including hue angle values, firmness, soluble solids content SSC and titratable acid TA, when the fruit were accessed at stage 6 Palapol et al., 2009.
Calyx freshness of mangosteen fruit strongly affects quality value during periods of storage. Fresh mangosteen fruit has green and fresh calyx, but the
freshness becomes brown after a few days. Research conducted by Suryanti et al. 1999 showed that mangosteen fruit harvested at green and fresh peel with purple
spots and calyx freshness could maintain its freshness for 6 days of storage. Optimum temperature for retention of peel and calyx color is 10
o
C Azhar, 2007. Ekaputri 2009 found that treatment of chitosan 1.5 could retain color of
mangosteen peel and calyx. Beeswax 6 treatment and BAP 20 ppm could retain calyx color for 21 days after treatment, but it started wrinkling after 15 days of
treatment Pratiwi, 2008. Anggraeni 2008 reported that combination of 0.01 mm- thick plastic wrapping and chitosan coating 1.5, and plastic wrapping with
wax Britex gave a better effect on inhibiting changes of peel and calyx color for 30 days of storage at room temperature, and 35 days at temperature 15
o
C.
2.3 Causes of Mangosteen Fruit Hardening
Generally the fruit will soften during a few days after harvested, but mangosteen fruit become harden that causes difficulty in opening fruits for
consumption. 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.
Storage temperature 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 skin Augustin and Azudin, 1986, although
the flesh may still be acceptable after 44 days. Ideal storage temperature for mangosteen is 15
o
C. Temperature above 15
o
C mangosteen fruit hardens and results in opening difficulties.
Anggraini 2008 reported that chitosan-coated treatment gave better effects on inhibiting pericarp hardening change, while shelf-life of mangosteen fruit
could be kept as long as 20 days after treatment Ekaputri, 2009. Dangcham et al. 2008 found that when pericarp hardening occurred, pericarp firmness and lignin
contents increased while total phenolics decreased and fruit at the red-brown and red-purple maturity stages stored at 6
o
C had higher lignin contents than of those stored at 12
o
C. Of the phenolic acids predominant in the hardened pericarp, p- coumaric acid declined whereas sinapic acid increased throughout the storage
time. Application of low O
2
0.25 to red-purple fruit during storage at 6
o
C 84 RH, or at room temperature 30
o
C, 71.5 RH following storage at 6
o
C, did not reduce pericarp hardening and there were no significant differences in
firmness, lignin and total free phenolics when compared with fruit in normal air conditions. The results also suggested that increase in pericarp firmness of
mangosteen fruits results from induction of lignin synthesis, associated with an increase in phenylalanine ammonia PAL and peroxydase POD activity and
gene expression. Recent research conducted by Palapol et al. 2009 showed that pericarp firmness of mangosteen fruit decreased from stage 1 to stage 6, 779.3,
201.3, 136.0, 98.4, 66.5 and 46.5 N, respectively when stored at temperature 25
o
C. Increases in pericarp lignin contents are at least part of the reason for the tissue hardening. Bunsiri 2003 found that 3 hours after impact, lignin contents
increased in the damaged pericarp.
2.4. Fruit Ripening and Senescence
