Agriculture Reference
In-Depth Information
When
O. ficus-indica
cladodes are administered as a
preventive therapy, they keep the gastric mucosa under
normal condition by preventing mucus dissolution caused
by ethanol and favouring mucus production. An increase of
mucus production is also observed during the course of the
curative treatment. The treatment with
O. ficus-indica
cladodes provokes an increase in the number of secretory
cells. Probably, the gastric fibroblasts are involved in the
antiulcer activity.
Table 13.3
Respiration Rates of Prickly Pear Fruit
at Different Temperatures.
Temperature
mg CO
2
kg
¯
1
h
¯
1
5
°
C
16 to 19
10
°
C
38 to 42
15
°
C
52 to 59
20
°
C
68 to 79
POST-HARVEST PHYSIOLOGY
The prickly pear is a CAM plant (Pimienta-Barrios
et al
.
2000), and therefore opens its stomata during the night to
fix CO
2
as malic acid, which is then converted into sugar
during the day. Therefore, the acid content and the flavour
of the cladodes may fluctuate greatly during the day.
The acid content of cladodes can also be affected by post-
harvest storage temperature. For example, the acidity of
young (10 cm) and commercial size (20 cm) cladodes
which have been harvested in the morning was maintained
or increased during storage at 5°C, and decreased at 20°C.
At the time of fruit set sugar content was very low in the
fruit peel (0.1%) and fruit pulp (0.16), whereas total
soluble solids were relatively high (4.5° to 5.5° Brix)
(Lakshminarayana
et al
. 1979; Alvarado 1978). From the
eleventh week onwards, sugars increased 100-fold both in
the peel and in the juice, but the major accumulation
occurred in the final 6 weeks of fruit development.
Glucose is generally the highest sugar, followed by
fructose and sucrose.
Opuntia
fruit are nonclimacteric. Respiration rate
declines during fruit development and is not different
for fruit harvested at different stages of ripeness
(Lakshminarayana
et al
. 1978, 1979; Moreno-Rivera
et al
.
1979). Respiration rates of fruit are temperature depend-
ent, but low during storage (Table 13.3). The fruit also
produce very low amounts of ethylene (about 0.2 μL kg
¯
1
h
¯
1
at 20°C), and are not sensitive to ethylene exposure, but
exposure at warm temperatures will enhance yellowing
(Schirra
et al
. 1997).
more chilling sensitive than autumn-harvested fruit
(Schirra
et al
. 1999). Applications of calcium chloride,
conditioning, and intermittent warming of fruit have been
reported to have variable success in reducing CI. Cladodes
are chilling sensitive when stored below 10
°
C, and symp-
toms may appear after 3 weeks at 5
C or sooner. CI dam-
age in cladodes may be manifested as a superficial bronzing
or unattractive surface discolouration and increased sus-
ceptibility to decay especially at the cut stem end. Fluid
(mucilage) loss and brown discoloration from the cut stem
end is commonly a potential quality problem.
°
DISEASES AND ROTS
Cladodes can be infected by various fungi, namely
Colletotrichum gloeosporoides
, which produces round
black necrosis under high humidity (Fucikovski 1992).
Phythophthora cactorum
and P.
omnivora
can cause
wilting and possible rot of cladodes (Cacioppo 1991), and
Phillosticta opuntia
can cause a certain type of scab. Other
moulds such as
Phyllostitica concave
,
Fusarium solani
and
F. oxysporum
produce black rot and soft rot,
respectively (Granados and Castañeda 1996). Bacteria of
the coliform group, with isolates similar to
Erwinia chry-
anthemi
and
E. carotovora
subspp.
caro tovora
and
atrosepica
were identified as agents of soft rots in cladodes
by Fucikovski and Jaimes (1981), and Vavaro and Gargata
(1990).
E. carnegieana
infect the plant through natural
holes, injuries, probably by direct contact or from root
to root, causes wilt and can destroy the cladode. Bacteria
of the genus
Leuconostoc, Bacillus
,
Pseudomonas
,
Micrococcus
and
Ruminicoccus
were identified in the
microflora of
O. ficus-indica
cactus stems in modified
atmosphere packages (Guevara
et al
. 2003). The moulds
isolated were of the genus
Absidia
,
Cladosporium
,
Penicillium
in addition to the yeast
Pichia
, but no patho-
genic microorganisms were identified. Modified atmos-
phere packaging (up to 8.6% O
2
and up to 6.9% CO
2
) at
5
PHYSIOLOGICAL DISORDERS
Cactus pear fruit and cladodes are chilling sensitive when
stored at lower than 5°C, but chilling injury (CI) may occur
in some varieties even at less than 10°C. CI symptoms in
fruit include pitting, surface bronzing and dark spots on the
peel, and increased susceptibility to decay. CI occurred in
a red-fruit variety after only 2 weeks at 6°C, but fruit from
other varieties were held for few weeks without signs of
chilling, and summer-harvested fruit were reported to be
C decreased the growth of mould and yeast and
mesophilic aerobic microorganisms in cladodes. Decay at
the cut stem end may be a problem if cladodes are stored
°
