ABSTRACT
The Vitreous Floaters compared the
soybean plant (Glycine max) to its processed byproduct: soymilk. Based on
carbohydrates, photosynthetic pigments, and enzymes, it was expected that
there would be similarities in the composition of both. In order to test our
prediction, we first performed four carbohydrate tests: Barfoed’s test,
Selivanoff’s test, Bial’s test and the Iodine test. After performing
these tests, results were obtained that refuted our hypothesis that the soybean
plant and soymilk have similar sugar compositions. The soybean plant was comprised
of monosaccharide ketoses, while, the soymilk consisted of di and polysaccharide
ketoses.
Although the soymilk was not green,
we were curious to see if any photosynthetic pigments from the plant remained
in the soymilk. It was predicted that since it was a product of the soybean
plant, soymilk would still contain some of these photosynthetic pigments.
To test this theory, a paper chromatography test was performed. The colors
presented on the strip were noted and Rf value was determined. As a result,
it was determined that no photosynthetic pigments remained in the soymilk
– contradicting our hypothesis.
To access the amount of protein present in our experimental samples, the Bradford
Assay was employed. It was expected that the soymilk sample would contain
a greater amount of protein than the soybean plant sample. Following the completion
of this test, it was revealed that we were correct in our predictions. Overall,
soymilk lacks substances that are present in natural soybean plants.
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Figure 1: Barfoed’s Test for reducing sugars. The test tubes above shown from left to right: soybean plant extract control (Cp), soybean plant extract trial 1 (1p), soybean plant extract trial 2 (2p), soymilk control (Cm), soymilk trial 1 (1m), soymilk trial 2 (2m). This figure shows the test tubes of soybean plant, soymilk, and two control groups, all containing 3 ml of Barfoed’s reagent. The test tubes labeled 1p, 2p, 1m, and 2m show results after two minutes of being placed in a boiling water bath. While the test tubes labeled Cp and Cm serve as control test tubes and received no boiling treatment. The soybean plant extract had a brown-red precipitate form in the bottom of the test tube. This dark brown-red precipitate indicated that there are traces of reducing monosaccharide sugars in the soybean plant. The lack of precipitate in the soymilk indicated that there are di and polysaccharide sugars. |
DISCUSSION
The main purpose of our experiment
was to analyze soymilk as it compares to the soybean plant (Glycine max) (Jung
et al., 2000). To accomplish this we broke our two types of experimental samples,
soymilk and soybean plant, down into their chemical compositions and analyzed
their different chemical make-up. We expected there would be similarities
in the composition of the soybean plant and soymilk. In order for us to test
our hypothesis, we had to perform numerous experiments that would allow us
to look at some of the major components that make up the soybean plant and
soymilk.
The first set of experiments that we
performed tested for different carbohydrates that comprise the soymilk and
soybean plant respectively. We created a soybean plant extract by blending
the soybean plant leaves in a blender and mixing with distilled water. Next,
we covered a 250 ml beaker with cheesecloth and filtered the extract to remove
any solids from the extract. We used the same batch of leaves (all collected
from the same group of plants at the exact same time) and concentration of
leaves to distilled water to make our extract throughout our experiment process
to maintain consistency. Our first carbohydrate test was the Barfoed’s
test, which determined if the sugars in the soymilk and soybean plant were
monosaccharides, disaccharides, or polysaccharides (Krha et al., 2003). We
expected to find the same sugars in both experimental groups since soymilk
originates from the soybean plant. The results from our experiment showed
that the soybean plant reacted in less than two minutes with a color change
and a precipitate. This reaction demonstrates a monosaccharide. However, soymilk
did not have a reaction to the Barfoed’s test, indicating di and polysaccharides.
Manufacturing soy alters its chemical make-up from the original soybean plant,
causing the monosaccharide sugar found in the plant to be lost in the milk
(Poysa et al., 2002). This could be due to preservatives that are used in
the milk. Therefore, the Barfoed’s test refuted our hypothesis.
The second carbohydrate experiment
that we performed was the Selivanoff’s test. With this test we where
able to see the difference between ketoses and aldoses. We found that the
milk reacted within less then a minute and turned a burgundy color in both
trials, indicating a ketose (Krha et al., 2003). The soybean plant extract
did not react until about a minute for trial one and over a minute for trial
two, indicating an aldose (Krha et al, 2003). With these results, the Selivanoff’s
test also refuted our hypothesis.
The third carbohydrate test that we conducted was the Bial’s test. We
tested the soybean plant and the soymilk to see if there were any furanoses
(five membered rings) in their chemical make-up. If either experimental group
did contain a five membered ring, it would react (Krha et al., 2003). Both
the soybean plant and the soymilk reacted creating an olive green color indicating
that pentose furanoses are present allowing us to support our hypothesis that
they do contain a similar sugar.
The fourth and final carbohydrate test
was the Iodine test. In this experiment, we looked for the presence of starch
in soymilk and soybean plant. Starch, a polysaccharide, would change the sample
to a bluish back color if it were present in either sample (Krha et al., 2003).
Our samples did not react to this test using 35µl. When using 70 µl
at first, the milk did change colors causing us to think that it did react,
but overtime, approximately twenty minutes, the milk returned to white. The
color change that we experienced was mainly due to the color of the Iodine
and not a reaction. The soybean plant did not react with the Iodine, agreeing
with Barfoed's test explained earlier, that the soybean plant is a monosaccharide.
The soymilk did not react to either test and the results refute our hypothesis
that the two experimental samples share similar sugars.
The second set of tests that we executed dealt with photosynthesis. We did
not expect to see similar pigments in the soymilk and the soybean plant because
of the chemical processing of the soymilk (Poysa et al., 2002). Using paper
chromatography, we obtained the results we expected. The leaves from the soybean
plant, that contain chlorophyll, resulted in all four-pigment colors: chlorophyll
a, chlorophyll ß, xanthophyll, and carotene. The samples of soymilk
contained no pigments. Next, we used a spectrophotometer, which allowed us
to compare the light absorbency between the soybean plant and soymilk samples.
This allowed us to see if any light absorbency is lost between the pure soybean
plant and the soymilk. We expected there to be a loss in light absorbency
between the pure forms of a substance, plant, to a manufactured version, milk.
As we expected, the absorbency of the soybean plant extract was nearly twice
that of the soymilk sample. The data obtained in these two experiments supports
our hypothesis.
The final experiment we tested dealt
with the amount of protein present in our two experimental samples. The experiment
that we conducted was the Protein (Bradford) Assay. The Bradford assay allows
us to see the amount of protein in each sample by using protein concentrations
vs. absorbance. We predicted that the amount of protein in the soymilk would
be higher than in the soybean plant. Our results showed that the Bradford
assay supported our hypothesis, that the milk contained more protein than
the plant. In fact, the milk contained almost 3.5 times more protein than
the soybean plant. According to Dr. Yiwu Chen, the expected amount of protein
contained in 50 grams of leaves equals only about one gram (Chen, 2003) therefore
leading us to believe that the soymilk would contain more protein.
What we can conclude from our experimental
results is that our predicted hypothesis was not completely upheld nor thrown
out, due to the fact that, fifty percent of our experiments were refuted while
fifty percent were supported. We were able to find some correlations and similarities
between the two samples, soybean plant and soymilk. However, it is evident
that the chemical alteration and manufacture of soybean plant will cause the
composition of the soy to change.
Even though we executed our experiments to the best of our abilities, it is possible that many sources of error occurred. These sources of error would have embellished the results that we obtained. The first source of error that could have clouded our results was making our assumptions using visual observations. Anytime someone uses sight to justify experimental data there is always the chance of human error occurring. Another type of error could have occurred when we were boiling our samples. We could have boiled our samples for too long causing us not to be able to obtain the correct results. A final cause of error with our experiment could be the freshness of our soybean plant extract. We wanted to keep the extract throughout our experimental process in order to have consistency in each experiment and not be vulnerable to having an old, or contaminated sample as the weeks went by. Although we took as great of care as we possibly could, we needed to make a new extract for the photosynthesis tests and a new extract for the protein assay. Even though the leaves came from the exact same plants and we used the same mass of leaves to the same amount of distilled water, the extract was different for each set of experiments. Ideally, we hoped that none of these possible errors would occur because we want our results to be as accurate as possible. We did our best to reduce the chance of error due to a different extract with each set of tests by making the extract in the most exact same way possible.
*Soy plant image taken from:
Karen Shelton (2003) Herb Picture Collection 2003, http://altnature.com/Herbs2003/pages/soy0803C.html