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