Dados do Trabalho

Título

EFFECT OF TEMPERATURE ON SALMONELLA INACTIVATION KINETIC DURING MILK CHOCOLATE CONCHING

Introdução

Salmonella is a Gram-negative bacterium, non-spore-forming, and belongs to the Enterobacteriaceae family. When it is exposed to stressful environments, it undergoes morphological and physiological changes, becoming more thermoresistant. Since 1970, at least 12 outbreaks of Salmonella in chocolate have been documented globally. During conching, a step in chocolate processing involving prolonged heating and agitation, microbial contamination may decrease. Therefore, this study aimed to determine the inactivation kinetics of two Salmonella enterica strains, previously selected for their thermoresistance, during milk chocolate (MC) conching at three temperatures.

Material e Métodos

The preparation of MC (sugar, cocoa butter, liquor, powdered milk, and emulsifiers) began with mixing, pre-refining, and refining stages. The resulting mixture was transferred to a jacketed reactor coupled to a thermostatic bath (set at 50, 60, or 70ºC) with a mechanical stirrer. Then, the mixture was inoculated (10^6 CFU/g) with suspensions of Salmonella Typhimurium 87.09 (S1) or Salmonella Agona 81.05 (S2), previously standardized (λ=600nm). Samples were collected at various time intervals (n=12) during conching and subjected to quantification of surviving bacteria by serial dilution in PBS, filtration, and membrane inoculation on XLD agar. Inactivation models were fitted to the data using Microsoft Excel® Solver, and secondary models were fitted by linear regression to describe the temperature effect. ANOVA analysis followed by Tukey's test (p≤0.05) was conducted on the obtained parameters.

Resultados e Discussão

The kinetics of S1 and S2 inactivation were adequately described by the Weibull model (R²>0.85), with p parameters equal to 0.20 and 0.18, respectively; and δ-values ranging from 0.8 to 46.9 minutes (S1) and from 0.3 to 7.9 minutes (S2). δ-values decreased with increasing temperature (50 to 70°C), as indicated by secondary models: sqrt(δ)= -0.296T +21.97 (S1; R²=0.96) and sqrt(δ)= -0.099T+7.54 (S2; R²=0.87).

Conclusão

Significant differences were observed among temperatures for S1, while only δ-value at 70ºC differed from other temperatures for S2. S1 consistently exhibited higher δ-values than S2 across all temperatures, and this strain effect was significant at 50ºC and 60ºC. These findings are crucial for understanding Salmonella behavior in MC and could inform strategies for preventing future outbreaks. Furthermore, extending this study to other chocolate matrices is recommended.