I. INTRODUCTION 1.1
Background
Indonesia is one of the major mangosteen producers in Southeast Asia. The production of mangosteen in 2007 was 112,722 ton with average yield of 9.42
tonha. Indonesia exports fresh mangosteen to China including Hong Kong and Taiwan, Japan, Singapore, the Netherlands, France and Saudi Arabia Osman and
Milan, 2006. The volume of export was 9,093,245 kg in 2007 and increased to 9,465,665 kg in 2008, which valued at USD 4,951,442 and USD 5,832,534 in
2007 and 2008, respectively Ditjen Hortikulura, 2009. Indonesian mangosteen export is only 8.06 from the total production 112,722 ton in 2007. Many issues
are involved in low fruit quality and have resulted in a barrier for exports and low export value, namely i gamboge, a physiological disorder evident by exudating
latex onto the fruit surface and aril rendering the fruit unsuitable for eating, ii brown spot burik on the fruit skin, and iii short shelf life of mangosteen fruits
pericarp hardening, color changes to dark blackish purple, and fruit calyx turns brown within a few day.
Generally, the fruit will soften within a few days after harvested. On the contrary, mangosteen fruit hardens and causes difficulty in opening after
prolonged storage. Mechanical injury of fruit during storage and handling of mangosteen often causes fruit hardening Kader, 2003. A drop of 10 cm can
cause slight pericarp damage, indicated as hardening at the point of impact within 24 h. Higher drops cause significantly greater damage and often lead to
downgrading of the fruit Tongdee and Suwanagul, 1989; Ketsa and Atantee, 1998.
Azhar 2007 reported that optimal temperature for endurance of skin color and calyx was 10
o
C, and temperature storage less than 10 °C 50
o
F leads to rapid hardening and darkening of pericarp when fruit are returned to ambient
temperature Uthairatanakij and Ketsa, 1995. Storage at 4 °C 39.2 °F or 8 °C 46.4 °F can lead to significant hardening of the pericarp Augustin and Azudin,
1986, although the flesh may still be acceptable after 44 days. However, storage of mangosteen fruit at temperature above 15
o
C can also cause hardening and result in opening difficulty. Anggraini 2008 found that chitosan coating
treatment was more effective to inhibit pericarp hardening, and shelf-life of mangosteen fruit could be kept as long as 20 days after treatment Ekaputri,
2009. Changes of fruit color are one of maturity parameter. Inayati 2009 found that fruits coated with wax, chitosan and coconut oil suspension could inhibit fruit
hardening from 14 days to 20 days. In climacteric fruits, ethylene production at the onset of ripening controls
the changes of color, aroma, texture, flavour, and other biochemical and physical attributes Lelievre et al., 1997. Since mangosteen fruit is climacteric fruit
Qanitah, 2004, postharvest quality changes may be related to climacteric respiration and ethylene production. Co
2+
is a potent inhibitor of ethylene biosynthesis. Application of cobalt sulphate is expected to change the climacteric
respiration of mangosteen during storage. Williams and Golden 2002 found that the enzyme ACC was inhibited by Cobalt sulphate CoSO
4
. Forchlorfenuron CPPU is a type of synthetic cytokinins, which is responsible for the maintenance
of chlorophyll, protein, and RNA levels. Although CPPU has been found to be effective in improving postharvest quality of many fruits when applied at
preharvest, its direct postharvest application has not yet been reported. Therefore, research on postharvest application of CPPU and CoSO
4
needs to be conducted.
1.2 Research Objective
The objective of the research was to study the effects of CPPU and CoSO
4
on postharvest quality and physiological changes of mangosteen fruit during storage.
1.3 Research Hypotheses
1. Ethylene production can be decreased by application of CoSO
4
because CoSO
4
can inhibit ethylene biosynthesis. This has resulted in better shelf- life of mangosteen fruit.
2. Application of CPPU can delay changes of sepal color because it can delay chlorophyll degradation.
3. Combination of CPPU and CoSO
4
can extend shelf-life of mangosteen fruit longer than individual application.
II. LITERATURE REVIEW
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