Modified Atmosphere Packaging of Fruits & Vegetables
The primary factors in maintaining quality and extending the post harvest life of fresh fruits and vegetables are harvesting at optimum maturity, minimizing mechanical injuries, using proper sanitation procedures and providing the optimum temperature and providing the optimum temperature and relative humidity during all marketing steps. Secondary factors includes modification of O2 ,CO2,C2H4 concentrations in the atmosphere surrounding the commodity to levels different from those in air. This is referred to as controlled atmosphere (CA) or modified atmosphere (MA). CA implies a greater degree of precision than MA in maintaining specific levels of oxygen, carbondioxide and other gases.
The beneficial effects of CA in extending the post harvest life of pome fruits were demonstrated about 60 years ago. Since then, more than 4000 research reports on CA and MA have been published and almost half of the reports deal with pome fruits.
Current applications of CA and MA technologies include long term storage of apples, pears, kiwifruits, cabbage and Chinese cabbage; temporary storage and /or transport of strawberries, bush berries, cherries, banana, and other commodities; and modified atmosphere packaging(MAP) of some cut or sliced (minimally Processed) vegetables such as lettuce, celery, cabbage, and broccoli. MAP facilitates maintenance of the desired atmosphere during the entire postharvest handling time between harvest and use.
Recent advances in the design and manufacturing of polymeric films with a wide range of gas-diffusion characteristics have stimulated renewed interest in MAP of O2 ,CO2,C2H4 and water vapors provides possible additional tools for manipulating the microenvironment within the MAP units. Such packages can be shipping containers, retail packages containing several intact or sliced commodity units or retail packages for individual units of commodity.
It provides an overview of the responses of fresh fruits and vegetables to MA, implications of MAP other than MA effects, methods of creating and maintaining MA and current status and future outlook of MAP. It aimed at reducing water loss with atmospheric modification of O2 , CO2, C2H4 concentrations as an incidental factor that may or may not have been monitored.
Prevention of ripening and associated changes in fruits is one of the main benefits of CA/MA. O2 concentration has to be lowered below 8% to have a significant effect on fruit ripening. The lower the O2 concentration, the greater the effect.Elevated CO2 levels (above1%) also retard fruit ripening and their effects are additive to those of reduced O2 atmosphere. The effects of CA/MA on delay or inhibition of ripening are greater at higher temperatures. Thus, use of CA/MA may allow handling of ripening (climacteric type) fruits at temperature higher than their optimum temperature. This is especially beneficial for chilling sensitive fruits such as tomatoes, melons, avocados, bananas and mangoes to avoid their exposure to chilling temperature.