CAUTION: Use appropriate safety guidelines in performing demonstrations.
Demonstration 1: "Light" Margarine, Paying More for Less
To demonstrate the amount of water in regular, light, and "extra light" margarines.
- Three kinds of margarine from one manufacturer (i.e., Regular, Light, and Extra Light Fleischmann's margarine)
- 3 Graduated cylinders, 10-mL (glass, heat-resistant)
- 3 Beakers, 100- or 250-mL (glass, heat-resistant)
- 3 Stirring rods
- Hot plate or burner
Prepare ahead of time:
- Melt 10 g of each margarine in separate beakers. Heat gently, stir constantly; do not allow to boil.
- While stirring continuously, pour each sample of melted margarine into a labeled 10-mL graduated cylinder, filling exactly to the 10.0-mL mark. Allow to cool. Keep covered and refrigerated until ready to perform the demonstration.
- Photocopy (or type) the nutritional labels from each kind of margarine and make overhead projections (OHPs) and/or copies for the students.
- Show the margarine packages. Show the OHPs and/or hand-outs and point out that the amount of fat is decreasing (just as the ads say), along with the calories, as one compares the different margarines: Regular - Light - Extra Light.
- What is the first ingredient listed in each label? [In Regular and Light, it is "liquid corn oil," but in Extra Light, it is water.]
- Show the students the prepared graduated cylinders, with the layer of water on the bottom of each. A light box or diffused light source behind the tubes will make the layers clearly visible. (One could also make a drawing on the OHP, showing the amount of water in each product.)
- List the percent water found by examining the graduated cylinders:
(NOTE: There is a white layer between the water and the oil layers; this is probably the whey that is listed in each ingredient list.)
- Regular - 3%
- Light - 20%
- Extra Light - 35%
- Discussion (the discussion of Topics f and g could lead to several student projects):
- Reasons why consumers buy Light and Extra Light.
- How many of the students use these products at home.
- What is the cost/pound for each type? (Recent purchase of Fleischmann's Regular = $1.29; Light = $1.39; Extra Light = $1.79)
- Why do Light and Extra Light cost more, even though they contain less fat and more water?
- What is the cost/pound of the actual fat in each margarine?
- What two types of fats are listed on the label? Why do they not add up to the total amount of fat in the margarine? What other kind of fat is present?
- Saturated vs. unsaturated fat controversy: What is the effect of dietary saturated fat on blood cholesterol levels?
Have the students bring in samples of other margarines, butter, "soft butter," and butter "taste-alikes" to test for water content.