Dynamic tracing of bacterial community distribution and biofilm control of dominant species in milk powder processing
Ni Wang, Yujie Jin, Guoqing He, Lei Yuan
Abstract
Thermophilic spore-forming bacteria are common contaminations in milk powder processing lines. In this study, a remarkable change of bacterial community structure was observed after heat sterilization, and thermophilic bacteria took significant advantages after high temperature treatment. Some culturable thermophilic spores survived from pasteurization and even ultra-high temperature sterilization. Feed tank before spraying drying proved to be a key point for controlling thermophilic bacteria. Benzalkonium chloride (BAC) is an effective disinfectant to remove biofilms formed by the isolated dominant species, Bacillus licheniformis. The synergistic reduction of B. licheniformis biofilm on stainless steel in skimmed milk was 3.89 log CFU/cm2 after combined treatment by 0.0625% (v/v) BAC and cleaning-in-place (CIP). This research provided meaningful proposals on determinations of critical control points in a milk powder processing line and removal strategies of B. licheniformis biofilm, which are of valuable significance on quality guarantees for dairy industry.