Abstract:
A study was undertaken to investigate the effect of modified atmosphere (MA)
packaging on the quality of avocados. Mature pre-climacteric avocados were packed in
several plastic films having a wide range of O2 and CO2 permeability and refrigerated at
4°, 7° and 10°C. The concentrations of O2 and CO2 in MA packs from each holding
temperatures were monitored daily. Each pack contains avocados giving similar ratios
between the weight of fruit to the area of the permeable film and the volume of free
space of 750 cm3 within the pack. The treated avocados along with fruits stored at
normal atmosphere (control) were ripened at 20 ± 0.5°C and the relative humidity of
90-95%. The flesh firmness, ascorbic acid, total sugar, oil, pH and fatty acid
composition were assessed during ripening following the combination treatments.
Ascorbic acid content of avocados was found to be affected by storage temperature,
duration and atmospheric composition. All samples showed loss in ascorbic acid during
ripening. Fruits stored at 7°C in MA of 4.8% 0 2 + 8.4% C 0 2 and air packs lost 11.7%
and 15.6% of its ascorbic acid during ripening. Flesh firmness decreased as ripening
progressed in both MA stored and control fruits. MA storage did not produce any
significant (p<0.05) effect on oil content of ripe fruits and indicated that the equilibrium
gas concentrations did not significantly affect the enzymes concerned with fat
metabolism. Nine fatty acids were identified in avocado oil. The major saturated fatty
acid is palmitic acid of 12.1 - 14.6% and the main unsaturated fatty acid is oleic acid of
69.3 - 73.7% in ripe fruits. Fruits sealed with insufficiently permeable film such as
polypropylene, polyolefin and a laminate of 2Op Nylon + 60p polyethylene has been
found to contain highly modified atmospheres of >20% CO2 + <2% O2 . Under these
conditions, fruits developed rind injury and produced off-flavours and off-odours
during ripening. The modified atmosphere storage of avocados in plastic film MY-15
having the O2 permeability of 3500 cm3/m2/day bar and the CO2 permeability of 8500
cm3/m2/day bar in combination with refrigeration would help to maintain the
biochemical quality of avocados throughout the marketing chain and to extend the shelf
life of fruits for the retailer and consumer.
