Ethylene treatment to non-climacteric fruit

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Degreening of Acid Lime
Article ID: 32593
Pooja Yaddanapudi1
1
Ph. D. Scholar, Department of Fruit Science.
Introduction
Consumers prefer bright coloured Acid lime fruit and are willing to pay a premium for them. Green coloured
fruits are considered unripe and fetch lower prices. Hence the colour of the rind is important for the aesthetic
value and as such it is the most important factor determining marketability (Ron, 2008). The external colour of
the citrus fruit is not a reliable index of the internal maturity, but it does indicate maturity to certain extent
when colour develops under normal conditions in the field. Despite citrus being a non-climacteric fruit, some
aspects of its ripening could be still sensitive to external exposure to ethylene. (Sdiri et al, 2012). In citrus
internal edible portion of the fruit (pulp) usually reaches maturity while the external peel is still green, therefore,
degreening practices were developed to accelerate fruit colour change and render the fruit more acceptable
for marketing (Ron, 2008).
Degreening of Citrus Fruits
1. Degreening is the process of degradation of chlorophyll by ethylene, where luxuriant growing conditions
cause chlorophyll to persist or reappear in the rinds of mature fruit. The degreening process is carried out in
special rooms designed to treat the fruit with air containing a low concentration of ethylene at controlled
temperature and humidity.
2. The development of chloroplast and chromoplast is influenced by endogenous growth regulators. Ethylene
causes loss of chlorophyll and produces the minor changes in carotenoids (Griersonand Newhall 1960).
3. The practice of postharvest degreening of green, mature and edible citrus fruit has developed in order to
promote external colour development, i.e., destruction of green chlorophyll pigments and accumulation of
orange/yellow carotenoid pigments. The degreening process is complicated, since it depends on various
endogenous and exogenous factors, such as fruit maturity at harvest and sensitivity of the fruit to ethylene, and
is influenced by ethylene concentrations and the duration of degreening process, temperature and relative
humidity used, efficiency of air circulation and ventilation (Ron, 2008).
4. Ethylene do not ripe the immature fruits completely in terms of skin and flesh colour development. It was
found that the ethylene has threshold level between 5-15ppm, optimum degreening temperature of 25°C,
relative humidity of above 80% which favours both chlorophyll destruction and carotenoid accumulation, (Ron,
2008).
Effect of Post-Harvest Degreening on Quality Parameters of Acid Lime
1. Physiological loss in weight (%): Physiological weight loss is a continuous phenomenon during storage due
to moisture loss. Moisture loss through respiration and transpiration during storage affects the salable weight
and eventually the fruit becomes unsalable as a result of shrinking. Ladaniya and Singh (2001) reported that, no
difference due to ethylene treatment but cumulative weight loss was higher in non-degreened fruits.
2. DA (IAD) meter Reading: DA meter measures the chlorophyll content in a fruit and, as a consequence, its
state of ripeness. DA reading showed significantly decreased as the ripening advanced during storage at
ambient conditions. The decreasing trend in DA reading with the advancement of ripening may be attributed
to the reason that, chlorophyll concentration reduced substantially, while carotenoids concentration increased
(Medlicott et al., 1990).

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3. Hedonic score: Degreening advanced, hedonic score increased progressively at ambient conditions.
Degreening of citrus fruits continued after removing from degreening chamber and resulted in elimination of
original treatment differences. It has been reported that once the colour development started with ethylene, it
remains unaffected by the break in ethylene supply (Ladaniya and Singh 2001).
4. Peel thickness (mm): The storage days increased there was a decreasing trend in peel thickness of citrus
(Asutosh et al, 2016). Because the pulp mass of fruit increases during ripening due to an increase in water
content, it could be due to the movement of water from peel to pulp and to the surrounding air (Ahmad et al,
2001).
5. O2 and CO2 (%): Degreening advanced, O2 progressively decreased at ambient conditions. The trend of
decreasing % of O2 with increasing degreening was observed by Ladaniya (2001) in Sweet Orange. Stimulation
of respiration by ethylene was dose-dependent. Treatment with ethylene induces an increase in respiration
similar to respiratory climacteric in banana. The rise in CO2 production is immediate and related to the time
duration of ethylene treatment (Dominguez and Vendrell 1994).
6. Fruit firmness (kg/cm2): Firmness of lime fruits was reduced with an increased storage. Ethylene encourages
the fruit ripening can progress into physiological development and the flesh and fruit can become soft (Hayat
et al, 2017).
7. TSS (Brix°): TSS of lime fruits were increased progressively with an increase in storage period. It may be due
to continues process of respiration and transpiration have resulted in weight loss and conversion of starch to
sugars by the activity of hydrolytic enzymes (Hayat et al, 2017).
8. Titrable Acidity (%): As the storage days increased there was a decreasing trend in titrable acidity of citrus.
This can be attributed due to the conversion of organic acids into soluble sugars and long chain polysaccharides
may also lead to decrease in acid content (Dhillon and Mahajan, 2011).
9. Content of Vitamin C: Vitamin C content was decreased with an increase in storage time. Degreening process
promotes the conversion of acids to sugars leads to decrease in the ascorbic acid content. With the
advancement of storage period, total soluble solids were increased while ascorbic acid and acidity of fruits
decreased in Kagzi lime (Piyush and Dashora 2000).
10. Juice recovery (%): Juice recovery was decreased with the prolongation of storage period. This decrease
might be due to the utilization of available organic acids at faster rate in respiration during ripening (Hayat et
al, 2017).
11. Shelf life: Shelf life was diminished with the prolongation of storage at ambient temperatures and decreased
with increased in ethylene dose. Sweet orange optimum response of degreening was recommended at 5-10ppm
ethylene concentrations, although higher concentrations (100-250) of ethylene treatments increased the rate
of post-harvest degreening decay losses (Ladaniya and Shyam 2001).
Conclusion
Finally, to conclude, degreening promote the colour development, increseses the rate of respiration, fruit
firmness, TSS and juice recovery. Degreening decreases the Titrable acidity. Degreening has no effect on
recovery of vitamin C. Shelf life is completely dose dependant. degreening of Acid lime through 15 ppm ethylene
with 4 pulsings in 24 hours @ 6 hrs. interval or 15 ppm ethylene with 2 pulsings in 24 hours @ 12 hrs. interval
can be recommended for Acid lime for uniform degreening and storage at ambient conditions.
Reference
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3. Dhillon WS. and Mahajan BVC., (2011). Ethylene and ethephon induced fruit ripening in Pear. A review Journal of Stored Products and
Postharvest Research. 2(3): 45-51.

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