Experiment 8C: Interfering with Crystal Formation
Time: Day 1: 50–55 minutes; Day 2: 10–15 minutes
Objectives
While completing this experiment, students will
• identify fat globules, sugar crystals, and cocoa particles under a microscope.
• observe the effect of fat levels on sugar crystal formation in fudge.
Equipment
Each lab group will need
1½ quart saucepan
100-mL graduated cylinder
metric measures
large metal or wooden spoon
candy thermometer
electric mixer
loaf pan
microscope slide
microscope
Supplies
Each lab group will need…
butter
75 mL liquid for the assigned variation
28 g (1 square) chocolate
250 mL (1 cup) sugar
2 mL vanilla
1 drop glycerin
Variation list:
Variation 1: water
Variation 2: fat-free milk
Variation 3: low-fat milk
Variation 4: whole milk
Variation 5: half-and-half
Variation 6: whipping cream
Procedure
Day 1
1. Butter the sides of a 1 ½ quart saucepan.
2. Measure 75mL of the liquid for the variation your group is assigned from the variation list. Combine the liquid,
chocolate, and sugar in the saucepan.
3. Place a candy thermometer in the pan so the bulb does not touch the bottoms or sides. Cook over medium heat
until the mixture comes to a boil. Stir only as need to prevent sticking. The mixture should boil gently over the
surface. Continue cooking to 112C or the soft ball stage.
4. Immediately remove from heat, leaving the candy thermometer in the pan.
5. Cool without stirring until the mixture reaches 48C. Add the vanilla.
6. Beat vigorously with an electric mixer until the fudge becomes thick and just loses its gloss.
7. Immediately spread the fudge in a buttered loaf pan.
Day 2
1. Place a pinch of fudge on a microscope slide and add a drop of glycerin. Examine the sugar crystals
under a microscope.
2. Note the differences in crystal size and shape.
3. Note any other substances that are visible underneath the microscope.
4. Taste a piece of each fudge variation and note the flavor, color, and texture.
Questions
1. What relationship did you observe, if any, between the flavour of the fudge and the liquid used?
2. Was there a relationship between the color of the fudge and the liquid used?
3. Which, if any, variations have a texture other than the creamy texture typical of good fudge?
4. Which fudge had the largest sugar crystals? Which had the smallest sugar crystal?
5.Which variation made the best quality of fudge?