Lecture 11 - Food Engineering Flashcards
What is Mass/Material balance?
The same amount of materials that comes into a processing in the form of raw ingredients must either leave the facility in the form of a final product, waste, or be accumulated in the warehouse as inventory for future use.
What is energy balance?
Similar concept to the conservation of energy; energy used in the production of the food from the raw materials must be equal to the energy of the final product
What are some examples of mass transfer?
- Diffusion
- Evaporation
- Migration
What are some examples of heat transfer processes?
- Cooling
- Freezing
- Sterilisation
- Pasteurisation
- Drying
What are the 3 modes of heat transfer?
-Conduction
The heat transfers occurs within a solid object from one body to another in direct contact (e.g. heating a pan)
-Convection (The heat transfer due to mass movement of molecules within gas or liquids.
E.g. A gas oven/cooking in boiling water)
-Radiation (The emission of energy in the form of electromagnetic waves or particles through space or a material medium
E.g. Toasting of bread/ Microwave oven
)
What is rheology?
Rheology is the study of the flow behaviour of fluids.
The flow behaviour of fluid affects heat and mass transfer dramatically.
Why is the study of rheology important?
- Provide information about a food’s structure
- Aid in the design of food processing equipment
- Rheology is correlated to sensory data
- Aids in design: improve the shape and material of the packaging or processing equipment.
What is viscosity?
resistance to flow of fluid
What is the relationship between viscosity and flavour perception?
Higher the viscosity, the lower its ability to flow -> hinders the flavour compounds in the food to diffuse from the food onto the taste buds on the tongue -> lower flavour perception
What is hard water and how is water hardness classified?
Hard water has much higher levels of minerals than soft water
Water hardness is classified based on the amounts of removable calcium carbonate salt it contains per gallon (unit is grams per gallon)
Soft: 1-3.5 gpg
Moderate: 3.6-7.0 gpg
Hard: 7.1-10.5 gpg
Very hard: ≥ 10.6 gpg
How can the hardness of water be altered?
By using an ion-exchange system
separate ionic contaminants from solution through a physical-chemical process where undesirable ions are replaced by other ions of the same electrical charge.
What are the negative impacts of water hardness on food processing?
Affects pH
Deposit minerals in heat exchangers, resulting in dramatic decreases in heat transfer (less efficient heating process -> increase COP -> reduce profits
