A review on modified atmosphere packaging and preservation of fresh fruits and vegetables: Physiological basis and practical aspects—part II

Currently, a few commercial storage systems are operated based on CA principles, normally controlling gas concentration, temperature and humidity. The gas composi- tions are created and controlled by several methods: N2 generati~n,~~ O2 control,78 and C02 removal by scrubbing79 or with a C02 selective membrane.73 The hypo- baric system 80381 may also be regarded as a CA system, as the partial pressure of O2 is reduced by maintaining a low pressure. Other gases may be added, such as carbon monoxide, and systems may be added to control eth~lene.~ It is now possible to use CA in transport systems (where the major post-harvest losses can result) with the introduction of hollow fibre membranes which are compact and can handle compressed gases (e.g. the Prism@ Alpha CA System of Permea Inc., St Louis, MO). However, with CA systems, mixed load storage is impractical and unecon- omical because of variable CA requirements and the incompatibility of different produce due to ethylene action and flavour contamination. Unfortunately, most fresh produce are still stored using conventional methods, hence significant post-harvest loss is still a problem. In contrast to CA systems, modified atmosphere (MA) technology can be more flexible in extending the CA benefits for improving shelf life to a larger number of fresh produce during distribution and storage. MA ,conditions can be realized via packaging, which is a passive system, by balancing produce respiration and gas exchange through package materials. Such systems, called modified atmosphere