Assessment of butylparaben (4-hydroxybenzoic acid butyl ester)-assisted heat treatment against Escherichia coli O157:H7 and Salmonella enterica serotype Typhimurium in meat and bone meal

摘要

Heat-resistant foodborne pathogens have been a concern in low-moisture foods and ingredients (LMFs). Due to low thermal conductivity of low moisture materials, thermal treatment is not efficient and may cause nutritional loss. This study investigated the enhancement of thermal treatment of meat and bone meal (MBM) at low water activity (a_w) by inclusion of butylparaben (BP) as a model antimicrobial compound. Stationary phase Escherichia coli O157:H7 (Shiga toxin-negative) or Salmonella enterica serotype Typhimurium was inoculated into MBM containing 0-2000 ppm BP and incubated at 55 or 60°C for up to 5 hr. A biphasic inactivation pattern was observed for both pathogens, indicating existence of potentially thermal resistant subpopulations. Addition of 1000 ppm BP to MBM (a_w = 0.4) significantly lowered the D-value at 55°C for E. coli O157:H7 (2.6 ± 0.5 hr) compared to thermal treatment alone (5.1 ± 0.6 h) during the treatment after the first 1 hr (p < 0.05), indicating that addition of BP accelerated the inactivation of thermal-resistant subpopulation of E. coli O157:H7 in MBM. Interestingly, similar enhancement in thermal inactivation upon addition of BP was not observed in either the sensitive or resistant sub-population of S. Typhimurium at a_w of 0.4 or 0.7, which is likely caused by the higher thermal resistance developed by S. Typhimurium within a low a_w environment (a_w < 0.85). These results suggest that addition of certain antimicrobial compounds can improve the thermal processing efficiency in LMFs, while their efficiency against different pathogens may vary.