Purpose: This study evaluates the effectiveness of recirculating, sanitizing chilled water infused with acidic EO water combined with nanobubble technology, in a proprietary raw beef manufacturing process, against a five-strain STEC surrogate cocktail, over a six-day commercial-scale processing scenario.
Methods: Inoculated beef trim (7.0 log CFU/g) was introduced into the chilled recirculating sanitizing water system [pH 5 and 5 ppm free available chlorine (FAC) targeted], twice daily every other day, over six days of continuous ground beef processing. Inoculated trim was sampled immediately following exposure to the sanitizing water (30 to 90 s). Uninoculated trim was sampled daily to determine residual surrogate contamination throughout the manufacturing system.
Results: Exposure to the sanitizing water reduced surrogate populations (P≤ 0.05) by 1.6 log CFU/g on inoculated meat. Approximately 2.7 log CFU/g of residual surrogates were recovered on uninoculated meat ~35 min after the inoculated meat entered the system; indicating that harborage of surrogates on equipment can subsequently contaminate product. Surrogates were recovered from uninoculated meat by enrichment only (0.4 log CFU/g detection limit) on alternate processing days, where no inoculated trimmings were introduced. Control of this carry-over surrogate contamination in the system, following inoculation, was accomplished through daily equipment sanitation and boosting FAC in recirculated processing water to 50 ppm during a four-hour system disinfection period at the end of each processing day.
Significance: Chilled, chlorinated nanobubble water was shown to be an antimicrobial process against surrogate bacteria representing enteric pathogens in this proprietary ground beef manufacturing system. Other applications of the antimicrobial technology may result based on these findings.