Enumeration of Total Bacteria in Raw and Pasteurized Milk by Reflectance Colorimetry: Collaborative Study

1994 ◽  
Vol 77 (3) ◽  
pp. 623-627 ◽  
Author(s):  
Gary H Richardson ◽  
James T C Yuan ◽  
Donald V Sisson ◽  
Barry O Stokes
Keyword(s):  
Collaborative Study ◽  
Plate Count ◽  
Pasteurized Milk ◽  
Standard Plate Count ◽  
Standard Plate ◽  
Total Bacteria

Abstract Seven out of 9 laboratories completed a collaborative study comparing a reflectance colorimetric (RC) bioactivity monitor (Omnispec™ 4000) method to the standard plate count (SPC) method for estimation of total bacteria in raw and homogenized pasteurized milk. Each laboratory analyzed 12 different samples by the SPC method and 24 samples (12 blind duplicates) by the RC method. For the RC method RSDr was 1.7%, and RSDR was 4.5%. RSDR for the SPC method was 20.8%. The method was adopted first action by AOAC INTERNATIONAL.

Enumeration of Total Bacteria and Coliforms in Milk by Dry Rehydratable Film Methods: Collaborative Study

1986 ◽  
Vol 69 (3) ◽  
pp. 527-531 ◽  
Author(s):  
Roy E Ginn ◽  
Vernal S Packard ◽  
Terrance L Fox ◽  
◽  
E Arnold ◽  
...  
Keyword(s):  
Collaborative Study ◽  
Plate Count ◽  
Standard Methods ◽  
Standard Plate Count ◽  
Milk Samples ◽  
Standard Plate ◽  
The Mean ◽  
Standard Deviations ◽  
The Difference ◽  
Total Bacteria

Abstract Eleven laboratories participated in a collaborative study to compare the dry rehydratable film (Petrifilm® SM and Petrifilm® VRB) methods, respectively, to the standard plate count (SPC) and violet red bile agar (VRBA) standard methods for estimation of total bacteria and coliform counts in raw and homogenized pasteurized milk. Each laboratory analyzed 16 samples (8 different samples in blind duplicate) for total count by both the SPC and Petrifilm SM methods. A second set of 16 samples was analyzed by the VRBA and Petrifilm VRB methods. The repeatability standard deviations (the square root of the between-replicates variance) of the SPC, Petrifilm SM, VRBA, and Petrifilm VRB methods were 0.0S104, 0.0444, 0.14606, and 0.13806, respectively; the reproducibility standard deviations were 0.7197, C.06380, 0.15326, and 0.13806, respectively. The difference between the mean Iog10 SPC and the mean logio Petrifilm SM results was 0.027. For the VRBA and Petrifilm VRB methods, the mean log10 difference was 0.013. These results generally indicate the suitability of the dry rehydratable film methods as alternatives to the SPC and VRBA methods for milk samples. The methods have been adopted official first action.

Collaborative Study of the Impedance Method for Examining Raw Milk Samples

1984 ◽  
Vol 47 (9) ◽  
pp. 707-712 ◽  
Author(s):  
R. FIRSTENBERG-EDEN
Keyword(s):  
Collaborative Study ◽  
Raw Milk ◽  
Plate Count ◽  
Impedance Method ◽  
Standard Plate Count ◽  
Milk Samples ◽  
Automated Method ◽  
Significant Difference ◽  
Standard Plate ◽  
Contamination Levels

The impedance method is a rapid automated method for determining bacteriological contamination levels. A collaborative study was done to establish the reproducibility of the impedance method in predicting counts of raw milk. Frozen and unfrozen raw milk samples, with counts in the range of 9 × 104 to 4 × 107 CFU/ml, were sent to six laboratories to be examined by the standard plate count method (SPC) and by the impedance method which produced Bactometer-predicted counts (BPC). The impedance results showed less variability than SPC among laboratories in all three trials. The variance between split samples was also smaller for the impedance method than for SPC. However, the variance between duplicate plates of the same sample was significantly smaller for SPC than for BPC. In one trial, the means of BPC and SPC were not significantly different, whereas in another trial there was a significant difference of ca. log10 0.27 between the means of the two methods. However, in this trial the extreme differences between laboratories counting the same sample were log10 0.42.

Comparison of 3M™ Petrifilm™ Aerobic Count Plates to Standard Plating Methodology for Use with AOAC Antimicrobial Efficacy Methods 955.14, 955.15, 964.02, and 966.04 as an Alternative Enumeration Procedure: Collaborative Study

2013 ◽  
Vol 96 (4) ◽  
pp. 717-722 ◽  
Author(s):  
Maria T Nelson ◽  
Robert A LaBudde ◽  
Stephen F Tomasino ◽  
Rebecca M Pines ◽  
M Bennett ◽  
...  
Keyword(s):  
Collaborative Study ◽  
Test Methods ◽  
Antimicrobial Efficacy ◽  
Plate Count ◽  
Matched Pair ◽  
Acceptance Criterion ◽  
Standard Plate Count ◽  
Test Organisms ◽  
Standard Plate ◽  
Viable Bacteria

Abstract A multilaboratory study was conducted to determine the equivalence of the 3M™ Petrifilm™ Aerobic Count Plate and standard plating methodology for measuring viable bacteria and spores recovered from hard-surface carriers (stainless steel and porcelain), also known as "control carrier counts," used in AOAC antimicrobial efficacy test methods. Six laboratories participated in the study in which carriers inoculated with Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella enterica, and spores of Bacillus subtilis were evaluated using 3M Petrifilm Aerobic Count (AC) plates and standard plating side-by-side. The data were analyzed using a matched-pair t-test to determine the between-method effect with confidence intervals. For all test organisms pooled across all laboratories, the mean difference in log10 concentration between the standard plate count method and 3M Petrifilm AC Plates was −0.012, with a 95% confidence interval of (−0.090, +0.066), which was well within the −0.5, +0.5 interval established as the acceptance criterion. The between-carrier SD averaged 0.139; the between-replicate SD was 0.050. The carrier reproducibility, given that a single replicate per carrier is done, was estimated to be 0.148. Although differences were seen in the final concentrations of the test organisms among laboratories, there were no statistical differences between the enumeration methods. Based on the results from this study, 3M Petrifilm AC Plates are equivalent to standard plating methodology and can be used as an alternative procedure for the enumeration of test organisms used in AOAC Methods 955.14, 955.15, 964.02, and 966.04.

EFFECT OF TEMPERATURE AND TIME OF PLATE INCUBATION ON THE ENUMERATION OF PASTEURIZATION-RESISTANT BACTERIA IN MILK1

1963 ◽  
Vol 26 (11) ◽  
pp. 357-363 ◽  
Author(s):  
W. R. Thomas ◽  
G. W. Reinbold ◽  
F. E. Nelson
Keyword(s):  
Incubation Temperature ◽  
Bacterial Count ◽  
Raw Milk ◽  
Effect Of Temperature ◽  
Plate Count ◽  
Resistant Bacteria ◽  
Pasteurized Milk ◽  
Standard Plate Count ◽  
Standard Plate

This study was undertaken to determine the effect of temperature and time of plate incubation upon the count of thermoduric bacteria in milk. Specific types of thermoduric bacteria in pure culture, as well as those present in the mixed flora of commercial milk samples, were enumerated. Plate incubation at 28 C for 4 days was the temperature-time combination that produced the highest thermoduric bacterial count with laboratory-pasteurized milk. Incubation at 21, 32 or 35 C gave lower counts. Thermoduric bacteria subjected to pasteurization were more exacting in their growth temperature requirements than were unheated bacteria. Cultures of Arthrobacter sp., Micrococcus varians and Streptococcus sp. grew over a much wider temperature range before laboratory pasteurization than after the heat treatment. The incubation temperature and time currently recommended for the standard plate count, while presumably adequate for the enumeration of bacteria in raw milk, may not be equally satisfactory for the determination of the maximum viable bacterial population of pasteurized milk.

Microtiter Technique for Enumeration of Mesophiles, Psychrotrophs, and Coliforms in Raw and Pasteurized Milk

1977 ◽  
Vol 40 (11) ◽  
pp. 795-797 ◽  
Author(s):  
IVÀN A. CASAS ◽  
NELSON LEÓN ◽  
PEDRO IZQUIERDO
Keyword(s):  
Viable Cell ◽  
Limiting Factors ◽  
Plate Count ◽  
Microbial Quality ◽  
Pasteurized Milk ◽  
Standard Plate Count ◽  
Cell Counts ◽  
Count Method ◽  
Time Space ◽  
Standard Plate

The Microtiter Count Method was compared with the Standard Plate Count (SPC) method in evaluating mesophile, psychrotroph, and coliform counts for raw and pasteurized milk samples. Statistical analysis showed that the Microtiter Count Method was reliable when compared with the SPC for making viable cell counts on these products. The Microtiter Count Method is advantageous because it saves time, space, and material; this method should be useful for developing countries where availability of testing materials, manpower, and costs are limiting factors in surveillance of microbial quality.

scholarly journals A Flow Cytometry Method for Rapid Detection and Enumeration of Total Bacteria in Milk

2000 ◽  
Vol 66 (3) ◽  
pp. 1228-1232 ◽  
Author(s):  
Thusitha S. Gunasekera ◽  
Paul V. Attfield ◽  
Duncan A. Veal
Keyword(s):  
Flow Cytometry ◽  
Milk Proteins ◽  
Raw Milk ◽  
Plate Count ◽  
Standard Plate Count ◽  
Heat Treated ◽  
Standard Plate ◽  
Microbial Analysis ◽  
Total Bacteria ◽  
Microscopic Counting

ABSTRACT Application of flow cytometry (FCM) to microbial analysis of milk is hampered by the presence of milk proteins and lipid particles. Here we report on the development of a rapid (≤1-h) FCM assay based on enzymatic clearing of milk to determine total bacteria in milk. When bacteria were added to ultra-heat-treated milk, a good correlation (r ≥ 0.98) between the FCM assay and the more conventional methods of plating and direct microscopic counting was achieved. Raw milk data showed a significant correlation (P < 0.01) and a good agreement (r = 0.91) between FCM and standard plate count methods. The detection limit of the FCM assay was ≤104 bacteria ml of milk−1. This limit is below the level of detection required to satisfy legislation in many countries and states.

A Collaborative Study of the Spiral Plate Method for Examining Milk Samples

1977 ◽  
Vol 40 (7) ◽  
pp. 462-464 ◽  
Author(s):  
J. T. PEELER ◽  
J. E. GILCHRIST ◽  
C. B. DONNELLY ◽  
J. E. CAMPBELL
Keyword(s):  
Collaborative Study ◽  
Raw Milk ◽  
Plate Count ◽  
Milk Analysis ◽  
Milk Chocolate ◽  
Components Of Variance ◽  
Standard Plate Count ◽  
Milk Samples ◽  
Standard Plate ◽  
Spiral Plate

The spiral plating procedure is a rapid method for determining bacteriological counts. Results from a collaborative study indicate that the procedure should be useful in milk analysis. Typical milk samples (homogenized milk, raw milk, chocolate drink, 2% milk, and 20% cream) were sent to six analysts to be examined by standard plate count (SPC) and spiral plate count (SPLPC). Analysis of duplicate samples shows that the SPC and SPLPC values did not differ at the a = 0.01 level. Components of variance for replicate determinations among laboratories and laboratory-sample interaction were computed. The standard deviation was 0.109 compared to the 0.110 estimate reported for SPC in state laboratories. Results from the SPLPC method compared favorably to the results of conventional (SPC) pour procedure.

Effects of Package Temperature and Days of Storage on the Flavor Score of Processed Milk1

1981 ◽  
Vol 44 (6) ◽  
pp. 455-458 ◽  
Author(s):  
J. J. JANZEN ◽  
A. B. BODINE ◽  
J. R. BISHOP
Keyword(s):  
Shelf Life ◽  
Flavor Score ◽  
Quality Parameters ◽  
Plate Count ◽  
Fluorescent Light ◽  
Second Phase ◽  
Pasteurized Milk ◽  
Standard Plate Count ◽  
Standard Plate ◽  
Shelf Life Studies

Shelf-life studies were made on commercially pasteurized milk packaged in fiberboard and blow-mold plastic containers, using two temperatures of storage {4.5 and 7 C) and 0, 7 and 14 days of storage. Quality parameters evaluated were flavor, Standard Plate Count, coliform count, oxidase-positive bacteria count and acid degree value. The data suggest a shelf-life (flavor score ⩾ 36.0) of 2–3 days at 7 C and 7 days at 4.5 C. No significant (P &gt; .01) differences, in the parameters measured, were noted between milk packaged in fiberboard and plastic jugs which were not exposed to fluorescent light. A second phase of this study examined the shelf-life of commercially pasteurized milk packaged in fiberboard containers only. The milks were tested at 0,3,5,7,9,11 and 13 days of storage, using the same parameters noted above. The results suggested a satisfactory shelf-life of 11 and 9 days, respectively, for storage temperatures of 4.5 and 7.0 C.

Automated Technique for Sampling Milk from Farm Bulk Tanks: Collaborative Study

1993 ◽  
Vol 76 (2) ◽  
pp. 297-305
Author(s):  
Vernal S Packard ◽  
Roy E Ginn ◽  
Dick T Metzger
Keyword(s):  
Collaborative Study ◽  
Microbiological Quality ◽  
Plate Count ◽  
Sampling Device ◽  
Entire Volume ◽  
Psychrotrophic Bacteria ◽  
Standard Plate Count ◽  
Automated Method ◽  
Standard Plate ◽  
Automated Technique

Abstract An automated, in-line, mechanical technique for sampling milk from farm bulk tanks was evaluated in a collaborative study. The automated sampling device, which is mounted on the milk intake line, contains an electronically controlled peristaltic pump. The device takes a representative sample of the entire volume pumped through the system. Samples taken can be analyzed for both composition and microbiological quality. The study was performed in 3 phases. In the first 2 phases, samples taken by manual and automated methods were compared in analyses for somatic cell count, antibiotics, fat, protein, lactose, and solids-not-fat. The third phase, using a modified procedure, was designed to compare sampling methods in analyses for total bacteria count (standard plate count), psychrotrophic bacteria count, and coliform count. Evaluation of the data by a nested ANOVA indicated no difference between results for samples taken by the automated and manual methods (P = 0.05) in Phases 1 and 2, irrespective of whether the bulk milk was agitated before sampling. By introducing a sanitizing step between farms in Phase 3, the automated method also provided samples comparable with those taken manually for microbial analyses. The automated method has been adopted first action by AOAC International.

EFFECT OF THE TYPE OF BACTERIOLOGICAL PEPTONE IN THE PLATING MEDIUM UPON THE ENUMERATION OF PASTEURIZATION-RESISTANT BACTERIA IN MILK1

1966 ◽  
Vol 29 (6) ◽  
pp. 182-186 ◽  
Author(s):  
W. R. Thomas ◽  
G. W. Reinbold ◽  
F. E. Nelson
Keyword(s):  
Raw Milk ◽  
Plate Count ◽  
Colony Development ◽  
Resistant Bacteria ◽  
Pasteurized Milk ◽  
Standard Plate Count ◽  
Standard Plate ◽  
Viable Bacteria

Summary Various bacteriological, peptones were studied as to effects on enumeration of pasteurization-resistant bacteria in milk. No appreciable differences were observed in colony counts of unheated cultures of thermoduric Micrococcus varians and Arthrobacter and Streptococcus sp. when plated with media containing different peptones. After laboratory pasteurization, colony counts differed substantially. Usually, media producing the highest counts yielded the largest and most easily discernible colonies. Bacto-Tryptone was deficient for colony development of thermoduric streptococci. Results indicate that, although seemingly adequate for enumeration in raw milk, the bacteriological peptone currently recommended for the standard plate count may not be satisfactory for the determination of the maximum viable bacteria population of pasteurized milk.

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