Yogurt Lab Directions

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• Aprons and Safety Goggles

• ring stand

• wire gauze pad

• Tirell burner

• 1000 ml glass beaker

• match cup w/H2O

• Universal clamp

• -10 to 110 Celsius thermometer

• #4 single hole stopper

• plastic tablespoon

• beaker tongs

• Yogurt, plain, active

• Cool down bucket and cold water

• Nonfat Dry Milk (share)

•Four 12 oz Solo cups and lids

• Milk (4% etc....)

• clock

• Sharpie

• matches in box

• clean roofing nails

• plastic spoons for testing


1. Get Data Table 1 ready. Appoint Timekeeper, Recorder, Observer, and Operator and discuss the safety issues everyone should be aware of. (hot, boiling, speed, carelessness…)

2. Obtain/Inventory all materials listed above.

3. Mark 4 Solo cups and lids (1 Control and 3 Exp trial cups) with the following information:, Control or Experimental, Date, Period#/ Lab Sta #, and Type Milk. (ie. Control, 4/24/04 Period 5/Sta 2, 2% milk)

4. Carefully wash 1000ml beaker and tablespoon in hot water. Glass beakers are $$. Therm in warm water.

5. Put safety goggles and aprons on. Check the set up of ring stand and gauze pad if needed. (If needed, Light and adjust Tirell Burner so tip of inner cone of Tirell Burner touches bottom of gauze pad, then shut off Tirell burner.)

6. Pour 900 ml milk and 2 rounded tablespoons of Nonfat Dry Milk into 1000ml beaker and carefully stir until mixed. Place securely on ring stand.

7. Slide thermometer down into beaker and off to the side a bit - Note: Observer reads to 0.1ūC - eye level for accurate readings!

8. Light off Tirell Burner. AT FIRST "Mark" from Timekeeper slide Tirell Burner under ring stand. READ & RECORD TEMP EVERY 00:30 sec FROM NOW ON!

9. Stir carefully, constantly, and deeply throughout. Avoid banging thermometer.

10. AT 80ūC shut off Tirell burner and call instructor. He will place beaker in water bath. Keep stirring and reading and recording temperatures. Change water bath every 5ūC once temperature reaches 70ūC.

11. When temperature reaches 40ūC stop taking readings/stirring and take the beaker out of water bath.

12. Pour Control sample 1/2 full. (DON"T add yogurt to it!)

13. Put 3/4 tablespoon plain active yogurt into 1000ml beaker. Stir the mixture carefully until smooth.

14. Pour starter mix from 1000 ml beaker equally into remaining 3 cups. Stir smooth.

15. Pour equal amounts of milk/yougurt mix from the 1000 ml glass beaker into the 3 labeled Solo cups.

16. Carefully put on marked lids and place all samples into your classes' incubator.

17. Carefully clean all glassware and other equipment in hot water. Place all equipment back where you got it from. Be sure to clean sink, wash clothes, sponges, & throw away all paper towels etc!!!!

18. CQC Data Table 1 / Graph 1 or Figure 1. Prepare for testing tomorrow!



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