Influence of aseptic surge tank venting on equipment sterilization

Abstract

Aseptic surge tank (AST) systems are applied to aseptic production in order to store sterile product until aseptic filling, maintaining the commercial sterility condition achieved from previous production steps. To avoid microbial recontamination of the product, a sterility condition must be achieved in the aseptic tank system through the application of a heating, venting, and sterilization cycle. This cycle must follow specific validation protocols to ensure operational integrity - FDA 21 CFR Part 113.40g (ii). The demand for larger capacity systems and the implication of this volume increase on sterilization efficiency require a review of results obtained from current validation protocols. The purpose of this work was to evaluate aseptic surge tank’s venting cycles, studying internal pressure and temperature distribution to better understand this operation and its efficiency. Tests carried out at an industrial setting showed that the venting cycle was insufficient, with 13%-23% of air remaining inside the tank. Consequently, the subsequent sterilization process was not conducted under saturated steam condition. This different condition may change the kinetics for thermal destruction of microorganism spores from a moist heat state to a drier state in which its thermal resistance is higher. This finding raises a question regarding the true efficacy of the sterilization process and validation protocols currently used by the industry. The apparent success of current sterilization processes could be due to the application of excessive temperature and longer times. New operational and validation criteria will result in improvements in product integrity protection and operational cost reductions.