Non-newtonian fluids

Definition

Non-newtonian fluids are substances whose viscosity changes under stress or strain, meaning they do not have a constant flow behavior like newtonian fluids. This unique property is significant in various applications, especially in food science, where the texture and stability of products can be influenced by their flow characteristics. Understanding how these fluids behave can help in the development and processing of various food products, ensuring desired quality attributes.

5 Must Know Facts For Your Next Test

1. Non-newtonian fluids can exhibit behaviors such as shear-thinning (viscosity decreases with stress) or shear-thickening (viscosity increases with stress).
2. Common examples of non-newtonian fluids in food science include ketchup, yogurt, and mayonnaise, where their flow properties are crucial for usability.
3. The behavior of non-newtonian fluids can be influenced by factors such as temperature, concentration, and the rate at which stress is applied.
4. Understanding non-newtonian fluid dynamics is essential for optimizing food processing methods like mixing, pumping, and extrusion.
5. These fluids play a significant role in determining the mouthfeel and texture of food products, impacting consumer acceptance and satisfaction.

Review Questions

• How does the viscosity of non-newtonian fluids change under different stress conditions, and why is this important for food processing?
  • The viscosity of non-newtonian fluids can either decrease or increase under applied stress depending on their specific type. This behavior is crucial in food processing as it affects how these products are mixed, pumped, and applied in various forms. For instance, when making sauces or dressings, understanding how these fluids behave allows manufacturers to create products that pour easily or maintain their desired texture during storage and application.
• Discuss the significance of shear stress in the context of non-newtonian fluids and how it impacts their behavior in food applications.
  • Shear stress plays a critical role in determining how non-newtonian fluids behave. When shear stress is applied to these fluids, their viscosity can change dramatically, influencing how they flow or maintain stability. In food applications, such as during mixing or heating processes, understanding shear stress helps optimize product consistency and quality, ensuring that the final product meets consumer expectations regarding texture and usability.
• Evaluate the implications of thixotropic behavior in non-newtonian fluids for the development of food products with desirable textural attributes.
  • Thixotropic behavior in non-newtonian fluids allows them to become less viscous over time under constant shear stress, which can be advantageous in creating food products that require specific textural attributes. For example, this property enables sauces to flow easily when stirred but regain thickness when at rest, enhancing both ease of application and consumer experience. Evaluating this behavior helps food scientists design products that not only meet functional requirements but also align with consumer preferences for texture and mouthfeel.

Related terms

Viscosity: A measure of a fluid's resistance to flow, which can change in non-newtonian fluids depending on applied stress.

Shear stress: The force per unit area applied parallel to the surface of a material, affecting how non-newtonian fluids deform or flow.

Thixotropic: A type of non-newtonian fluid that becomes less viscous over time when subjected to constant shear stress, allowing it to flow more easily.