Behavior of spoilage bacteria and Salmonella enterica subspecies enterica O:4,5 in vacuum-packaged beef during refrigeration / Comportamento de bactérias deteriorantes e Salmonella enterica subespécie entérica O:4,5 em carne bovina embalada a vácuo durante refrigeração

ABSTRACT: In this study, the kinetic parameters of mesophilic, psychrotrophic and lactic acid bacteria in vacuum-packed beef at 1 °C and 4 °C were estimated from experimental growth curves produced by samples stored during 21 and 60 days, respectively. In a separate experiment, the survival of multidrug resistant (MDR) Salmonella enterica O:4,5 at 1°C was also characterized. The shelf-life of vacuum-packed beef stored at 4 °C was estimated at 16.1 days (95% CI: 14.8 - 17.3 days), whereas at 1 °C it was longer than 21 days because the mesophiles count estimated towards the end of the experiment was 12.5 ln CFU.g-1 (95% CI: 11.8 - 13.3 ln CFU.g-1) which is lower than the shelf-life reference value. At 1 °C, inoculated Salmonella was reduced in 6.61 ln CFU.g-1 (2.87 log CFU.g-1). These results demonstrated the importance of establishing in legislation, especially in Brazil, standard values of deteriorating microorganisms in beef for maintaining product quality.

RESUMO: Neste estudo, os parâmetros cinéticos de bactérias mesófilas, psicrotróficas e ácido lácticas foram estimados em carne bovina embalada a vácuo a 1 °C e 4 °C, a partir de curvas experimentais produzidas em amostras estocadas durante 21 e 60 dias, respectivamente. Em um experimento separado, a sobrevivência de Salmonella enterica O:4,5 multirresistente (MDR) a 1°C também foi caracterizada. A vida de prateleira da carne bovina embalada a vácuo, estocada a 4°C, foi estimada em 16.1 dias (95% CI: 14.8 - 17.3 dias), enquanto que a 1 °C o período foi maior que 21 dias, porque a contagem estimada de mesófilos ao final do experimento foi de 12.5 ln UFC.g-1 (95% CI: 11.8 - 13.3 ln UFC.g-1), o qual é mais baixo que o valor referência de shelf-life. A 1 °C, Salmonella inoculada reduziu em 6.61 ln UFC.g-1 (2.87 log UFC.g-1). Estes resultados demonstram a importância de estabelecimento em legislação, especialmente no Brasil, de valores padrões para contagem de microrganismos deteriorantes em carnes visando manter a qualidade do produto.

Modelo de predicción de Bacillus cereus para definir las condiciones de calidad y consumo de leche en polvo / A prediction model of Bacillus cereus to define conditions for quality and consumption of milk powder

RESUMEN El objetivo del artículo fue lustrar mediante modelos de predicción microbiológica, la probabilidad de conformidad del producto terminado, estimando el ciclo de vida de la leche en polvo una vez que ha sido reconstituida, enfocado en los aspectos fisicoquímicos y microbiológicos (Bacillus cereus), por medio del modelo cinético de Arrhenius, con redes neuronales artificiales, entrenadas para pronosticar productos conformes respecto a la bacteria. A través del algoritmo de la red neuronal, se concluyó que, una vez la leche en polvo ha sido reconstituida debe mantenerse refrigerada entre 4°C y 6°C, para obtener una vida útil alrededor de los 19 días, pronosticando el 98% de productos conformes.

ABSTRACT The aim of this paper was to show a microbiological prediction model to determine the probability of conformity in products and estimate the life cycle of reconstituted powdered milk, focusing on the physicochemical and microbiological aspects of Bacillus cereus. We used the kinetic model Arrhenius, built under artificial neural networks designed to measure conformity to Bacillus cereus products. Using the neural network algorithm, we found that once milk powder was reconstituted, the temperature should be between 4°C and 6°C to obtain a lifespan around 19 days and 98% conformity.

Use of modified Richards model to predict isothermal and non-isothermal microbial growth

Abstract Mathematical models are often used to predict microbial growth in food products. An important class of these models involves the adaptation of classical sigmoid functions, such as the Gompertz and logistic functions. This study aimed to validate the use of the modified Richards model in various situations, which have not previously been tested. The model was obtained through solving a system of two differential equations and could be applied to both isothermal and non-isothermal environments. To test and validate this model, we used published datasets containing data for the growth of Pseudomonas spp. in fish products. The results obtained after fitting the model showed that it could be effectively used to describe and predict the Pseudomonas growth curves under various temperature regimens. However, the influence of the shape parameter on the growth curve is an issue that needs further evaluation.

Modelling the growth of lactic acid bacteria at different temperatures

ABSTRACT Mathematical models are widely used to predict the shelf life of foods. Lactic acid bacteria (LAB), particularly Lactobacillus plantarum, Weissella viridescens and Lactobacillus sakei, are the main spoilage bacteria of refrigerated, vacuum-packed meat products, stored in modified atmosphere, and their growth determines the shelf life length of these products. The objective of this study was to model the growth of L. plantarum, W. viridescens and L. sakei under different isothermal cultivation conditions and establish secondary models to describe the effect of temperature on the growth parameters of these bacteria. The LAB growth was evaluated in culture medium at temperatures of 4, 8, 12, 16, 20 and 30 ºC. The fit of Baranyi and Roberts (BAR) and Gompertz (GO) primary models to the growth curves of LAB was compared by statistical indices, in which the BAR model showed slightly better fits to the experimental data. The BAR growth parameters were used to establish the secondary models, µmax and Nmax were established for the three LAB. The power model described the influence of temperature on the parameter λ for L. plantarum, and other bacteria showed no lag phase. The growth of LAB was strongly influenced by storage temperature and the obtained models allow predicting the growth of these bacteria within the temperature range from 4 to 30 ºC.

Avaliação quantitativa do risco de Salmonella e Listeria monocytogenes em vegetais minimamente processados / Quantitative risk assessment of Salmonella and Listeria monocytogenes in minimally processed vegetables

A ocorrência de surtos de doencas associadas aos vegetais minimamente processados (VMP) tem chamado a atenção para a sua segurança microbiológica. A avaliação quantitativa de riscos permite que o impacto das materias-primas e processamento seja avaliado e os resultados obtidos sejam usados para gestão e comunicação do risco. Desta forma, o presente estudo objetivou quantificar o risco de infecções por Salmonella spp. e Listeria monocytogenes a partir do consumo de VMP no Brasil. Um total de quinhentas e doze amostras de VMP foram analisadas e foi possivel enumerar e detectar Salmonella em 0,4% e 0,4% das amostras, respectivamente. L. monocytogenes foi enumerada e detectada em 0,97% e 3,1% das amostras analisadas, respectivamente. Os isolados de Salmonella spp. (n=4) e L. monocytogenes (n=69) foram confirmados por PCR e caracterizados por sorotipagem tradicional. Os isolados de L. monocytogenes foram caracterizados quanto ao ribotipo, resistencia ao cloro, taxa de multiplicação (µ), capacidade de formação de biofilmes e presença de genes de virulência. O sorovar predominante entre Salmonella spp. foi S. Typhimurium. Em relação a L. monocytogenes, observou-se prevalência do sorotipo 4b e do ribogrupo DUP-1038 e presenca de genes de virulência em 100% (inlA) e 97% (inlC e inlJ) dos isolados. A maioria dos isolados de L. monocytogenes foi resistente a exposição a 125 ppm de cloro livre, e todos foram capazes de aderir ao aco inox, atingindo concentracoes acima de 4 log UFC/cm2. Testes-desafio foram conduzidos para determinar o potencial de multiplicação (δ) de cepas de Salmonella e L. monocytogenes em nove diferentes tipos of VMPs armazenados a 7°C e 15°C por 6 dias. O armazenamento a 15°C por 6 dias resultou nos maiores aumentos nas populações de L. monocytogenes em couve picada (δ= 3,34) e rúcula ((δ= 3,22), enquanto para Salmonella, as maiores populações foram observadas em rúcula (δ= 4,05) e escarola (δ= 2,80). Testes-desafios posteriores indicaram que a multiplicação dos dois patógenos em VMP foi mais pronunciada quando os mesmos foram embalados sob atmosfera modificada em comparação a embalagem em filmes perfurados. Modelos preditivos primários e secundários descrevendo a taxa de multiplicação e tempo de lag de Salmonella spp. e L. monocytogenes em VMP em função da temperatura de armazenamento (7, 10, 15, 20, 25 e 30°C) foram gerados. Verificou-se que os modelos gerados apresentaram a precisão necessária e foram adequados para modelagem da multiplicação dos dois patógenos em VMP. Os modelos de avaliação quantitativa de risco (AQR) foram construidos para determinar a probabilidade de infecção por Salmonella spp. e L. monocytogenes devido ao consumo de VMPs. Os modelos construidos com base nos dados levantados da literatura indicaram risco de infecção por Salmonella spp. e L. monocytogenes de 8.66 x 10-3 e 1.87 x 10-8, respectivamente, sendo necessário que medidas de mitigação do risco sejam adotadas

The occurrence of foodborne disease outbreaks linked to minimally processed vegetables (MPV) is concerning industries, consumers and governments worldwide. Quantitative risk assessments can estimate the impact of raw materials and processing practices and these estimates are used for risk management and risk communication. This study aimed at quantifying the risks of infection by Salmonella spp. and Listeria monocytogenes due to consumption of MPV in Brazil. A total of five hundred and twelve samples of MPV were analyzed and Salmonella was detected and enumerated in 0.4% and 0.4% of the samples, respectively. L. monocytogenes was enumerated and detected in 0.97% and 3.1% of the samples analyzed, respectively. Isolates of Salmonella spp. (n=4) and L. monocytogenes (n=69) were confirmed through PCR and characterized by traditional serotyping. The isolates of L. monocytogenes were characterized for their ribotype, resistance to chlorine, growth rate, (µ) and ability to form biofilms and presence of virulence factors. Among Salmonella spp., S. Thyphimurium was the most prevalent serovar. Among L. monocytogenes, prevalence of serotype 4b and ribotype DUP-1038 was observed. Virulence gene inlA was present in 100% of the isolates, and genes inlC and inlJ in 97%. The majority of L. monocytogenes isolates were resistant to up to 125 ppm of free chlorine and all isolates were able to attach to stainless steel coupons, reaching populations of up to 4 log10 CFU/cm2. Challenge tests were carried out to determine the growth potential (δ) of Salmonella and L. monocytogenes in nine types of MPV stored at 7°C and 15°C for 6 days. The storage of MPV at 15°C for 6 days resulted in the greatest increases in L. monocytogenes populations in shredded collard green (δ= 3.34) and arugula (δ= 3.22), whereas for Salmonella, the highest populations were found in arugula (δ= 4.05) and escarole (δ= 2.80). Further challenge tests indicated that multiplication of both pathogens in MPV was more pronounced when these products were packaged under modified atmosphere in comparison to packaging in perforated films. Primary and secondary predictive models describing the growth rate and lag time of Salmonella and L. monocytogenes in MPV as a function of storage temperature (7-30°C) were generated. The generated models were accurate and suitable for modeling the growth of pathogens in MPVs. Quantitative risk assessment (QRA) models were built to determine the probability of infection by Salmonella and L. monocytogenes due to consumption of MPVs. The models built using data available in the literature indicated that the risks of infection by these pathogens were 8.66 x 10-3 and 1.87 x 10-8, respectively, evidencing the need for adoption of risk mitigation measures

Validation of a predictive model describing growth of Salmonella in enteral feeds / Validação de um modelo preditivo para descrever o crescimento de Salmonella em dietas enterais

The growth of Salmonella enterica subs. enterica sorovar Typhimurium at 25ºC was monitored in industrialized and hospital formulated enteral feeds and the results were used to validate the mathematical model of Salmonella growth presented by the Pathogen Modeling Program (PMP) 7.0 (USDA-USA). The generation time of Salmonella in enteral feeds ranged from 21 to 34.8 min and, the maximum growth rate (µmax) varied from 1.28 to 1.95 h-1, resulting in a population increase from 5 to 6 log10 cycles within 14 to 24 h incubation. Growth was faster in the hospital formulated feed containing vegetables and eggs. The growth kinetic's parameters as lag phase; µmax and maximum population density (MPD) were similar to those predicted by the PMP 7.0, with exception of lag phase in enteral diet at pH 6.3. The results of this study validated the PMP 7.0 model for describe Salmonella growth in enteral feeds and demonstrates the appropriateness of use such model to determine the pathogen behavior in a wide range of storage conditions in this food.

O crescimento de Salmonella enterica subs. enterica sorovar Typhimurium a 25ºC foi determinado em dietas enterais industrializadas e formuladas em hospital e os resultados obtidos foram usados para validar um modelo matemático de crescimento de Salmonella apresentado no Programa de Modelagem de Patógenos (PMP), versão 7,0 (USDA-EUA). O tempo de geração de Salmonella em dietas enterais variou de 21 a 34,8 min e a velocidade específica máxima de crescimento (µmax) foi de 1,28 a 1,95 h-1, resultando em aumento de 5 a 6 ciclos logarítimos em um período de 14 a 24 h de incubação. O crescimento foi mais rápido na dieta formulada em hospital contendo vegetais e ovos. Os parâmetros cinéticos como fase lag, µmax e densidade populacional máxima (MDP) foram similares aqueles previstos no PMP 7.0, com exceção da fase lag em dietas enteral com pH 6,3. Os resultados deste estudo validaram o modelo do PMP 7,0 para descrever o crescimento de Salmonella em dietas enterais e demonstraram a propriedade desse modelo para determinar o comportamento do patógeno em uma variedade de condições nesse tipo de alimento.

The Role of Predictive Microbiology in Food Safety Risk Assessment / 微生物学通报

With the development of the food industry in China,it has been found that food safety is becoming the biggest issue in the food manufacture and logistics. Accurate and timely to establish a risk assessment method in produce market is the challenge for food safety system. Predictive microbiology is a core early warning technology in the food safety risk assessment. According to the microorganism predicting model,the pathogen and spoilage microorganism's growth in food can be fast judgment in advance. And it plays an important part in controlling the growth of pathogen and the spoilage microorganism in food. This paper summarized the predictive microbiology model's establishment and the present research situation,and discussed the present situation and application of predictive microbiology in food safety risk assessment. The future trend of predictive microbiology in food safety risk assessment was prospected as well.

Simplified prediction of Staphylococcus aureus growth in a cooked meat product exposed to changing environmental temperatures in warm climates / Predición simplificada del crecimiento de Staphylococcus aureus en productos cárnicos cocidos expuestos a temperaturas ambientes cambiantes en climas cálidos

In this work, a simplified method is used to estimate the growth of Staphylococcus aureus in a pasteurized meat product left for several hours at environmental temperatures (diurnal time) in warm climates of different cities in Argentina. Hourly temperature data for a warm January (the hottest month of the year) day, and literature data on the kinetics of S. aureus growth inoculated in a pasteurized meat product were used for calculations. As shown by results, if a cooked meat product is left exposed to environmental temperature at diurnal time, predictions made when using a constant temperature value (i.e. average daily) may not be accurate. Growth estimations in contaminated food left under ambient conditions during diurnal time, should consider the changing environmental temperature for correct results.

En este trabajo se utiliza un método simplificado para predecir el crecimiento de Staphylococcus aureus en un producto cárnico pasteurizado dejado por varias horas a temperatura ambiente diurna en zonas de clima cálido. En la predicción, se utilizaron datos de la temperatura horaria para un día caluroso típico de enero (mes más caliente del año) en varias ciudades de la Argentina y datos de la literatura sobre tiempos de generación y tiempo lag de la bacteria inoculada en un producto cárnico pasteurizado. Los resultados indicaron que cuando el producto se deja a temperatura ambiente diurna durante varias horas, no se debe utilizar para la predicción un valor de temperatura promedio (ej.: temperatura media diaria), sino que hay que tener en cuenta la evolución de este parámetro a lo largo del período considerado.