MAP as a basis for active packaging
No matter what the packaging technology employed, however, the capacity of active packaging to deliver and maintain functional and beneficial atmospheres is partly or wholly dependent upon the factors that control the passively modified atmospheres in MAP. MAP usually depends upon the respiratory activity of the enclosed product as a driving force for atmosphere modification and the permeability of the packaging material to maintain atmospheres within desired limits. It is the continued depletion of O
or the release of CO
(and water vapor) by the product that enables the modified atmosphere to persist after flushing and sealing. For the success of any packaging approach, factors that must be controlled or incorporated include film permeability, film area, film thickness, temperature, and the respiratory behavior (responses to O
, and temperature) of the product. The aim of MAP (passive, active, or intelligent in design) is to take
advantage of physiological responses of the enclosed plant material or plant or human pathogens to the respiratory gases O
. Presumably, MAP use is intended to maintain product quality, thereby ensuring appropriate value to the consumer and adequate cash flow back through the marketing and handling chain such that the production and marketing system is sustainable (Figure 3.1). Knowledge of the physiological responses to atmosphere modification is beneficial in terms of anticipating improved quality retention as a result of technology investment. This chapter will describe factors that influence the decision to modify atmospheres using MAP, the generation of target atmospheres, and the design of the MAP system to achieve target atmospheres.