can mayonnaise be considered both a colloidal dispersion and a permanent emulsion?

• a) It is a temporary mixture that will eventually separate into its components.
• b) The oil droplets are stabilized by the emulsifier, preventing them from coalescing.
• c) It is a mixture of two immiscible liquids that have been forced together.
• d) It is a mixture of two miscible liquids that have been mixed together.

7. What factors contribute to the stability of a permanent emulsion like mayonnaise?

• a) The size and distribution of the dispersed phase particles.
• b) The presence of an emulsifying agent like the phospholipids in egg yolk.
• c) The viscosity of the continuous phase.
• d) All of the above.

8. Explain how the properties of a colloidal dispersion like mayonnaise differ from those of a true solution

• a) Colloidal dispersions are cloudy due to light scattering, while true solutions are clear.
• b) Colloidal particles are larger than individual molecules and can be separated by filtration, while true solutions cannot.
• c) Colloidal dispersions are not affected by the presence of electrolytes, while true solutions are.
• d) True solutions are always homogeneous, while colloidal dispersions can be heterogeneous.

9. What is the safe storage temperature for homemade mayonnaise?

• a) Room temperature (around 70°F)
• b) Refrigerator temperature (around 40°F)
• c) Freezer temperature (around 0°F)
• d) Any temperature is safe.

10. What is the main reason why raw eggs are a food safety concern in mayonnaise?

• a) They can contain salmonella bacteria.
• b) They can cause allergies in some people.
• c) They are not a good source of protein.
• d) They can be difficult to digest.