Mango - Crop Post-Harvest: Science and Technology - page 126

there should not be any survivor from a treated population
of 30 000 target pests to meet Probit security level of treat-
ment (Paull & Armstrong 1994). Jacobi et al . (2001b)
presented a comprehensive review on heat treatments in
mango and described the methods used to heat treat mango
varieties for insect disinfestation.

POST-HARVEST INSECT PEST
DISINFESTATION
The insect pests of mango have remarkably retarded the
growth and expansion of world trade of fresh fruit. Mango
fruit is the host of many species of Tephritidae fruit flies
distributed in a particular geographical region of produc-
tion. The major fruit fly species infesting mangoes in
different parts of world include the Mexican fruit fly
( Anastrepha ludens , Loew), West Indian fruit fly
( Anastrepha obliqua , Macquart), the Queensland fruit
fly ( Bactrocera tryoni , Froggatt), the Mediterranean fruit
fly ( Ceratitis capitata , Wiedemann), the papaya fruit fly
( B. papayae , Drew and Hancock), the Oriental fruit fly
( B . dorsalis , Hendel) and the Zapote fruit fly ( A . serpen-
tina , Wiedemann) (Hallman 1999; Heather et al . 1997;
Sharp 1986; Sharp et al . 1988, 1989). There are very strict
quarantine regulations which demand post-harvest
treatments to eliminate the risk of entry of a new pest into
the importing country. Due to these legal restrictions, the
world's largest mango producing country, India, could not
have access to US in the past and Japanese markets.
Quarantine treatments against fruit flies are not mandatory
for fruit entering the European Union and Canada because
fruit flies have not been perceived as a threat due to freez-
ing winter temperatures prevailing in these countries
(Johnson et al . 1997). Moreover, the use of fumigants such
as ethyl dibromide (EDB) and methyl bromide, for insect
disinfestations has already been phased out by many coun-
tries. This necessitated the quest for chemical free and
biologically safe alternatives to achieve post-harvest insect
disinfestation in order to have wider access to international
markets. In this section, the application of heat treatments,
irradiation and insecticidal controlled atmospheres (ICA)
for post-harvest insect pests is reviewed.

Forced hot-air treatment (FHAT)
Hot and humidified air is circulated over the fruit surface to
raise the temperature of fruit core to a desired level (Jacobi
et al . 2001b, Lurie 1998). The speed of air circulation is
precisely controlled at a specified temperature. Forced hot-
air treatment will heat the fruit faster than a regular heating
chamber (Lurie 1998). The control of relative humidity
during FHAT is essential to prevent fruit weight loss and
shrivelling (Mangan & Ingle 1992). The application of
FHAT has been found to be useful as a quarantine treatment
in mango (Mangan & Ingle 1992) but it also causes accel-
erated softening, yellowing of skin colour, peel pitting
(McGuire 1991, Miller et al . 1991) and enhanced rate of
respiration (Mitcham & McDonald 1993). Miller et al .
(1991) observed that FHAT at 51.5°C for 125 min caused
skin pitting and accelerated fruit softening in 'Tommy
Atkins' mangoes. A parallel work by McGuire (1991)
showed that FHAT at 47°C for 3.25 h or 48°C for 2.5 h
resulted in uniform yellow skin colour in addition to fruit
softening in three mango cultivars 'Tommy Atkins', 'Keitt'
and 'Palmer'(Sharp 1992).

Hot-water immersion treatment (HWT)
Hot-water immersion involves submerging of fruits in a
hot-water bath at a specified temperature for a specified
time based on the fruit tolerance to heat and the target
pests' mortality (Jacobi et al . 2001b). It is currently being
used to treat mangoes in various parts of world with the
prime objective of providing an assurance to the importing
countries that the fruit is free of target pests. The use of
hot-water immersion treatments has been found to be
satisfactory for meeting quarantine requirements for most
of the species of fruit flies infesting mangoes (Sharp 1986;
Sharp et al . 1988, 1989; Sharp & Spalding 1984). The
water serves as a better heat transfer medium than air and,
therefore, the rate of heating of skin is considerably faster
when fruit are immersed in hot water than when the same
temperature of air is passed over the fruit in FHAT (Couey
1989). Jacobi et al . (2001b) reviewed the status of com-
mercial scale adoption of HWT in different parts of world.
The use of HWT has been more widespread in the United
States and Central America; but in Australia, the commer-
cial use of HWT technology has not been adopted because

Heat treatments
There has been growing interest in the use of post-harvest
heat treatments to control insect pests in order to meet
quarantine requirements. There are mainly three methods
in use to heat the commodities; hot air, hot water and
vapour heat (Lurie 1998). All these three methods have
been in use for mangoes in different parts of world (Jacobi
et al . 2001b). The heat treatments must ensure a prescribed
degree of statistical probability that over 99.9968% insect
mortality is achieved; this is called Probit 9 security level
of insect control. In the United States, the Probit value
implies that no more than 3.2 individuals survive out of a
population of 100 000 at the 95% confidence level after the
quarantine treatment (McGuire 1991). However, in Japan,