CASE STUDIES MAP BAG Modified Atmosphere Packaging of fresh horticultural produce
MAP BAG Modified Atmosphere Packaging (MAP) . It uses the gases produced and consumed during the respiration of fresh produce, that is carbon dioxide (CO2) and oxygen (O2) respectively, to produce a favourable atmosphere in a specially designed polymeric film package. a unique atmosphere for that product is created, enriched in CO2 and reduced in O2. This favourable atmosphere slows the metabolic activity of the produce to a very low level, and thus MAP enables the storage of highly perishable produce for prolonged periods.
The ability to store produce, while retaining its food and nutritional value, increases market flexibility.
Industries can add value to produce, by storing it during market gluts and releasing it when demand increases and by branding and differentiating produce as high quality and high value.
Exporters can use relatively cheap and available Sea freight transport, which increases competitiveness in existing markets and allows access to new markets.
MAP is essential for the successful marketing of these products, which are expected to add up to $1 billion to the value of the Australian vegetable industry.
All fresh produce is alive and must burn up food reserves to keep it alive. The chemical reactions involved are generally termed respiration. In normal healthy plants, respiration involves the uptake of oxygen (O2) by the plant tissue to oxidise food reserves, usually sugars, to produce energy, carbon dioxide (CO2) and water. In simple terms, the energy produced is used to maintain essential life processes, while the CO2 and some of the water are ‘waste’ products and are released to the surrounding environment.
When fresh produce is sealed inside a map bag, respiration will lower the in-package O2 level and increase the CO2 level. A major challenge in designing MA packages, is to match the rate of O2 uptake and CO2 production of the produce, with the O2 and C02 permeability of the package. Gas levels inside the package will equilibrate within a range which benefits the produce.
Optimum CO2 and O2 concentrations are product specific and vary enormously between products. It should be noted that exact recommendations are rare and often a therapeutic range is quoted, as optimum gas levels can vary according to cultivar or genotype, production area, harvest maturity and several other factors.
When optimum atmosphere for a product is achieved, its storage life can be increased by many times that which can be expected using conventional refrigerated air storage. Elevated CO2 and reduced O2 levels slow quality loss in several ways. The principal effect is usually considered to be in suppressing respiratory activity
The post-harvest life of fresh horticultural produce is inversely proportional to its storage life. That is, the lower the respiration rate, the longer food reserves are conserved, and the longer life processes can be maintained. This effect is often termed ‘putting the produce to sleep’. However, there are several other benefits. High CO2 and low O2 atmospheres can:
- Block the mode of action and biosynthesis of ethylene, a ubiquitous plant hormone which promotes aging and senescence.
- Reduce rots by directly inhibiting the growth of pathogens and by maintaining the health and integrity of the plant tissue, which reduces its susceptibility to infection.
- Slow yellowing of green tissues by preventing chlorophyll degradation
- Maintain the food and nutritional value and flavour of produce by slowing the loss of food reserves, particularly sugars, inhibiting the loss of labile vitamins such as vitamins C and A, and by slowing the accumulation of undesirable secondary metabolites in the plant’s tissues, such as free ammonia.
- Slow cell membrane degradation and loss of cellular compartmentation and function.
- Inhibit discoloration of cut surfaces.
MA/MH package provide significant benefits to fresh produce in reducing quality loss and extending storage and market life. MAP provides the horticultural industry with a means to add value to their crops by expanding existing and developing new domestic and export markets.
The Minister for Primary Industries, Mr Simon Crean, stated that the development of MAP will add $300 million per annum to the value of Australian horticultural exports.