As shown in Table 4 control fruit had higher hue angle and significantly different from fruit treated with CPPU 0 ppm + CoSO
4
2000 ppm, CPPU 20 ppm + CoSO
4
2000 ppm, and CPPU 30 ppm + CoSO
4
2000 ppm at day 22. Hue angle of fruit treated with CPPU 0 ppm + CoSO
4
1000 ppm was significantly higher from the combination of CPPU 30 ppm + CoSO
4
2000 ppm, and control fruit at day 26.
Table 4. Effects of CPPU and CoSO
4
interaction on hue angle of sepal of mangosteen fruit during storage at day 22 and 26
Day CPPU ppm
CoSO
4
ppm 500
1000 2000
22 75.13
a
73.03
abc
74.81
ab
69.90
d
10 71.88
bcd
73.20
abc
73.20
abc
73.53
abc
20 71.52
bc
73.66
abc
72.80
abc
70.99
cd
30 73.91
abc
73.24
abc
71.56
cd
71.51
cd
26 71.33
bc
72.94
abc
75.01
a
70.43
cd
10 70.22
cd
72.56
abc
72.80
abc
71.54
cd
20 70.83
cd
73.18
abc
70.96
bc
70.32
cd
30 73.18
abc
73.69
ab
72.17
abc
67.64
d
Note: Different letters indicate significant differences among treatment means P 0.05
by Duncan‟s multiple range test DMRT.
4.1.6. Visual Observation
Visual appearance of the fruit is very important factor which strongly affect consumers‟ acceptance whether to buy the product or not. In general, mangosteen
fruit sepal turns brown soon after a few days of storage in ambient air, but the sepal freshness can be maintained longer when stored in cold storage at 15
o
C, and proper postharvest treatment. In this experiment, mangosteen fruit sepal was very
green and fresh during initial days of storage. However, some parts of sepal turned brown as from storage day14 and the brown part had gradually spreaded on to the
whole part of the sepal from day 18. Visual effects of the treatment on the fruit was almost the same with control fruit, but CPPU 30 ppm was likely to maintain
better greenness of the sepal Appendix 19. This was an indicator that manogsteen fruit were less marketable as from day 18.
The color of mangosteen fruit was reddish pink stage 3 at the start of storage, and changed to reddish purple stage 4 after 2 days of storage. The color
of mangosteen fruit was not developed into black purple as stored in room 30
temperature. Instead, brown spots on fruit skin were observed at storage day 8 and the spots were gradually enlarged up to the end of storage Appendix 19.
4.2. Chemical Changes of Mangosteen Fruit
4.2.1. Total Soluble Solids TSS
Total soluble solids of the fruit are considered one of the basic criteria for quality evaluation. Total soluble solids of mangosteen fruit during storage
decreased linearly over storage time Figure 18, 19. CoSO
4
did not affect TSS at all observed days Appendix table 14. At day 12 response of CPPU 30 ppm was
the same with control, but significantly different from CPPU 10 ppm and CPPU 20 ppm. CPPU 30, 10 and 0 ppm gave the same response, and statistical different
from CPPU 20 ppm at day 16. The reduction of total soluble solids was around 4- 5 in all treatments at the end of storage Appendix table 14. According to
Palapol et al. 2009, TSS of mangosteen harvested at stage 1 was around 15 and linearly increased to 17 at stage 5 and 6 during storage at 25
o
C. The findings revealed that mangosteen fruit underwent fast physiological changes
under room temperature. However, those changes become very slow when fruit were stored at 15
o
C as indicated in our results. Generally, TSS increases during ripening process and tends to decrease during prolonged storage which was
caused by the breakdown of simple sugar content into alcohol, aldehide, and amino acids Winarno and Aman, 1981. As reported in litchi fruit, concentrations
of ascorbic acid, phenols, sugars and organic acids decrease during storage Holcroft and Mitcham, 1996; Chen et al., 2001.
