Inhibitory effect of oregano, laurel and rosemary extracts obtained by supercritical fluid extraction on growth of Listeria monocytogenes in a vegetal model system

[SPA] Existe un limitado número de estudios sobre la actividad antilisteriana de hierbas y especias en medio de cultivo y aún menos en alimentos. Las propiedades antimicrobianas de extractos de orégano, romero y laurel, obtenidos mediante Extracción por Fluidos Supercríticos (EFS), han sido estudiadas frente a Listeria monocytogenes CECT 4032 en un sistema modelo alimentario preparado a partir de jugo de brócoli, a 30 y 8 ºC. En general, los extractos obtenidos en el segundo separador (fracción 2) mostraron mayor actividad que los obtenidos en el primer separador (fracción 1). La fracción 2 de los extractos de laurel y orégano produjo reducciones de aproximadamente 3 unidades logarítmicas en la población del patógeno. En la presente investigación, las dos fracciones de romero provocaron un efecto bactericida tanto a 30 como a 8 ºC tras 20 horas y 25 días de incubación, respectivamente. Los datos aquí presentados sugieren que alguno de los extractos obtenidos por EFS podría ser potencialmente útil en el control de la calidad microbiológica de vegetales frescos. [ENG] There are limited reports on antilisterial effect of spices and herbs in culture media and fewer still in foods. Antimicrobial properties of oregano, rosemary and laurel extracts obtained by Supercritical Fluid Extraction (SFE) are studied against Listeria monocytogenes CECT 4032 in broccoli juice, chosen to represent a model food system, at 30 and 8ºC. In general, the extracts collected in the second separator (fraction 2) showed a higher activity than those obtained in the first separator (fraction 1). The fraction 2 of laurel and oregano shown reductions of approximately 3 logarithmic units. In the present investigation, both rosemary fractions have shown bactericidal effect against the target microorganism, at 30 and 8ºC after 20 h and 25 days of incubation, respectively. The data presented here suggest that the some of the extracts obtained by SFE could be potentially useful in the effective control of microbiological quality of fresh vegetables.Este trabajo ha sido posible gracias a la financiación recibida por el Ministerio de Educación y cultura, proyecto AGL2002-04059-C02-02, así como a la beca concedida por la Fundación CajaMurcia

Comparison of Probabilistic and Deterministic Predictions of Time to Growth of Listeria monocytogenes as Affected by pH and Temperature in Food

8 pages, 2 tables, 4 figures.-- Online Ahead of Print: October 8, 2010.-- This is a copy of an article published in the Foodborne Pathogens and Disease © 2011 [copyright Mary Ann Liebert, Inc.]; Foodborne Pathogens and Disease is available online at: http://www.liebertonline.com.Stochastic models are useful for estimating the risk of foodborne illness and they can be integrated, besides other sources of variability, into microbial risk assessment. A stochastic approach to evaluate growth of two strains of Listeria monocytogenes influenced by different factors affecting microbial growth (pH and storage temperature) was performed. An individual-based approach of growth through optical density measurements was used. From results obtained, histograms of the lag phase were generated and distributions were fitted. Histograms presented increased variation when the factors applied were suboptimal for L. monocytogenes and they were combined. The extreme value distribution was ranked as the best one in most cases, whereas normal was the poorest fitting distribution. To evaluate the influence of pH and storage temperature on L. monocytogenes CECT 5672 in real food, commercial samples of courgette and carrot soup were inoculated with this pathogen. It was able to grow in both soups at storage temperatures from 4°C to 20°C. Using the distributions adjusted, predictions of time to growth (102 cfu/g) of L. monocytogenes were established by Monte Carlo simulation and they were compared with deterministic predictions and observations in foods.Dr. Marina Muñoz thanks Fundación CAJAMURCIA for awarding her a fellowship. This project was funded by Ministerio de Educación y Ciencia Español (ref. AGL 2006-13320-C03-02=ALI)Peer reviewe

Comparison of Probabilistic and Deterministic Predictions of Time to Growth of Listeria monocytogenes as Affected by pH and Temperature in Food

Abstract Stochastic models are useful for estimating the risk of foodborne illness and they can be integrated, besides other sources of variability, into microbial risk assessment. A stochastic approach to evaluate growth of two strains of Listeria monocytogenes influenced by different factors affecting microbial growth (pH and storage temperature) was performed. An individual-based approach of growth through optical density measurements was used. From results obtained, histograms of the lag phase were generated and distributions were fitted. Histograms presented increased variation when the factors applied were suboptimal for L. monocytogenes and they were combined. The extreme value distribution was ranked as the best one in most cases, whereas normal was the poorest fitting distribution. To evaluate the influence of pH and storage temperature on L. monocytogenes CECT 5672 in real food, commercial samples of courgette and carrot soup were inoculated with this pathogen. It was able to grow in both soups at storage temperatures from 48C to 208C. Using the distributions adjusted, predictions of time to growth (10 2 cfu=g) of L. monocytogenes were established by Monte Carlo simulation and they were compared with deterministic predictions and observations in foods

Efecto de tratamientos isotérmicos sobre la supervivencia de Listeria monocytogenes evaluada in vitro

Uno de los principales protagonistas de interés en la industria alimentaria es Listeria Monocytogenes causante de la listeriosis, la cual presenta una alta incidencia en humanos, debido a que se encuentra asociada al consumo de alimentos contaminados con el microorganismo, debido a su presencia en gran cantidad de productos. El objetivo de esta investigación fue evaluar el efecto de los tratamientos isotérmicos, para el control de L. Monocytogenes. Para poder determinar el efecto de estos tratamientos, se aplicaron tratamientos isotérmicos a 55º C y 60ª C, sobre la cepa L. monocytogenes CETC 4032. Después de cada tratamiento, se recuperó el microorganismo en un medio no selectivo y en uno selectivo, obteniéndose una mayor reducción en la población en el medio de recuperación con un factor de inhibición.Asociación de Jóvenes Investigadores de Cartagena, (AJICT). Universidad Politécnica de Cartagena. Escuela Técnica Superior de Ingeniería Industrial UPCT, (ETSII). Escuela Técnica Superior de Ingeniería Agronómica, (ETSIA), Escuela Técnica Superior de Ingeniería de Telecomunicación (ETSIT). Cátedra Bancaja Jóvenes Emprendedores. Hero. Parque Tecnológico de Fuente Álamo. Grupo Aquiline