Bio+PT+report

Carrissa Ting Gin Qing (311/26) Biology Performance Task: Report

Aim:To test if the kitchen myth “red (purple) lettuce juice when added to egg white causes it to turn green instead of purplish-red” is true.

Prediction:The egg white will indeed turn green which confirms the myth.

Assumptions:The effects of the red lettuce juice was not affected when the lettuce was microwaved.

Difficulties:As a step was miss while planning the methodology, the experiment had to be repeated to retrieve the red cabbage juice. Thus, the filming had to be repeated as well.

Precautions:Great care was taken in ensuring that that mixture was purely made out of egg white and red cabbage juice and did not contain egg yolk as the result would be affected.

Apparatus needed: -1 egg -1 red cabbage -2 small bowls and 1 larger bowl -paper towel

Methodology: -Coarsely chop about half a cup of red cabbage. -Fill up the cup with water till it reaches the same level as the cabbage. -Microwave the cabbage for 4 minutes till it is soft. -Take the cabbage out and allow it to cool. Setting it in the refrigerator speeds up the cooling process. -While waiting, crack an egg and separate the egg white and egg yolk. Put them in separate bowls. -Place a paper towel over a bowl and pour the cabbage in. Then, squeeze out the juice. -Add a small amount of red cabbage juice to the egg white and mix well. -Observe if the egg white turns uniformly green.

Result:Even though the juice added to the egg white was purplish red, the mixture turned green in color.

Analysis of result:The water added to the cabbage turned purplish-red after being microwaved as it is mixed with the colored pigments from the red cabbage. The mixture of egg white and the red cabbage juice turns green as the red cabbage juice acts as a PH indicator instead of a purplish-red dye. The red cabbage contains pigments which are called anthocyanins (commonly found in red/purplish fruits and vegetables). Anthocyanin changes color in response to changes in acidity or pH level. Red cabbage juice is purplish-red under acidic conditions but changes to a blue-green color under alkaline conditions. Egg whites are alkaline (the PH value of an egg white is 9) and thus, when the red cabbage juice is added into the bowl of egg white, the change in color to the pigment causes the mixture to turn blue-green. However, the water did not affect the juice and cause color change to the pigments as the PH value of water is neutral (7).

Final Conclusion:The kitchen myth that red (purple) lettuce juice when added to egg white causes it to turn green instead of purplish-red is confirmed. The color change that occurred was due to the anthocyanin pigments present in the red cabbage.

Table:

Table of color change of anthocyanin to PH value PH 2 4 6 8 10 12 Color Red Purple Violet Blue Blue-Green Greenish Yellow

References:

Use Red Cabbage Juice to Make an Egg White Turn GreenBy Anne Marie Helmenstine, Ph.D., About.com GuideAccessed on 17 July 2010Retrieved from:http://chemistry.about.com/od/chemistryhowtoguide/a/friedgreenegg.htm

Red Cabbage pH IndicatorHow to Make Red Cabbage pH IndicatorBy Anne Marie Helmenstine, Ph.D., About.com GuideAccessed on 17 July 2010Retrieved from:http://chemistry.about.com/od/acidsbase1/a/red-cabbage-ph-indicator.htm