Pineapple - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 328

found that preconditioning the fruit at 10 ◦ Cor15 ◦ Cfor
24 hours allowed the fruit to be stored at 5 ◦ C for up to
6 weeks with less symptoms of CI compared to the control.
Endogenous brown spot (EBS), black heart, and inter-
nal browning (IB) are other names used to describe CI.
EBS symptoms are water-soaked, brown areas that be-
gin as spots around the core that enlarge and the entire
center turns brown to black in severe cases. Fruit matu-
rity significantly affects black heart susceptibility; imma-
ture and overmature fruit developed less black heart in-
jury (Dahler et al., 2002). Enhanced polyphenoloxidase
(PPO) and phenylalanine ammonia-lyase (PAL) activity is
observed during chilling temperatures. Nevertheless, chill-
ing inhibited the increase of ascorbate peroxidase (Zhou
et al., 2003). Waxing is effective in reducing CI symptoms
and EBS (Paull and Rohrbach, 1985). A heat treatment
(40 ◦ -45 ◦ C for 24 hours) ameliorated EBS symptoms in
pineapples transported at 12 ◦ C (Teisson et al., 1979) by in-
hibiting activity of PPO and, consequently, tissue browning
(Tang et al., 1997). Weerahewa and Adikaram (2005) ob-
served that a hot water dip induced pineapple fruit tolerance
to cold injury and in turn reduced IB during prolonged low
temperature storage (10 ◦ C).
To increase shelf life while maintaining fruit quality,
different postharvest treatments have been evaluated. Coat-
ing the fruit with a wax, frequently polyethylene/paraffin or
carnauba/paraffin-based, often with a fungicide, reduces IB
symptoms of CI and maintains fruit appearance by reduc-
ing postharvest water loss (Rohrbach and Paull, 1982; Paull
and Rohrbach, 1985; Paull and Chen, 2003). Other coat-
ings such as alkyl polyglucosides (APGs) and polyethylene
glycol glycosides (PEGG) also extend pineapple posthar-
vest shelf life and prevent black heart (Jin et al., 2004).
De la Cruz Medina et al. (2007) and Phrutiya et al. (2008)
observed that the application of methyl jasmonate reduces
CI symptoms when the fruit was stored at 5 ◦ Cor10 ◦ C,
respectively. Similarly, Selvarajah et al. (2001) and Dan-
tas J unior et al. (2009) found that fruit treated with 1-
methylcyclopropene (1-MCP) prior to being stored at 10 ◦ C
for4weeksor7 ◦ C for 32 days, respectively, developed
less CI symptoms and IB when transferred to room con-
ditions than the untreated fruit. Hewajulige et al. (2003)
found greater browning symptoms associated with CI in
the core and in the flesh adjacent to the core when lower
calcium concentrations are found; symptoms are minimal
in the flesh near the shell, where the concentrations are
significantly higher. The use of preharvest calcium treat-
ments increased fruit calcium concentration and thereby
reduced CI (Hewajulige et al., 2003; Wijeratnam et al.,
2006). Calcium hydroxide in combination with abscisic

acid and wax sprays or the application of malic hydraxide
plus wax sprays significantly reduces the intensity of IB,
moisture loss, and malic acid content in the crown leaves
and in the fruit (Nanayakkara et al., 2005b).
Controlled atmospheres (CA) are only minimally effec-
tive in reducing CI (Akamine and Goo, 1971), though fruit
stored in polyethylene bags developed less IB, the PPO
activity is reduced, and the fruit maintained a higher ascor-
bic acid content (Paull and Rohrbach, 1982; Rohrbach and
Paull, 1982; Abdullah et al., 1985; Paull and Rohrbach,
1985). Nimitkeatkai et al. (2006) observed that fruit bagged
with 10% O 2 and 5% CO 2 showed less CI than those bagged
with air.

Flesh translucency
Pineapple fruit translucency is expressed as water-soaked
flesh. The translucency develops in the field, and sunburned
fruit is more likely to show the condition (Keetch, 1977).
The cause or causes of translucency are unknown but have
been related to the cultivar grown, high nitrogen, large
vigorous plants, spring-ripened fruit, treatment with fruit-
enlarging agents, irrigation, planting density, larger crowns,
and environmental factors (Paull and Reyes, 1996) as well
as an increase in cell wall hydrolases and membrane per-
meability (Soler, 1994; Chen, 1999). Chen and Paull (2000)
suggested that there were at least three major factors asso-
ciated with flesh translucency: low calcium, high sugars,
and high temperatures.
The enhanced sucrose levels associated with translu-
cency make the pineapple sweeter, and fruits that exhibit
mild translucency are favored by many customers over nor-
mal fruits (Chen and Paull, 2000). However, as the disorder
progresses to more severe levels, the result is increased
senescence, eventually leading to decay, off flavors (Bow-
den, 1967), and greater susceptibility to postharvest me-
chanical damage (Py et al., 1987).
Translucent fruit have fewer and smaller air bubbles in
the intercellular spaces and have a higher specific gravity
(Sideris and Krauss, 1933). Specific gravity is employed as
a nondestructive method for the detection of fruit translu-
cency. In commercial handling when fruits are unloaded
from field bins using water dumps, translucent fruit do
not float and are referred to as “sinkers” and are removed
separately from the tank. Specific density of water can be
adjusted with salts to allow a fraction of the translucent
fruit to float. Haff et al. (2006) indicate that X-ray imag-
ing is another potential nondestructive method for selecting
pineapples that are most likely to be free of translucency
(95% accurate) and those most likely to suffer from extreme
translucency (86% accurate).