Similarities of Macromolecules and Pigments and Differences of Potassium Content in Organically and Commercially Grown Apples |
Abstract |
| The question that was investigated was whether or not there was any difference in the chemical composition of organic apples versus commercially grown apples, specifically in regards to the types of sugars and pigments present, the amount of proteins and whether or not potassium is present or absent in each apple. Commercially grown fruits and vegetables have been exposed to fertilizer and/or pesticides whereas organically grown fruits and vegetables were not, as such it might have been possible for the chemicals in the fertilizers and pesticides to have affected the commercially grown apples. Several methods were used to test for chemical differences. The overall hypothesis is that there is a difference in the composition between organically grown and commercially grown apples. First, a series of sugar tests were performed, specifically Barfoed's Test for monsaccharides or polysaccharides, Selivanoff's Test for ketoses or aldoses, and the Iodine test for the presence or absence of coiled polysaccharides. The results of these tests showed no differences in the sugars present in organic and commercially grown apples. Secondly, Thin Layer Chromatography was used to test for differences in pigments in the peels of the apples. The pigments present were chlorophyll a, chlorophyll b and xanthrophyll and there was a difference between the organic and commercial golden apple. Finally, a Bradford Assay for determining how much protein is present in each apple and a Flame Test for detecting Potassium was performed. It is predicted that the Bradford Assay will show that there is very little to almost no protein in any of the apples and that the flame test will show Potassium present in the organically grown apples but not the commercially grown apples. |
Discussion |
| Commercially grown apples are grown using the aid of pesticides, bactericides, and fertilizers in order to keep insects off the plants, while organically grown apples are steered away from such harmful additives. The question being asked is whether these pesticides and other additives break down the chemical composition of apples. The standing prediction is that these pesticides would have an affect on the sugars, pigments, protein content, and potassium present in apples. A breakdown of polysaccharides in organic apples to monosaccharides in commercially grown, less pigments in commercially grown apples due to a breakdown of chlorophyll, no protein in either, and for organically grown apples to have a greater presence of potassium was predicted. Two different color apples, Golden Delicious and Braeburn red, were tested to ensure that the difference between the apples was truly due to organic versus commercial as opposed to color. The first test performed was Barfoed's test to determine whether the apples contained monosaccharides, or disaccharides and polysaccharides. This test revealed that all the apples contained monosaccharides. The second test performed was Selivanoff's test. This test determined that all the apples contained ketoses, and not aldoses. The third and final test performed was Iodine test. Results showed that all the apples tested negative for starch and uncoiled polysaccharides. A photosynthesis lab was performed using the method of thin-layer chromatography (TLC) of apple skin pigments to determine if different pigments exist in organic versus commercially grown apples. Results showed organic Golden Delicious contained chlorophyll a, chlorophyll b, and xanthophylls while the other three apples, commercial Golden Delicious, commercial Braeburn red, and organic Braeburn red consisted of only xanthophylls and chlorophyll b. To test for protein content, a Bradford Assay was performed. It was found that no protein was present in any of the four types of apples. The final test of this project was a Flame test specifically designed for potassium. By using Oceanoptics equipment, potassium was found in organic Golden Delicious as well as organic Braeburn red apples, but not in commercially grown types of either. Commercially grown apples are grown in the presence of pesticides and bactericides that may be harmful to humans (Epstein, 2003). Based upon the evidence found, the hypothesis that fertilizers, pesticides, and bactericides breakdown the chemical composition of apples is partially supported. It is supported with the results of the Bradford Assay and the potassium test, as well as partially supported by the pigment test. It is rejected however with the results of the carbohydrate testing and partially by the pigment test. |
Figures |
Fifty microliters of apple extract, from four different apples were added to three milliliters of Barfoed's solution and placed in boiling water for two minutes. |
