Sugar, Protein, and Vitamin C Tests Reveal

Organic Capsicum annum is More Nutritious than Genetically Modified

By: Chelsea Hannert, Ilsa Ittner, Laura Most, Jami Pawlowski



The practice of genetically modifying (GM) foods has created much controversy as to whether its health benefits surpass that of organically grown foods.  To research this we used Capsicum annuum, the bell pepper, which changes color and Vitamin C content during maturation. We tested the difference in carbohydrates, proteins, pigments, and Vitamin C between GM red and green peppers to that of organic green and red peppers.

            Four different sugar tests were used in comparing the peppers to determine the kind of sugar present as well as its structure: Benedict’s test, Barfoed’s test, Selivanoff’s test and Bial’s test.  We performed the Protein (Bradford) assay to compare the protein content, the iodine test to determine the presence of starch, and paper chromatography to test the differences in pigments between red and green peppers.  Finally, we tested the Vitamin C content.

            We found that both GM peppers and organic peppers contained monosaccharide ketoses.  GM peppers showed higher concentrations of sugars when the precipitates were massed, by weighing them. Fructose (hexo-furanose) was present in both red peppers, and glucose (pyranose) was present in both green peppers. Neither the organic or GM peppers tested positive for starch.  There was a higher content of protein in the organic peppers.  The organic and GM red peppers contained only one pigment, carotene, while the organic and GM green peppers contained two pigments: xanthophyll, chlorophyll b.  Lastly the red organic pepper was determined to have the most Vitamin C content followed by the organic green pepper, the GM red pepper, and lastly the GM green pepper.


Our laboratory investigation was designed to identify any differences between genetically modified (GM) green and red peppers, to that of organically grown green and red peppers (C. annuum). The question we strived to answer throughout our experiment was whether or not organically grown peppers are nutritionally healthier than GM peppers. Nutritionally healthier meaning that the food provides nourishment to the body’s processes through growth and replacement of tissue cells (Lexico, 2005). We hypothesized that overall the organic peppers are more nutritional than the GM peppers. We predicted that the organic peppers contained more Vitamin C in them than the GM peppers, and that the GM peppers contained a higher concentration of sugars. We also predicted that the organic red peppers contained more Vitamin C than the organic green peppers.  This prediction was based on the nutritional evidence that red peppers contain nearly twice the amount of Vitamin C as green peppers (Anonymous-6, 2000).

In lab one, we conducted four sugar tests, the starch test, and the protein test. For the Benedict’s test all solutions created a red precipitate and tested positive for reducing sugars. These results supported our initial predictions that we made based on the knowledge that bell peppers contain glucose and fructose and would therefore test positive (Tarrach, 1986). The precipitates from each of the pepper samples were filtered, dried, and weighed.   The values were then averaged as follows: Organic red peppers with 0.0023g, GM red with 0.007g, Organic green with 0.0037g, and GM green with 0.005g.  This data allowed us to determine that GM peppers, both red and green, contain more sugar than the organic versions, since the average mass of the precipitate was higher in both cases.  This supports our initial prediction which was based on the knowledge that genetically modified vegetables have sugars added to enhance the flavor (Wikipedia, 2001). 

In the Barfoed’s test we found positive results for all pepper solutions; a red precipitate formed in each of the samples, signifying the presence of monosaccharides.  These results verified our initial predictions, which again were made based on the knowledge that glucose and fructose are present sugars in peppers, both of which are monosaccharides. We also made the initial prediction that the GM peppers would produce a greater mass of precipitate and therefore contain more sugars, similar to Benedicts.  This prediction was again supported by our results; we found that the average precipitate mass for organic red peppers was 0.031g, GM red with 0.0523g, Organic green with 0.0287g, and GM green with 0.055g.

 In Selivanoff’s test we initially predicted that the genetically modified peppers would turn red in less than one minute, signifying monosaccharide ketose.  We made this prediction based on previous research (Bonilla et al, 2002). We also assumed that the organic peppers would show the same results, because genetic modification does not change the sugars present, but rather the concentrations of the sugars present (Wikipedia, 2001).  All of these predictions were supported with the results of our experiment, which found that all pepper samples changed to a reddish color in less than a minute’s time.  This signified that all four pepper types contained monosaccharide ketose. 

During the last sugar test, Bial’s test, the GM and organic red pepper solutions turned a brownish color when the reagent was added, while the GM and organic green pepper solutions showed no color change.   We initially had two separate predictions as to what would happen, because research shows that equal quantities of glucose and fructose exist in the peppers (Tarrach, 1986).  Fructose, a hexo-furanose would turn the solution brown and glucose, a pyranose, results in no color change.  Our results showed that while there may be the same amount of these sugars overall, the immature green pepper showed more fructose present, while the mature red pepper had higher amounts of glucose.  Although these results were determined from our experiment, an error did occur in the process.  When using xylose as a positive test for pentose-furanose, the solution was expected to turn an olive color when the reagent was added, but instead became bluish.  Something may have been wrong with the 1% sugar solution used, since a blue colored outcome was not an expected option.

In the Iodine test, we found that all pepper solutions did not contain starch; when the I2KI reagent was added to each test tube they did not experience a bluish-black color change. This was the outcome expected for the Organic peppers.  However the results negated our initial prediction that the GM peppers would contain starch, since research shows that the flavor can be enhanced by its addition to food (Wikipedia, 2001).  Starch may not be added to GM peppers for the simple reason that it is not present in the original version of the fruit/vegetable. Although none of the samples tested turned to the bluish black color one of the replications for the GM green peppers experienced a brownish color change.  A brownish color is not an expected outcome and does not signify the presence of starch.  However the change is an interesting error to note.  Problems could have occurred in the procedure by not adding enough/too much GM green pepper solution to the test tube or not adding enough/too much I2KI reagent.

During the Protein assay we tested for the protein concentration present in the peppers. Our initial prediction was that the genetically modified peppers would have more protein present in them than the organic peppers. We based this on the knowledge that organic red and green peppers contain one gram of protein in them, and genetically modified foods contain increased amounts to enhance the flavor of the food and/or the nutritional value (Anonymous-4, 2005).  This prediction was refuted by our results; we found that both Organic red and green peppers had higher concentrations of protein compared to their GM counterparts.  The Organic red pepper solution was found to contain 0.215 μg/μl, GM red with 0.188 μg/μl, Organic green with 0.424 μg/μl, and GM green with 0.152 μg/μl.  The higher concentration of protein in the organic peppers may be due to the importance placed on the soil in the growing process.  Since organic farmers put much emphasis on the health and nutrients present in the soil as opposed to the mass manufacturing of the GM peppers, the overall concentration of protein later found in the peppers may be affected.  The organic peppers will take in more nutrients and proteins components through their roots from the nutrient-rich soil.

In lab two we preformed the paper chromatography test. We predicted that the organic red pepper and the GM red pepper would show the same results for this test, and therefore contain the same pigments. For the organic green and the GM green peppers we also predicted that they would test the same and have the same pigments present (Bonilla et al, 2002). Based on previous group’s results for this test we predicted that the pigments present in the green peppers would be xanthophylls, chlorophyll a, and chlorophyll b. In the red peppers we predicted that the pigments present would be carotene, and chlorophyll b (Birkmeier et al., 2003).  However after determining the Rf values for each pigment we found the calculations to be skewed.  For the organic green pepper, the Rf value average of the green band was 0.0727, and 0.946 for the yellow band.  For the GM green pepper, the green band was 0.0784, and yellow band was 0.946 (same as organic green).  The organic and GM red peppers both had yellow bands with an Rf value of 1. With these values we conclude that because the Rf value for the green band in the green peppers was of low value it pertains to chlorophyll b because chlorophyll b has a low Rf value. The yellow band in the green peppers represents the pigment xanthrophyll.  Even though the  Rf  values did not match that of xanthrophyll the yellow band cannot be carotene (xanthrophyll showed up where carotene was suppose to appear) because one, the color did not contain any tint of orange and two, which was already stated from previous research, that green peppers do not contain the pigment carotene.  The organic and GM red peppers because the Rf  values were 1 we concluded that these peppers must contain the pigment carotene even though no orange color was evident on the pigment strips.  The reasoning for this is that carotene is a strong pigment, has an Rf value of 1, and pervious research found that red peppers contain this pigment.

Several errors could have occurred while doing the paper chromatography.  Due to the time constraint in LBS 145 lab we did not have time to finish the whole experiment in one day.  The strips were left unattended for 2 days.  On the second day the strips were put into the petroleum ether chloroform solvent and results were taken then.  The time laps could have created the skewed results.  Another problem could have occurred during the actual procedure by adding ethanol to the phosphate buffer, this is unlikely but it is worth mentioning.  Also when placing the strips into the petroleum ether chloroform, this solvent contained little particles floating at the bottom of the flask.  These particles could have contaminated the petroleum ether chloroform.

In lab three, during our independent research a Vitamin C test was performed to see which type of bell pepper contained more Vitamin C. We confirmed our hypothesis that the organic peppers contained more Vitamin C than the GM peppers and therefore turned the blue-black solution clear with less addition of the pepper solution. The results expressed the following comparison (starting with most content average to least content): organic red pepper 70.3 drops > organic green pepper 80.7 drops > GM red pepper 91 drops> GM green pepper 141 drops.  This finding verifies that organic foods contain natural nutrients that are known to have a larger diversity of vitamins and minerals when compared to GM foods (Anonymous-3, 2005).

In the experiment that compared the shelf life of the organic green pepper to that of the GM green pepper, we predicted that the GM version would take longer to decay; green peppers are the immature form of a bell pepper and as they age the peppers will turn red.  This prediction was based on the knowledge that the genetically modified foods have specific genes added to them that allow foods to have a longer shelf life, larger size, more desirable texture, and better taste (Wikipedia, 2001).  After the 9th day of study the experiment was terminated due to the strong scent the peppers gave off in the dorm room as well as increasing decomposition.  It took the organic green pepper 6 full days to turn completely red before it began decomposing (turning black and shriveling).  The GM green pepper never matured to a red color, instead by the 7th day it began decomposing.  This experiment reveals that some sort of gene was added to the GM pepper’s DNA to make it fulfill its immature state longer and thus increase shelf life. 

Through all of the tests that we performed throughout the biology stream we have conclude that our results support our hypothesis; organic peppers are more nutritious than genetically modified peppers with respects to sugar, protein, and Vitamin C content.  These components are extremely important for survival.  The body requires protein for tissue growth and replenishment.  Vitamin C, an essential vitamin, must be taken in through food daily because the body cannot produce it. By eating organic peppers more of the Vitamin is consumed and will help build tissues as well as fight off infections.  The lower sugar content in organic peppers helps against excess sugar consumption. Overall organic peppers win the nutrition battle because GM peppers contain higher sugar content, less protein, and less Vitamin C concentration.

Continuing research on bell peppers could focus on places of error in our experiments by redoing the paper chromatography test, the iodine test, and the Bial’s test.  Other studies could also test different colors of bell peppers such as; purple, orange, yellow or brown, to determine how they differ with respects to the red and green peppers.  Research could also compare organic peppers to GM peppers by focusing in on other vitamins that would benefit health.  Studies could also test the soil of both the organic and GM industries to find out what specific vitamins and minerals they contains as well as the concentration of each and then compare those finding to the finding of the peppers.  Future comparative research on these two industries could create break-through findings that actually may strengthen the capability of determining which is more beneficial for the body’s nutritional nourishment.


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