Agriculture Reference
In-Depth Information
(Collin 1984). High concentration of CO (5 to 10%) added
to CA can reduce decay development (El-Goorani &
Sommer 1981). Moderately high concentrations of CO
2
(up to 10%) were shown to ameliorate CI in 'Taylor' avo-
cados (Vakis
et al
. 1973). Spalding and Reeder (1972)
found less internal and external CI in CA than in air storage
of 'Booth 8' and 'Lula' avocados. Intermittent high CO
2
treatment (3 treatments during 21 days) reduced CI symp-
toms (Marcellin & Chaves 1983). 'Fuerte' avocados had
less pulp spot and blackening of cut vascular bundles after
storage in 2% O
2
and 10% O
2
at 5.5°C for 28 days, or after
a 'shock' treatment of 25% at 5.5°C for 3 days and an addi-
tional 28 days at normal atmosphere at 5.5°C (Bower
et al
.
1990). Spalding (1977a) concluded that the CO
2
must be
kept below 15% to prevent other fruit injury. Pre-storage of
'Fuerte' avocados in 3% O
2
(balance N
2
) atmosphere for 24
hours at 17°C significantly reduced CI symptoms after
storage at 2°C for 3 weeks (Pesis
et al
. 1993, 1994). Fruit
pre-stored in 97% N
2
had lower respiration and ethylene
production, lower ion leakage, higher reducing power
(expressed as SH groups, mainly cysteine and glutathione),
and longer shelf life than the untreated fruit.
'Booth 8' and 'Lula' avocados were reported to be held
successfully for up to 8 weeks in a CA of 2% O
2
with
10% CO
2
at 4-7°C and 98-100 RH, and removal of ethyl-
ene further improved the keeping quality of the 'Lula'
fruits (Spalding & Reeder 1972). Fruits of 'Booth 8' had
slight CI at 4.5°C. 'Fuerte' and 'Anaheim' fruits were
stored in Brazil for up to 38 days in 6% O
2
and 10% CO
2
at 7°C, but only for 12 days in air (Bleinroth
et al
. 1977a).
Storage of 'Waldin' and 'Fuchs' avocados in 2% O
2
and
10% CO
2
for up to 4 weeks at 7°C was also reported to
prevent development of anthracnose and CI (Spalding &
Reeder 1974, 1975). 'Hass' avocado was reported to be
stored for up to 60 days in atmospheres of 2% O
2
and 5%
CO
2
(Faubian
et al
. 1992; Jordan & Barker 1992;
McLauchlan
et al
. 1992). Four commercial CA rooms
were constructed in Florida in the season of 1972/73 for
storage of 'Lula' avocados in bulk bins (Spalding &
Reeder 1974). The rooms were run at 2% O
2
and 10%
CO
2
at 7.2°C and 95% RH, and fruits were reported to be
marketed in excellent conditions after 5 weeks of storage,
except for some fruits with rind discoloration (CI) where
temperature dropped below 4.4°C. In South Africa,
Bower
et al
. (1989) suggested that even though fruit
stored in CA (2% O
2
and 10% CO
2
) were superior than in
other storage systems the economic and logistical reali-
ties were not significant. Oudit and Scott (1973) reported
a considerable extension in the storage life of 'Hass'
avocados sealed in polyethylene bags. 'Hass' avocados
sealed in polyethylene bags (0.015 to 0.66 mm) ranging
in permeability from 111 to 605 cc O
2
/m
2
.hr.atm., and
from 0.167 to 0.246 gr H
2
O/m
2
.hr.atm. and stored at 5°C
for up to 4 weeks lost less weight and firmness compared
with unsealed fruits (Gonzalez
et al
. 1990; González-
Aguilar
et al
. 1997; Yahia & Gonzalez 1998).
Low-pressure atmosphere (LP), especially below
100 mm Hg, markedly prolonged the storage life of 'Hass'
avocados (Apelbaum
et al
. 1977). Optimum conditions for
LP storage of Florida avocados were suggested to be
20 mm Hg at 4.5°C (Spalding & Reeder 1976a; Spalding
1977a). Fruit held in these conditions for up to 3 weeks
were firmer, and had less decay and CI than fruit held in 76
or 760 mm Hg, however, gases such as CO
2
and CO, can
not be added when LP system is used. CO
2
is considered to
be essential for control of decay and to ameliorate CI in
avocados. 'Hass' avocados maintained in MA (0.1-0.44%
O
2
, 50-75% CO
2
, balance N
2
) for up to 5 days at 20°C had
higher CO
2
production compared to fruit stored in air, most
likely reflecting anaerobiosis (Carrillo-Lopez & Yahia
1990; Carrillo-Lopez & Yahia 1991; Yahia 1993b; Yahia
and Carrillo-Lopez 1993; Rivera and Yahia 1994; Rivera
et al
. 1993). Fruit stored in this MA and then ripened in air
had mesocarp and exocarp injury after 2 days. On the basis
of these results Yahia (1993b) and Yahia and Carrillo-Lopez
(1993) concluded that 'Hass' avocado fruit is very sensi-
tive to insecticidal atmospheres, tolerating only one day at
20°C. These findings were confirmed by Yahia and Kader
(1991) and Ke
et al
. (1995). 'Hass' avocados kept in 0.25%
O
2
alone or in combination with 80% CO
2
for 3 days at
20°C, had higher concentrations of acetaldehyde and
ethanol (Ke
et al
. 1995).
MA and CA are commonly used for transporting
avocado fruit by sea to distant markets in refrigerated
shipping containers (Yahia 1998). The atmosphere used
and technology for controlling the atmosphere vary
between shipping companies. Generally O
2
levels of 2-5%
and 3-10% CO
2
are commonly used.
Low O
2
injury may appear as irregular brown to dark
brown patches on the skin and may additionally cause
diffuse browning of flesh beneath affected skin (Yahia,
1997a; Carrillo-Lopez and Yahia 1991; El-Mir
et al
. 2001;
Loulakakis
et al
. 2006; Yahia & Rivera 1994). CO
2
atmospheres above 10% can be detrimental by leading to
discoloration of the skin and development of off-flavour,
particularly when the O
2
concentration is less than 1%.
Reducing ethylene levels to <1 μL L
−1
by using ethylene
scrubbers during CA storage may provide additional
benefits for retarding ripening and decreasing the
development of internal CI (Faubion
et al
. 1992).
