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Physical properties of foods are very crucial in product development, process design, shelf life and quality. Knowledge of physical properties is important in handling, preparing, processing, preserving, packaging, storing and distribution of foods. Let's find some examples to demonstrate the application.

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Watch the following videos. In your wiki page, explain the principles of fruit sorting equipment. What are the physical properties being utilized in the sorting operation?

Fruit sorters (You Tube)

Frumac Grading and packing equipment for apples


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Chocolate? Bubble gum? Hmm...yummy! Watch this video showing the steps in producing the mouth watering chocolate and bubble gum. Observe very carefully and discuss the importance of physical properties in the processing of the products. What are the unit operations involved? Why is it important to understand the rhelogical properties and flow behavior of the material during the processing?

How is chocolate made (You Tube)

Bubble Gum - How is made


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Watch the following video clip on liquid filling line. It shows a liquid (food) being dispensed into a bottle/cup. Discuss the importance of getting the "right" rheological properties of the liquid to ensure the process does not end up very messy.

Filling machine for honey
2 head gravity filler (You Tube)
Rotary cup filling machine


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This video (High Speed Centrifugal Spray Drier) demonstrates the principles of spray drying process -- an important food processing operation to produce food powders (e.g., milk power). Before spray drying, the viscosity of liquid food has to adjusted in order to get optimum conditions during the atomization of the liquid into small, fine droplets. Discuss why this step is important.

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Most foods are complex dispersion systems. Two special types of dispersion systems that are commonly found in food are emulsions and foams. These systems play important roles in a number of food products. They are similar in that they both involve a surface active agent in their formation and stabilization. An emulsion has been defined as a dispersed system consisting of a liquid dispersed in another liquid (e.g., oil dispersed in water). Foams are agglomeration of gas bubbles that are separated from each other by thin liquid films. They are gas in liquid dispersions.

In this article "To Foam or not to Foam", the author described in detail the nature of foam, formation and stabilization mechanisms in various foods, ranging from carbonated beverages to dairy products. Read it carefully, make a note and try to answer some questions based on the article.