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).

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.

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.

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.

scholarly journals Determination of Fat, Protein, and Lactose in Raw Milk by Fourier Transform Infrared Spectroscopy and by Analysis with a Conventional Filter-Based Milk Analyzer

1996 ◽  
Vol 79 (3) ◽  
pp. 711-717 ◽  
Author(s):  
Dominique Lefier ◽  
Remy Grappin ◽  
Sylvie Pochet
Keyword(s):  
Fourier Transform ◽  
Fourier Transform Infrared ◽  
Raw Milk ◽  
Milk Composition ◽  
Milk Samples ◽  
Bulk Milk ◽  
Different Seasons ◽  
Standard Deviations ◽  
True Protein ◽  
Single Calibration

Abstract The accuracy of fat, crude protein (CP), true protein (TP), and lactose determinations of raw milk by Fourier transform infrared (FTIR) spectroscopy and by analysis with a conventional filter-based milk analyzer was assessed in 6 trials performed over a 10-month period. At each trial, 30 bulk milk samples collected from 15 European countries and 11 reconstituted milks made from raw milk components were analyzed. When calibrations were performed with reconstituted milks at each trial, accuracy standard deviations for fat, CP, TP, and lactose were, respectively, 0.050,0.048,0.035, and 0.076 g/100 g for the filter instrument and 0.047, 0.046,0.042, and 0.065 g/100 g for the FTIR instrument. When a single calibration was made instead of calibrations at each trial, accuracy standard deviations increased for the filter instrument to 0.130, 0.119,0.121, and 0.083 for fat, CP, TP, and lactose, respectively, and for the FTIR instrument to 0.082, 0.053,0.044, and 0.084 g/100 g. Because the FTIR instrument provides more spectral information related to milk composition than does the filter instrument, single-calibration FTIR analysis of milk samples collected in different seasons is more accurate. Using reconstituted milks, prepared such that there is no correlation between fat, CP, and lactose, provides a more robust calibration than using genuine bulk milk, especially when milks with unusual composition are analyzed.

Low Incidence of Foodborne Pathogens of Concern in Raw Milk Utilized for Farmstead Cheese Production

2008 ◽  
Vol 71 (8) ◽  
pp. 1580-1589 ◽  
Author(s):  
DENNIS J. D'AMICO ◽  
ERROL GROVES ◽  
CATHERINE W. DONNELLY
Keyword(s):  
Foodborne Pathogens ◽  
Microbiological Quality ◽  
Goat Milk ◽  
Raw Milk ◽  
Pasteurized Milk ◽  
Milk Samples ◽  
Cell Counts ◽  
Standard Plate ◽  
Low Incidence ◽  
Raw Milk Cheese

Overall milk quality and prevalence of four target pathogens in raw milk destined for farmstead cheesemaking was examined. Raw milk samples were collected weekly from June to September 2006 from 11 farmstead cheese operations manufacturing raw milk cheese from cow's, goat's, and sheep's milk. Samples were screened for Listeria monocytogenes, Staphylococcus aureus, Salmonella, and Escherichia coli O157:H7 both quantitatively (direct plating) and qualitatively (PCR). Overall, 96.8% of samples had standard plate counts of <100,000 CFU/ml, 42.7% of which were <1,000 CFU/ml. Although no federal standards exist for coliforms in raw milk, 61% of samples tested conformed to pasteurized milk standards under the U.S. Pasteurized Milk Ordinance (PMO) at <10 CFU/ml. All cow and sheep milk samples and 93.8% of goat milk samples were within the limits dictated by the PMO for somatic cell counts. Of the 11 farms, 8 (73%) produced samples that were positive for S. aureus, which was detected in 34.6% (46 of 133) of milk samples. L. monocytogenes was isolated from three milk samples (2.3%), two of which were from the same farm. E. coli O157:H7 was recovered from one sample of goat's milk for an overall incidence of 0.75%. Salmonella was not recovered from any of the 133 samples. The findings of this study suggest that most raw milk intended for farmstead cheesemaking is of high microbiological quality with a low incidence of pathogens. These data will help inform risk assessments associated with the microbiological safety of farmstead cheeses, particularly those manufactured from raw milk.

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 QUALITY OF RAW MILK FROM SELECTED OHIO MARKETS.

1966 ◽  
Vol 29 (4) ◽  
pp. 118-121 ◽  
Author(s):  
S. P. Ohri ◽  
W. L. Slatter
Keyword(s):  
Raw Milk ◽  
Plate Count ◽  
High Count ◽  
Coliform Count ◽  
Standard Plate Count ◽  
Milk Samples ◽  
Bacteriological Method ◽  
Standard Plate ◽  
Bulk Tank

Summary An 8-month survey of the bacteriological quality of bulk tank produced fluid milk supplies for four major markets in Ohio, was made utilizing the Standard Plate Count (SPC), the preliminary incubation count (PI), the thermoduric (pasteurized milk) count, and the coliform count. In terms of maximum standards of 200,000 and 100,000 organisms/ml, the SPC would have eliminated 13% and 20% of the milk samples, respectively. A SPC of 50,000/ml, a PI count of 200,000/ml, a thermoduric count of 500/ml, and a coliform count of 100/ml would have eliminated 37%, 34%, 40%, and 40%, respectively, of the samples but not all of the samples eliminated by one test were eliminated by another test. All of the tests employed showed a seasonal trend especially in the high count categories but the trend was less noticeable in the results of the preliminary incubation count. A combination of two of the methods was superior to any single bacteriological method employed in detecting unsatisfactory milk. Of the tests used, the combination of the thermoduric count (500/ml) and the coliform count (100/ml) was the most effective in the detection of unsatisfactory milk samples.

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.

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