| Congresso Brasileiro de Microbiologia 2023 | Resumo: 343-1 | ||||
Resumo:Listeria monocytogenes is a food-borne pathogen, related to food outbreaks and deaths worldwide, as occurred in 2022 in the USA, where the incriminated food was ice cream. This pathogen can be found in vegetables, meat, poultry, and seafood but it is mainly associated with dairy foods, including cheese, yogurt, and even ice cream. This last product is a frozen dairy dessert and its process consists of steps such as homogenization, pasteurization, maturation, air incorporation and freezing. Inadequate hygiene practices or flaws in the processing line can favor the survival and multiplication of microorganisms along the production chain. Thus, the aim of this work was to model the behavior of L. monocytogenes in three different ice cream formulations during the maturation stage, at different temperatures. The process of strawberry, traditional and chocolate ice creams (fat content of 8.20%, 8.80% and 8.96%, respectively) was simulated in the laboratory, with adaptations based on formulations described in the literature. The raw materials were weighed and mixed (with a culinary mixer), and the obtained mixture, called “syrup”, was pasteurized (70 °C/30 min) and then inoculated (102 CFU/mL) with a pool of three strains of L. monocytogenes serotype 1/2b (CLIST4352, CLIST4355, CLIST4357), previously isolated from ice cream. For the inoculum preparation, the strains were activated, twice grown in TSB, washed and the final concentration was adjusted to obtain L. monocytogenes suspension. After inoculation, the syrup was submitted to the maturation process under 4 different temperatures (4, 7, 10 and 12 °C) in a jacketed reactor coupled to a thermostatic bath and a mechanical stirrer. Two genuine repetitions of each condition were carried out, totaling 24 trials. For each experimental condition, analyses of water activity, pH, and soluble solids content were performed; and approximately 15 samples were collected over time to monitor L. monocytogenes population. The microbiological quantification was carried out using the spread plate technique on TSA-YE (incubated at 30 °C/48 h). Therefore, for each condition, the L. monocytogenes growth curve was generated and, after fitting the Baranyi and Roberts model (1994) by DMFit (a Microsoft Excel® add-in), the growth kinetic parameters were estimated. Finally, such parameters were submitted to ANOVA followed by Tukey's test, considering p≤0.05. It was possible to observe a reduction in the lag phase time as the maturation temperature increased, which varied from 198 h (4 °C) to 7 h (12 °C), and an increase in the growth rate from 0.009 h-1 (4°C) to 0.054 h-1 (12°C). Among the matrices analyzed, the traditional ice cream was the most favorable for the growth of the pathogen, since the other flavors present barriers such as lower pH in the strawberry ice cream, or potentially antimicrobial compounds, such as flavonoids in the chocolate ice cream. The results also indicated that, for traditional ice cream, in the scenario of highest microbiological risk (12 °C), L. monocytogenes would be able to leave the lag phase after 5 hours, increasing the population by up to 1.2 cycle-log within 24 hours, which represents a potential risk to the consumers health. With the generated data, it is expected to help industries and control bodies in predicting the behavior of L. monocytogenes in ice cream, preventing the occurrence of contamination and, consequently, outbreaks, thus contributing to public health. Palavras-chave: Ice cream processing, food safety, predictive microbiology, frozen dairy desserts Agência de fomento:Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) | |||||