Introduction to modified atmosphere packaging

Modified atmosphere packaging (MAP) is an integral part of the food industry. The objectives of MAP are to extend the shelf life of food products and to prevent any undesirable changes in the wholesomeness, safety, sensory characteristics, and nutritive value of foods. MAP achieves the objectives based on three principles: it reduces undesirable physiological, chemical/biochemical, and physical changes in foods; it controls microbial growth; and just like any other packaging technique, it prevents product contamination. The three main gases used in MAP are nitrogen, oxygen, and carbon dioxide. The role and the importance of each gas in MAP are related to its properties. Nitrogen is an inert and tasteless gas, without any antimicrobial activity. It is not very soluble in water, and it is primarily used to displace oxygen and prevent package collapse. Oxygen inhibits the growth of anaerobic microorganisms, but promotes the growth of aerobic microbes. As carbon dioxide is soluble in both water and lipids, and its solubility increases with decreasing temperatures, the dissolution of CO2 in the product can result in package collapse. Carbon dioxide has a bacteriostatic effect, and it slows down the respiration of many products. The atmosphere inside a package can be modified by either passive or active means. In the first case, the rate of change and the final gas composition in the package depends largely on both the packaged product and the permeability of the packaging material. While in case of an active vacuum, it is considered as a method of active atmosphere modification.