Rheological Properties in Food Science

What is viscosity?

• The elasticity of a food product

• The resistance of a fluid to flow

• The temperature at which food boils

• The ability of food to conduct heat

Which of the following is a Newtonian fluid?

• Ketchup

• Mayonnaise

• Water

• Yogurt

Why are rheological properties important in food product design?

• To enhance food color

• To improve shelf life only

• To determine texture, stability, and processing behavior

• To reduce the need for refrigeration

A sauce that becomes thinner when stirred is an example of what kind of flow behavior?

• Dilatant

• Newtonian

• Pseudoplastic

• Elastic

Which instrument would be most appropriate to measure the viscosity of a thick yogurt?

• Thermometer

• Brookfield Viscometer

• pH meter

• Hygrometer

A food engineer needs to design a pumping system for chocolate. Which property must be considered primarily?

• Color

• Water activity

• Flow behavior and viscosity

• Nutrient content

What flow behavior does a Bingham plastic food exhibit?

• Flows freely at all shear rates

• Requires a minimum yield stress to start flowing

• Thickens as shear rate increases

• Behaves like a gas under pressure

If large particles settle in a fluid food over time, what does this suggest about its viscosity?

• High viscosity

• No effect on viscosity

• Low viscosity

• Elastic behavior

What could be the reason for two batches of sauce showing different mouthfeel despite having the same ingredients?

• Different fat content

• Variation in viscosity due to process differences

• Addition of preservatives

• Differences in packaging

Which method is best suited to distinguish between pseudoplastic and dilatant behavior in sauces?

• Taste test

• pH measurement

• Shear stress vs. shear rate analysis

• Moisture content determination