THE EFFECTS OF ETHYLENE GLYCOL VAPOR ON THE CONCENTRATION OF
CHLORPHYLL A AND B DURING RIPENING PROCESS OF BABY BANANA (Musa).
Noora Mosafaei Shirazi, Samouel Hanna and Pedram Khonsari.
Department of Biological Sciences
Saddleback College
Mission Viejo, CA, 92692.
During this experiment, individual bananas were taken from a green banana bunch and
placed into 3 groups (n=5). One group was exposed to 50 µL of water, another to 50 µL of
ethylene glycol and a reference group was designated. Banana ripening cycle involves
biosynthesis of ethylene, bananas in ethylene glycol group were expected to ripen a greater
amount during the 7 days of experiment. The peels of the reference banana group were
removed, weighed, and their juice was extracted. Then spectrophotometric data was
obtained. This procedure was repeated for the other groups. The mean of the total
concentration of chlorophyll a and b was calculated for all groups. Mean absorbance level
± SEM (4.22 ± 1.49, 2.09 ± 0.47, 0.73 ± 0.05, ANOVA p-value = 0.053). Comparing to the
reference group, chlorophyll a and b concentrations decreased by a factor of 2 in the water
vapor group and factor of 4 in the ethylene glycol group. No significant statistical
difference existed. For carotenoid concentrations ANOVA was performed (p-value =
0.0002), and a post-hoc Bonferonni test showed no significant statistical difference among
any of the groups.
Introduction
Many physical changes of fruits are believed to be hormone triggered processes that involves
biochemical cycles which induce a response on the cellular level. Deleted unnecessary sentence
In terms of the life cycle of bananas, ripening is a stage that allows for both the propagation of
seeds and the production of more fruit from the flowering part of the plant (Liu et al., 1999).
Factors influencing banana ripening are important in the world market since the banana, as a
food source, plays a significant part in the socio-economic lives of millions of people in the
developing world, its efficient and healthy production is always required (Aquil et al., 2012).
Initiation of ethylene cycle causes bananas to ripen; therefore, in the course of this experiment
the group of unripened bananas exposed to ethylene glycol vapor is hypothesized to ripen more
during the 7 days of the experiment. As the banana ripens the concentrations of chlorophyll a and
b decrease causing the green color of the peel to change to yellow as more carotenoids are
unmasked. Therefore, in this experiment, the quantitative measure of banana ripening is the
decrease in the concentration of chlorophyll a and b.
Materials and Methods
One bunch of green baby bananas (Musa) was purchased from a local grocery store. During the
experiment, individual bananas were taken from a green banana bunch and placed into 3 groups
(n=5). One group was exposed to 50 µL of water, another to 50 µL of ethylene glycol and a
reference group was designated. At the first day of this experiment, the peels of the reference
bananas were removed, weighed, and their juice was extracted by crushing the peels with a juicer
and adding 15 mL of acetone to the peel. After 10 minutes the liquid was poured in to a test tube.
It was centrifuged for 5 min, then the liquid portion was transferred to another test tube for
spectrophotometric readings. Concentrations of chlorophyll a and b as well as carotenoids were
calculated by using concentration formulas (Boyer,1990 ).
The bananas in the water vapor group and ethylene glycol group were both placed in a small
specimen jar, 50 µl of water was poured on a small patch and placed next to each banana in each
jar. Also, 50 µl of ethylene glycol was poured on each patch and placed next to each banana in
ethylene glycol group. The opening of the jar was sealed by a number 13 rubber stopper to
contain the vapors . Both groups were placed in Saddleback College stock room. The bananas in
both groups were photographed every day and Banana Ripeness Chart was used as a reference
for staging the ripening process (UC Davis Postharvest Technology Maintaining Produce Quality
and Safety, 2013).
At the end of 7th day of experiment, the bananas in both ethylene glycol group and water vapor
groups were peeled. And the same procedure of juice extraction was repeated and
spectrophotometric data was obtained. Concentration of chlorophyll a and b as well as
carotenoids were calculated using the same concentration formulas.
Ca = 11.24A661.6 - 2.04-A644.8
Cb = 20.13A644.8 - 4.19A661.6
Ca+b = 7.05A661.6 + 18.09A644.8
Cx+c = (1000A470 - 1.90Ca - 63.14Cb)/214
where: Ca = concentration of chlorophyll a in micrograms per milliliter of plant extract solution
(µg/ml), Cb = concentration of chlorophyll b in µg/ml, Ca+b = concentration of total chlorophyll in p,g/ml, Cx+c = concentration of total carotenoids (Boyer, 1990).
Results
Reference
Water Vapor
Ethylene glycol
µg/ml
µg/ml
µg/ml
Cx+c
2.130223791
2.257797911
1.273085952
Cx+c
2.455843065
1.577404463
1.273085952
Cx+c
4.082144584
1.836880631
1.014713605
Cx+c
3.994501374
1.461752656
1.247784053
Cx+c
3.774739417
1.869735372
1.014810173
Figure 1. Table containing the concentration of carotenoids in bananas in the reference, water
vapor, and ethylene glycol groups.
ANOVA: Single Factor
SUMMARY
Groups
Count
Sum
Average
Variance
Column 1
5
16.43745223
3.28749
0.849914
Column 2
5
9.003571033
1.800714 0.09494
Column 3
5
5.823479736
1.164696 0.01884
ANOVA
Source of
Variation
SS
df
MS
Between
Groups
11.86879883
2
5.934399 18.47392 0.000217 3.885294
Within Groups
3.854775175
12
0.321231
Total
15.72357401
14
Comparison
Mean1 - Mean2
F
P-value
95% CI of difference
1: Reference vs. Water Vapor
+ 1.486776239
- 10.297749407 to + 13.271301885
2: Reference vs. Ethylene glycol
+ 2.122794499
- 9.661731147 to + 13.907320145
3: Water Vapor vs. Ethylene glycol
+ 0.636018260
- 11.148507386 to + 12.420543906
Comparison
Significant? (P <0.05?)
t
1: Reference vs. Water Vapor
No
0.965
2: Reference vs. Ethylene glycol
No
1.378
3: Water Vapor vs. Ethylene glycol
No
0.413
Comparison
F crit
Mean 1
Mean 2
N1
N2
1: Reference vs. Water Vapor
+ 3.287490446
+ 1.800714207
5
5
2: Reference vs. EG
+ 3.287490446
+ 1.164695947
5
5
3: Water Vapor vs. Ethylene glycol
+ 1.800714207
+ 1.164695947
5
5
Mean absorbance level ± SEM (4.22 ± 1.49, 2.09 ± 0.47, 0.73 ± 0.05, ANOVA p-value = 0.053).
When compared to the reference group, chlorophyll a and b concentrations decreased by a factor
of 2 in the water vapor group and by a factor of 4 in the ethylene glycol group. No significant
statistical difference was demonstrated. For the carotenoid concentrations ANOVA was
performed (p-value = 0.0002), and the post-hoc test showed no significant statistical difference
among any of the groups.
C a+b
Reference Group µg/ml
2.2368
Water Vapor Group µg/ml
2.18439
Ethylene glycol Group µg/ml
0.84799
C a+b
3.09648
1.24317
0.84799
C a+b
10.1244
1.73985
0.62997
C a+b
2.28402
3.8697
0.75857
C a+b
3.36504
1.44336
0.60785
Figure 2. Total chlorophyll a and b concentrations of the reference, water vapor, and ethylene
glycol groups.
Anova: Single Factor
SUMMARY
Groups
Count
Sum
Average
Variance
Column 1
5
21.10677
4.221354
11.13416
Column 2
5
10.48047
2.096094
1.108481
Column 3
5
3.69237
0.738474
0.013307
ANOVA
Source of
Variation
SS
Between
Groups
df
MS
F
P-value
F crit
30.81719 2
15.4086
3.771702 0.05359 3.885294
Within Groups
49.02379 12
4.085316
Total
79.84098 14
Discussion
During the course of experiment different chemical reactions contributed to the ripening of
bananas. This type of ripening process is present in many fruits; in fact “ Apples, avocados,
bananas, and many peer fruits exhibit a marked increase in respiration rate, the climacteric
during ripening. It is during this period of accelerated respiratory activity that fruits soften, lose
chlorophyll, and develop flavor and aroma” (Frenkel et al., 1968).The banana ripening cycle
(Yang Cycle) involves biosynthesis of ethylene, which causes the yellowing of the banana peel
and softening of the pulp. When the bananas were purchased they were unripened and at the
third stage of the ripening: there were still shades of green present toward the tip of the bananas
and the lower half of the fruit and banana bodies were firm. During the course of ripening
different physical changes indicate the onset of ripening cycle in the fruit. “Bananas are
climacteric fruit in which ripening is regulated by ethylene. Once initiated, ripening involves
numerous changes including the conversion of starch to sugars, alterations in fruit texture and the
synthesis of volatile compounds.” (Drury et al., 1999). Although a majority of clues concerning
the ripening of banana are represented in the appearance of both peel and pulp, some of these
changes vary between the peel and pulp. “The peel tissue in the banana appears to share many
ripening related events with the pulp including softening and starch degradation, but the presence
and degradation of chlorophyll (Chl) are unique to the peel” (Drury et al., 1999).
Citations
Aquil, B., Jan, A.T., Sarin, N.B. and Haq, Q.R. (2012). Micropropagation and genetic
transformation of banana for crop improvement and sustainable agriculture. Journal of Crop
Science. 3(2): 64-77.
Boyer, R.F. (1990). Isolation and spectrophotometric characterization of photosynthetic
pigments. Biochemical Education. 18(4): 203-206.
Liu, X., Shiomi, A., Nakatsuka, A., Kubo, Yasutaka., Nakamura, R. and Inaba, A. (1999).
Characterization of ethylene biosynthesis associated with ripening in banana fruit. Plant
Physiology. 121: 1257-1265.
UC Davis Postharvest Technology Maintaining Produce Quality and Safety
[Internet].c2013.California: Regents of the University of California; [cited 2013 Sep 29].
Available from:
http://postharvest.ucdavis.edu/PFfruits/BananaPhotos/?repository=29280&a=83211
Xiao, Y., Chen, J., Kuang, J., Shan, W., Xie, H., Jiang, Y. and Lu, W. (2013). Banana ethylene
response factors are involved in fruit ripening through their interactions with ethylene
biosynthesis genes. Journal of Experimental Botany Advance Access. 1: 1-12.
Review Form
Department of Biological Sciences
Saddleback College, Mission Viejo, CA 92692
Author (s): Noora Mosafaei Shirazi, Samouel Hanna and Pedram Khonsari
Title: THE EFFECTS OF ETHYLENE GLYCOL VAPOR ON THE CONCENTRATION OF CHLORPHYLL A AND B
DURING RIPENING PROCESS OF BABY BANANA (Musa).
Summary
Summarize the paper succinctly and dispassionately. Do not criticize here, just show that you understood the paper.
The group obtained a green banana bunch and placed them into 3 groups. One was a reference group,
the other two were placed in a closed container containing a patch of paper coated in either water or
ethylene glycol. After 7 days the bananas were qualitatively analyzed using a chart from UC Santa Cruz
as well as analyzed juices spectrophotometrically. No significant differences in ripeness were found in
any of the groups.
General Comments
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state of knowledge.
Serious grammatical errors that were distracting and added difficulty to understanding the paper. A few
minor spelling errors were present causing some distraction. Paper construction was solid overall.
Authors would do well to repeatedly proofread to ensure their research paper is devoid of errors and
logical conclusions can be drawn.
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