1. Measuring and Manipulating the pH Level of Egg Yolks Lab Protocol: pH Testing Food Safety Scientist Curriculum © 2014 Board of Regents, South Dakota State University iGrow.org This project was supported by the USDA NIFA grant number 2011-38411-30625

2. iGrow.org Equipment 1 Dozen Hard Boiled Eggs 7-Sampling Cups Water Quick Test pH Strips Mixing Bowl Whisk Measuring Cups Writing Utensil © 2014 Board of Regents, South Dakota State University iGrow.org

3. iGrow.org Preparing Samples 1. Remove the egg yolks from the hard boiled eggs and break down using a mortar & pestle or a whisk. 2. Add 1 cup of water to yolks and whisk together until a slurry is formed. © 2014 Board of Regents, South Dakota State University iGrow.org

4. iGrow.org Procedure Prepare the samples as shown above and label each one © 2014 Board of Regents, South Dakota State University iGrow.org SampleEgg Yolk Slurry (mL) Vinegar (mL)Water (mL) Standard25-------------------- # 125--------------------5 # 225--------------------10 # 325--------------------15 # 4255 # 52510 # 62515 2 1 45 6 3

5. iGrow.org Conversions If beakers or funnels are unavailable, household items such as measuring spoons can be used. The following conversions include: © 2014 Board of Regents, South Dakota State University iGrow.org Metric UnitsConversion to Tablespoons/ Teaspoons 5 mL1 tsp. 10 mL2 tsp. 15 mL1 TBS. 25 mL2 tsp. + 1 TBS.

6. iGrow.org Using pH Test Strips 1. Cut 7-pH test strips 8 cm long for each sample including the standard 2. Dip each strip in the sample and remove immediately 3. Compare the color of the strip to the standard included with the strip dispenser. © 2014 Board of Regents, South Dakota State University iGrow.org

7. iGrow.org pH Meter (field unit) Using a pH meter is also an effective instrument for testing the pH of foods It is important to calibrate the meter before use to ensure accuracy © 2014 Board of Regents, South Dakota State University iGrow.org

8. iGrow.org Microorganisms: survival and growth Similar to humans, microorganisms need nourishment and ideal conditions to grow Intrinsic Factors: Inherent parts of plant & animal tissue Extrinsic Factors: Properties of storage environment that affect both the foods and the environment © 2014 Board of Regents, South Dakota State University iGrow.org INTRINSIC FACTORSEXTRINSIC FACTORS pH Moisture (aW) Oxidation-Reduction Potential Nutrients Antimicrobial Constituents Biological Structures Temperature of storage Presence/Concentration of Gasses Presence & Activities of other microorganisms Relative Humidity of environment

9. iGrow.org Discussion Questions 1. What solutions, other than vinegar, would increase the acidity? 2. Why is it important to have a higher level of acidity when preserving food? 3. What controls the growth of microorganisms other than changing the pH? 4. The pH range has an inverse relationship to acidity, what does this mean? 5. Do you think there would be a significant change in taste after adding the vinegar? Why or Why not? 6. If a company is developing a salsa that would be shelf stable in a jar, what pH range does it need to be in and why? © 2014 Board of Regents, South Dakota State University iGrow.org