DISCUSSION

The main purpose of our experiment was to try to discover why corn tastes sweeter after it has been boiled. We compared the chemical composition of corn after it had been boiled to that of uncooked corn which had encountered the enzyme amylase to decipher if heat performs the same function as this enzyme (breaking down starch). We hypothesized that heat does, indeed, perform this same function, and breaks down starch into simpler sugars to create this sweeter flavor. In order to test this hypothesis, we needed to determine what sugars are found in raw, boiled, and amylase-enriched corn. The same type of corn ("bi-colored sweet") from the same store was tested throughout the entire experiment because past studies have shown that different species of corn have different contents of starch (Reyes et al.,1989). We also wanted to find out how the observable color change after corn has been boiled effects its pigments and light absorbency. We predicted that raw and boiled corn will contain the same pigments, but have different maximum light absorbencies (Figure 7). More specifically, boiled corn will have a higher light absorbency than raw since it seems to turn a darker shade of color as heat is added. Lastly, we also wanted to test the environmental effects on amylase efficiency. We hypothesized that amylase works the best when it is at normal human body temperature (37.2ºC) and at a pH of 7.0. Therefore, our group predicted that as this ideal state is altered, the effectiveness of amylase will decrease.
Trying to discover whether or not corn's composition changes as heat and amylase are added was found using two carbohydrate identification tests, Barfoed's and the Iodine test. Starch is the major form of stored carbohydrate in plants (Freeman, 130). When starch breaks down, it produces the simple sugars glucose (a monosaccharide) and maltose, (two glucoses bonded together, and therefore a disaccharide) (Freeman, 2002). So, the only sugars we needed to test for were starch, glucose, and maltose. Barfoed's test is a test that can distinguish monosaccharides from di- and polysaccharides because monosaccharides produce a color change and a red/orange precipitate. The Iodine test simply determines the presence of starch, a color change to blue-black will occur if starch is present. Three different concentrations of each solution were made (3, 5, and 10 % corn) and tested for the best possible results and repetition purposes. Since these tests are based primarily on color changes, the spectrophotometer was used to determine quantitative results (the light absorbencies at 400 nm), as well as qualitative results (our observations), after Barfoed's test was performed (to 10% solution). There should be a direct correlation between the amount of color change and the light absorbency value (Table 5 and Figure 8).
For Barfoed's test, there were no observable color changes among the solutions, but the light absorbencies directly support our hypothesis (Table 5 and Figure 8). The cooked and amylase-enriched solutions both have high absorbencies compared to the raw solution, evidence that more monosaccharides might be present (Tables 1, 2, and 3). We could not perform the spectrophotometer tests on the Iodine test products because there was not a sufficient blank to zero it with (since there is no heat involved). So, our results are based solely on our physical observations. Our results do support our hypothesis that more starch is present in raw corn then in boiled and amylase-enriched corn since the most color change occurs in the raw corn solution, a slight amount of change occurs in the amylase-enriched corn solution, and there is almost no change at all in the cooked corn solution (Tables 1, 2, and 3). Overall, our proposed hypothesis was supported since both these carbohydrate tests confirmed our expected results.
The paper chromatography test supported our hypothesis that corn most likely contains the same pigments, regardless of its raw or boiled nature. Our results show that both the raw and boiled solutions contain pigments similar to chlorophyll a and b. Chlorophyll a produces a blue-green color on the paper and has a Rf of approximately .38 (ours was .41) while chlorophyll b produces a pale green color and has a Rf of approximately .23 (ours was .21) (Table 4). Next, we used the spectrophotometer to compare the maximum light absorbency values of boiled corn verses raw corn (Table 7). Both maximum absorbencies were found at a wavelength of 430 nm, with raw corn at 1.03 and boiled corn at 1.23 (Table 5 and Figure 8). These results support our hypothesis that as corn is boiled, its color changes to a darker shade, therefore increasing its absorbency.
Last, the effectiveness of amylase was tested using the two same carbohydrate identification tests, Barfoed's and the Iodine test. As stated earlier, the optimal environment of amylase is at body temperature (which makes sense because amylase is produced in saliva) and at a neutral pH of 7.0. So, we wanted to determine how amylase works at boiling temperature, in an acidic environment, and a basic environment. As a control, we tested the effectiveness of amylase under its ideal conditions. As amylase is added to the corn, starch should start to break down into glucose and maltose, therefore Barfoed's test should produce a color change, while the color change should decrease, if not cease, in the Iodine test, proving less starch (Figure 3 & 6). Our results reiterated the effect of amylase at these optimal conditions (Table 6 & 7). However, if heat is then added to the environment (reaching a temperature of 100ºC), our results support our hypothesis that amylase does not work as efficiently (Table 7). There is no color change in the simple sugar test and it becomes apparent from the Iodine test that measurable amounts of intact starch still remain (Table 7). The result is the same for the amylase-enriched corn at acidic and basic environments (Table 8 and 9). Therefore, the results support our hypothesis that at non-ideal conditions, the effectiveness of amylase decreases considerably. Although our experiment was performed as carefully and accurately as possible, there are many sources of error that could have affected our results. The fact that most of our tests were based on visual observations could have lead to data errors. While one person believed a certain color to be one shade of red, another person could disagree entirely. Pictures were taken to try to avoid these errors, but the pictures do not always give an accurate description (dependent on lighting, angling, etc.). This is especially true for the Iodine test results, since no spectrophotometer values were even taken. Also, because of time restraints, not enough trials were run to completely support or negate our hypotheses. More specific experimental errors include the fact that since salivary amylase is a clear fluid, this might have distorted the spectrophotometer results regarding light absorbency values at different wavelengths. This greatly affects our experiment since some of our results depended on these values to determine color variation in the carbohydrate tests. In addition, not enough amylase may have been added to properly break down starches. We never found a typical ratio of amylase to starch in the human mouth. This would directly affect the carbohydrate test results, as more simple sugars would have been produced in the solutions if it requires more or less amylase. Hopefully none of these possible errors distorted our results as to make them completely unreliable.