The Effects of Ethylene Glycol Vapor on the Concentration of Chlorphyll a and B During

THE EFFECTS OF ETHYLENE GLYCOL VAPOR ON THE CONCENTRATION OF CHLORPHYLL A AND B DURING RIPENING PROCESS OF BABY BANANA (Musa).

NooraMosafaeiShirazi, Samouel Hanna and PedramKhonsari.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 water, another to 50 µL ethylene glycol and a reference group was designated. As banana ripening cycle involves biosynthesis of ethylene, bananas in ethylene glycol group are expected to ripen more during the 7 days of experiment. The peels of the reference banana group were removed, weighted, and their juice was extracted, then spectrophotometric data was obtained. This procedure was repeated for 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 the post-hoc 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. Banana ripening is a physiological event that affects different physical properties. 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 fruits from the flowering part of the plant (Liu et al., 1999). Factors influencing banana ripening are important in the world market since 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 in banana causes bananas to ripen for that matter; therefore, in the course of this experiment the group of baby bananas exposed to ethylene glycol vapor is expected to ripen more during the 7 days of the experiment. As the banana ripens the concentration of chlorophyll a and b decreases causes 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 chlorgphylla and b.

Materials and Methods

One bunch of green baby banana (Musa) was bought from a local grocery store. 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 water, another to 50 µL ethylene glycol and a reference group was designated. At the first day of this experiment, the peels of the reference bananas were removed, weighted, and their juice was extracted by crushing the peels with a juicer and adding15 mL 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. Concentration of chlorophyll a and b as well as carotenoids were calculated by using concentration formulas(Boyer,1990 ).

The bananas of water vapor group and ethylene glycol group were both placed in a small specimen jar, 50µl of water was poured on a small patch and placed next to each banana in each jars. Also, 50µl of ethylene glycol was poured on each patch and placed next to each banana in ethylene glycol group. The opening of the jar will be sealed by rubber stopper number 13 to prevent the vapors from exiting the jars.Both groups were placed in Saddleback College stock room. The bananas in both groups were photographed every day and Banana Ripeness Chart will be 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 by 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 chloro- phyll in p,g/ml, Cx+c = concentration of total carotenoids (Boyer, 1990).

Results

Figure 1.Table containing the concentration of carotenoids in bananas in the reference group, water vapor group and ethylene glycol group.

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 the post-hoc test showed no significant statistical difference among any of the groups.

Figure 2. Total chlorophyll a and b concentration of reference group, water vapor group and ethylene glycol group.

Discussion

During the course of experiment different chemical reactions contribute to the ripening of bananas. This type of ripening process is present in many fruits; in fact “ Apple, avocado, banana, and 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, develop flavor and aroma” (Frenkelet al., 1968).The banana ripening cycle (Yang Cycle) involves biosynthesis of ethylene which causes the yellowing of banana peel and softening of the pulp. When bananas were bought they were un-ripen- at the third stage of the ripening. In this stage the shades of green were still present toward the tip of the bananas and the lower half of the fruit and banana body were hard. 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 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 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).

Citation

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:

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.