Agriculture Reference
In-Depth Information
Table 8.7
Some Reported Effects on Avocado Fruit in Different Conditions of Modified and Controlled
Atmospheres.
Variety
%O
2
%CO
2
Temperature °C
Remarks
Hass
2-10
4-10
7
Storage time of 7-9 weeks
Lula, Booth 8, Fuchs
2
10
7.5
Increase shelf life twofold
Fuerte, Edranol, Hass
2
10
—
Reduces internal disorders
Nonspecific
—
25
—
Reduces disorders and
increases anthracnose
Fuerte
—
25
—
Delays maturation
Fuerte
2
10
5.5
Less dark spots in the pulp
Fuerte
—
25
5.5
Less dark spots in the pulp
Fuerte
3
0
24 h at 17°C
After this treatment, fruit can
be stored at 2°C for 3 weeks
Booth 8, Lula
2
10
4-7
Storage time of 8 weeks
Fuerte, Anaheim
6
10
7
Storage time of 38 days
Waldin, Fuchs
2
10
7
Storage of 4 weeks, prevents
anthracnose and CI
Hass
2
5
—
Storage time of up to 60 days
Source: Yahia (2003).
Very early research by Overholser (1928) reported that the
storage life of 'Fuerte' avocados was prolonged one month
when fruit was held in an atmosphere of 4 to 5% O
2
and 4 to
5% CO
2
at 7.5°C compared to air storage. Brooks
et al
.
(1936) reported that fruit could be held in atmospheres
containing 20−50% CO
2
at 5−7.5°C for 2 days without
causing any injury. Atmospheres with CO
2
levels below 3%
prolonged the storage life of Florida avocados at all
temperatures, and reduced the development of brown
discoloration of the skin (Stahl & Cain 1940). Extensive
work was later done also with 'Fuerte' avocado, and
concluded that the time for the fruit to reach the climacteric
is extended in proportion to the decrease in O
2
concentration
from 21% to 2.5% (Biale 1942, 1946). In later years Young
et al
. (1962) demonstrated that the delay of the climacteric
could also be achieved by 10% CO
2
in air, and the
combination of low O
2
and high CO
2
suppresses further the
intensity of fruit respiration. Hatton and Reeder (1965,
1969b, 1972) and Spalding and Reeder (1972; 1974) found
that a CA of 2% O
2
and 10% CO
2
at 7.5°C doubled the
storage life of the cultivars 'Lula', 'Fuch', and 'Booth 8'.
The percentage of acceptable fruit after storage was increased
by absorption of ethylene during CA storage (Hatton &
Spalding 1974). 'Reed' and 'Hass' avocados were reported
to be stored for up to 3, and 2 months, respectively, in CA
(Sive & Resnizky 1989a). Jordan and Smith (1993) reported
that 'Hass' avocados remained firm and unripe for 7 to 9
weeks in CA of 2-10% O
2
and 4-10% CO
2
at 7°C. Below
4% CO
2
storage life was 5-6 weeks. Truter and Eksteen
(1987a, 1987b) reported that a mixture of 2% O
2
and 10%
CO
2
extended the shelf life and reduced the grey pulp and
virtually eliminated pulp spot of 'Fuerte', 'Edranol' and
'Hass', but an increase in anthracnose was observed. Truter
and Eksteen (1987b) found that a 25% CO
2
shock treatment
applied one day after harvest reduced physiological dis-
orders without any increase in anthracnose. Allwood and
Wolstenholme (1995) were able to delay ripening of 'Fuerte'
fruit using a 25% CO
2
shock treatment applied in pulses 3
times every 24 hours. Marcellin and Chavez (1983) reported
that intermittent exposure to 20% CO
2
of 'Hass' avocados
stored in air delayed senescence at 12°C, reduced CI at 4°C
and controlled decay at both temperatures.
CA delays the softening process, and thus maintains the
resistance of the fruit to fungal development (Spalding &
Reeder 1975). In addition, Prusky
et al
. (1991, 1993)
reported that 30% CO
2
(with 15% O
2
) for 24 hours
increased the levels of the antifungal compound 1-acetoxy-
2-hydroxy-4-oxo-heneicosa-12,15-diene in the peel and
flesh of unripe avocado fruits, and delayed decay
development. This diene has been suggested as the basis
for decay resistance in unripe avocados (Prusky
et al
. 1982,
1988, 1991). 20% CO
2
can be tolerated by thick-skinned
avocados such as 'Hass' and 'Lula', but causes browning
of the skin in thin-skinned varieties such as 'Ettinger'
