Quantitative Tests Show Sugar, Enzyme, and Photosynthetic Variants in Organic Vs. Commercial Carrots, Apples and Baby Food

Laura Elgood, James Kelly, and Kristen MacKool

LBS 145: Cell and Molecular Biology

Monday 7-10 pm

Rick Chalmers

Amy Estry

February 24, 2003

Abstract

Throughout this experiment, our goal was to determine any differences in the sugar compositions, enzymes, and photosynthetic pigments present in organically and conventionally grown foods. In order to establish these differences, we ran coordinating tests on organic and commercially grown carrots, apples, and baby food. There were five tests preformed to identify various sugars in each food type. The tests we used were Bials, Barfoeds, Selivanoffs and Benedicts Test. We also used the iodine test to test for starch. To identify the amount of polyphenoloxidase (PPO) enzyme present in apples, we found how active the PPO enzyme was by finding the amount of light absorption over time. Paper Chromatography was used to find the different pigments in the commercial and organic baby foods. Also, the differing absorbency levels that were present in the carrots and apples were measured at different wavelengths to test for the photosynthetic process. After completing all three areas of this experiment, we believe that there are no significant differences between organic and commercial products. In all of the organic foods there was about the same concentrations of PPO as commercial products. In the commercial baby food there was no added pigment that was not present in the organic baby food. Sugars were alike in all of the foods and their absorption spectrums were very similar when looking for pigment differences. When looking at these results, we concluded that no major differences were present in tested areas of our samples.

Figure 8. The PPO concentration in Commercial Apples vs. Organic Apples. PPO, standing for polyphenoloxidase, is the enzyme that turns apples brown. The absorbency reading shows how the colors of the apples change. If the apple solution gets browner the absorbency gets higher. The Organic apples have a slightly higher slope of .0014 due to the fact that it has a higher PPO concentration or PPO is more efficient. The Commercial apples have a slightly lower slope of .0011 due to the fact that it has a lower concentration of PPO or PPO is less efficient. This reading was taken over ten minutes once every minute. We did 3 trials for both the organic and commercial apples and took an average of the data.

Discussion

In this experiment, we tested the differences of organically and commercially produced carrots, apples, and peach baby food. Organic foods of course are those grown and handled in an absence of the modern chemicals and enhancements of technology, and conventionally produced foods involve the interventions of technology for greater production efficiency and yield (Sullivan, 2001). Since organically grown food is considered to be healthier, we hypothesize that it would have different enzyme reaction times, less dyes, unalike photosynthetic pigments, and have a different array of simple sugars like glucose and fructose compared to commercial produce. (Sullivan, 2001)

When doing this experiment, our group collected data that neither supported nor rejected our hypothesis. Although we found some small differences between organic and conventional produce, many of our experiments produced nearly identical results. Other research also found very few differences between organic and commercial foods. There has not been enough time devoted to running controlled studies in order to see if they are profoundly healthier then commercial products. (Williams, 2002)

In order to find the different kinds of carbohydrates present in each food type, we ran a series of different tests. The data in Table 1 is representative of our results. The tests that we ran are as follows: Benedict’s test for reducing sugars, Barfoed’s test for reducing monosaccharides, Selivanoff’s test to distinguish ketoses or aldoses, Bial’s test to determine if a furanose ring is present, and Iodine test for the presence of starch. (Maleszewski, 2003)

From the results of Benedict’s test, we could assume that all of our solutions contained a reducing sugar. Barfoed’s test allowed us to further presume that all solutions contained a monosaccharide reducing sugar. This does not mean that no di- or poly- saccarides exist it just means that mono-saccarides are in the solution. The results of the Selivanoff’s test suggested that there are carbohydrates present in our solutions that are ketoses. This again does not mean that aldoses are not present. Bial’s test allowed us to deduce that a hexose furanose ring was present in the commercial and organic apples and commercial and organic baby foods, but that a pentose furanose ring was present in both types of carrots. Lastly, the Iodine test results indicated that our apples had no starch present; the carrots did have starch present, and returned an unsatisfactory product on both types of baby food. Both baby food solutions turned a greenish brown, which leads us to believe that there is probably some starch present. These results neither confirm nor discredit our hypothesis. We feel that from all of these tests, while we cannot say that we found the organic foods to have higher concentrations of carbohydrates, we were able to determine which ones were present in each solution.

In Figure 6, we graphed the wavelength of light versus the corresponding absorbance levels. This graph shows that both the apple and the carrot are absorbing light at greater values towards the low end, or “blue end” of the visible spectrum. Such results for the apples were expected because of the red skin, which should reflect red light and absorb the other colors of light. The closer the wavelengths get to red, the lower absorbency got. We hypothesized that this is because the color of the specific wavelength is becoming more similar to that of red light Also these results were expected for the carrots since they are colored orange, and thus should reflect the orange wavelength of the spectrum, which is close to red, and absorb the rest. There was no pattern identified between the organic and commercial apples and carrots by using the absorbance spectrum. There is a point in our graph that is an outlier to the rest of the data in the organic apples (Figure 6). We believe this is caused by a finger smudge or improper placing of the cuvette. (Maleszewski, 2003)

We preformed paper chromatography in order to test for extra dyes added into the baby food. The commercial peach baby food looked a much more orange color but when paper chromatography was performed we did not see any extra dyes because both of the peach baby foods only showed one pigment each (Figure 7). Both of the Rf values were one. We hypothesized that the pigment is carotene based on the color and Rf value similarities.

In Figure 8, the absorbency of light versus time was graphed. In this experiment, we were testing for the concentrations of the specific enzyme polyphenoloxidase, PPO, within our specimens. We first tested the pH of both of the apples. The organic apples and commercial apples both had a pH of 5. Since they were the same value, the pH of apples should not factor into the PPO reactions we preformed. The absorbance of the solution rises due to the fact that PPO reacted with the clear substrate catechol and turned it into the brown product OBenzoquinone. The slope, .0014, of the organic apple solution was slightly higher, telling us that the PPO reaction rate in organic apples was slightly faster. The commercial apple solution had a lower slope of .0011 showing that the commercial reaction rate is slightly slower. We believe this is because the organic apples either have more PPO per volume or that the PPO in the organic solution is for some unknown reason more efficient at catalyzing the reaction. When calculating the Michaelis-Menten constant we only used one concentration for both of the samples tested. When we applied the formula to our numbers the constant was the same for both solutions. During our presence of PPO test, we could see PPO working more efficiently in our organic solutions, which quickly turned brown when in contact with the catechol. (Maleszewski, 2003)

The data we collected does not support our hypothesis fully. Due to this do not believe there is a significant difference between organic and commercial produce composition in terms of sugars, photosynthetic pigments, and enzymes. But it may still be healthier to eat organic food due to the lack in pesticides and artificial fertilizer free. (Sams, 2000) There was a small difference of 24% in the amount or efficiency of PPO but it was not substantial enough for us to call this a big enough percent difference. We believe there might still be more difference between commercial and organic products but do to restrictions in the lab we could not perform in depth experiments.