IJERD – International Journal of Environmental and Rural Development (2015) 6-2

Research article
erd

Effect of Nitrous Oxide on Physiological and Biochemical
Changes during Fruit Drop of Longkong Postharvest
INTIRA LICHANPORN*
Faculty of Agricultural Technology, Rajamangala University of Technology Thanyaburi,
Phathum Thani, Thailand
Email: lintira@yahoo.com

NUNCHANOK NANTHACHAI
Faculty of Agricultural Technology, Rajamangala University of Technology Thanyaburi,
Phathum Thani, Thailand

PALIDA TANGANURAT
Faculty of Agricultural Technology, Rajamangala University of Technology Thanyaburi,
Phathum Thani, Thailand

UNCHALIN SINGKHUM
Faculty of Agricultural Technology, Rajamangala University of Technology Thanyaburi,
Phathum Thani, Thailand
Received 23 February 2015

Accepted 1 April 2015(*Corresponding Author)

Abstract Longkong (Aglaia dookkoo Griff) is a popular tropical fruit which currently has
about 99.37% consumer demand. In the case of exporting, the main problem is that
longkong fruit drops from its bunch after harvesting. Therefore, the objective of thisresearch is to study the effect of nitrous oxide on physiological and biochemical changes
during fruit drop of longkong postharvest. The addition of 90% nitrous oxide (at times 1, 3,6, 12 and 24 h) induced the reduction of loosening of longkong fruit after harvest. Exposure
to nitrous oxide delayed the onset of fruit drop of the longkong bunches with the mosteffective treatment being fumigation with 90% nitrous oxide for 6 h. Longkong fruit
exposed to 90% nitrous oxide for 24 h, showed an increased respiration rate and ethyleneproduction. While Longkong fruit exposed to 90% nitrous oxide, there was no significant
effect on the activity of enzymes polygalacturonase (PG), pectinesterase (PE), cellulase(Cx) and peroxidase (POD) during storage.
Keywords longkong, fruit drop, nitrous oxide

INTRODUCTION
Longkong (Aglaia dookkoo Griff.) is a subtropical fruit which can be grown in various parts ofThailand. The quality deterioration of longkong leads to consumer rejection that makes the productcannot be sold. Besides, there is a loss of economic value for both producers and consumers.
Senescence of longkong can be seen as browning, disease, and fruit drop, which is a criticalproblem that results in a lower sales price. The study of morphology shows change in abscission
zone (AZ) area which has cell wall degradation in the middle lamella (Oberholster et al., 1991;
Sexton et al., 1983) as well as microfibril expansion and disorganization in the primary cell wall in
the AZ (Sexton and Robert, 1982). Enzymes associated with degradation of the cell wall are pectin
esterase (PE), endo-polygalacturonidase (PG), exopolygalacturonase, rhamnogalacturonase, ∞galactosidase and cellulase (Downs et al., 1992). In grapes, the stem of the fruit becomes detachedfrom the fruit in the area which gradually extends from the sides of the phloem until the middle ofthe tissue and causes fruit drop. The fruit drop of grapes is related to an increase of the cellulose
enzymes hydrolases and polygalacturanase in AZ (Deng et al., 2007). Nitrous oxide (N2O) is anatural occurrence of atmospheric gas principally produced by aerobic denitrifying bacteria in soil,
which has been demonstrated to inhibit ethylene action and synthesis in higher plants (Frontiera etⒸ ISERD

6IJERD – International Journal of Environmental and Rural Development (2015) 6-2al., 1994; Gouble et al., 1995; Leshem and Wills, 1998). N2O, like CO2, has an isosteric linear
structure that confers similar physical properties such as relative stability and high solubility toboth molecules (Leshem and Wills, 1998; Benkeblia and Varoquaux, 2003). This biophysicalsimilarity of N2O to CO2 might be pertinent to the control of ethylene in the controlled atmospherestorage of postharvest climacteric fruit (Leshem andWills, 1998). In addition, N2O is not toxic. It is
used in medical practice as an anaesthetic (Gouble et al., 1995), and it is a permitted additive forfood (Benkeblia and Varoquaux, 2003). Other studies report the inhibition of postharvest decay offruit by N2O, which have also been carried out in the non-climacteric strawberry and mandarin, andin the climacteric fruit apple, persimmon and tomato (Qadir and Hashinaga, 2001). Therefore, inthis study, we determined the effects of N2O gas on the reduction of fruit drop of longkong afterharvest.
OBJECTIVES
The objective of this study was to determine effects of N2O gas on the reduction of fruit drop oflongkong after harvest.
METHODOLOGY
Freshly harvested bunches of longkong with full yellow fruits were procured from a commercialorchard. Each bunch longkong was separated into individual bunches, which were placed intosealed plastic chambers with 90% N2O with 20% O2 for 0, 1, 3, 6, 12 or 24 hours at 20qC. After
treatment, the fruits were stored at 13qC with 90+5% relative humidity. The treatments werereplicated three times with 25 fruit bunches per replication. Standard procedures were followed inmeasuring fruit drop, weight loss, respiration rate (Gemma et al., 1994), ethylene production(Gemma et al., 1994), PG (Lohani et al., 2004; Pathak and Sanwal, 1998), PME (Abu-Goukh andBashir, 2003; Nagel and Patterson, 1967), Cx and POD activities (Lohani et al., 2004).
RESULTS AND DISCUSSIONLongkong fruit was fumigated with 90% nitrous oxide (N2O) for 0, 3, 6, 12 and 24 hours followed
by storage at 13 qC. The result showed that the longkong fumigated with 90% N2O for 0, 6 and 24hours delayed the fruit drop for 6 days. At hour 6, the fruit drop of longkong was 11.69%, whereas
longkong fumigated with 90% N2O for 12 hours had the highest occurrence of fruit drop with84.21% on day 12 of storage (Fig. 1A). Weight loss of longkong fumigated with N2O increased
over the duration of storage, which averaged 4% weight loss (Fig. 1B).
There was no statistical comparison of the relative effect of weight loss and nitrous oxide
because the low temperature storage delayed the weight loss and reduced deterioration of thelongkong.The respiration rate of longkong fumigated and non-fumigated with N2O slowly
increased during storage time, the control fruit had a lower respiration rate than the longkong
fumigated with N2O, especially with fumigation for 24 hours which had the highest rate ofrespiration in day 12 of storage (76.77 mL CO2.kg-1.h-1 ) (Fig. 2C).
Fruit fumigated with N2O for long time may result in an increase in respiration and ethylene
production rates (Oszmianski et al., 1985: Macheix et al., 1990). Ethylene production of longkong
fumigated with N2O for 24 hours rapidly increased more than that of other fumigations on day 3
and day 6 of storage. However, longkong fumigated with N2O less than 3 hours had lower theethylene production on day 3. It is possible that N2O may delay deterioration through twomechanical formulas (Gouble et al, 1995; Bemish et al, 1996). In the first form, N2O bonded withethylene. In the second form, N2O inhibited ACC Oxidase (ACO) and synthesis ACC synthase(ACS) with N2O and CO2, which both forms had similar functions. However, the effect of N2O andCO2 maintained the quality of strawberry (Qadir et al., 2000). If N2O bonded with ethylene, thenethylene could not bond with itself. It was resulting in delay of the senescence for a short time,Ⓒ ISERD7

IJERD – International Journal of Environmental and Rural Development (2015) 6-2

which ripening or senescence occurred. At day 12, there was no significant difference for theethylene production in all treatments (Fig. 2D).
Research in other fruit species indicates that hydrolytic enzymes, including endo-beta-1, 4glucanase (cellulose), polygalacturonase (PG), pectinmethylesterase (PME), play a significant rolein the abscission stage by affecting middle lamella dissolution and cell-wall degradation andstimulating with exogenous ethylene (Tucker et al., 1984; Taylor et al., 2001), as well as with highactivity when there was fruit drop such as with grapes (Deng et al., 2007). As a result, pectin
methylesterase (PME) activity in the first day was equal to 0.040 unit/mg protein, after that theactivity decreased in the longkong fumigated with N2O for 3 hours on day 3 and 6 of the storage.
Subsequently, activity of enzymes increased at first and then decreased in the end of storage, while
longkong fumigated with N2O for 12 and 24 hours maintained the activity of PME during storage(Fig. 2E). Polygalacturonase activity increased after storage until day 6 and reduced over thestorage. Longkong fumigated with N2O for 6 and 12 hours had lower polygalacturonase activity
than the control fruit on 3 day of storage. (Fig. 2F). Cellulase activities increased until themaximum on day 6 and then reduced after that. On day 3, Longkong fumigated with N 2O for eachtime period had higher cellulase activity than the control fruit (Fig. 2G). Peroxidase enzymes
activities of fumigation and control fruit showed no statistical difference in the peroxidase activity
on 3 days of storage, reduced the activity on day 6, and increased on day 9 of storage. Longkong
fumigated with N2O for 3 and 6 hours had the peroxidase enzyme activity equal to 0.280 and 0.353
unit/mg protein, while longkong fumigated with N2O for 0, 1, 12 and 24 hours had the activity
equal to 0.570, 0.507, 0.570 and 0.597 unit/mg protein, respectively (Fig. 2H).

Fruit drop (%)

100
80

90% N2 O, 0 hr.
90% N2 O, 1 hr.
90% N2 O, 3 hr.
90% N2 O, 6 hr.
90% N2 O, 12 hr.
90% N2 O, 24 hr.

A60402000Weight loss (%)

10836912

Days after storage

90% N2 O, 0 hr.
90% N2 O, 1 hr.
90% N2 O, 3 hr.
90% N2 O, 6 hr.
90% N2 O, 12 hr.
90% N2 O, 24 hr.

B

64
200

36912

Days after storage

Fig. 1 Change in fruit drop (A), weight loss (B) in abscission zone of longkong exposed to
90% nitrous oxide for 0, 1, 3, 6, 12 or 24 h and then stored at 13 qCⒸ ISERD

8IJERD – International Journal of Environmental and Rural Development (2015) 6-2Fig. 2 Change in respiration rate (C), ethylene production (D), pectin methylesterase (E),polygalacturonase (F), peroxidase (G), cellulose (H) in abscission zone of longkong
exposed to 90% nitrous oxide for 0, 1, 3, 6, 12 or 24 h and then stored at 13 qC
CONCLUSION
Longkong fumigated with 90% N2O for 6 hours, delayed the fruit drop but showed no effect on
activities of PG, PME, Cx and POD during storage.

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IJERD – International Journal of Environmental and Rural Development (2015) 6-2

ACKNOWLEDGEMENTS
This work was supported by Faculty of Agricultural Technology, Rajamangala University ofTechnology Thanyaburi (RMUTT) and Thailand Toray Science Foundation (TTSF).
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