Dados do Trabalho

Introdução

Salmonella is a pathogenic bacterium able to develop survival mechanisms under stress conditions. In low-moisture foods, such as chocolate, its survival during the process chain may be favored, resulting in final product contamination. The most recent outbreak involving chocolate (Belgium, 2022) caused at least 445 cases of salmonellosis. Thus, the objective of this work was to determine and compare the thermal resistance of 12 Salmonella enterica strains in milk chocolate (MC).

Material e Métodos

Strains of different Salmonella serotypes [Typhimurium (n=1); Agona (n=1); Agreement (n=1); Children (n=1); Enteritidis (n=2); Saint Paul (n=1); S. Anatun (n=2); Senftenberg (n=1); 4,5.12:i (n=1); 5.4,5.12:i (n=1)] were individually used to obtain standardized concentration suspensions. The ingredients (cocoa mass, cocoa butter, milk powder, and emulsifiers) were subjected to mixing, pre-refining, refining, and then melting (45°C/30 min). The resulting MC base was divided into 25g portions, in sterile bags, inoculated (~106CFU/g) separately with Salmonella suspensions, and heat treated in a water bath (at 50, 55, or 60°C) for 6 hours, in triplicate. In all conditions, the initial and final Salmonella populations were quantified through membrane filtration with XLD agar plating to determine the number of decimal reductions (γ). Results were submitted to ANOVA followed by Tukey or Scott-Knott test (p≤0.05).

Resultados e Discussão

At 50°C, the γ-value varied between 1.7 and 3.4 log(CFU/g), while at 60°C it varied between 3.0 and 4.5 log(CFU/g). The increase in temperature tended to increase γ, with the average value among the 12 strains at 50, 55, and 60°C being 2.39±0.44, 3.08±0.40 and 4.01±0.50 log(CFU/g), respectively. At 55 and 60°C, the Scott-Knott test clustered the strains into two groups. At 60°C the least resistant strains were S. Saint Paul 126.05 and 5.4,5.12:i 298. In turn, S. Typhimurium 87.09 and S. Agona 81.05 were the most thermal-resistant strains (lowest γ) at all temperatures and were selected for further inactivation kinetics study during conching. Data on the variability of pathogen thermal resistance is crucial in supporting studies on inactivation kinetics. The utilization of lower heat-resistant strains can lead to kinetic parameters underestimating the microorganism's survival capacity, which raises concerns about their suitability for safe application within the food industry.