Regulation of Banana Fruit Ripening with Ethylene Application

This report investigates the regulation of banana fruit ripening through the exogenous application of ethylene. The study focuses on understanding the ripening process in climacteric fruits like bananas, where ethylene plays a crucial role. The experiment involved treating green, mature bananas with varying concentrations of ethylene gas and monitoring their ripening at a controlled temperature. Key observations include the impact of ethylene on endogenous ethylene production, respiration rates, and peel color development. Results showed that the amount of endogenous ethylene increased with higher exogenous ethylene concentrations. The report also analyzes the effects of ethylene on respiration rates and the resulting changes in peel color, which is a critical factor in determining fruit quality and marketability. The findings highlight the significance of ethylene in post-harvest physiological processes and the overall quality of the harvested product.

Running head: BANANA FRUIT RIPENING 1
Regulation of Banana Fruit Ripening with Exogenous Application of Ethylene
Student’s Name
Institutional Affiliation
Abstract

BANANA FRUIT RIPENING 2
Ripening represents the maturation of fruits. Bananas are a good example of climacteric fruits,
they only need to mature to ripen. Upon detaching from the plant, the fruits produce their own
ethylene that initiates the ripening process. Similarly, the exogenously applied ethylene does not
only induce ripening but also facilitates endogenous ethylene production. The study aims at
understanding the process of fruit ripening, as well as studying the effects of ethylene application
on banana ripening and its influence on the production of endogenous ethylene, respiration rate,
and banana peel colour development.
The experiment involved green mature bananas which were fumigated with ethylene gas and
later allowed to ripen at a temperature of 20±10C. For the treated batches, the amount of
endogenous ethylene produced increased with an increase in the exogenous ethylene, with the
100 μlL-1 batch producing the most amount of endogenous ethylene. Control experiment reported
a consistent green peel colour throughout the ripening period while the other trials had a
consistent improvement in terms of colour. The experiment was designed to operate at a
temperature of 20 ±10C and from the TinyTag sensors, the temperature recorded shows no
significant difference from the recommended temperature.
Regulation of Banana Fruit Ripening with Exogenous Application of Ethylene

BANANA FRUIT RIPENING 3
Objectives
1. To understand the process of fruit ripening, it’s regulations and implications in
addressing the requirements of the consumers and consequently facilitating marketing.
2. To study the effects of ethylene application on banana ripening and its influence on
production of endogenous ethylene, respiration rate and banana colour development.
Introduction
Fruits are classified as either climacteric or non-climacteric depending on how they
respire as well as their reaction upon exposure to ethylene production. For the climacteric fruits,
ethylene gas plays a very important role in their ripening, that is, exposure to ethylene will
initiate the process of ripening. Ethylene gas is produced as a fruit ripens. Non-climacteric fruits,
on the other hand, do not respond to ethylene but instead have to grow, mature and ripen while
they are still attached to the mother plant failure to which they will not ripen. For climacteric
fruits, ripening need not happen while attached to the plant but instead, as long as the fruits are
ripe, ethylene gas can be dosed to the fruits initiating the ripening process. Bananas are a good
example of these fruits, they only need to mature to ripen. Upon detaching from the plant, the
fruits produce their own ethylene that initiates the ripening process. Similarly, the exogenously
applied ethylene induces ripening and the endogenous ethylene production (Marriott and
Gravani, 2006).
As with bananas, they exhibit a sharp rise in ethylene gas followed by a sudden decrease
in production, this allows for a quick pick at the onset of ripening. Ripening is associated with
the increase in respiration and a change in the physiological and biochemical properties of the
fruit which include; change in fruit color, fruit softening, conversion of starch into sugars,
organic acid metabolism, and production of aroma and flavor (Bharat 2014). The endogenous

BANANA FRUIT RIPENING 4
ethylene production in a fruit is responsible for controlling these changes. In bananas, ethylene
production is categorized into two; ethylene system I an ethylene system II. Ethylene system I
trigger ethylene system II, which causes the autocatalytic climatic peak during fruit ripening
(Plange et al., 2012). During this process, the peel color changes from green to yellow, the
texture, and softness of the fruits changes as well as the sweetness that results from the
conversion of starch into sugars (Wills et al., 2007).
Despite the fact that endogenous ethylene is most crucial in fruit ripening, exogenous
application improves the ripening and the quality of the end product. Previous studies show that
external ethylene can either be the manufactured type or artificial by the use of ethylene
generating fruits. Fruits such as passion fruits, apples, and avocados are ranked as ethylene
generators and therefore mixing bananas with these fruits doses ethylene into them, initiating
ripening and its associated biochemical and physiological changes (Cornelius and James, 2007).
Ripening indicates the maturation of fruits and particularly occurs as a result of unique
coordination between the developmental and biochemical pathways and as a result, peel colour,
texture, aroma and nutritional quality are affected. Through this process, fruits become more
palatable and how well this is achieved determines how well the fruits become commercially
marketable. Exposure of bananas to ethylene gas advances the onset of an irreversible shoot in
respiration and consequently a rapid ripening. It marks the end of growth of a banana fruit and
the start of senescence, cellular delay of the tissues. It is an irreversible process that results from
complex changes in the banana probably independently of each other. For commercial purposes,
ripening plays a crucial role. This paper, therefore, aims at collecting relevant data related to
banana ripening and demonstrate how they impact post-harvest physiological processes and the
quality of harvested product (Saeed et al., 2006).

BANANA FRUIT RIPENING 5
Materials and Methods
Fruit treatment: The experiment involved green mature bananas, Musa sp. AAA group,
Cavendish subgroup. The fruits which were harvested at the pre-climacteric stage were sourced
from Woolworths limited. The different batches of bananas were placed in 60 liters container
and fumigated with varying concentrations of ethylene gas, that is, 0, 10, 50 and 100 μlL-1 for 24
hours. The plastic containers were then sealed. The ethylene gas was obtained from a cylinder
containing ethylene in nitrogen from where it was injected into the sealed container through the
injection port located on the lid of the container.30 grams of soda lime was also added to the
container to prevent accumulation of CO2 which impacts respiration and consequently the
ripening process.
After injection of the ethylene, the containers were placed in ambient conditions and
allowed to ripen at the temperature of 20±10C. During the ripening process, changes in ethylene
production, respiration rate, and colour development were recorded on every alternate day. A
completely randomized block design with three replications was used, with each replication
being five fingers.
Determination of ethylene production: The endogenous levels of ethylene in the treated
and the control experiment was measured using a Sensor Sense B.V, Nijmegen, the Netherlands.
Pranamornkith et al., (2012) procedure was used for this purpose. Each sample was run for 20
minutes at a flow rate of 4.0 L per hour and the average reading of last 15 minutes recorded as
the endogenous ethylene from the fruit.
Determination or respiration rate: the rate of respiration of the fruits was estimated as the
production of CO2 using an infra-red gas analyser (Servomex Series 1400, Sussex, UK). The
fruits were incubated for one hour in an airtight glass jar which contained rubber septum.

BANANA FRUIT RIPENING 6
Changes in peel colour: A colour chart was used to determine the banana skin colour.
Measurement was recorded on every other day during the ripening process and was based on a
scale of 1 to 8, with 1 representing very green bananas and 8 being speckled and over-ripe fruits.
Results
Maximum temperature recorded= 230C
Minimum temperature recorded= 190C
Required temperature of the indoor ripening=20±10C
Mean Ethylene production (μmol C2H4 kg-1 h-1)
Treatments
(μlL-1)
Ripening period
Day 1 Day 2 Day 3 Day 4 Day 5 Day 6
0 0.04167 0.04467 0.04033 0.04333 0.04667 0.05300
10 0.06633 0.07433 0.09800 0.09433 0.09067 0.08333
50 0.09000 0.08667 0.10467 0.09633 0.08833 0.07800
100 0.09800 0.09667 0.11467 0.10667 0.09833 0.08200
Table 1: Mean ethylene production by the ripening bananas
Mean Respiration Rate CO2 mlkg-1.h-1
Treatments
(μlL-1)
Ripening period
Day 1 Day 2 Day 3 Day 4 Day 5 Day 6
0
32.5021
8 23.26143 27.08286 26.90082
25.7037
0
23.9724
1
10
74.8652
7 76.61659 110.77210 106.36714
96.7829
7
92.8272
6
50 77.3993 99.20366 109.92063 66.63398 80.6365 84.9040

BANANA FRUIT RIPENING 7
9 5 3
100
61.5889
5 110.19882 121.68880 117.47991
67.7077
4
87.7749
8
Table 2: Mean rate of respiration by the ripening bananas
Effects of ethylene treatments on changes in peel colour of banana fruit during
ripening
Treatment
s (μlL-1)
Ripening period
Day 1 Day 2 Day 3 Day 4 Day 5 Day 6
0 1.0 1.0 1.0 1.0 1.0 1.0
10 1.0 1.0 1.2 2.3 3.0 4.4
50 1.0 1.2 2.0 4.2 5.0 5.1
100 1.0 1.6 3.1 4.9 5.4 5.9
Table 3: Rating of the peel colour based on the colour chart
Discussion
Effects of ethylene treatments on changes in ethylene production in banana fruit during
ripening
From table 1 above the four treatments indicated a significance difference when it comes
to endogenous ethylene production. The non-treated batch, the control, produced a consistent
amount of ethylene gas throughout the ripening period. For the treated batches, the amount of
endogenous ethylene produced increased with increase in the exogenous ethylene, with the 100
μlL-1 producing the most amount. The difference between the batch treated with 10 μlL-1 and 50
μlL-1, is large as compared to the difference between that treated with 50 μlL-1 and 100 μlL-1.
This is well illustrated in figure 1 below. Contrary to the control which reported a linear increase

BANANA FRUIT RIPENING 8
in production throughout the 6-day ripening period, the ethylene from the treated samples
increases from day 1 to day 3 from which the amount reduces consistently.
0 1 2 3 4 5 6 7
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
Rate of Ethylene Production Aganist Ripening Period
0 μlL-
1
Polyn
omial
(0
μlL-1)
10
μlL-1
Polyn
omial
(10
μlL-1)
50
μlL-1
Ripening period (days)
Ethylene production (μmol kg-1 h-1)
Figure 1: Rate of ethylene production against the ripening period
The ripening process utilizes oxygen gas in the respiration process which breaks
down starch to sugars. Ethylene gas is of utmost importance as it initiates and determines the rate
of ripening. Carbon (iv) oxide is released in the process which slows down the ripening process.
It is for this reason why soda lime was added into the plastic containers to prevent CO2
accumulation. Ethylene gas which is produced as the fruit matures plays a very crucial role in the
ripening of fruits (Hailu, et al., 2012).
Effects of ethylene treatments on respiration rate in banana fruit during ripening
Form table 2, there is no defined pattern for the rate at which the fruits respire. This is
best illustrated in figure 2 below. The rate of respiration is least for the control experiment as
compared to the other trials. The batch treated with 100 μlL-1 recorded the highest rates of

BANANA FRUIT RIPENING 9
respiration. In all the trials, the rate of respiration is high for the first 3 days from which it
gradually decreases.
0 1 2 3 4 5 6 7
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0 Respiration Rate Against the Ripening Period
0
μ
l
L
-
1
Ripening period (days)
Respiration rate (CO2 mlkg-1.h-1)
Figure 2: Rate of respiration against the ripening period
Peel Colour
The study revealed that color is a very important parameter when it comes to banana
quality. It’s is one of the aspects that any buyer will consider before they make any purchase
decision. From table 3 above, the control experiment showed a consistent green colour
throughout the ripening period, that is, a 1-day banana indicated no colour difference with a day
6 banana. Colour improved with increase in the applied exogenous and endogenous ethylene.
Bananas treated with 100 μlL-1 appeared more yellow compared to the other batches. There was
a significant difference between the non-treated batch and the batch treated with 10 μlL-1, with
the non-treated illustrating a very green banana, the 10 μlL-1 portrayed a more yellow peel
colour.

BANANA FRUIT RIPENING 10
Treated bananas showed improve quality as far as colour is concerned. Colour
development is more uniform throughout the ripening period than is the case with the control.
This is attributed to the consistent diffusion/ production of endogenous ethylene from the fruits
(Lelievre et al, 1997). The colour of the banana peels has been related to changes in the pigments
contained within the skin of the banana. It has also been related quite well to the sugar content,
flavor development as well as a change in the textural properties of the pulp (Salvador, Sanz and
Fiszman, 2007).
Temperature
Banana ripening is done at a well-controlled temperature and relative humidity. Air
circulation is also required so as to vigorously disperse ethylene gas and facilitate the removal of
carbon dioxide and the heat produced as a result of respiration. Too high temperatures result in
increased rate of respiration and irregular ripening of the fruits which results in poor keeping
quality. Lower temperatures result in slow rates of ripening and may cause slight taste
degradation. Very low temperatures cause chilling injury. The experiment was designed to
operate at a temperature of 20 ±10C. From the TinyTag sensors, the temperature recorded shows
no significant difference from the recommended temperature.
A good place for ripening fruits should provide optimum conditions of 60-75% relative
humidity as well as the reduced temperature of about 16-220C which is optimum for banana
ripening. Therefore, any ripening room requirements are; adequate size to avoid damaging of
bananas through heaping and sufficiently ventilated to disperse carbon dioxide. Adequate
cooling to prevent cellular heat damage on bananas, room temperature control and humidity
control to prevent water loss from the banana peels (Mohapatra et al., 2010).

BANANA FRUIT RIPENING 11
Temperature influences the ripening rate of any climacteric fruit. An increase in
temperatures from 14-300C enhances the rate of ripening and softening of fruits. Respiration and
the rate of ethylene production also increase with an increase in temperature. High temperature
causes damage to ripe fruits while the low temperature of below 140 C will cause uneven
ripening as a result of the chilling injury (Horton 2012).
Conclusion
Ethylene gas which is produced as the fruit matures plays a very crucial role in the
ripening of fruits. Exposure of climacteric fruits to ethylene advances the onset of an irreversible
rise in respiration and rapid ripening. Exogenous ethylene plays a major role in fruit ripening as
well as in the production of the endogenous ethylene. Post-harvest losses occur from either
unripe or overripe fruits as it affects the rate at which bananas are accepted by the consumer.
There is, therefore, a need to improve and expand ripening methods and infrastructure to address
market needs, where fruits acquire the right eating quality.

BANANA FRUIT RIPENING 12
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