Influencing parameters of vaporized hydrogen peroxide on the sterilization of polyethylene terephthalate bottles

Hydrogen peroxide vapor sterilization of containers is commonly used in aseptic filling processes for liquid food such as dairy products. The sterilization of polyethylene terephthalate (PET) bottles presents a considerable challenge because of their temperature sensitivity. Therefore, the influence of the vapor temperature between 65 °C and 115 °C was considered, as it was significantly higher on other substrates in previous studies. An extensive Design of Experiments was conducted to determine the effects of different parameters and their interactions on the count reduction rate. The maximum observable count reduction rate was log (N₀/N) = 6.6 for Bacillus atrophaeus DSM 675 spores. The count reduction rate could be positively influenced by increasing the gas temperature at liquid hydrogen peroxide (35% (v/v)) amounts above 0.186 mL for 500 mL bottles. Gas temperatures above 80 °C, in combination with the injection of vaporized H₂O₂ twice instead of once, increased the count reduction rates. By preheating the PET bottles to at least 35 °C and using a gas temperature of 80 °C, count reduction rates were higher than at lower temperatures. Not only the individual parameters but also their combinations had a significant effect on the inactivation of the spores.