Avocado - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 425

phytopathogenic fungus for avocados. Use of ellagic acid
as part of the edible film had an important effect in the
improvement of the shelf life and quality of avocados by
controlling fungus growth and minimizing respiration.
Maftoonazad et al. (2007) evaluated the effectiveness
of a pectin-based emulsion coating in controlling the inci-
dence and spread of stem-end rot in avocados. The coating
was prepared with sorbitol and beeswax, and the quantities
of the components were previously optimized based on
their influence on mechanical and barrier properties of
the formed film. Avocados were immersed in the coating
solution for 1 min at 20 ◦ C and then drained. The treated
fruits were dried in a cold-air draft for 10 min to set a coat
of the film on their surface, followed by storage at 20 ◦ C.
Treated avocados were then inoculated with the fungus.
The pectin-based coating was effective in controlling the
spread and severity of stem-end rot thereby improving
shelf life.

Hershkovitz et al. (2010) studied the contribution of the
seed to avocado ripening, emphasizing its role in ethylene
biosynthesis and response pathways. Seedless mature fruit
had a shorter preclimacteric lag, faster softening, and higher
respiration during ambient temperature than seeded fruit.
Ethylene inhibitor, 1-MCP, equally and effectively delayed
softening and reduced ethylene and carbon dioxide produc-
tion and expression of genes involved in ethylene biosyn-
thesis and ethylene action in seeded and seedless fruit. It
was demonstrated that respiration was higher in seedless
than in seeded fruits, both at ambient temperature and in
the cold storage.
It may be concluded that research on factors that have
an effect on the extension of shelf life of avocados, such
as ethylene regulation, pathogen inhibitors, coatings, and
edible films, will propose new combinations of these tech-
niques as well as optimum refrigeration temperatures,
which will indeed preserve the quality and extend the shelf
life of avocados.

Shelf life extension and quality
As with any fruit product, quality assurance must consider
all the stages in the life of avocado, from growing in the or-
chard until reaching the retail market and consumer. Good
agricultural practices (GAPs) must be applied in the fields,
together with a good supervision of the growth of trees and
fruits and proper nutrition. During harvest, fruits with a pe-
duncle larger than 8.0 mm must be cut, avoiding any contact
with the ground and therefore potential pathogens. Several
techniques have been in place to extend the useful mar-
keting distances and holding periods for fresh horticultural
commodities after harvest.
Cold storage of avocados delays ripening and prolongs
storage life, but decay and chilling injury can result in
serious problems during prolonged storage such as vascular
browning and mesocarp discoloration. Maftoonazad and
Ramaswamy (2005) studied the postharvest shelf life
extension of avocados using coating with methyl cellulose
base. Avocados were initially surface disinfected, washed,
and air-dried. They were then immersed in the coating so-
lution for 1 min at 20 ◦ C, air-dried for 10 min, and stored at
20 ◦ C in open boxes. Coated avocados demonstrated lower
respiration rates, greener color, and higher firmness as com-
pared with the uncoated control during the entire storage.
The appearance of brown spots and mesocarp discoloration
normally associated with fruit ripening were delayed in
the coated fruits, which kept good quality for 10 days of
storage, compared to control, which lasted only 6 days
at 20 ◦ C.

MINIMALLY PROCESSED OR FRESH-CUT
PRODUCTS
The main problems to consider in preparing minimally pro-
cessed or fresh-cut fruits are microbial safety, the poten-
tial of browning or discoloration, and/or texture or flavor
changes. Regarding microbial safety, most fruits have a pH
between 3 and 5, which make them less prone to microbial
growth. However, avocado is an exception, with a pH of
around 6.7, which offers a good medium for pathogens to
survive and multiply. Another problem is a higher browning
potential in avocados, caused by the oxidation of polyphe-
nols and catalyzed by polyphenol oxidase (PPO). Reduction
of pH may help to reduce both problems, but chlorophylls
may convert to pheophytins and therefore change the orig-
inal green color to yellowish green. In addition, avocado
texture and flavor is delicate and their quality deterioration
is rapid in cut fruit.
Given the aforementioned quality changes, preparing
fresh-cut avocado is a challenge, though there are some
studies reporting on fresh-cut avocado (e.g., Bower and
Dennison, 2003) (Fig. 23.4). Pinheiro et al. (2009) studied
the quality of fresh-cut avocados at three different temper-
atures (0 ◦ ,5 ◦ , and 10 ◦ C) evaluated at five different storage
periods (0, 2, 3, 5, and 6 days). The storage of fresh-cut
avocado at 5 ◦ C was reported to be the best for better
maintenance of quality based on lower darkening of pulp,
better scores for appearance and acceptability, and lower
softening and polyphenol oxidase activity, in comparison to
those stored at 0 ◦ and 10 ◦ C. The fresh-cut avocados stored