Compatibility of Process Conditions and Material Characteristics

There are three methods for manufacturing commercial antimicrobial packaging materials other than independent antimicrobial inserts such as sachets, labels, or pads: 

(1) coating of antimicrobial packaging material mix on films or paper surfaces, (2) blending antimicrobials with plastic resins for extrusion film processes, and (3) immobilization of antimicrobials on film surfaces. Film/ container casting methods, that is, extrusion coating or wet casting, are important to maintain antimicrobial effectiveness. In the case of extrusion, the critical variables related to the residual antimicrobial activity are extrusion temperature and specific mechanical energy input. The extrusion temperature is related to the thermal degradation of the antimicrobial agent, and the specific mechanical energy indicates the severity of the process conditions that also induce the degradation of the agents showed a severe decrease in the activity of lysozyme in an extruded starch container as the extrusion temperature increased. In many cases, this thermal degradation is the reason for selecting solvent compounding (i.e., wet casting/coating) methods. In the case of wet casting (i.e., using solvent to cast films and containers such as cellulose films and collagen casing), the solubility and reactivity of the antimicrobial agents and polymers to the solvents are the critical factors. The solubility relates to the homogeneous distribution of the agents in the polymeric materials, while the reactivity relates to the activity loss of the reactive antimicrobial agents.