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Abstract

Fruits of a winter tomato (Lycopersicum esculentum L.) hybrid were harvested at mature green stage and a first lot was exposed to ethylene gas (100 ppm) for 24h in a ripening chamber at 20±1°C and the second lot was treated by immersion in a solution of ethephon {(2-chloroethyl) phosphonic acid} at 2 different concentrations (500 and1000 ppm) and for two different lengths of times (5 and 10 min). The fruits were air dried and placed in plastic crates followed by storage in a ripening chamber at 20±1°C and 90-95% RH. The colour, texture and flavour parameters of fruits from mature green to senescent stage of maturation were analyzed. The most striking effect of treatment was on colour development of fruits. It was found that treatment with ethylene gas (100 ppm) for 24h inside the ripening chamber or immersion in ethephon solution (500 ppm) resulted in better ripening of tomato fruits with uniform red colour, desirable firmness and acceptable quality as compared to other treatments. The length of time of the ethephon dip treatment did not reveal any significant effect on colour development. The fruits in the control showed very poor ripening and were hard in texture with poor quality attributes.
Effect of Ethephon and Ethylene Gas on Ripening and Quality of
Detached Winter Tomato
R.K. Dhall, B.V.C. Mahajan and A.S. Dhatt
Punjab Horticultural Post-Harvest Technology Centre
Punjab Agricultural University
Ludhiana-141 004
India
Keywords: ethephon, ethylene gas, quality, ripening, tomato
Abstract
Fruits of a winter tomato (Lycopersicum esculentum L.) hybrid were
harvested at mature green stage and a first lot was exposed to ethylene gas
(100 ppm) for 24h in a ripening chamber at 20±1°C and the second lot was treated
by immersion in a solution of ethephon {(2-chloroethyl) phosphonic acid} at 2
different concentrations (500 and1000 ppm) and for two different lengths of times (5
and 10 min). The fruits were air dried and placed in plastic crates followed by
storage in a ripening chamber at 20±1°C and 90-95% RH. The colour, texture and
flavour parameters of fruits from mature green to senescent stage of maturation
were analyzed. The most striking effect of treatment was on colour development of
fruits. It was found that treatment with ethylene gas (100 ppm) for 24h inside the
ripening chamber or immersion in ethephon solution (500 ppm) resulted in better
ripening of tomato fruits with uniform red colour, desirable firmness and acceptable
quality as compared to other treatments. The length of time of the ethephon dip
treatment did not reveal any significant effect on colour development. The fruits in
the control showed very poor ripening and were hard in texture with poor quality
attributes.
INTRODUCTION
The colour and quality of ripe tomatoes are important considerations to the
consumer and hence to the commercial grower. During the growth and development
period, there are many chemical and physical changes occurring in tomato that have an
impact on fruit quality and ripening behaviour after harvest. Tomato ripening is
characterized by loss of chlorophyll and rapid accumulation of carotenoids, particularly
lycopene, as chloroplasts are converted to chromoplasts (Khudairi, 1972). However,
ripening is a problem in tomato during the winter months (December-Mid February) due
to foggy weather and low temperature which does not allow tomatoes to mature on the
plant (Gonzalez, 1999). The low temperature also slows down the degradation of
chlorophyll and synthesis of lycopene (Koskitalo and Omroh, 1972). Such conditions
interfere with colour, texture and flavour development of the fruits. As a result, tomato
fruit fail to ripen and develop full colour and flavour, irregular (blotchy) colour
development, premature softening, surface pitting, browning of seeds and increased decay
(especially Black mold caused by Alternaria sp.). A ripening agent like calcium carbide is
often utilized in India to speed up the ripening process during winter months. As the use
of calcium carbide is prohibited in India due to health reasons (PFA, 2003), an alternative
of this chemical is required. In this direction, ethylene gas and ethephon chemical have
been found to accelerate the ripening of mature green tomato fruits and has already been
used commercially in other countries for uniform and early ripening of tomatoes
(Kasmire, 1981; Contwell, 1994; Gonzalez, 1999; Sargent, 2000). But in the Indian
context, there is need to standardize the method of ripening of winter tomatoes by use of
ethylene gas and by use of safe chemicals like ethephon so that uniform ripened tomato
can fetch remunerative prices in the domestic and export markets. Considering these
points, the present studies were undertaken.
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Proc. 6th International Postharvest Symposium
Eds.: M. Erkan and U. Aksoy
Acta Hort. 877, ISHS 2010
MATERIALS AND METHODS
Fully mature green tomato (Lycopersicum esculentum L.) was harvested in the
first week of February from the field of a progressive farmer of district Ludhiana
(Punjab). The bruised and diseased fruits were sorted out and healthy, uniform sized fruits
were selected for the present studies. Ten tomato fruits were randomly selected from the
lot of experimental fruits and their physico-chemical qualities were assessed before giving
the ripening treatments. Tomato fruits were divided into 2 lots. The first lot was exposed
to ethylene gas (100 ppm) inside the ripening chamber for 24h (20±1°C and 90-95% RH)
using portable ethylene gas generator (Model 9002, Ventech Agrionics, South Africa).
The second lot was treated by immersion in a solution of ethephon {(2-chloroethyl)
phosphonic acid} at 2 different concentrations (500 and 1000 ppm) and for two different
lengths of times (5 and 10 min). The fruits under control were dipped in tap water only.
The surface of fruits was air dried and were packed in plastic crates (20 kg each) and
stored at 20±1°C and 90-95% RH in a walk-in ripening room. The experiment was laid
out in completely randomized design, consisting of 3 replications for each treatment and
each replication comprised 2 kg fruits. The experimental data on ripening percentage,
physiological loss in weight (PLW), colour, firmness, total soluble solids (TSS), titratable
acidity and rotting percentage were recorded daily for 5 days starting from the 3rd day
after the treatment. The ripening percentage of the fruits was estimated by counting the
total number of ripened fruits on the basis of their appearance and desirable colour. The
physiological loss in weight (PLW) of the fruits was calculated as cumulative percent loss
in weight based on the initial fruit weight (before LT storage) and loss in weight recorded
at the time of periodical sampling during LT storage. The firmness of the fruit was
measured with the help of a Texture Analyzer (Model TA-HDi make, stable
Microsystems, UK) using compression platen (75 mm diameter) and expressed in gram
force. The total soluble solids (TSS) of the juice was determined with the help of an Erma
hand refractometer, and expressed in percent after making the temperature correction at
20°C. The titratable acidity was estimated as per AOAC (1990) procedures. The rotting
percentage of the fruits was estimated by counting the rotted fruits from the total number
of fruits and expressed in percent. For colour determination of each sample, the
reflectance spectra were measured at 2 different points on the fruit surface and then the
mean reflectance spectrum was obtained. These measurements were taken with a colour
difference meter (model: Mini Scan XE Plus, Hunter Lab, USA) and expressed as L, a
and b Hunter colour values (Hunter, 1975).
RESULTS AND DISCUSSION
The maximum average ripening percentage of tomato fruits (72.6%) was observed
with ethylene gas (100 ppm) and minimum in control (47.9%) irrespective of treatments
(Table 1). Similarly, irrespective of duration of days, the ripening was maximum (83.8%)
on the 7th day and minimum (46.6%) on the 3rd day of treatment. As regards to interaction
between treatments and ripening days, the highest ripening percentage (52.4%) was
observed with ethylene gas after the 3rd day which gradually increased up to the 7th day
(92.5%) followed by ethephon (1000 ppm for 5 min) where initially the ripening
percentage was 50.2% after 3 days, which increased to 87.8% on the 7th day. Sims (1969)
also observed that application of ethephon to green mature tomato not only accelerates
maturity but also results in more uniform ripening. However, the lowest ripening
percentage was recorded in control fruits, which ranged from 30.8 to 62.4% between 3
and 7 days. Better performance of ethylene in ripening of tomato may be due to the fact
that ethylene is undoubtedly considered as the most multifunctional plant hormone, which
triggers the respiration rate leading to dramatic changes during the ripening process,
ensuring faster and uniform ripening (Cantwell, 1994; Sargent, 2000)
There were significant differences among the various ripening treatments with
regard to physiological loss in weight (PLW) (Table 1), which, in general increased
during the ripening period and resulted in the highest mean PLW (6.5%) on the 7th day as
compared to the 3rd day (1.6%). On the other hand, the ethephon (1000 ppm for 10 min)
1026
treated fruits registered the highest mean PLW (5.3%) and the lowest was in the control
(2.6%). The interaction between treatments and ripening days revealed that the highest
PLW (1.2-6.9%) was observed with ethephon (500 ppm for 10 min) during the ripening
period of 7 days which was followed by 500 ppm for 5 min, 1000 ppm for 5 min,
1000 ppm for 10 min ethephon and ethylene gas (100 ppm). However, the lowest PLW
(0.8-4.1%) was in the control fruits during the 7 days of the ripening period. The
increased loss in weight during the ripening of tomato fruits by ethephon or ethylene
application may be due to an upsurge in respiration rate of fruit, leading to faster and
uniform ripening, which is a desirable trait for developing consumer acceptability and
fetching remunerative prices in the market. Similar observations were also reported by
Mahajan et al. (2008).
Fruit firmness in general followed a declining trend with the advancement in the
ripening period (Table 1). The highest mean fruit firmness was observed in the control
(952.4 g force) and the lowest (796.8 g force) in ethephon (1000 ppm for 10 min).
Similarly, the loss of firmness was more on the 7th day (752.9 g force) and less on the 3rd
day (935.5 g force). In fruits treated with ethylene gas (100 ppm), the loss of firmness was
minimum (942.2-774.7 g force) whereas the maximum (898.8-692.8 g force) was in
ethephon (1000 ppm for 10 min) fruits. The decrease in firmness during ripening may be
due cellular disintegration occurring as a result of an enhanced respiratory rate leading to
membrane permeability (Brinston et al. 1988).
The rotting of tomato fruits increased during storage, irrespective of the pre-
storage treatments (Table 1). The maximum spoilage was observed in fruits treated with
ethephon 1000 ppm for 10 min while it was minimum in case of the control fruits. The
ethylene gas or ethephon 500 ppm treated fruits recorded 6.0-8.5% of spoilage on the 7th
day and it was significantly less than ethephon (1000 ppm) and other treatments. The
rotting with the higher dose of ethephon is obvious due to the faster respiration rate
leading to oversoftening and spoilage of fruit (Bondad and Pantastico, 1972).
The highest mean total soluble solids (TSS) content (4.7%) was recorded with
ethylene gas (100 ppm) and ethephon (500 ppm for 5 min) treated fruits and the lowest in
the control (4.4%). Similarly the highest mean TSS (5.1%) was observed on the 7th day.
The fruits treated with ethylene gas (100 ppm) recorded the highest TSS content on the 7th
day (5.2%) where the control recorded the lowest (4.8%). The increase in TSS during
ripening may result from an increase in concentration of organic solutes as a consequence
of water loss (Ryall and Pentzer, 1982). Our results are in agreement with those reported
by CenturianYan et al. (1998) and Mahajan et al. (2008).
Titratable acidity of tomato showed a declining trend during ripening and was
found to be maximum (0.77%) on the 3rd day and minimum (0.34%) on the 7th day (Table
1). Titratable acidity (0.58%) was highest in the ethephon (500 ppm, 10 min) treated fruits
while the lowest acid component (0.50%) was in control fruits. The decrease in acidity
during ripening may be due to utilization of organic acid in the respiratory process
(Ulrich, 1974). The present studies confirm the results reported by CenturianYan et al.
(1998) and Mahajan et al. (2008).
Regarding fruit colour, there was consistent increase in redness value (a) and
decrease in yellowness value (b) of fruit pericarp with the advancement in the ripening
period for all the treatments except the control fruits. Shewfelt et al. (1987) also reported
similar ‘L a b’ colour change as tomatoes turn from green to red. In the control, the
greenness value (-a) decreases up to 4 days thereafter the redness value (+a) increased up
to 7 days. The redness value of control fruits was much lower than ethylene or ethephon
treated fruits as a result the control fruits were yellowish to pink due to non uniform
distribution of red colour. The similar trend in change of colour was reported by Paynter
and Jen (1976). They further also observed that tomato fruits exposed to ethylene gas
become uniformly red in colour with desirable softening, however, non-treated fruits
become uneven ripened, shriveled with dull appearance during ripening. Gonzalez (1994)
also noticed the uniform red colour of tomato fruits with postharvest application of
ethephon.
1027
In conclusion, it appears that ethephon and ethylene gas triggered fruit ripening
and advanced maturity and uniform maturation process, but did not have any marked
effect upon the quality parameters under consideration. The exposure of winter tomato to
ethylene gas (100 ppm) for 24h inside a ripening chamber or dipping in ethephon solution
(500 ppm) followed by storage at 20±1°C and 90-95% RH ensures faster and uniform
ripening and enhanced the consumer acceptability of fruits. The effect on fruit ripening
was indicated by an enhanced climacteric peak, increased skin colour, increased total
soluble solids and decreased flesh firmness and titratable acidity.
Literature Cited
AOAC. 1990. Official methods of analysis. 12th ed. Association of Official Analytical
Chemists, Washington DC.
Bondad, N.D. and Pantastico, E.B. 1972. Ethrel induced ripening of immature and mature
green tomato fruits. Econ. Bot. 26:238-240.
Brinston, K., Dey, P.M., John, M.A. and Pridhan, J.B. 1988. Postharvest changes in
mangifera indica (mesocarp walls and cytoplasmic polysaccharides). Phytochem.
27:719-725.
CenturianYan, A.R., Gonzalec Novelo, S.A., Tamayo Cortes, J.A., Argumedo, J.J. and
Sauri Duch. 1998. The effect of ethephon on the colour, composition and quality of
mango (Mangifera indica cv. Kent). Food Sci. Tech. International 4:199-205.
Cantwell, M. 1994. Optimum procedures for ripening tomatoes. Perishable Handling
Newsletter 80:24-26. University of California, Davis.
Gonzalez, S.A. 1999. Use of ethylene (ethephon) in uniform ripening of processing
(Lycopersicon esculentum) tomato in California. Acta Hort. 487:179-182.
Hunter, S. 1975. The measurement of appearance. John Wiley and Sons. New York.
p.304-305.
Kasmire, R.F. 1981. Continuous flow ethylene gassing of tomatoes. In: California
Tomatorama. Fresh Market Tomato Advisory Board Information Bulletin No 29.
Khudairi, A.K. 1972. The ripening of tomatoes. Amer. Sci. 60:696.
Koskitalo, D.N. and Omroh, D.P. 1972. Effects of sub-optimal ripening temperatures on
the colour quality and pigment composition of tomato. J. Food Sci. 37:56-59.
Mahajan, B.V.C., Singh, G. and Dhatt, A.S. 2008. Studies on ripening behaviour and
quality of winter guava with ethylene gas and ethephon treatments. J. Food Sci.
Technol. 45:81-84.
Paynter, V.A. and Jen, J.J. 1976. Comparative effects of light and ethephon on the
ripening of detached tomatoes. J. Food Sci. 41:1366-1369.
PFA. 2003. Prevention of Food Adulteration Act 1954 Rules, 1955. 19th ed. International
Law Book Co, Delhi, p.140-141.
Ryall, A.L. and Pentzer, W.T. 1982. Handling, transportation and storage of fruits and
vegetables, vol 2, AVI Publ Co, West Post, Connecticut, p.1-40.
Sargent, S. 2000. Ripening Tomatoes with Ethylene. VC-29, one of a series of the
Department of Horticultural Sciences, Florida Cooperative Extension Services,
Institute of Food & Agricultural Sciences, University of Florida.
http://edis.ifas.ufl.edu.
Shewfelt, R.L. 1987. Quality of minimally processed fruits and vegetables. J. Food Qual.
10:143.
Sims, W.L. 1969. Effect of ethrel on fruit ripening in tomatoes. California Agriculture
23:12.
Ulrich, R. 1974. Organic acids. p.89-115. In: A.C. Hulme (ed.), Biochemistry of fruits
and their products. Vol I. Academic Press, London.
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Tables
Table 1. Effect of ethylene gas and ethephon treatments on Physico-chemical properties of tomato during storage (20±1°C & 90-95%
RH).
3D 4D 5D 6D 7D Mean 3D 4D 5D 6D 7D Mean
Treatment Ripening (%) Physiological loss in weight (%)
Ethylene gas, 100 ppm 52.4 65.8 72.4 80.1 92.5 72.6 1.3 2.7 4.2 5.4 6.1 3.9
Ethephon, 500 ppm, 5 min 46.9 55.4 65.8 72.8 85.8 65.3 1.5 2.9 4.9 5.8 6.8 4.4
Ethephon, 500 ppm, 10 min 49.2 56.8 68.4 75.2 86.1 67.1 1.2 2.5 4.2 6.0 6.9 4.2
Ethephon, 1000 ppm, 5 min 50.2 59.6 69.9 76.4 87.8 68.8 2.2 4.2 5.5 6.2 7.4 5.1
Ethephon, 1000 ppm, 10 min 50.0 60.2 70.1 76.8 88.2 69.1 2.4 4.3 5.8 6.4 7.5 5.3
Control 30.8 38.9 50.4 56.8 62.4 47.9 0.8 1.9 2.5 3.6 4.1 2.6
Mean 46.6 56.1 66.2 73.0 83.8 1.6 3.1 4.5 5.6 6.5
Firmness (g) Rotting (%)
Ethylene gas, 100 ppm 942.2 902.4 854.6 802.8 774.7 855.3 - - 2.0 3.8 6.0 2.4
Ethephon, 500 ppm, 5 min 910.4 875.5 820.9 788.8 734.7 826.1 - 1.0 3.2 5.0 8.0 3.2
Ethephon, 500 ppm, 10 min 922.6 880.6 835.1 798.2 753.0 837.9 - 1.2 3.8 5.6 8.5 3.8
Ethephon, 1000 ppm, 5 min 901.6 864.4 804.8 752.4 700.2 804.7 1.0 3.2 5.4 8.2 10.1 5.8
Ethephon, 1000 ppm, 10 min 898.8 850.5 800.2 741.7 692.8 796.8 1.2 3.8 5.8 8.8 12.0 6.3
Control 1037.2 1008.4 952.3 901.8 862.4 952.4 - - 1.8 3.4 5.6 2.2
Mean 935.5 897.0 844.7 797.6 752.9 0.4 1.5 3.7 5.8 8.4
TSS (%) Titratable acidity (%)
Ethylene gas, 100 ppm 4.0 4.3 4.8 5.0 5.2 4.7 0.80 0.68 0.56 0.42 0.32 0.56
Ethephon, 500 ppm, 5 min 3.9 4.3 4.9 5.1 5.1 4.7 0.76 0.67 0.54 0.40 0.35 0.54
Ethephon, 500 ppm, 10 min 4.0 4.4 4.7 5.0 5.1 4.6 0.80 0.70 0.58 0.44 0.38 0.58
Ethephon, 1000 ppm, 5 min 3.9 4.4 4.8 5.0 5.1 4.6 0.76 0.68 0.54 0.41 0.34 0.55
Ethephon, 1000 ppm, 10 min 3.9 4.3 4.7 4.9 5.0 4.6 0.78 0.70 0.56 0.44 0.36 0.57
Control 3.8 4.2 4.5 4.8 4.8 4.4 0.74 0.62 0.50 0.38 0.26 0.50
Mean 3.9 4.3 4.7 5.0 5.1 0.77 0.68 0.55 0.42 0.34
1029
1029
1030
Table 2. Effect of ethylene gas and ethephon treatments on colour of tomato during ripening.
3 days 4 days 5 days 6 days 7 days
Treatment L a b L a b L a b L a b L a b
Ethylene gas,
100 ppm 51.85 2.66 22.41 48.76 6.45 20.75 44.05 13.11 19.03 40.52 14.01 17.42 39.24 16.92 13.42
Ethephon,
500 ppm, 5 min 52.62 2.62 22.63 49.24 5.99 20.05 40.73 12.82 18.29 39.25 13.26 14.87 34.65 14.69 12.40
Ethephon,
500 ppm, 10 min 50.08 2.42 21.82 48.34 5.92 20.42 46.53 11.72 19.08 42.44 12.80 15.42 40.01 13.90 13.02
Ethephon,
1000 ppm, 5 min 51.44 2.75 23.82 49.08 6.64 21.05 43.88 12.92 20.45 40.08 14.08 18.90 38.24 15.05 16.87
Ethephon,
1000 ppm, 10 min 54.08 2.62 24.10 50.01 5.92 22.26 45.20 12.44 20.26 44.26 13.68 19.35 41.52 15.10 15.08
Control 50.01 -5.21 16.63 50.08 -2.64 20.82 49.97 0.35 20.05 51.95 2.93 22.60 53.13 4.20 23.74
1030
... Ethylene promotes the ripening process and improves colour development of the fruits. Dhall et al. (2001) reported that ethephon solution (500 ppm) resulted in better ripening of tomato fruits with uniform red colour, desirable firmness and acceptable quality as compared to 1000 ppm. At present ethrel is being utilized for ripening of mature or immature tomato indiscriminately without using optimum doses. ...
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