Antimicrobial Effectiveness of Beverage Containers Made of Silver Doped PET

Active packaging based on a release of silver ions (Ag+) has become a focus of increasing interest. However, applications are rare for beverages in particular, and the question remains whether the amount for antimicrobial effectiveness is below the migration limit of 0.05 mg Ag/kg food proposed by the EFSA. Experiments were performed using E. coli (10(6) cfu/mL) in distilled water and Z. bailii (<10 cfu/mL) in iced tea by directly adding AgNO3 at concentrations of 0.015 and 0.05 mg/L Ag, and by using manufactured PET bottles containing silver phosphate glass enabling these concentrations to be reached by a release of Ag+ into the medium. The results showed that these Ag concentrations can inhibit bacteria in distilled water, as well as in iced tea. Ag concentrations of 0.05 mg/L reduced E. coli in distilled water by 10(5) cfu/mL and 0.015 mg/L by 10(2) cfu/mL. Z. bailii population was significantly reduced by 0.05 mg/L Ag, but cells started to grow again.