Interference of beef matrix in the magnetic separation of Escherichia coli O157:H7 by immunomagnetic beads and the underlying mechanism

Abstract Escherichia coli O157:H7 is a major food safety hazard in beef processing and products, and it can even cause death in severe cases. Immunomagnetic separation (IMS) is an effective sample pretreatment strategy for isolating and enriching target bacteria from food samples, increasing the sensitivity and accuracy of the assay. In this study, an IMS method for E. coli O157:H7, a key safety factor in beef processing and products, was developed, and the interference of the beef matrix was studied. The developed method was highly specific and showed a capture efficiency of 99.98% ± 1.65% for E. coli O157:H7 in a buffer system, but it decreased significantly in beef samples, which indicated that the matrix has a negative effect on the IMS. By investigating the structure-function relationship between the physicochemical properties of beef and magnetic separation efficiency, sarcoplasmic and myofibrillar proteins were found to be the primary factors affecting IMS efficiency in a dose-dependent manner. Proteins can alter the probe surface, lowering antibody loading and target-binding affinity and ultimately reducing IMS magnetic separation efficiency. Our study provides a theoretical basis for optimizing IMS pre-treatment protocols and enables the development of targeted strategies to mitigate protein-mediated interference, thereby enhancing the sensitivity and reliability of E. coli O157:H7 detection in ground beef.