AN EVALUATION OF SIMPLIFIED METHODS FOR DETERMINING VIABLE COUNTS OF RAW MILK

1960 ◽  
Vol 23 (9) ◽  
pp. 275-277 ◽  
Author(s):  
C. B. Donnelly ◽  
L. A. Black ◽  
K. H. Lewis
Keyword(s):  
Rapid Method ◽  
Raw Milk ◽  
Accurate Method ◽  
Bacterial Counts ◽  
Milk Samples ◽  
Standard Plate ◽  
Plate Counts ◽  
Oval Tube

When statistically analyzed, the results of comparative, examinations of raw milk samples revealed that bacterial counts by oval tube and microplate methods were essentially equivalent to standard plate counts. The oval tube provides an economical and accurate method for determining the count of producers' milk and may be used in the laboratory or on the platform. The microplate provides an equally accurate but more rapid method than either the oval tube or standard plate since counts be obtained in 20 hours.

BACTERIAL COUNTS OF RAW MILK AND FLAVOR OF THE MILK AFTER PASTEURIZATION AND STORAGE

1972 ◽  
Vol 35 (4) ◽  
pp. 203-206 ◽  
Author(s):  
G. B. Patel ◽  
G. Blankenagel
Keyword(s):  
Raw Milk ◽  
Bacterial Counts ◽  
Psychrotrophic Bacteria ◽  
Milk Samples ◽  
Standard Plate ◽  
Plate Counts ◽  
Subsequent Storage ◽  
And Storage ◽  
Common Defect

A total of 216 raw milk samples with a variety of Standard Plate Counts and psychrotrophic bacteria counts were laboratory-pasteurized, stored at 7 C, and then evaluated for flavor after 1 and 2 weeks. Results showed that milk with counts of >1,000,000/ml before heating frequently developed objectionable flavors after pasteurization and subsequent storage. The most common defect was a bitter flavor which appeared within 2 weeks after pasteurization in nearly all samples which as raw milk had counts exceeding 10,000,000/ml. This off-flavor developed in spite of small numbers of organisms in the pasteurized product and in the absence of post-pasteurization contamination.

Effect of Five Surface Area-to-Sample Volume Ratios During Preliminary Incubation on The Bacterial Count of Raw Milk1,2

1979 ◽  
Vol 42 (12) ◽  
pp. 968-970
Author(s):  
J. A. RITTER ◽  
B. E. LANGLOIS ◽  
J. O'LEARY
Keyword(s):  
Surface Area ◽  
Incubation Temperature ◽  
Bacterial Count ◽  
Raw Milk ◽  
Sample Volume ◽  
Bacterial Counts ◽  
Milk Samples ◽  
Standard Plate ◽  
Plate Counts ◽  
Incubation Temperatures

Effects of ratio of surface area to volume of sample during preliminary incubation (PI) and of different plate incubation temperatures on bacterial counts of raw milk samples were studied. One hundred and twenty Grade A raw milk samples collected during a 10-month period were divided into five 100-ml aliquots and allotted to one of five surface area to volume ratios. The ratios during PI ranged from 0 cm2/100 ml to 149.74 cm2/100 ml. Following PI, pour plates of each treatment were incubated at 26, 30 and 32 C for 72 h. The Standard Plate Counts (SPC) ranged from 89 × 101 to 20 × 108/ml, with the SPC of 73.6% of the samples being less than 1 × 105/ml. Counts after PI tended to be higher as the plate incubation temperature decreased from 32 to 26 C and as the ratio of surface area to volume of sample increased. None of the differences between the counts for the 15 treatment-incubation temperatures was significant. Counts of 61 samples increased less than one log count during PI, while counts of 33 and 16 samples increased one to two log counts and over two log counts, respectively. The greater the SPC, the smaller the increase in count during PI. Of the 81 samples with SPC less than 1 × 105/ml, 29 had counts after PI that exceeded 2 × 105/ml.

PREDICTION OF STANDARD PLATE COUNT OF MANUFACTURING-GRADE RAW MILK FROM THE PLATE LOOP COUNT1

1970 ◽  
Vol 33 (4) ◽  
pp. 168-170 ◽  
Author(s):  
Earl O. Wright ◽  
George W. Reinbold ◽  
Leon Burmeister ◽  
James Mellon
Keyword(s):  
Raw Milk ◽  
Plate Count ◽  
Adjustment Factor ◽  
Bacterial Counts ◽  
Standard Plate Count ◽  
Milk Samples ◽  
Count Range ◽  
Standard Plate ◽  
Plate Counts

Plate Loop Counts and Standard Plate Counts of manufacturing grade raw milk samples were compared. With bacterial counts of 200,000/ml and less, the Plate Loop Count approximated the Standard Plate Count very closely. With counts greater than 200,000, the agreement was not as close. Differences between counts from the two methods, however, were not statistically significant (P<0.05) within either count range. An adjustment factor was determined to enable the Plate Loop Count to more accurately predict the Standard Plate Count of milk with a Standard Plate Count >200,000/ml. The Standard Plate Count can be reasonably predicted from the Plate Loop Count by the formula:

Determination of Viable Bacterial Populations in Raw Milk within 20 Minutes by Using a Direct Epifluorescent Filter Technique

1997 ◽  
Vol 60 (7) ◽  
pp. 874-876 ◽  
Author(s):  
CLAUDE P. CHAMPAGNE ◽  
NANCY J. GARDNER ◽  
JULIE FONTAINE ◽  
JACQUES RICHARD
Keyword(s):  
Raw Milk ◽  
Plate Count ◽  
Bacterial Populations ◽  
Filter Technique ◽  
Milk Samples ◽  
Standard Plate ◽  
Plate Counts ◽  
Direct Epifluorescent Filter Technique ◽  
Triton X

The results from a shortened procedure for the direct epifluorescent filter technique (DEFT) determination of viable bacterial populations in raw milk were compared to standard plate counts. Shortening the prefiltration trypsin-Triton X-100 incubation period from 10 to 3 min enabled the completion of the analysis within 20 min. The short DEFT method results had a correlation coefficient (r) of 0.81 with plate counts. With respect to precision, the average difference between values of duplicate plate count analyses was 0.16 log units; that of the short DEFT was 0.14 log units. The slopes of the regressions equations were less than 1, indicating that a direct correlation is not achieved. Short DEFT values were 0.17 log units higher than those of plate counts on milk samples containing less than 10,000 CFU/ml. For milk samples containing counts over 10,000 CFU/ml, short DEFT values averaged only 0.05 log units above plate count readings. Daily preparation of the stain appears unnecessary since acridine orange solutions stored for up to 2 days at 4°C did not produce results significantly (P > 0.05) different from those obtained with fresh solutions. The short DEFT method has potential for the assessment of the bacteriological quality of raw milk in tanker deliveries.

Preliminary Incubation Count as an Index of Raw Milk Microbiological Quality During Storage

1984 ◽  
Vol 47 (3) ◽  
pp. 206-208 ◽  
Author(s):  
J. J. RYAN ◽  
R. H. GOUGH ◽  
C. H. WHITE
Keyword(s):  
Microbiological Quality ◽  
Storage Period ◽  
Raw Milk ◽  
Plate Count ◽  
Bacterial Counts ◽  
Sample Group ◽  
Psychrotrophic Bacteria ◽  
Standard Plate Count ◽  
Milk Samples ◽  
Standard Plate

During a 5-month period, 200 raw milk samples were collected from two Louisiana milk plants. Standard Plate Count (SPC), Psychrotrophic Bacteria Count (PBC), and Proteolytic Count (PC) of each sample were initially determined, then monitored daily during a 5-d storage period at 2.2°C. As hypothesized, all bacterial counts increased during the storage period. The magnitude of the increase in bacterial numbers during storage was further investigated by dividing the milk samples into bacteriologically acceptable and unacceptable groups based on SPC or Preliminary Incubation (PI) count. An SPC of 1.0 × 105/ml and PI counts of 1.0 × 105/ml, 1.5 × 105/ml, 2.3 × 105/ml, and 3.0 × 105/ml were used to repeatedly dichotomize the 200 raw milk samples into two groups. Median SPC, PBC, and PC for each acceptable and unacceptable group were then calculated. Dichotomization based on PI counts yielded acceptable sample groups having consistently lower bacterial counts during storage than did the acceptable sample group, which resulted from the dichotomization based on a SPC of 1.0 × 105/ml. The results of this study indicated that the PI count is of considerable value for raw milk quality control.

THE EFFECT ON BACTERIAL COUNTS OF THE GRADUAL WARMING OF MILK SAMPLES

1963 ◽  
Vol 26 (12) ◽  
pp. 389-391
Author(s):  
J. L. Courtney
Keyword(s):  
Room Temperature ◽  
Bacterial Counts ◽  
Pasteurized Milk ◽  
Milk Samples ◽  
Average Maximum ◽  
Standard Plate ◽  
Plate Counts

Summary Samples of retail pasteurized milk were allowed to stand at room temperature for 4 hr during which the temperature of the samples increased 33 F to an average maximum of 81 F. Coliform and standard plate counts were made during this period. Only 2 samples out of 16 showed extensive coliform growth. Increases in standard plate counts were surprisingly small.

PRELIMINARY INCUBATION OF RAW MILK SAMPLES AS AN AID IN EVALUATING BACTERIOLOGICAL QUALITY1

1964 ◽  
Vol 27 (11) ◽  
pp. 333-338 ◽  
Author(s):  
M. N. Desai ◽  
T. J. Claydon
Keyword(s):  
Raw Milk ◽  
Growth Ratio ◽  
Milk Samples ◽  
Count Range ◽  
Before And After ◽  
Different Seasons ◽  
Standard Plate ◽  
Plate Counts ◽  
The Relationship ◽  
Summer Growth

A total of 194 milk samples were obtained from 35 bulk tank grade-A milk producers in the Manhattan, Kansas, milk-shed during different seasons, and examined for standard, coliform, and psychrophile plate counts both before and after preliminary incubation (P.I.). Samples also were tested for inhibitory substances. Farms were ranked I, II, or III in general sanitation on the basis of visible conditions, with rank I most desirable. Except for one doubtful sample, all tests for inhibitory substances were negative. With standard plate counts, when no consideration was given to initial count level, there was no statistically significant relation between P.I. counts and season or sanitation rank, although summer growth ratios were always lowest. When data were grouped on the basis of initial count range, P.I. counts and growth ratios increased with increased sanitation rank in the lower count ranges. In initial count ranges > 50,000/ml the relationship between growth ratio and sanitation rank declined. With coliform counts, considerable inconsistency occurred in P.I. counts among seasons and sanitation ranks. Initial and P.I. coliforms counts showed little relationship with standard plate counts (except in summer) or with psychrophile counts. With psychrophile counts, growth ratios during P.I. were influenced by season, being highest in winter and lowest in summer. P.I. counts generally increased with increase in sanitation rank. The relation between growth ratios and sanitation rank was statistically significant (P <0.05).

COMPARISON OF THE OVAL TUBE WITH THE STANDARD PLATE COUNT METHOD FOR DETERMINI NG VIABLE COUNTS OF RAW MILK

1966 ◽  
Vol 29 (6) ◽  
pp. 191-196
Author(s):  
S. G. Wilson
Keyword(s):  
Goodness Of Fit ◽  
Raw Milk ◽  
Plate Count ◽  
Chi Square ◽  
Standard Plate Count ◽  
Significant Difference ◽  
Standard Plate ◽  
Plate Counts ◽  
Comparison Of The Results ◽  
Oval Tube

Summary Standard plate counts (SPC) and oval tube counts (OTC) were compared and analyzed by the statistical method on 547 samples of raw milk from the Wichita milk shed. 389 of these milks were paired as routine two-dilution standard plates vs. single tube estimates of viable bacteria; 127 were set in duplicate by each method; and 31 samples were set in replicates of five for the purpose of two-factor variance analysis. Using the criterion of the IAMFES Committee on Applied Laboratory Methods, the experimental results indicated that the comparison odds were approximately even for equivalent counts between methods (48.9% of samples); two out of five random samples showed that the oval tube counts were higher (39.6% of samples) and that one out of ten of the standard plate counts was superior (11.5% of samples). Also, revised data of differences between two-dilution SPC's and single OTC's that passed the chi-square test for goodness of fit for a normal distribution gave a significant difference of means at the 1% level (89 samples). However, with another trial run, two-factor analysis did not yield a significant difference between methods (33 samples × 5 replicates), and the F ratio of the means of the pooled variance data showed no difference in precision between methods; the interaction between samples and methods was highly significant. A comparison of the results from these experiments with data obtained in five other laboratories over a span of 25 years is shown in Table form. It was concluded that there is no significant difference between the two methods where paired estimates are based on replication, but the oval tube is preferred where time and economy are important.

SOME FACTORS AFFECTING THE CORRELATION OF METHYLENE BLUE REDUCTION TIMES AND STANDARD PLATE COUNTS OF RAW MILK

1966 ◽  
Vol 29 (8) ◽  
pp. 255-259
Author(s):  
A. Richard Brazis ◽  
L. A. Black
Keyword(s):  
Methylene Blue ◽  
Standard Procedure ◽  
Raw Milk ◽  
Bacterial Counts ◽  
Factors Affecting ◽  
Methylene Blue Reduction ◽  
Standard Plate ◽  
Plate Counts

Summary Standard plate and psychrophilic bacterial counts, on 312 samples of milk collected from farm bulk tanks and milk cans, were compared with methylene blue reduction times using the standard procedure or preliminary incubation of samples at 55 F for 18 hr prior to testing. When psychrophilic bacterial counts were less than 100,000/ml, according to standard plate counts a high proportion of methylene blue reduction times were properly classified. However, psychrophilic bacterial counts greater than 100,000/ml did not significantly decrease reduction times, thus a high proportion of such milks was not properly classified by methylene blue reduction times. The proportion of misclassification of samples having standard plate counts in excess of 200,000/ml and methylene blue reduction times of 5 and 6 hr was determined.

scholarly journals Major Mammary Pathogens as Contributors to Total Bacterial Counts in Raw Milk

2009 ◽  
Vol 78 (3) ◽  
pp. 455-461 ◽  
Author(s):  
Dušan Ryšánek ◽  
Monika Zouharová ◽  
Vladimír Babák
Keyword(s):  
Geometric Mean ◽  
Raw Milk ◽  
Coliform Bacteria ◽  
Geometric Means ◽  
Gram Negative ◽  
Bacterial Counts ◽  
Standard Plate ◽  
Plate Counts ◽  
Positive Correlations ◽  
Environmental Pathogens

The purpose of this study was to assess the contribution of major mammary pathogens, as well as of coliform and Gram-negative non-coliform bacteria to standard plate counts (SPCs) of bulk tank milk samples (BTMSs). Randomly selected anonymous BTMSs were collected from 268 dairy herds (with approximately 29,000 cows) in the Czech Republic during 2007. The most frequently detected pathogens were found to be E. faecalis (16.1%; geometric mean 9.8 × 102 CFU/ml) and S. uberis (13.6%; 9.0 × 102 CFU/ml). Highly significant positive correlations (P < 0.01) between the bacterial counts of the dominant pathogens and the relevant SPC were found for E. faecalis and S. dysgalactiae, as were significant correlations (P < 0.05) for S. uberis, E. faecium, and S. aureus. Highly significant positive correlations (P < 0.01) were found between SPC and coliform count and between SPC and Gram-negative non-coliform bacteria count. The results suggest, therefore, a recent dominance of environmental pathogens especially streptococci and enterococci, over contagious mammary pathogens in BTMSs. The geometric means of SPC in BTMSs with mammary pathogen (7.7 × 104 CFU/ml for environmental; 7.4 × 104 CFU/ml for contagious pathogens) exceed significantly (P < 0.05) the geometric means of SPC of pathogen free BTMSs (4.4 × 104 CFU/ml). This study revealed that the major mammary pathogens contribute significantly to SPCs of BTMSs.

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