Presence and Activity of Psychrotrophic Microorganisms in Milk and Dairy Products: A Review

Cousin, M. A.

doi:10.4315/0362-028x-45.2.172

Cited by 476 publications

(328 citation statements)

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“…Dentre os isolados Gram-negativos (75,2%), 27% e 48% foram, respectivamente, Gram-negativos fermentadores e Gram-negativos não-fermentadores. A predominância do isolamento de bactérias Gram-negativas, observada nas amostras de leite cru refrigerado está de acordo com resultados de outras pesquisas, nas quais elas são consideradas como contaminantes mais freqüentes [11,15] 58%, 58% e 47% possuíam atividade de proteases, lipases e de lecitinase, respectivamente [43].…”

Section: -Isolamento E Caracterização De Bactérias Psicrotróficas Prounclassified

“…Porém, pode ocasionar problemas tecnológicos associados à atividade de enzimas proteolíticas e lipolíticas de bactérias psicrotróficas. Muitas destas enzimas são termorresistentes [23,33] e estão relacionadas às perdas de qualidade e à redução da vida de prateleira do leite UHT e de outros produtos lácteos [8,9,11,17,18,22,24,28,35,39,40].…”

Section: -Introduçãounclassified

“…Bactérias do gênero Pseudomonas têm sido isoladas com maior freqüência do leite e de produtos lácteos refrigerados [11,13,14,15,43], embora não representem mais do que 10% da microbiota do leite cru recém-ordenhado [35]. Esse gênero inclui espécies que apresentam um tempo de geração curto, entre 0 °C e 7 °C, e uma temperatura mínima de crescimento baixa, de até -10 °C [35].…”

Section: -Introduçãounclassified

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Qualidade microbiológica de leite cru refrigerado e isolamento de bactérias psicrotróficas proteolíticas

Pinto¹,

Martins²,

Vanetti³

2006

Ciênc. Tecnol. Aliment.

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RESUMOA estocagem do leite cru refrigerado na fonte de produção reduz perdas econômicas por atividade acidificante de bactérias mesofílicas, mas permite a seleção de bactérias psicrotróficas relacionadas a problemas tecnológicos e econômicos na indústria de laticínios. Com o objetivo de avaliar a qualidade microbiológica de leite cru, foram analisadas amostras provenientes de tanques de refrigeração individual, coletivos e do silo de uma indústria processadora de leite. Além disso, bactérias psicrotróficas proteolíticas foram isoladas do leite cru refrigerado e caracterizadas quanto à reação ao Gram e fermentação de glicose. O leite cru refrigerado mantido no silo industrial não atendeu ao padrão microbiológico legal e apresentou contagens microbianas significativamente superiores às do leite mantido em tanques individuais ou coletivos. Diferença significativa na contaminação por mesófilos e psicrotrófilos proteolíticos e não proteolíticos e por Pseudomonas foi observada entre as amostras coletadas nos tanques de refrigeração e no silo industrial. A microbiota Gram-negativa foi isolada com maior freqüência, especialmente bactérias Gram-negativas não fermentadoras de glicose. Palavras-chave: leite refrigerado, microbiota psicrotrófica, qualidade microbiológica. SUMMARYMICROBIAL QUALITY OF RAW REFRIGERATED MILK AND ISOLATION OF PSYCHROTROPHIC PROTEOLYTIC BACTERIA. Storing refrigerated raw milk in the source of production reduces economic losses which occur due to the acidifying activity of mesophilic bacteria. Nevertheless, this process selects psychrotrophic bacteria that cause technological and economic problems to the dairy industry. Samples of individual and collective refrigerated tanks and samples from an industrial silo in a dairy industry were collected and analyzed to evaluate the microbiological quality of raw milk. Furthermore, proteolytic psychrotrophic bacteria were isolated from refrigerated raw milk and characterized according to the Gram reaction and glucose fermentation. The refrigerated raw milk from the industrial silo was not compatible with legal microbiological standards, and its microbial count was significantly higher than milk from individual and collective tanks. A significant difference of contamination by mesophiles, proteolytic and non-proteolytic psychrotrophs, and Pseudomonas was observed in samples collected from refrigeration tanks compared to samples collected from the industrial silo. The Gram-negative microbiota was isolated more often, especially the glucose non-fermentative Gram-negative bacteria.

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Section: -Isolamento E Caracterização De Bactérias Psicrotróficas Prounclassified

Section: -Introduçãounclassified

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Qualidade microbiológica de leite cru refrigerado e isolamento de bactérias psicrotróficas proteolíticas

Pinto¹,

Martins²,

Vanetti³

2006

Ciênc. Tecnol. Aliment.

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“…Additionally, a relatively wide range of microorganisms in the raw milk are present and they can either be thermophilic, mesophilic or psychrophilic [7]. Therefore, the presence of more PEFresistant microorganisms [15] would reduce the effect of PEF processing.…”

Section: Bacterial Inactivationmentioning

confidence: 99%

Continuous raw skim milk processing by pulsed electric field at non-lethal temperature: effect on microbial inactivation and functional properties

Floury

Grosset

Leconte

et al. 2005

Lait

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-Pulsed electric field (PEF) is an emerging non-thermal processing technology used to inactivate microorganisms in liquid foods such as milk. The objective of this research was to study the effectiveness of continuous PEF equipment (square wave pulses) on total microorganisms of raw skim milk and on Salmonella enteritidis inactivation under moderate temperatures (T < 50 °C). Processing parameters (electric field and pulse width) were chosen as follows: 45 kV·cm -1 /500 ns and 55 kV·cm -1 /250 ns, with increasing pulse frequencies from 40 to 120 Hz, that corresponds to an energy input varying from range 0-100 kJ·kg -1 . In these conditions, the effectiveness of PEF processing on microbial inactivation was very limited: 1.4-log reduction of total microflora and S. enteritidis was the maximal inactivation ratio obtained. The effect of these PEF treatments on physicochemical and technological properties of the milk was also evaluated. These process conditions had an effect on proteinic components of milk such as casein micelles, since viscosity of PEF-treated milk decreased and coagulation properties were enhanced for high field levels (45-55 kV·cm -1 ) with 2.1 to 3.5 µs cumulated treatment time and square waves. This study demonstrated that, contrary to numerous previous studies, PEF treatments had an impact on some food constituents. Résumé -Traitement de lait écrémé cru par champs électriques pulsés à température non létale : efficacité au plan de la destruction microbienne et effet sur les propriétés fonctionnelles. La tendance actuelle de l'industrie alimentaire est de proposer des alternatives aux traitements thermiques de pasteurisation. Ces traitements alternatifs doivent être efficaces sur le plan de la destruction bactérienne, mais moins sévères au plan physico-chimique, afin de garantir la qualité hygiénique des aliments tout en préservant leurs qualités nutritionnelles, sensorielles et fonctionnelles. Les traitements par champs électriques pulsés (CEP) sont souvent reconnus dans la littérature comme un des procédés innovants capables de répondre à ces nouvelles exigences. L'objectif de cette étude était donc ici d'évaluer l'efficacité de traitements en continu par CEP (impulsions élec-triques rectangulaires) réalisés à température non létale (T < 50 °C) sur la destruction de la flore endogène et des coliformes du lait ainsi que sur du lait préalablement inoculé avec Salmonella enteritidis. Les paramètres de traitements choisis (champs électriques et largeur des impulsions) étaient les suivants : 55 kV·cm -1 /250 ns et 45 kV·cm -1 /500 ns, avec des fréquences d'impulsion variant de 40 à 120 Hz, ce qui se traduit par un apport d'énergie compris entre 0 et 100 kJ·kg -1 . Dans ces conditions, l'efficacité des traitements est très limitée puisque au maximum 1,4 log de réduction microbienne a pu être atteint sur la flore endogène et S. enteritidis. Parallèlement, l'effet des traitements par champs électriques pulsés sur les principales caractéristiques physico-chimiques et techno-fonctionnelles du la...

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“…The Pseudomonas species like P.fluorescens, P. putida, P. fragi, P. putrefaciens, and less frequently P. aeruginosa constitute the predominant microorganisms limiting the shelf life of processed fluid milk (Liu et al 2009). A common and well studied strain of Pseudomonas species that grow in raw milk is Pseudomonas fluorescens (Cousin 1982). They often become the predominant microbial flora during cold storage of raw milk.…”

Section: Introductionmentioning

confidence: 99%

Purification and properties of heat-stable extracellular protease from Pseudomonads fluorescens BJ-10

Zhang

2012

J Food Sci Technol

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Pseudomonas fluorescens BJ-10, a kind of psychrotrophic bacteria, was isolated from raw milk. It produced an extracellular protease of 47 kDa by SDS-PAGE. The crude proteases were purified by ammonium sulfate fractionation, ion-exchange and gel filtration chromatography. The specific activity of purified protease increased 61.38-fold. The optimum pH and temperature were pH 7.0 and 30°C, respectively. The purified protease was partially inhibited by DL-dithiothreitol, and the activity increased a little upon Fe 2+ addition. The protease showed typical heatstable behavior. After treatment at 100°C for 3 min, more than 94% activity remained. This work might lay the foundation for possible relationship between the heat stable protease and gelation of UHT milk.

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Presence and Activity of Psychrotrophic Microorganisms in Milk and Dairy Products: A Review

Cited by 476 publications

References 0 publications

Qualidade microbiológica de leite cru refrigerado e isolamento de bactérias psicrotróficas proteolíticas

Qualidade microbiológica de leite cru refrigerado e isolamento de bactérias psicrotróficas proteolíticas

Continuous raw skim milk processing by pulsed electric field at non-lethal temperature: effect on microbial inactivation and functional properties

Purification and properties of heat-stable extracellular protease from Pseudomonads fluorescens BJ-10

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