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A Comparison of the Macromolecule Content in Boiled Brassica oleracea versus Steamed Brassica oleracea
A Comparison of the Macromolecule Content in Boiled Brassica oleracea versus Steamed Brassica oleracea
By: Nicole Biluk, Renee Hilber and Terese Muto
LBS 145L
Section TH 02
Jamie Mooney
Rebecca Degraff
October 16, 2004
ABSTRACT:
The steaming method of cooking Brassica olerecea was compared to the boiling cooking method based upon the macromolecule content. Macromolecule analysis was completed using Benedict䴜s, Barfoed䴜s, Selivanoff䴜s, Bial䴜s and Iodine test for carbohydrates, paper chromatography for photosynthetic pigment identification and the Bradford Assay for total protein concentration. The water from the boiling process was also analyzed to either support or refute the hypothesis that macromolecule content of boiled broccoli would be lower then the content in steamed broccoli due to macromolecule loss to the water used in the boiling process (Bale, Amanda et al.). Largely, there was no significant difference between the macromolecule content of the different cooking procedures of broccoli. No photosynthetic pigments were found in any of our samples. All three samples contained identical concentrations of protein. The fact that the water from the boiling process did test positive for both carbohydrate and protein content supports the hypothesis that broccoli does lose some of its macromolecules to the water. No directly quantitative carbohydrate test was preformed but differences in positive results were observed. All carbohydrate tests were analyzed through color change and in general, the steamed broccoli solutions showed a greater color change than those observed for the boiled broccoli and the boiled broccoli solutions also showed a greater color change than the water from the boiling process.
DISCUSSION:
From the tests performed, a quantitative macromolecule comparison for the different cooking methods of broccoli could not be obtained. What we can show is evidence of lost macromolecules as a result of the boiling process, as shown by the positive results in both the carbohydrate tests and the Bradford assay of the water from the boiling process. We predicted the macromolecule content would differ based on the cooking process. Our only quantitative results from the Bradford Assay have shown that there was no significant difference in the concentration of protein between the steamed and boiled broccoli. Yet, in our analysis of the carbohydrate tests we found the overall trend to be the steamed broccoli demonstrated a stronger response to all of the tests. These solutions tended to be brighter or more vibrant in color compared to those prepared from the boiled broccoli. The boiled water showed either a negative response or a color change slighter than that of the boiled broccoli solutions (Figures 2-6). Based on all of the positive results, one can conclude there is a wide variety of carbohydrates in broccoli. From their olive green color we know that the steamed and boiled broccoli solutions, and the water from the boiling process all contain furanose rings (Figure 2). The negative result from the Iodine test shows the absence of starch. A positive result would yield a blue-black color (Figure 3). An orange/red precipitate from Barfoed䴜s test indicates monosaccharides were present (Figure 4). The results from Selivanoff䴜s Test indicated the presence of ketose sugars because the color turned red in less than 1 minute for all solutions (Figure 5). The results from Benedict䴜s Test showed that the steamed broccoli and the boiled broccoli contained reducing sugars because of the red precipitate formed. The water from the boiling process had no precipitate present (Figure 6). But, based on the fact that there are so many different kinds of carbohydrates and our limited scope of carbohydrate determination, one cannot accurately state which kinds of carbohydrates are present in broccoli from our experiments alone. When comparing our results to that of the raw broccoli tested by the Smurfs we may be able to conclude both cooking processes had an effect on the type of carbohydrate found in broccoli (Table 4).
Table 4:
Data from the previous LBS Bio 145 group The Smurfs on the carbohydrate content of raw broccoli.
Benedict's Barfoed's Selivanoff's Iodine
Raw Broccoli Solution Trial 1: No Change Green and a slight red precipitate Red @ 45 seconds No change
Raw Broccoli Solution Trial 2: No Change Green and a slight red precipitate Red @ 45 seconds No change
Raw Broccoli Solution Trial 3: No Change Green and a slight red precipitate. Red @ 45 seconds No change
Based on the presence of carbohydrates and proteins found in the boiling water we can safely assume that some carbohydrate and protein macromolecules are either polar or amphiphilic in nature (Bruice, Paula Y. pg. 86-87). We can assume this because their presence in the water from the boiling process suggests that the macromolecules were drawn out into the water due the attraction of polar forces.
The negative results from the paper chromatography test were indicated by the lack of colored pigments bands on the chromatogram strips (Figure 8). Our results are supported by the Smurf䴜s negative results (Bale, Amanda et al.) from their cooked broccoli. Their positive results for raw broccoli support our hypothesis that the cooking process does indeed have an effect on the macromolecule content of broccoli. Both results can be explained by the fact that heating the broccoli results in the denaturing of proteins (Freeman, Scott). Therefore, the pigments that were initially present in the raw broccoli would have become altered in their chemical characteristics, such as light absorption, which would cause them to lose their color, or even polarity, thereby rendering them undetectable by the chromatography test.
Some errors that could have occurred throughout our experiment were in the preparation of the broccoli. We designed our experiment around steamed versus boiled broccoli, and the water left over from the boiling technique. We did not realize that the water left over from the steamed broccoli would be slightly green also. This may have interfered with the interpretation of our results. What we may have termed a positive result of Bial䴜s test may actually been a negative result, but because of the green color of our solution we may have recorded the wrong result.
Another error occurred in our preparation of the solutions for the paper chromatography tests. We initially prepared our solutions with water instead of Phosphate buffer. Other likely errors could have stemmed from a mix up of reagents and test tubes that contained different ratios of solutions.
To improve this experiment in the future it would be necessary to run the tests on the left over water from the steamed broccoli along with boiled. Also, we should have run tests on raw broccoli to compare to our results. We were able to access the results from the Smurfs, but they did not conduct the Bradford Assay for protein concentration so the comparison was incomplete.