Minimal water activity for growth of Listeria monocytogenes as affected by solute and temperature

Daza, M. S. Tapia De; Villegas, y María V.; Martínez, Amaury Jiménez

doi:10.1016/0168-1605(91)90125-9

Cited by 41 publications

(9 citation statements)

References 12 publications

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“…This frequent occurrence is mainly explained by its ability to survive and grow at conditions associated with normal processing and distribution of food, such as refrigeration temperatures (27), high NaCl concentrations (20), or water activities (a w ) as low as 0.92 (24). Although L. monocytogenes is a neutrophile, it is tolerant to acidic conditions (5,8), and Shabala et al (22) demonstrated that L. monocytogenes maintained a constant intracellular pH (pH i ) at extracellular pH (pH ex ) values as low as 4.0.…”

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confidence: 99%

Osmotic Stress Leads to Decreased Intracellular pH of Listeria monocytogenes as Determined by Fluorescence Ratio-Imaging Microscopy

Fang

Siegumfeldt

Budde

2004

Appl Environ Microbiol

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Intracellular pH (pH i ) of Listeria monocytogenes was determined after exposure to NaCl or sorbitol in liquid and solid media (agar). Both compounds decreased pH i , and recovery on solid medium was impaired compared to that in liquid medium. N,N-dicyclohexylcarbodiimide abolished pH i recovery, and lowering a w with glycerol showed no effect on pH i .Listeria monocytogenes is a ubiquitous gram-positive foodborne pathogen, with a widespread occurrence in, e.g., fresh meat and poultry (10), processed ready-to-eat meats (15), seafood (17), soft-style cheeses (18), and butter (19). This frequent occurrence is mainly explained by its ability to survive and grow at conditions associated with normal processing and distribution of food, such as refrigeration temperatures (27), high NaCl concentrations (20), or water activities (a w ) as low as 0.92 (24). Although L. monocytogenes is a neutrophile, it is tolerant to acidic conditions (5, 8), and Shabala et al. (22) demonstrated that L. monocytogenes maintained a constant intracellular pH (pH i ) at extracellular pH (pH ex ) values as low as 4.0. Information on the effect of osmotic stress on pH i of L. monocytogenes seems not to be available, and therefore the main objective of the present study was to investigate the relationship between pH i of L. monocytogenes and osmotic stress in liquid brain heart infusion broth (BHI) as well as on solid BHI (agar) by using fluorescence ratio-imaging microscopy according to the methods of Budde and Jakobsen (4).The strains of L. monocytogenes, EGD (kindly provided by Werner Goebel, Biozentrum, Universität Würzburg, Germany) and 4140 (the Danish Meat Research Institute, Roskilde, Denmark), were grown in BHI adjusted to pH 6.0 with HCl at 37°C for 10 h before use. Fluorescent labeling of the cells and image acquisition were performed essentially as previously described (4, 23), where washed cells were stained with 30 M 5,6-carboxyfluorescein diacetate-succinimidyl ester at 30°C for 30 min. Excitation with 490-and 435-nm wavelengths was performed through a 510-nm dichroic mirror, and emission was recorded through an 515-to 565-nm band pass filter on a Coolsnap fx camera (Photometrics, Tucson, Ariz.). Ratio imagings were performed by using MetaFluor, version 4.5 (Universal Imaging Corporation, West Chester, Pa.), and a minimum of 40 single cells was analyzed in each experiment. For pH calibration, labeled cells were permeabilized with ethanol (63% [vol/vol]) and were suspended in either BHI broth or were immobilized on the surface of BHI agar adjusted with HCl or NaOH to a pH in the range 5.5 to 8.5 (steps of 0.5), allowing pH i to equilibrate to pH ex . A polynomial model fitted to the data was subsequently used to calculate pH i .In liquid BHI the labeled cells were immobilized on the surface of an 8-well chamber slide (Lab-Tek II Chambered cover glass; Nalge Nunc International) by adding 100 l of bacterial suspension and allowing the cells to settle, followed by a brief rinse with phosphate-buffered saline before addition of liqui...

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Osmotic Stress Leads to Decreased Intracellular pH of Listeria monocytogenes as Determined by Fluorescence Ratio-Imaging Microscopy

Fang

Siegumfeldt

Budde

2004

Appl Environ Microbiol

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“…A preservação de alimentos por métodos combinados tem se mostrado uma alternativa aos métodos tradicionais de conservação, muitas vezes reduzindo o custo relativo e permitindo obter maior eficiência e menor rigor comparativamente a aplicação de um método isolado (DAZA et al, 1991). Consiste na reunião adequada de vários parâmetros como, tratamento térmico brando ou moderado, leve redução da atividade de água (Aa), redução de pH, adição simples ou combinada de agentes químicos e outros (CHIRIFE e FAVETO, 1992;ALZAMORA et al, 1993;WELTI-CHANES et al, 1997).…”

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Qualidade De Polpa De Pêssegos Preservada Por Métodos Combinados

Araújo

Rodrigues

Duarte

2007

RBTA

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Este trabalho teve por objetivo verificar a qualidade de polpa de pêssegos (Prunus pérsica) preservada por métodos combinados e armazenada a temperatura ambiente, produzida por empresa localizada na região de Pelotas-RS. A região caracteriza-se pela cultura do pessegueiro cujos frutos são destinados quase que na sua totalidade ao aproveitamento industrial. Foram coletadas amostras de polpa durante 6 meses, contados a partir do terceiro mês do processamento inicial da empresa, quando a mesma teve início à utilização do material, no período considerado como entressafra da fruta, nas quais determinou-se pH, acidez total, sólidos solúveis, açúcares totais, redutores e não-redutores, teor de pectina, viscosidade aparente na água de armazenamento da polpa e na polpa drenada-triturada, além da contagem de bolores e leveduras. De acordo com os resultados obtidos durante a pesquisa observou-se que a polpa de pêssegos preservada por métodos combinados e armazenada a temperatura ambiente manteve-se estável microbiologicamente até 9 meses de armazenamento, mostrando, contudo diferenças marcantes nas suas características físico-químicas.

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“…agrotec., Lavras, v. 30, n. 4, p. 715-723, jul./ago., 2006. Este tipo de tecnologia é de simples aplicação, podendo ser utilizada como técnica alternativa à refrigeração, congelamento, desidratação e outros procedimentos que, geralmente, necessitam de alto investimento em equipamentos e ainda consomem muita energia (DAZA et al, 1997).…”

Section: Introductionunclassified

Influência da adição de sacarose na estabilidade da polpa de bacuri conservada por métodos combinados

et al. 2006

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RESUMOO estudo do processo de conservação da polpa de bacuri (Platonia insignis Mart.), através da aplicação da tecnologia de obstáculos, foi feito pela combinação dos seguintes fatores: adição de benzoato de sódio (1000 ppm) e metabissulfito de sódio (400 ppm), tratamento térmico (100ºC/2 min.) e redução da atividade de água pela adição de sacarose (0, 17,4 e 28,6% (p/p)). A estabilidade dos produtos foi avaliada segundo suas características físico-químicas, microbiológicas e sensoriais, a cada 30 dias, durante quatro meses de armazenamento, à temperatura ambiente (25 o C±2 o C). As características físico-químicas dos produtos obtidos sofreram pouca alteração durante o armazenamento, sendo os teores de açúcares redutores e o teor de dióxido de enxofre as características mais afetadas nos três produtos. Os resultados mostraram que os tipos de obstáculos usados e sua intensidade foram capazes de assegurar a estabilidade microbiológica e uma boa aceitação sensorial dos produtos durante o período de armazenamento.Termos para indexação: Platonia insignis Mart., métodos combinados, alimentos auto-estáveis, estabilidade. ABSTRACTThe study of preservation process of the bacuri pulp (Platonia insignis Mart.) through the application of hurdle technology was done by the application of the following preservation factors: addition of sodium benzoate (1000 ppm) and sodium metabissulphite (400 ppm), thermal treatment (100ºC/ 2 min.) and reduction of the water activity by the addition of sucrose (0, 17,4 and 28,6% (w/ w)). Stability was assessed monthly by means of physico-chemical, microbiological and sensorial methods, each 30 days, during four months of storage at room temperature (25 o C±2 o C). Physico-chemical characteristics of the products obtained little changed during the storage, being the reduced sugars and sulfite dioxide contents the most affected characteristics in three products. Results showed that the obstacles used and their intensities were capable to assure the microbiological stability and a good sensory acceptability of the products during the storage time.

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Minimal water activity for growth of Listeria monocytogenes as affected by solute and temperature

Cited by 41 publications

References 12 publications

Osmotic Stress Leads to Decreased Intracellular pH of Listeria monocytogenes as Determined by Fluorescence Ratio-Imaging Microscopy

Osmotic Stress Leads to Decreased Intracellular pH of Listeria monocytogenes as Determined by Fluorescence Ratio-Imaging Microscopy

Qualidade De Polpa De Pêssegos Preservada Por Métodos Combinados

Influência da adição de sacarose na estabilidade da polpa de bacuri conservada por métodos combinados

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