Comparing Carbohydrates, Protein, Amino Acids, and Lycopene in Roma, Regular, and Grape Tomatoes for a Healthier Diet.


Cynthia Harry and Farah Farah


LBS 145

Section: Wednesday 7pm-10pm

Lab instructors: Laura Miller and James Hardie

January 25, 2006






            Written by: Farah Farah

            Edited by: Farah Farah and Cynthia Harry

When investigating the differences between roma, grape, and original tomatoes it was believed that the grape tomatoes would have a different carbohydrate composition than the other tomatoes because of it’s compact size and the fact that it contains ten times more flavanol  (Hunt, 1999).  Flavanols, are the red pigments in tomatoes and they act as antioxidants that reduce a person’s chance of heart disease (Flavanol, 2006).   It is also believed that grape tomatoes will have a higher protein concentration because they contain more arginine per sample (Nutritional 4, 2006). Therefore, the grape tomato will yield a higher absorbency than its counterparts because arginine reacts better in the Bradford’s assay.  When testing for available amino acids it is likely that all three tomatoes will have the same amino acids (Nutritional 1, 2006).  When testing the lycopene amount of all tomatoes, it’s believed that the grape tomato will have a higher lycopene concentration because it contains more flavanol.  Before testing began each type of tomato was pureed and put through a cheese cloth twice.  Barfoed’s and Selivanoff’s test revealed that all three tomato types contained monosaccharide carbohydrates with a ketose formation.  Also, there was no starch present in any of the tomatoes as indicated by an Iodine test. Bradford’s test concluded that the grape tomatoes had 7µg/g of protein per one gram of sample, which was significantly higher than both roma and normal tomatoes combined. The Amino acid TLC showed Lysine, Arginine, Histidine, Aspartate, and Glutamate present in all three tomatoes types. The Lycopene test yielded that roma tomatoes have more Lycopene per one gram of sample.  Therefore, when comparing the heath benefits of the three types of tomatoes it would be preferable to eat grape tomatoes if one desires a high protein diet. However, if a man wants to reduce their chance of prostate cancer and heart disease roma tomatoes would be beneficial.


            Written by Cynthia Harry

            Revised by Farah Farah and Cynthia Harry

Through these test the hypothesizes formulated were supported or refuted. The carbohydrate tests performed seemed to be inconclusive with the hypothesis. It turned out that grape tomatoes do not have a different carbohydrate structure from that of roma and original tomatoes. However, they all have the same main structure which consists of a monosaccharide determined by the Barfoed’s test (Figure 1), ketose verified by the Selivanoff’s test (Figure 2), and non-starch element confirmed by the Iodine test (Figure 3). The sugar that possesses these characteristics is fructose. This is true because fructose is a monosaccharide or a single sugar. Fructose also has a carbonyl group located in the middle of its structure making it consistent with a ketose and it’s also a non-starch. Therefore it has been determined that fructose is present in roma, grape, and original tomatoes (Table 1). This is consistent with nutritional evidence found on tomatoes provided by the USDA. Which indicated that grape, roma, and original tomatoes had fructose present (Nutritional 1, 2006).  However, fructose is not the only monosaccharide present in all types of tomatoes. Glucose is also found in all of the following tables but it didn’t appear in the test because it seems that the sugar glucose is less abundant in tomatoes then fructose (Nutritional 4, 2006).

            The protein analysis from the Bradford’s test supported the hypothesis. Grape tomatoes had a significantly higher protein concentration then that of roma and original tomatoes (Figure 5). Through test analysis (Figure 4) the concentration of protein in grape tomatoes was determined to be 7 µg/(g of tomato), in original tomatoes 3 µg/(g of tomato), and for roma tomatoes 2.6 µg/(g of tomato). This data was compared to that of prier research, which also concluded that grape tomatoes had a higher concentration of protein then that of original and roma tomatoes (Nutritional 1, 2006). Nutritional information provided from calorie-count also supported the evidence found in this research. It seems that grape tomatoes have a higher amount of arginine then the other two types of tomatoes (Nutritional 4, 2006). This is important because arginine is the amino acid that binds to the Bradford’s reagent in the Bradford’s test (Bradford, 1976). Therefore, a higher concentration of arginine will lead to higher binding potential, resulting in higher protein concentration. This is exactly what occurred with grape tomatoes. Grape tomatoes seem to be a better source of protein then roma and regular tomatoes.

            It was hypothesized that all of the tomatoes would have the same amino acids present.  The research performed confirmed this assumption (Figure 6). It seems that the main amino acids found in all the tomatoes were Lysine, Arginine, Histidine, Aspartate, and Glutamate (Table 2). This evidence was also supported by the nutritional facts provided by the USDA (Nutritional, 2006). However, it seems that there are a lot more amino acids present in the tomatoes then have been provided above. The reason these may not have been noticed could be due to the fact that they compose a smaller portion of the tomatoes then the other amino acids present.

            The final test preformed was the lycopene test. It seems that the hypothesis for the lycopene test was inaccurate according to the actual data obtained. The roma tomatoes had the highest lycopene concentration at 31.9µg/ g of sample, next grape tomatoes with a concentration of 24.4µg/ g of sample, and original tomatoes with a concentration of 18.0µg/ g of sample (Graph 1). In, “Heat treatment and progression of chilling injury and pigmentation of tomatoes during postharvest,” by Henrique et. al the lycopene concentration of original tomatoes at 20şC (just below room temperature) was 16.5µg/g of sample (Henriquez et. al., 2004). This value is not to far off from the observed value obtained in this research. The potential difference in concentration may have been due to a slight temperature change. A lycopene concentration of 25.73µg/g of sample in raw tomatoes was also recorded in research conducted by Canene-Adams et. al. (Canene-Adams et. al., 2005). The values observed in both researches are consistent with the recorded values of this research.  So when it comes to determining the healthier tomato based on lycopene concentration roma tomatoes seem to be the way to go.   

            Some possible sources of error that may have occurred during experimentation include human and technical error. During the Selivanoff’s test it was hard to determine whether a color change occurred during or after a minute timing. In other carbohydrate test it was hard to determine the color of the resulting solution. These examples of error during the carbohydrate test are mostly human error. The results however seemed to be accurate but may have not been if repetitions were not performed. During the Bradford’s test the main difficulty was using the spectrometer. There was constant repetition performed due to negative or impossible readings determined by the spectrometer. If repetitions were not made then the data would have been inaccurate and the amount of protein in each tomato would be increasingly smaller. The amino acids found on the strip were hard to determine at first without the use of UV lights. There seemed to be a few areas on the TLC strip where amino acids were abundant and hard to differentiate. If this was not so more amino acids may have been found. Finally, errors that occurred during the lycopene test also occurred due to spectroscopy errors. Theses were minor errors that didn’t occur as much as in the Bradford’s test. If the spectrometer absorbency measurements were recorded inaccurately it could have resulted in lower or higher values for lycopene concentration.

            The research conducted has concluded that grape tomatoes seem to be a better source of protein then the other two types. Roma tomatoes on the other hand are a good source for lycopene. So the main question here is what determines the health of a tomato? Is it the higher protein concentration or is it higher lycopene concentration.

Graphs & Figures:

Figure 4: Bradford’s Assay: The bar graph above shows the distribution of protein in each type of tomato estimated by the Bradford’s test. It is clear that the grape tomatoes have a higher concentration of protein, followed by original tomatoes, and then roma tomatoes with the least amount of protein.






Graph 1: Lycopene TLC Test: This is a scatter plot of the lycopene concentration of roma, grape, and original tomatoes determined by a lycopene spectroscopy test. As it can be seen roma tomatoes have the highest concentration of lycopene, preceded by grape, and then original tomatoes.