Detection of Alicyclobacillus acidoterrestris in apple juice concentrate by enzyme-linked immunosorbent assay

Alicyclobacillus acidoterrestris (A. acidoterrestris) is a thermoacidophilic, spore-forming bacterium that can survive through pasteurization and cause spoilage of acidic foods. In order to monitor and control of A. acidoterrestris in the food processing, sensitive and rapid detection methods are required. In this study, a novel Staphylococcal protein A enzyme-linked immunosorbent assay (SPA-ELISA) was developed for the rapid detection of A. acidoterrestris, by using polyclonal antibodies from rabbits. The antibodies were isolated from rabbit serum that had been immunized with A. acidoterrestris via ear vein. The detection limit of this assay was 105 CFU/mL, and no cross-reactions were found with five common food-borne micro-organisms. The coefficients of variation (CV) within and among independent runs were both less than 10%, indicating of satisfactory repeatability of this assay. Coupled with selective incubation for 12 h, This SPA-ELISA assay was successfully applied to detect A. acidoterrestris in apple juice samples, and the results were agreed well with those obtained from the routine K medium method, validating the use of this newly developed assay in real food products like apple juice.