Agriculture Reference
In-Depth Information
simulated marketing conditions of 20°C with 56% RH.
They observed that both types of coatings modified
atmospheres, reduced decay, weight loss and improved
appearance by imparting a subtle shine. Polysaccharide
based coating delayed ripening and increased concentra-
tions of flavour volatiles in mango (Baldwin et al . 1999).
The activities of softening related enzymes such as
pectinesterase (PE), polygalacturonase (PG) and cellulase
were also suppressed in pre-climacteric 'Manila' mangoes
coated with a composite mixture containing maltodextrins,
carboxymethylcellulose, propyleneglycol and a mixture of
sorbitan esters (Diaz-Sobac et al . 1997).
The use of petroleum based waxes on fresh produce has
been banned by some countries. Therefore, there is a
growing interest and scope for commercialisation of
natural edible coatings in fresh mangoes. A few consumers
may be allergic to some edible waxes containing wheat
gluten, which may be an obstacle to their popularity.
Another issue is the permeability characteristics of these
edible coatings which may alter with the environmental
conditions (Baldwin et al . 1999) and may lead to off-
flavour in fruit. Despite the complexities of the interaction
between fruits and surface coatings, there is no doubt great
scope for exploiting this technology in mango.
(27± 1°C; 65% RH) and without any microbial growth and
off- flavour (Srinivasa et al . 2002). Being biodegradable
and eco-friendly, chitosan-based films can serve as an
alternative to synthetic packaging films in the storage of
freshly harvested mangoes.
Edible coatings
The growing demand by consumers for eco-friendly and
safe packages has driven researchers to develop new
systems of packaging. One of the most popular alternatives
in the last few years is edible coating - a transparent film
that covers the fruit, imparts gloss and acts as a barrier to
water and gases (O 2 and CO 2 ). Edible coatings increase a
fruit's skin resistance to gas diffusion, modify its internal
atmosphere composition and depress its respiration rate
(Banks et al . 1993). These coatings can also be used as a
carrier of some other preservatives which can have a
synergistic effect on the post-harvest life of fruit.
Semi-permeable coatings can create a modified atmos-
phere (MA) similar to CA storage, but the concentrations
of O 2 and CO 2 can change in response to environmental
conditions such as temperature and humidity (Baldwin
1994; Baldwin et al . 1999). A variety of coating materials
have been tested on mangoes including carnauba wax,
shellac, zein, cellulose derivatives, chitosan and its
derivatives and other composite mixtures containing
sucrose esters of fatty acids and a sodium salt of carboxy-
methylcellulose. Results obtained were variable (Baldwin
et al . 1999; Carrillo-Lopez et al . 2000; Dhalla & Hanson
1988; Diaz-Sobac et al . 1997, 1996, 2000; Hoa et al . 2002;
Kittur et al . 2001). This variation in results may arise due
to different coating materials, concentrations, methods of
application and maturity stages of fruit selected for
experimentation. The application of different coating
formulations containing carnauba wax, shellac, zein and
cellulose derivatives reduced the respiration rate, develop-
ment of external and internal colour and delayed fruit
ripening in 'Kent', 'Tommy Atkins' and 'Lirfa' mangoes
(Hoa et al . 2002). Shellac and carnauba based coatings led
to the higher levels of ethanol, although they did not affect
the flavour quality. Another study by Carrillo-Lopez et al .
(2000) showed that coating of 'Haden' mangoes with
different concentrations of 'Semperfresh' resulted in
higher acidity, firmness and green colour and reduced
weight loss in coated fruits compared to non-coated ones,
while decay development was not influenced by the coat-
ing treatments. Baldwin et al . (1999) tested polysaccha-
ride-cellulose and carnauba based coatings for their effects
on external and internal mango atmospheres and quality
during storage at 10-15°C with 90-99%RH followed by
Irradiation
The use of ionizing radiations for achieving increased shelf
life, insect disinfestation and reducing microbial load in
mango is widely studied and reviewed. Several reports on
irradiation have shown good response of mango to irradia-
tion treatment. The response of mango fruit to irradiation
depends upon cultivar, maturity status and post-harvest
handling system (Akamine & Moy 1983; Boag et al . 1990;
Gonzalez-Aguilar et al . 2001; Janave & Sharma 2005;
Moreno et al . 2006; Spalding & Von Windeguth 1988;
Thomas 1986; Thomas & Janave 1975; Uthairatanakij
et al . 2006). Irradiation of mature green 'Alphonso'
mangoes with a dose of 250 Gy delayed ripening to 16 days
against 10 days in control as evidenced by fruit texture and
skin colour (Dharkar et al . 1966). Deleterious effects on
the skin, such as lenticel spotting and darkening, were
observed with higher doses of irradiation (500 to 2000 Gy),
but these could be negated by equilibrating the fruit in
nitrogen for 3 hours before treatment followed by irradia-
tion in the same atmosphere (Dharkar et al . 1966).
Similarly, irradiation with ≥ 250 Gy increased skin scald
and internal breakdown in mature green 'Keitt' and
'Tommy Atkins' mangoes. 'Tommy Atkins' fruit were
relatively more tolerant to higher doses than 'Keitt'
(Spalding & Von Windeguth 1988). A higher dose causing
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