Lesson Food Packaging

Learning Objectives

After this activity, students should be able to:

• Identify four functions of a food package.
• Explain how each food package design works.
• Identify the chemical and physical changes different types of materials prevent or facilitate.
• Explain what a food packaging engineer does.

Educational Standards

Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.

All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).

In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

NGSS: Next Generation Science Standards - Science

International Technology and Engineering Educators Association - Technology

State Standards

Worksheets and Attachments

Pre-Req Knowledge

Prior to this activity, students should have a basic understanding of the following:

Physical properties of matter: mass, volume, melting point, boiling point and texture.

Chemical properties of matter: combustibility, solubility, flammability.

Physical changes: phase change, shape change.

Chemical changes: oxidization, evolution of gas.

Introduction/Motivation

(Have handy an assortment of food packaging examples to show students, such as a plastic or glass soda bottle, bag of flour, soup or noodles that can be cooked or heated in their containers, food in a plastic bag, milk carton, cracker or cereal box, chips bag, candy wrapper.)

Did you know that a huge field of engineering exists with the purpose of designing packages for different food products? Today, we are going to look at some packages that engineers have already designed and see why they made them the way they did. Do you ever drink a beverage from a plastic or glass bottle? (Hold up a soda bottle.) Have you ever wondered why a bottle is designed the way it is? What are some of the qualities of this bottle and the reasons why the bottle has those characteristics? (Listen to student ideas and write them on the classroom board.)

Now, lets look at this bag of flour. (Hold up a bag of flour.) What is different about the characteristics of this bag compared to those of a soda bottle? (Main differences: material and structure.) Why do you think that the bag is so different from the bottle?

Now look at these two other packages. (Hold up a package of soup or noodles that can be heated and a food in a plastic bag.) Please write down the qualities of these packages and why you think they have those characteristics.

Considering all these packaging examples and the reasons for each of the packages, let's brainstorm three important functions of food packages, besides contaiig the food.

1. To keep the food clean.
2. To protect the food product from unwanted physical and chemical changes (such as oxidation and destruction from insects) and to facilitate in desired physical changes (such as heating or cooling).
3. To identify the product and provide sales appeal.

Now please write beside each characteristic you wrote down, what function is being fulfilled. As you can see, the materials that make a package plays a huge role in its functioning. If you want to be able to put your food and package in the microwave, would you make the package of metal? Why not? If you want to make sure your food will not be crushed by something heavy, would you put your food in a plastic bag? Would you put a liquid in a package made of paper?

Besides a package's materials, its structural design is very important for its functions. What type of food package structures can you think of?

• cartons (milk carton)
• boxes (cereal box)
• bags (bag of chips/bag of vegetables)
• cans (can of soup)
• bottles (bottle of soda)
• wrappers (candy)

What are the advantages and disadvantages of these package structures?

Let's look at these two different packages for the same food. (Bring out a food packaged aesthetically and the same food packaged less appealingly.) Which one would you rather buy? What qualities does that package have that the other does not? (A symmetrically shaped package, a pretty label, a nicely colored package, etc).

Lesson Background and Concepts for Teachers

Food packages have four main functions besides providing food containers.

1. To keep the food clean.
2. To protect the food product from unwanted physical and chemical changes (such as oxidation and destruction from insects) and to facilitate in desired physical changes (such as heating or cooling).
3. To identify the product and provide sales appeal.
4. To be inexpensive and economical, both in its materials and its transportation.

In this lesson, a focus on the first three functions of food packages provides a great introduction to how package materials are chosen. The first function is pretty simple to fulfill; packaging materials prevent dirt from getting into food. Fresh produce is an exception to this approach since a fruit or vegetable's skin protects its insides from contamination and consumers are expected to clean the produce before eating. Thus, natural fruit and vegetables are basically "self-packaged."

The second function of food packages is probably one of the hardest to understand. A number of physical changes can be considered for this function. The main physical change that can occur is physical damage. Food can be crushed and damaged without the proper protection from its package. Chalenge students to design a packaging of their own following the mentioned functions with the Package Those Foods! activity.

Another physical change that children can relate to is soda going flat. The scientific word for this happening is effervescence, which is the escape of air bubbles from a liquid. This physical change occurs when a carbonated beverage is opened. The carbonation quickly escapes through the opening. Students should consider this physical change in the packaging of beverages. Bottles can be resealed to prevent the further escape of air bubbles while cans cannot.

Also many children are familiar with mixing. By mixing, we mean to disperse one substance throughout another, usually by swirling. A food example is dissolving a lemonade powder in water. This process is not a chemical change because the water and powder do not form a new chemical. The powder is solely dispersed evenly throughout the water to make a mixture of individual water and lemonade molecules.

One example of a major physical change is phase change. Phase changes occur if a food changes state between solid, liquid or gas. An example of a food whose package must consider phase change is ice cream. An ice cream carton is meant to hold an almost solid ice cream. However, the design must also anticipate liquid in case of melting. The design must also be capable of being put in the freezer and also taken out by the consumer. Thus, a good point to make is that a food package designer would not make an ice cream package of metal because it would be too cold to touch and remove from the freezer. Also, designs for packages for foods that are meant to be warmed up in microwaves must take into account the melting point (the temperature at which a material changes from solid to liquid) of the package materials. If a package is to be microwaved, a material with a low melting point would not be a good choice, since the package would melt into the food!

A major chemical change involved in the creation of food packages is organic growth in foods. Organic growth occurs by microorganisms, which feed on foods. As microorganisms feed, the food rots and the microorganisms multiply. It is not eating the rotten food that makes a person sick, but eating the vast number of microorganisms on that food. Microorganism growth can include the growth of bacteria, molds and yeast. Microorganisms grow and affect different foods at different rates.The package in which a food is held affects a food's rate of organic change.

Such organic change affects how long a food can be stored before and after its opening. Plastics and cans do not allow moisture to seep into the food product that they hold. Thus, they keep microorganisms from outside away from the food. Vacuum sealing removes all of the oxygen from a food. Without oxygen, microorganisms cannot grow and so the food does not rot. If a food's microorganisms are removed through processing, these packages prevent most organism growth in the food and enable its shelf life to be long. These non-perishable foods can last for two years or longer.

After opening a food package, however, microorganisms in the air can quickly get into the package to start an organic degradation of the food. This event is why food packages say, "refrigerate after opening." Microorganisms can only grow in certain temperatures so refrigeration slows rotting and freezing usually stops degradation altogether. In spite of this, naturally non-perishable foods whose majority is not fruit, vegetable, nut oil or dairy are okay if not refrigerated for a reasonable amount of time since their rate of organic change is very slow.

Many different processes exist to make a food non-perishable, as discussed earlier. A common process is thermal processing, in which foods are treated with heat to destroy all microorganisms. Thermal processing takes less energy for plastic-packaged foods than-metal packaged foods. Thus, taste is preserved more in plastic-packaged food than canned food. This is a major advantage to use plastic in packaging rather than metal.

Since paper packages permit the entrance of oxygen and moisture, they usually hold foods whose rate of organic change is very slow or foods whose consumption is assumed to happen within days of production.

Despite the physical and chemical changes that some materials may prevent or encourage, all materials have advantages and disadvantages, which are listed in the Food Packaging Materials Worksheet.

Associated Activities

• Package Those Foods! - Students create their own food packages, meeting the requirements of the three main functions of food packages.

  Watch this activity on YouTube

Vocabulary/Definitions

boiling point: The temperature at which a substance changes from liquid to gas.

melting point: The temperature at which a substance changes from solid to liquid.

phase change: A transition between liquid and gas or liquid and solid.

solubility: The ability of a substance, the solute, to dissolve in a solvent.

Assessment

Food Analysis: Ask students to analyze the physical properties of foods and identify the chemical and physical changes that they need to pay attention to in the creation of their food packages. Have them describe how they would address each of the functions of a food package.

References

Copyright

Contributors

Supporting Program

Acknowledgements

This content was developed by the MUSIC (Math Understanding through Science Integrated with Curriculum) Program in the Pratt School of Engineering at Duke University under National Science Foundation GK-12 grant no. DGE 0338262. However, these contents do not necessarily represent the policies of the NSF, and you should not assume endorsement by the federal government.