Passively achieved MAP systems may be slow to reach a target EMA, creating a sufficient lag time for significant growth of psychrotrophic aerobic spoilage organisms such as Pseudomonas spp. O2 scavengers incorporated into packaging materials as sheets, labels, trays, or films can be used as an active strategy to more rapidly reach EMA. Commercially available O2 scavengers such as Ageless® (Mitsubishi Gas Chemical Co., Japan) and Freshpax® (Multisorb Technologies, Inc., USA)  are based on iron oxidation.
O2 scavenging technology has been used successfully in MAP stored bakery and dairy products, and applications in MAP stored produce are being explored. Charles and others  created a mathematical model based on the respiration rate of produce, film permeability, and oxygen absorption kinetics of the scavenger. Validation using LDPE pouch packaged tomato and a commercial iron-based O2 scavenger system at 20° C showed that target EMA was actively established within 50 hours; without the absorber, the EMA was passively reached within 100 hours. When using O2 absorbers, the possibility exists that anaerobiosis may occur. In order to optimize MAP produce safety, more information is needed about how O2 scavengers function or respond in different MAP environments with different commodities .
Alternatively, CO2 generators can be used to achieve high levels of CO2 (60 to 80%), which can inhibit microbial growth on produce surfaces. CO2 generators may pose a safety risk; moderate to high levels of CO2 will inhibit growth of aerobic spoilage organisms that usually warn consumers of spoilage, and growth of pathogens may be enhanced due to lack of competition and the altered environment [1,10].
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