Purpose: The objective of this work was to evaluate the efficacy of sodium hypochlorite (NaOCl), and peroxy-acetic acid (PAA) at reducing Salmonella on the surface of green skin avocados using a laboratory scale spray brush roller system.
Methods: Avocados were inoculated on the smooth middle section with a five-strain cocktail (seven-log CFU/avocado) of rifampicin resistant Salmonella, dried for one hour, and submitted to spray washing for 0, 5, 15, 30, and 60 s, using 100 ppm NaOCl (pH: 7.0) or 85 ppm PAA, and a water control. Salmonella populations were enumerated following removal from avocados using a rub-shake-rub in Dey/Engley (DE) neutralizing broth and spreading dilutions on tryptic soy agar (TSA) and bismuth sulfite agar (BSA) supplemented with rifampicin. Experiments of triplicate samples were repeated five times (n=15). Average log CFU/avocado reduction of Salmonella were calculated for each spray time and sanitizer, and compared using Analysis of Variance (ANOVA) and Tukey’s HSD (P≤ 0.05) for each medium.
Results: Salmonella populations were reduced significantly more (P≤0.05) by the presence of NaOCl and PAA compared to the water control, for all treatment times on both media types; there were not significantly differences (P>0.05) in Salmonella population reductions between NaOCl and PAA treatments in 15, 30, and 60 s. Salmonella populations were reduced by >3.93±0.30 log CFU/avocado with NaOCl and PAA treated for 15 s versus 2.13±0.63 log CFU/avocado reduction achieved with water.
Significance: Addition of NaOCl or PAA can significantly reduce Salmonella populations on the surface of green skin avocados compared to water alone, and may be used as a reduction strategy to prevent or minimize avocado contamination during postharvest practices in Florida packinghouses.