Behaviors of Salmonella enterica serovar Typhimurium and Listeria monocytogenes on whole avocado during storage at 21 or 7°C and their reduction by aqueous chlorine dioxide and peroxyacetic acid

Abstract

The microbiological safety of avocado is concerning in light of associated foodborne illness outbreaks. Avocados were inoculated with 7 log CFU/fruit of Salmonella enterica serovar Typhimurium or Listeria monocytogenes and stored at 21 °C for 10 days and 7 °C for 14 days. S. Typhimurium level increased by 0.71 log CFU/fruit at 21 °C and decreased by 0.93 log CFU at 7 °C (P < 0.05). L. monocytogenes remained stable at 6.95–7.27 log CFU/fruit at both temperatures. In the sanitation experiment, avocados were inoculated with 8 log CFU/fruit of the bacteria and treated with chlorine dioxide (ClO2) produced with HCl or malic acid (10, 15, 20 ppm) and peroxyacetic acid (PAA; 60, 80, 100 ppm) for 5 min. Fifteen and twenty ppm malic-acid-produced ClO2 and 100 ppm PAA reduced S. Typhimurium to an undetectable level. Twenty ppm ClO2 produced with malic acid showed the highest L. monocytogenes reduction of 6.93 log CFU. This study revealed the potential survival and growth of pathogenic bacteria on fresh avocado stored under household conditions. ClO2 or PAA showed potential to serve as alternative sanitizers in avocado washing, although further confirmation in the industrial settings and the evaluation of their impact on avocado sensory properties are warranted.