Assessing the efficacy of novel and conventional disinfectants on Salmonella cross contamination during washing of fresh-cut lettuce and their impact on product shelf life

The effect of the application of different disinfectants on the microbial load and sensory quality of fresh-cut lettuce was evaluated during washing, and after subsequent storage at 4 °C under modified atmosphere packaging (MAP). Different families of potential alternative sanitizers were tested: quaternary ammonium compounds (QACs) as benzalkonium chloride (BZK), and didecyldimethylammonium chloride (DDAC); isothiazolinones (mixture of chloromethylisothiazolinone and methylisothiazolinone, CMIT:MIT 3:1); and, essential oils (carvacrol, CAR). All these disinfectants were effective to inactivate Salmonella (103 CFU/mL) present in wash water. In addition, all tested chemicals could reduce Salmonella on produce to levels >95%, with chlorine and BZK-CAR reaching maximum reductions of 99.0%. These disinfectants also enhanced a reduction in natural microbiota present on the produce. The highest reduction corresponded to free chlorine (50 mg/L) (95.1%), CMIT:MIT (50 mg/L) (Kathon®) (94.5%), and BZK (300 mg/L) (91.3%). However, only free chlorine (50 mg/L), CMIT:MIT (50 mg/L) (Kathon®), and DDAC (100 mg/L) resulted in minimal negative impact on end-product quality during 14-day storage. On the contrary, an adequate sensory quality could be only maintained up to 7 days for produce treated with BZK (300 mg/L).