scholarly journals Inactivation of Mycobacterium paratuberculosis by Pulsed Electric Fields

2001 ◽  
Vol 67 (6) ◽  
pp. 2833-2836 ◽  
Author(s):  
Neil J. Rowan ◽  
Scott J. MacGregor ◽  
John G. Anderson ◽  
Douglas Cameron ◽  
Owen Farish
Keyword(s):  
Electric Fields ◽  
Pulsed Electric Fields ◽  
Cellular Level ◽  
Treatment Temperature ◽  
Cow’S Milk ◽  
Mycobacterium Paratuberculosis ◽  
Cow's Milk ◽  
High Temperature Short Time ◽  
Peptone Water ◽  
Short Time

ABSTRACT The influence of treatment temperature and pulsed electric fields (PEF) on the viability of Mycobacterium paratuberculosiscells suspended in 0.1% (wt/vol) peptone water and in sterilized cow's milk was assessed by direct viable counts and by transmission electron microscopy (TEM). PEF treatment at 50°C (2,500 pulses at 30 kV/cm) reduced the level of viable M. paratuberculosis cells by approximately 5.3 and 5.9 log10 CFU/ml in 0.1% peptone water and in cow's milk, respectively, while PEF treatment of M. paratuberculosisat lower temperatures resulted in less lethality. Heating alone at 50°C for 25 min or at 72°C for 25 s (extended high-temperature, short-time pasteurization) resulted in reductions ofM. paratuberculosis of approximately 0.01 and 2.4 log10 CFU/ml, respectively. TEM studies revealed that exposure to PEF treatment resulted in substantial damage at the cellular level to M. paratuberculosis.

Factors affecting the inactivation of the natural microbiota of milk processed by pulsed electric fields and cross-flow microfiltration

2011 ◽  
Vol 78 (3) ◽  
pp. 270-278 ◽  
Author(s):  
Oscar Rodríguez-González ◽  
Markus Walkling-Ribeiro ◽  
Shesha Jayaram ◽  
Mansel W Griffiths
Keyword(s):  
Electric Fields ◽  
Skim Milk ◽  
Cross Flow ◽  
Pulsed Electric Fields ◽  
Effect Of Temperature ◽  
Factors Affecting ◽  
High Temperature Short Time ◽  
Solids Content ◽  
Microbial Groups ◽  
Short Time

Prior to processing milk and cream were standardised and homogenised. Skim milk was cross-flow microfiltered (CFMF) prior to treatment with pulsed electric fields (PEF) or high temperature short time (HTST) pasteurization. The effect of temperature of the skim milk and product composition on the efficacy of PEF treatment was determined. The electrical conductivity of the product was related to fat and solids content and increased 5% for every g/kg increase of solids and decreased by nearly 0·7% for every g/kg increase of fat. From the three microbial groups analyzed (mesophilic, coliform, and psychrotroph) in milks differences (P<0·05) in the inactivation of mesophilic microorganisms were observed between the counts following PEF treatment, while HTST pasteurization resulted in higher reductions in all different counts than those obtained after PEF. Increasing the skim milk temperature prior to PEF treatment to about 34°C showed equivalent reductions in microbial counts to skim milk treated at 6°C in half the time. The reductions achieved by a combination of CFMF and PEF treatments were comparable to those achieved when CFMF was combined with HTST pasteurization. A higher reduction in coliform counts was observed in homogenised products subjected to PEF than in products that were only standardised for fat content.

scholarly journals Occurrence of enterococci in mastitic cow’s milk and their antimicrobial resistance

2019 ◽  
Vol 63 (1) ◽  
pp. 93-97 ◽  
Author(s):  
Hanna Różańska ◽  
Aleksandra Lewtak-Piłat ◽  
Maria Kubajka ◽  
Marcin Weiner
Keyword(s):  
Antimicrobial Resistance ◽  
Enterococcus Faecalis ◽  
Antimicrobial Susceptibility ◽  
High Rate ◽  
Cow’S Milk ◽  
Cow's Milk ◽  
Milk Samples ◽  
Predominant Species ◽  
Peptone Water ◽  
Mastitic Milk

Abstract Introduction: The aim of the study was to evaluate the occurrence of enterococci in inflammatory secretions from mastitic bovine udders and to assess their antimicrobial resistance. Material and Methods: A total of 2,000 mastitic milk samples from cows were tested in 2014–2017. The isolation of enterococci was performed by precultivation in buffered peptone water, selective multiplication in a broth with sodium azide and cristal violet, and cultivation on Slanetz and Bartley agar. The identification of enterococci was carried out using Api rapid ID 32 strep kits. The antimicrobial susceptibility was evaluated using the MIC technique. Results: Enterococci were isolated from 426 samples (21.3%). Enterococcus faecalis was the predominant species (360 strains), followed by E. faecium (35 isolates), and small numbers of others. The highest level of resistance was observed to lincomycin, tetracycline, quinupristin/dalfopristin (Synercid), erythromycin, kanamycin, streptomycin, chloramphenicol, and tylosin. Single strains were resistant to vancomycin and ciprofloxacin. All isolates were sensitive to daptomycin. E. faecalis presented a higher level of resistance in comparison to E. faecium, except to nitrofurantoin. Conclusion: The results showed frequent occurrence of enterococci in mastitic cow’s milk and confirmed the high rate of their antimicrobial resistance.

scholarly journals Effect of Commercial-Scale High-Temperature, Short-Time Pasteurization on the Viability of Mycobacterium paratuberculosis in Naturally Infected Cows' Milk

2002 ◽  
Vol 68 (2) ◽  
pp. 602-607 ◽  
Author(s):  
Irene R. Grant ◽  
Edward I. Hitchings ◽  
Alan McCartney ◽  
Fiona Ferguson ◽  
Michael T. Rowe
Keyword(s):  
High Temperature ◽  
Cetylpyridinium Chloride ◽  
Raw Milk ◽  
Holding Time ◽  
Mycobacterium Paratuberculosis ◽  
Pasteurized Milk ◽  
Milk Samples ◽  
Commercial Scale ◽  
High Temperature Short Time ◽  
Short Time

ABSTRACT Raw cows' milk naturally infected with Mycobacterium paratuberculosis was pasteurized with an APV HXP commercial-scale pasteurizer (capacity 2,000 liters/h) on 12 separate occasions. On each processing occasion, milk was subjected to four different pasteurization treatments, viz., 73�C for 15 s or 25 s with and without prior homogenization (2,500 lb/in2 in two stages), in an APV Manton Gaulin KF6 homogenizer. Raw and pasteurized milk samples were tested for M. paratuberculosis by immunomagnetic separation (IMS)-PCR (to detect the presence of bacteria) and culture after decontamination with 0.75% (wt/vol) cetylpyridinium chloride for 5 h (to confirm bacterial viability). On 10 of the 12 processing occasions, M. paratuberculosis was detectable by IMS-PCR, culture, or both in either raw or pasteurized milk. Overall, viable M. paratuberculosis was cultured from 4 (6.7%) of 60 raw and 10 (6.9%) of 144 pasteurized milk samples. On one processing day, in particular, M. paratuberculosis appeared to have been present in greater abundance in the source raw milk (evidenced by more culture positives and stronger PCR signals), and on this occasion, surviving M. paratuberculosis bacteria were isolated from milk processed by all four heat treatments, i.e., 73�C for 15 and 25 s with and without prior homogenization. On one other occasion, surviving M. paratuberculosis bacteria were isolated from an unhomogenized milk sample that had been heat treated at 73�C for 25 s. Results suggested that homogenization increases the lethality of subsequent heat treatment to some extent with respect to M. paratuberculosis, but the extended 25-s holding time at 73�C was found to be no more effective at killing M. paratuberculosis than the standard 15-s holding time. This study provides clear evidence that M. paratuberculosis bacteria in naturally infected milk are capable of surviving commercial high-temperature, short-time pasteurization if they are present in raw milk in sufficient numbers.

Influence of treatment temperature on the inactivation of Listeria innocua by pulsed electric fields

LWT ◽  
2005 ◽  
Vol 38 (2) ◽  
pp. 167-172 ◽  
Author(s):  
D.R. Sepulveda ◽  
M.M. Góngora-Nieto ◽  
M.F. San-Martin ◽  
G.V. Barbosa-Cánovas
Keyword(s):  
Electric Fields ◽  
Pulsed Electric Fields ◽  
Treatment Temperature ◽  
Listeria Innocua

scholarly journals Mycobacterium paratuberculosis detection in cow's milk in Argentina by immunomagnetic separation-PCR

2016 ◽  
Vol 47 (2) ◽  
pp. 506-512 ◽  
Author(s):  
Liliana Rosa Gilardoni ◽  
Bárbara Fernández ◽  
Claudia Morsella ◽  
Laura Mendez ◽  
Ana María Jar ◽  
...  
Keyword(s):  
Immunomagnetic Separation ◽  
Cow’S Milk ◽  
Mycobacterium Paratuberculosis ◽  
Cow's Milk

Instantaneous detection of αs-casein in cow's milk using fluorogenic peptide aptamers

2020 ◽  
Vol 12 (10) ◽  
pp. 1368-1373
Author(s):  
Chinmay Phadke ◽  
Seiichi Tada ◽  
Izumi Kono ◽  
Asami Hiyama ◽  
Yuki Takase ◽  
...  
Keyword(s):  
Cow’S Milk ◽  
Peptide Aptamers ◽  
Cow's Milk ◽  
Peptide Aptamer ◽  
Short Time ◽  
Fluorogenic Peptide

We present a novel, fluorogenic peptide aptamer that strongly enhances its fluorescence just after mixing it with a milk allergen αs-casein. Notably, our system can detect αs-casein in an exceptionally short time of 20–25 seconds.

Inactivation of Pseudomonas fluorescens in Skim Milk by Combinations of Pulsed Electric Fields and Organic Acids

2005 ◽  
Vol 68 (6) ◽  
pp. 1232-1235 ◽  
Author(s):  
JUAN J. FERNÁNDEZ-MOLINA ◽  
BILGE ALTUNAKAR ◽  
DANIELA BERMÚDEZ-AGUIRRE ◽  
BARRY G. SWANSON ◽  
GUSTAVO V. BARBOSA-CÁNOVAS
Keyword(s):  
Acetic Acid ◽  
Organic Acids ◽  
Pseudomonas Fluorescens ◽  
Propionic Acid ◽  
Electric Fields ◽  
Skim Milk ◽  
Pulsed Electric Fields ◽  
Treatment Temperature ◽  
Initial Concentration ◽  
Ph Range

Pseudomonas fluorescens suspended in skim milk was inactivated by application of pulsed electric fields (PEF) either alone or in combination with acetic or propionic acid. The initial concentration of microorganisms ranged from 105 to 106 CFU/ml. Addition of acetic acid and propionic acid to skim milk inactivated 0.24 and 0.48 log CFU/ml P. fluorescens, respectively. Sets of 10, 20, and 30 pulses were applied to the skim milk using exponentially decaying pulses with pulse lengths of 2 μs and pulse frequencies of 3 Hz. Treatment temperature was maintained between 16 and 20°C. In the absence of organic acids, PEF treatment of skim milk at field intensities of 31 and 38 kV/cm reduced P. fluorescens populations by 1.0 to 1.8 and by 1.2 to 1.9 log CFU/ml, respectively. Additions of acetic and propionic acid to the skim milk in a pH range of 5.0 to 5.3 and PEF treatment at 31, 33, and 34 kV/cm, and 36, 37, and 38 kV/cm reduced the population of P. fluorescens by 1.4 and 1.8 log CFU/ml, respectively. No synergistic effect resulted from the combination of PEF with acetic or propionic acid.

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