52. The Bacteriological Examination of Milk. I. Modification of the Agar Plate-Count Method. II. The Use of the Methylene Blue Reductase Test at 15·5°C. as a Method of Determining the Keeping Quality of Milk

1932 ◽  
Vol 4 (1) ◽  
pp. 105-121 ◽  
Author(s):  
E. R. Hiscox ◽  
W. A. Hoy ◽  
K. L. Lomax ◽  
A. T. R. Mattick
Keyword(s):  
Methylene Blue ◽  
Yeast Extract ◽  
Agar Plate ◽  
Plate Count ◽  
Bacteriological Examination ◽  
Keeping Quality ◽  
Plate Counts ◽  
Plate Count Method ◽  
Quality Of Milk

It has been shown that neither lactose, nor other sugars tested, casein peptone, nor yeast extract can satisfactorily replace milk as a means of correcting discrepancies which are frequently observed between the plate counts of the 1/100 c.c. and 1/1000 c.c. dilutions of milir on standard agar. Experiments are in progress by which it is hoped that the objections to the addition of milk to standard agar either at the time of making or at the time of plating will be removed, and a medium be evolved which will combine the ease of making and the transparency of standard agar with the efficiency of the medium enriched with milk.

The Microbiological Quality of Honey as Determined by Aerobic Colony Counts

1993 ◽  
Vol 56 (4) ◽  
pp. 336-337 ◽  
Author(s):  
JOSEP SERRA BONVEHI ◽  
ROSSEND ESCOLÁ JORDÁ
Keyword(s):  
Membrane Filter ◽  
Microbiological Quality ◽  
Plate Count ◽  
Filter Method ◽  
Filter Methods ◽  
Plate Counts ◽  
Multifloral Honey ◽  
Plate Count Method ◽  
Membrane Filter Method

The number of mesophilic aerobic colonies was determined in 72 samples of mono- and multifloral honey from various sources by the plate count and the membrane filter methods. The presence of motile colonies made the plate counts unreliable. The microorganism producing these colonies was identified as Bacillus alvei. Colony counts could only be carried out in 27 of the samples when using the plate count method, while with the membrane filter method the number of colonies was counted in all the samples.

Comparison between the EC plate count test at 21 °C and an accelerated plate count method for assessing the keeping quality of pasteurized milk

1992 ◽  
Vol 59 (3) ◽  
pp. 431-436 ◽  
Author(s):  
Sarah A. Langford ◽  
Rohan G. Kroll
Keyword(s):  
Plate Count ◽  
Gram Negative ◽  
Rapid Methods ◽  
Pasteurized Milk ◽  
Psychrotrophic Bacteria ◽  
Commercial Interest ◽  
Count Method ◽  
Keeping Quality ◽  
Plate Count Method

The keeping quality of properly refrigerated pasteurized milk and cream is primarily determined by post-pasteurization contamination by Gram-negative psychrotrophic bacteria (Phillips et al. 1981; Schröder et al. 1982). Reliable and rapid methods of assessing the levels of contamination by these organisms are therefore of commercial interest.

Impedance Measurement as an Alternative to the Plate Count Method for Estimating the Total Count of Bacteria in Raw Milk

1987 ◽  
Vol 50 (8) ◽  
pp. 665-668 ◽  
Author(s):  
F. F. J. NIEUWENHOF ◽  
J. D. HOOLWERF
Keyword(s):  
Standard Deviation ◽  
Microbiological Quality ◽  
Impedance Measurement ◽  
Raw Milk ◽  
Plate Count ◽  
Impedance Method ◽  
Count Method ◽  
Plate Counts ◽  
Plate Count Method

An improved impedance method is described with a good standard deviation of repeatability (sm = 0.05 log unit) and a fair standard deviation of the estimate of the plate count from the detection time [(sy)x = 0.33 log unit]. Compared with the standard deviation of repeatability of the plate count method (0.07 log unit), the standard deviation of repeatability of the impedance method described is a significant improvement. The impedimetric experiments were done with a Bactometer M123. The detection times as measured by this instrument were compared with the plate counts at 30°C for samples of raw refrigerated farm milk. With this technique a good indication of the microbiological quality of raw milk can be obtained within 15 h.

204. The methylene blue reduction test and the keeping quality of milk

1938 ◽  
Vol 9 (3) ◽  
pp. 351-355 ◽  
Author(s):  
C. H. Chalmers
Keyword(s):  
Methylene Blue ◽  
Considerable Importance ◽  
Poor Correlation ◽  
Reduction Test ◽  
Methylene Blue Reduction ◽  
Keeping Quality ◽  
Different Temperatures ◽  
Quality Of Milk ◽  
The Relationship

The keeping quality of milk is a factor which is of considerable importance from the commercial aspect, yet the relationship which exists between the keeping quality and the bacteriological standards as laid down in the Milk Special Designations Order, 1936, has not been fully explored. Wilson compared the keeping quality at 17·5°C. of samples of mixed morning and evening milk with the reduction times at different temperatures and found, in each case, a relatively poor correlation. Since the samples consisted of mixed morning and evening milk it is not possible to state the age of the milk when the tests were commenced. Much of the Tuberculin Tested milk sold in the Provinces is bottled on the farm, and consequently the milk produced in the morning is bottled separately from that produced in the evening.

scholarly journals COMPOSITION AND QUALITY OF FRESH COW MILK OFFERED FOR SALE IN PARTS OF PLATEAU STATE OF NIGERIA.

2021 ◽  
Vol 22 (1) ◽  
pp. 81-84
Author(s):  
J. A. IBEAWUCHI ◽  
D. M. DALYOP
Keyword(s):  
Methylene Blue ◽  
Agar Plate ◽  
Cow Milk ◽  
Plate Count ◽  
Methylene Blue Reduction ◽  
Methylene Blue Test ◽  
Microscopic Count ◽  
The Mean ◽  
Plateau State

The gross composition and quality of fresh cow milk purchased from Fulani milk vendors in three locations of Plateau State were investigated. Milk quality was assessed by the methylene blue reduction test while bacterial contamination was by the agar plate count and the direct microscopic count. The mean contents of total solids, butterfat, protein and ash of a total of 100 samples from Barkin Ladi, Jos and Bukuru markets were 12.45, 4.77, 3.90, 0.92; 12.85, 4.50, 3.68, 0.93; and 12.41, 5.26, 3.72, 0.91% respectively. The proximate constituents did not differ significantly between locations. The methylene blue test indicated that only 23.5% of the sample were of good quality while 41.2 and 35.3% were rated fair and poor respectively. No sample merited excellent rating. The agar plate count showed a range of 1.97 x 106 for Bukuru to 2.54 x 106 cells/ml for Jos market. The direct microscopic count showed the highest mean bacteria value for Barkin Ladi samples. The high bacterial counts as observed were probably indicative of poor milking hygiene and handling. It is suggested that such milk should be properly pasteurized before consumption and delivered/marketed early at source to reduce the time for microbial multiplication.

317. The resazurin and methylene-blue tests as a measure of the keeping quality of milk

1945 ◽  
Vol 14 (1-2) ◽  
pp. 21-27 ◽  
Author(s):  
E. B. Anderson ◽  
G. S. Wilson
Keyword(s):  
Methylene Blue ◽  
Correlation Coefficients ◽  
Raw Milk ◽  
Accurate Estimate ◽  
Human Consumption ◽  
Methylene Blue Reduction ◽  
Keeping Quality ◽  
Methylene Blue Test ◽  
Quality Of Milk

1. During four periods equally spaced throughout the year raw milks coming from surrounding farms into the Buckingham receiving station were examined by (a) the 10 min. resazurin test, (b) the 1 hr. resazurin test, (c) the resazurin test in which the time to reach disk 1 was recorded, (d) the modified methylene-blue test, and (e) a keeping quality test based on taste and alcohol precipitation. Altogether, 2588 samples were examined.2. Table 2, in which the correlation coefficients are worked out between the results of the dye and the K.Q. tests, shows that there is little to choose between the methylene-blue test and the time to reach disk 1 in the resazurin test; but since an average of only 15 min. was saved by carrying out the resazurin test, there seems little advantage to be gained by the use of this test. Both of these tests are superior to the 10 min. and the 1 hr. resazurin tests.3. A comparison of Tables 5–7, in which the average K.Q. of the milks corresponding to different disk numbers or reduction times is recorded, shows that the methylene-blue test affords the best indication of the K.Q.4. A study of Table 3, setting out the relation between the 10 min. resazurin and the methylene-blue reduction tests, shows that 99% of milks giving a 0–½ reading in the resazurin test reduce methylene blue within 30 min. and 80 % of them within 10 min.; but that, of milks reducing methylene blue within 30 min., only 53% give a disk reading of 0–½ in the 10 min. resazurin test. If it is agreed that no raw milk on arrival at the creamery which reduces methylene blue within 30 min. and which has, according to Table 7, an average K.Q. of only about 5 hr. at the time of testing, is fit for human consumption, then it is clear that the present rejection standard in the 10 min. resazurin test passes nearly 50% of unsatisfactory milks.5. The data recorded in this paper all go to show that the best indirect index of the K.Q. of raw milk is afforded by the methylene-blue test as carried out by the method officially laid down by the Ministry of Health.6. On the other hand, if time is an overruling consideration, then a slightly less accurate estimate of the K.Q. of raw milk is afforded by the 1 hr. resazurin test. It must be pointed out, however, that the figures given in Table 6 suggest that below disk 2 there is some irregularity in the relation between the disk numbers and the K.Q. If the 1 hr. resazurin test should come into use for the routine grading of milk, a revision of the present tints at the lower end of the scale might prove desirable.

143. The Comparative Values of the Plate Count and the Modified Methylene-Blue Reduction Test as Routine Methods for Grading Milk

1936 ◽  
Vol 7 (3) ◽  
pp. 258-270 ◽  
Author(s):  
A. A. Nichols ◽  
S. J. Edwards
Keyword(s):  
Methylene Blue ◽  
Marked Improvement ◽  
Plate Count ◽  
Reduction Test ◽  
The Past ◽  
Hygienic Quality ◽  
Methylene Blue Reduction ◽  
Quality Of Milk

During the past twenty years the plate count has been largely employed as a means of assessing the hygienic quality of milk. There is no doubt that for this purpose it has proved to be of great value, and the marked improvement which has taken place in the quality of the milk of many producers is largely attributable to its use.

91. A Statistical Examination of the Interrelationship and Variability of Plate Count, Presumptive Coliform Content and Keeping Quality of Raw Milk

1935 ◽  
Vol 6 (1) ◽  
pp. 26-48 ◽  
Author(s):  
H. Barkworth
Keyword(s):  
Standard Deviation ◽  
Raw Milk ◽  
The Other ◽  
Plate Count ◽  
One Stage ◽  
Hygienic Quality ◽  
Keeping Quality ◽  
Quality Of Milk ◽  
The Relationship

The writer seeks to establish the interrelationship and variability of the three tests used for gauging the hygienic quality of milk, plate count, coliform content and keeping quality. Keeping quality is denned, and after discussing previous work and source of material, and noting the technique followed, the method of classification is described. Plate count and coliform content are treated logarithmically. Treatment of keeping-quality results presents especial difficulties, and the test is described in detail to disclose these, and reasons given for tabulating by half-days. The relationship between plate count and keeping quality is linear, but non-linearity occurs in those relationships which concern coliform content. This is because the first group “absent from 1 ml.” is not truly a definite class, but contains samples of superior quality. It is shown that an increase of one “stage” of coliform contamination reduces the average keeping quality as much as an increase of 0–54 in the logarithm of the plate count (approximately seven times). Variability of each term is discussed. The standard deviation of keeping quality is of the order of 1 half-day, that of logarithm of plate count is 0·77 and that of logarithm of coliform content in excess of unity. These variabilities are too great to permit of reasonable forecast of one term from the other two.

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