Influence of antimicrobial packaging on kinetics of spoilage microbial growth in milk and orange juice

The influence of antimicrobial packaging on the microbial growth in pasteurized milk and orange juice was examined. The liquid foods were located in contact with paperboard coated with nisin and/or chitosan in a binder of vinyl acetate ethylene copolymer at 3, 10 and 20 °C, and were measured for counts of aerobic bacteria and yeasts in the milk and orange juice, respectively. Paperboard coated only with plain binder was used as a control. The effect of antimicrobial packaging on the microbial growth was analysed by using Baranyi's growth model. The paperboard coated with nisin and/or chitosan significantly improved the microbial stability of milk and orange juice at 3 and 10 °C, but not so noticeably at 20 °C. Of those tested, paperboards that included a combination of nisin and chitosan in the coating gave the highest microbial inhibition, and this was most apparent at 10 °C. The effectiveness of antimicrobial paperboard in suppressing the microbial growth was indicated by low maximum temperatures, extended lag time and reduced specific growth rates. Analysis by Ratkowsky equations showed that foods in contact with antimicrobial paperboards showed higher minimum growth temperatures and greater temperature dependence than did foods in contact with plain paper.