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.

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.

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.

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:

THE ENUMERATION OF PSYCHROPHILIC MICROORGANISMS IN DAIRY PRODUCTS1

1963 ◽  
Vol 26 (11) ◽  
pp. 351-356 ◽  
Author(s):  
D. P. Baumann ◽  
G. W. Reinbold
Keyword(s):  
Dairy Products ◽  
Incubation Temperature ◽  
Bacterial Count ◽  
Raw Milk ◽  
Cottage Cheese ◽  
Preferential Growth ◽  
Bacterial Counts ◽  
Incubation Temperatures

The eleventh edition of Standard Methods for the Examination of Dairy Products sanctions optional use of incubation temperatures and times (5–7 C for 7–10 days) for determination of the psychrophilic bacterial count of dairy products. This study shows that this 2 degree difference in incubation temperature, the 3 day difference in incubation time and a combination of these factors could be responsible for a significant variation in psychrophilic bacterial counts. A total of 67 raw milk, 58 pasteurized milk, 19 ice cream and eight cottage cheese samples were plated at 5 and 7 C for 7 and 10 days. Significantly higher counts were obtained after 10 days than after 7 days incubation at both temperatures; however, greater increases in counts resulted from raising the temperature from 5 to 7 C. Highest counts were obtained at 7 C for 10 days. A total of 559 isolates were picked from plates of 12 milk samples that had been incubated at 5 and 7 C for 7 days and 7 C for 10 days. Classification of the isolates indicated that variations in counts were due to differing abilities of organisms within genera to grow at low temperatures and not to preferential growth of different genera. Adoption of one incubation temperature and time for the determination of psychrophilic bacterial counts is recommended.

EFFECT OF PLATE INCUBATION TEMPERATURE ON BACTERIAL COUNTS OF GRADE A RAW MILK1

1973 ◽  
Vol 36 (3) ◽  
pp. 152-154 ◽  
Author(s):  
H. E. Randolph ◽  
B. K. Chakraborty ◽  
Otto Hampton ◽  
D. L. Bogart
Keyword(s):  
Incubation Temperature ◽  
Statistical Significance ◽  
Correlation Coefficients ◽  
Raw Milk ◽  
Plate Count ◽  
Bacterial Counts ◽  
Standard Plate Count ◽  
Standard Plate ◽  
The Mean ◽  
Incubation Temperatures

Bacterial counts on 155 raw milk samples obtained with plate incubation temperatures of 27 and 32 C were closely correlated (r = 0.96) . Correlation coefficients between counts obtained at both 27 and 32 C and psychrotrophic (7 C-10 days) counts for all samples were relatively low, but statistically significant ( P < 0.01). The correlation to psychrotrophic counts was especially low and in some instances lacking in statistical significance in the sample groups with counts ( 27 and 32 C) <100,000/ml. Eighty-four of the samples had higher counts at 32 C and 62 samples had higher counts at 27 C. The mean psychrotrophic count of the samples with higher counts at 27 C was higher than the mean psychrotrophic count of the other samples. However, the correlation coefficients were higher for samples with counts higher at 32 C. Incubation at 27 C does not appear to offer significant advantages over the 32 C incubation temperature used in the Standard Plate Count.

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.

scholarly journals Microbiological Profile of the Traditionally Collected Industrial Raw Milk from the Milk Pocket Zones of Bangladesh

1970 ◽  
Vol 25 (1) ◽  
pp. 17-20 ◽  
Author(s):  
Gouranga C Chanda ◽  
Gazi M Noor Uddin ◽  
Aparna Deb ◽  
Tahmina Bilkis ◽  
Sharmin Chowdhury ◽  
...  
Keyword(s):  
Bacterial Count ◽  
Raw Milk ◽  
Total Coliform ◽  
Plate Count ◽  
Coliform Count ◽  
Standard Plate Count ◽  
Milk Samples ◽  
Bacteriological Profile ◽  
Standard Plate ◽  
Viable Bacteria

The study was aimed to evaluate the bacteriological profile of the traditionally collected industrial raw milk from the milk pocket zones of Bangladesh. About 365 raw milk samples were collected from the milk tanker, who brought raw milk from the mother chilling centre where raw milk was chilled at 4°C following traditional method. All milk samples were subjected to perform standard plate count and total coliform count. The average standard plate count was found to be 4.37 x 106 cfu/ml and the highest occurrence of standard plate count was found to be 6.70 x 106 cfu/ml in October and the lowest (3.28 x 106 cfu/ml) in March. The highest occurrence of total viable bacteria was found to be 5.64 x 106 cfu/ml in autumn and the lowest was found to be 3.78 x 106 cfu/ml in summer. On the other hand, the average of the coliform bacterial count was found to be 3.88 x 105 cfu/ml with the highest (5.70 x 105 cfu/ml) occurrence in May and the lowest (1.90 x 105 cfu/ml) in January. Moreover, the highest occurrence of coliform count was found to be 4.84 x 105 cfu/ml in rainy season and the lowest was 2.75 x 105 cfu/ml found in winter.DOI: http://dx.doi.org/10.3329/bjm.v25i1.4849 Bangladesh J Microbiol, Volume 25, Number 1, June 2008, pp 17-20

COMPARISON OF PLATE LOOP AND AGAR PLATE METHODS FOR BACTERIOLOGICAL EXAMINATION OF MANUFACTURING GRADE RAW MILK1,2

1967 ◽  
Vol 30 (4) ◽  
pp. 112-115 ◽  
Author(s):  
Sita Ramayya Tatini ◽  
Roger Dabbah ◽  
J. C. Olson
Keyword(s):  
Agar Plate ◽  
Bacterial Count ◽  
Raw Milk ◽  
Substantial Improvement ◽  
Plate Count ◽  
Bacteriological Examination ◽  
Standard Plate Count ◽  
Milk Samples ◽  
Standard Plate ◽  
Bulk Tank

Summary Plate loop counts and standard plate counts on each of several manufacturing grade raw milk samples (handled in cans or in farm bulk tanks) have been compared. On the average, the plate loop count (PLC) was lower than the standard plate count (SPC) regardless of the type of handling of milk on the farm, can or bulk tank. Agreement between the SPC and PLC seemed to depend upon the bacterial-count levels present in milk. Statistical analyses indicated significant differences, at 1% level of probability, between the average bacterial count by SPC and PLC methods regardless of count level (≤100,000/ml or >100,000/ml) in case of can milk samples. On the other hand, in case of farm bulk tank milk samples, no significant differences, at the 1% level of probability, between the average bacterial count by SPC and PLC methods were obtained, when the counts were equal to or less than 100,000 per ml; when the counts exceeded 100,000 per ml, significant differences were present. Since the bacterial counts of manufacturing grade raw milk samples are likely to exceed 100,000/ml, the data presented in this investigation indicate that, until the bacteriological quality of manufacturing grade milk supplies undergoes substantial improvement, the PLC method does not appear to be a suitable substitute for the SPC method for routine bacteriological examination of such milk supplies.

THE EFFECT OF PLATE INCUBATION TEMPERATURES ON COUNTS OF SODIUM DESOXYCHOLATE-TOLERANT BACTERIA

1970 ◽  
Vol 33 (10) ◽  
pp. 442-444 ◽  
Author(s):  
G. Blankenagel
Keyword(s):  
Milk Samples ◽  
Bulk Milk ◽  
Standard Plate ◽  
Plate Counts ◽  
Incubation Temperatures

Farm bulk milk samples from 54 producers were analyzed for Standard Plate Counts (SPC), thermoduric counts, and counts of bacteria that can tolerate 0.5% sodium desoxycholate (SDC). For the latter test, plates were incubated at 21, 25, 28, and 32 C for 48 hr. More milk samples had maximum counts at 25 C than at any other temperature used, whereas 32 C yielded the lowest number of colonies per plate. Median counts were 250/ml at 21, 290/ml at 25, 275/ml at 28, and 160/ml at 32 C.

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