Survival kinetics, membrane integrity and metabolic activity of Salmonella enterica in conventionally and osmotically dehydrated coconut flakes

Many outbreaks involving Salmonella enterica in dehydrated coconut have been reported. Little is known about the survival of S. enterica in dehydrated coconut flakes at common retail or domestic storage conditions. This study evaluated the behavior of a S. enterica cocktail (S. Enteritidis PT4, S. T...

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Published in:International journal of food microbiology Vol. 370; p. 109669
Main Authors: da Silva, Ruthchelly Tavares, Schaffner, Donald W., de Souza Pedrosa, Geany Targino, de Albuquerque, Thatyane Mariano Rodrigues, Maciel, Janeeyre Ferreira, de Souza, Evandro Leite, Alvarenga, Verônica Ortiz, Magnani, Marciane
Format: Journal Article
Language:English
Published: Netherlands Elsevier B.V 02-06-2022
Elsevier BV
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Summary:Many outbreaks involving Salmonella enterica in dehydrated coconut have been reported. Little is known about the survival of S. enterica in dehydrated coconut flakes at common retail or domestic storage conditions. This study evaluated the behavior of a S. enterica cocktail (S. Enteritidis PT4, S. Typhimurium PT4, S. Bredeney, S. Muenster and S. Agona) in conventionally and osmotically dehydrated coconut flakes under four storage regimes: 25 °C for 120 days, 25 °C for 30 days then 7 °C for 90 days, 7 °C for 30 days then 25 °C for 90 days, and 7 °C for 120 days. S. enterica membrane integrity (using with propidium iodide and bis-1,3-dibutylbarbutyric acid) and metabolic activity (using 5-cyano-2,3-ditolyl tetrazolium chloride) were assessed by flow cytometry analysis after dehydration and storage at 7 °C or 25 °C for 120 days. Lower S. enterica inactivation rates (kmax 0.02 to 0.04 1/days) were observed in conventionally dehydrated coconut flakes compared to osmotically dehydrated coconut flakes (kmax 0.16 to 0.20 1/days). Changes in storage temperature did not affect the behavior of S. enterica in conventionally or osmotically dehydrated coconut flakes. Results show that S. enterica inactivation in conventionally dehydrated coconut flakes could be described by log-linear with tail models. S. enterica inactivation in osmotically dehydrated coconut flakes could be described by log-linear with shoulder and tail models. Subpopulations of S. enterica cells with damaged membranes and without metabolic activity were larger in conventionally (32.1% and 90.9%, respectively) than osmotically dehydrated coconut (18.5% and 82.2%, respectively) flakes at the beginning of the storage. Subpopulations of S. enterica cells with damaged membrane decreased by 9.4–14.4%, while cells with membrane potential and intact membrane increased by 23.7 and 24.2% in conventionally dehydrated coconut flakes after 120 days of storage at 7 °C or 25 °C, respectively. Subpopulations of S. enterica with damaged membranes did not change significantly in osmotically dehydrated coconut flakes. Our findings suggest that S. enterica populations decline during storage occurs due in part to membrane integrity losses. These data can contribute to the development of risk management strategies for S. enterica in dehydrated coconut flakes. •S. enterica survived better in conventionally dehydrated coconut than in osmotically dehydrated coconut.•Storage at 7 vs. 25 °C did not affect S. enterica behavior in coconut flakes.•The fraction of cells with damaged membranes decreased in conventionally dehydrated coconut flakes.•Cell fraction with damaged membranes did not decrease in osmotically dried coconut.
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ISSN:0168-1605
1879-3460
DOI:10.1016/j.ijfoodmicro.2022.109669