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.

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.

Bacteriological Standards for Perishable Foods

1952 ◽  
Vol 72 (4) ◽  
pp. 404-410
Author(s):  
Arthur Rowlands
Keyword(s):  
Heat Treatment ◽  
Dairy Products ◽  
Rapid Test ◽  
Raw Milk ◽  
Human Consumption ◽  
Treatment Processes ◽  
Keeping Quality ◽  
Methylene Blue Test ◽  
General Compliance

For milk and dairy products complete freedom from pathogens is the only accept able standard. To achieve this, pasteurisation or some other form of heat treatment is necessary, adequate precautions being taken to prevent subsequent reinfection of the milk. Physical checks of plant coupled with the use of the phosphatase test, rather than bacteriological methods, serve to ensure the bactericidal efficiency of heat treatment processes and the safety of milk supplies. Bacteriological standards are desirable also to ensure milk which will keep sweet until it is utilized. For this purpose a keeping quality of twenty-four hours after delivery to the consumer may be considered a satisfactory minimum standard. At present, different modifications of the methylene blue test are in use officially for raw and pasteurised milk. In general, compliance with the standards imposed ensures a satisfactory keeping quality, but there is much to be said for a common test and standard for all milk sampled during distribution to the consumer. Direct measurement of keeping quality, using clot-on-boiling to determine the end-point, deserves serious consideration as a method for routine control purposes. For milk to be used for processing or manufacture, a rapid test to be applied to all milk as received is the first consideration. The I0-minute reszaurin test, despite its limitations, is now in general use for this purpose. In addition, however, it is desirable to carry out tests on samples from all producers at intervals, in order to maintain their interest in milk quality and to encourage improvement where necessary. There are no official bacteriological standards for dairy products. There is, in fact, little call for such standards, although manufacturers must, in their own interest, maintain strict bacteriological control over the quality of the raw milk and manufac turing processes. Failure to do so may lead to faults in the products which seriously impair their marketable value or make them entirely unsuitable for human consumption.

Keeping quality and raw-milk grading: I. Dye tests as measures of the keeping quality of milk

1950 ◽  
Vol 17 (2) ◽  
pp. 159-191 ◽  
Author(s):  
A. T. R. Mattick ◽  
A. Rowlands ◽  
H. Barkworth ◽  
Zena Hosking ◽  
O. Kempthorne
Keyword(s):  
Raw Milk ◽  
Keeping Quality ◽  
Quality Of Milk

The experiments analysed in this series of papers were undertaken as the result of a discussion on methods of measuring the keeping quality of milk, at a Conference of Advisory Bacteriologists of the Ministry of Agriculture and Fisheries.Owing to the disturbance and difficulty following the outbreak of war and the dislocation of handling and distribution, a serious decline in the keeping quality of raw-milk supplies was threatened.

scholarly journals The source of bacteria in fresh cream, and the methylene blue reduction test as a guide to hygienic quality

1969 ◽  
Vol 67 (3) ◽  
pp. 401-408 ◽  
Author(s):  
H. R. Jenkins ◽  
R. J. Henderson
Keyword(s):  
Methylene Blue ◽  
County Council ◽  
Test Results ◽  
Reduction Test ◽  
Hygienic Quality ◽  
Methylene Blue Reduction ◽  
Methylene Blue Test ◽  
Manual Handling ◽  
The Many

SUMMARYOne hundred and twenty-nine samples of fresh cream collected in Worcestershire were examined bacteriologically. Sixty (46·5 %) creams had counts of over 100,000 bacteria/ml. The bacteria present were of many varieties, the commonest being Bacillus spp. (aerobic spore formers), Gram-negative bacilli, staphylococci and micrococci. Since most of the creams had been either pasteurized as cream or manufactured from pasteurized milk it was thought that the many bacteria were present because of contamination after pasteurization due to three main causes; unsatisfactory or unhygienic premises, unsuitable equipment, manual handling during the filling and capping process.The methylene blue test results related well with bacterial counts but there were seven (5·4 %) anomalous results. Although the methylene blue reduction test therefore could serve as a simple and reasonable guide to the hygienic quality of fresh cream, 5·4 % of anomalous results would perhaps make it unsuitable as a statutory test.We thank Mr R. Colenso, M.A.P.H.E., M.A.P.H.I., Chief Public Health Inspector, and Mr H. Beckett, Milk Sampling Officer of the Worcestershire County Council, for arranging the supply of samples.

QUALITY ASSESSMENT OF RAW MILK IN KOSOVO

2018 ◽  
Vol 28 (4) ◽  
pp. 1305-1309
Author(s):  
Emine Uka ◽  
Nexhdet Shala ◽  
Arsim Elshani
Keyword(s):  
Negative Impact ◽  
Raw Milk ◽  
The Other ◽  
Human Consumption ◽  
Monitoring Point ◽  
Milk Processing ◽  
Milk Samples ◽  
Fresh Milk ◽  
Quality Of Milk

Since milk is one of the most consumable products of human consumption and in Kosovo, it is one of the most prosperous agriculture branches and the continued support to farmers from the Ministry of Agriculture, European Commission and USID, through which we will offer knowledge about the quality of this milk. Quality milk production is the ultimate goal and goal of any milk producer and processor. On the other hand, the low quality of milk has a negative impact on all segments of the dairy industry, especially in the fresh milk processing segment.Our work provides testing of raw milk samples taken by farmers who send milk to milk collection points and dairies in order to determine the quality of your milk. As a monitoring point we have received the Vita dairy and Aldi dairy in the period January 2017 - October 2018, and we have presented a comparison of their results.

SOME OBSERVATIONS ON THE BACTERIOLOGICAL KEEPING QUALITY OF MILK PROCESSED BY HIGH TEMPERATURES WITH A 0.6 SECOND HOLDING TIME1 2

1963 ◽  
Vol 26 (10) ◽  
pp. 332-336 ◽  
Author(s):  
D. A. Evans ◽  
Eleanor L. Lachman ◽  
Warren Litsky
Keyword(s):  
Heat Treatment ◽  
Raw Milk ◽  
Plate Heat Exchanger ◽  
Plate Heat ◽  
Milk Samples ◽  
Whole Milk ◽  
Keeping Quality ◽  
Quality Of Milk ◽  
Sterilized Milk

Summary Raw milk was processed through a commercial sized plate heat exchanger at temperatures of 160 F through 260 F with a 0.6 sec hold. Milk samples were collected at increments of 10 F during processing and analyzed for psychrophilic, mesophilic and thermophilic counts initially and at weekly intervals thereafter. All samples were held at 40 F after processing. Results indicated that temperatures of processing at 160 F and 170 F were not sufficient to impart acceptable keeping qualities to whole milk held at 40 F for a period of one week. By comparison, processing temperatures of 180 F through 210 F with 0.6 sec hold appeared to impart to whole milk keeping qualities which were approximately comparable to those observed in milk pasteurized according to present standards. When heat treatment in the range of 220 F through 260 F were used, it was indicated that bacteriological keeping quality of the milk was improved to an extent far beyond that experienced with present day commercial pasteurization. There appeared to be somewhat of a tendency for higher count raw milk related to the level of population in the processed product although the magnitude of this relationship was not clearly defined in all cases. It was evident that this process did not produce “commercially sterilized” milk at the processing temperatures and holding time used.

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.

435. Keeping quality and raw-milk grading: II. The effect of storage on the results of keeping quality and dye tests

1951 ◽  
Vol 18 (1) ◽  
pp. 43-71 ◽  
Author(s):  
R. T. Eddison ◽  
O. Kempthorne ◽  
Zena Hosking ◽  
H. Barkworth ◽  
C. P. Cox ◽  
...  
Keyword(s):  
Methylene Blue ◽  
Raw Milk ◽  
Practical Method ◽  
Atmospheric Temperature ◽  
Test Results ◽  
England And Wales ◽  
Keeping Quality ◽  
Methylene Blue Test ◽  
The Times ◽  
Morning Milk

1. The experiments described in this part of the report were designed to obtain information about the effect of time and temperature of pre-test storage on test results and, in particular, about the possibility of a practical method of compensating test results to eliminate or minimize their dependence on the time and temperature of pre-test storage.2. Four separate experiments were planned and carried out in three widely separated areas in England and Wales. Samples of morning milk, brought to the laboratory with the minimum of delay, were divided into a series of subsamples which were subsequently stored at controlled temperatures ranging from 3 to 24°C, and at shade atmospheric temperature, for periods ranging from 7 to 30 hr. before examination by one or more of the following tests: keeping quality at 18, 22 and 24° C. using clot-on-boiling (C.O.B.), and precipitation with 68% alcohol (A.P.T.) or 50% alcohol; methylene-blue test at 37–5° C. and at 18, 22 or 24° C. The results for the different tests were the times to end-point after transfer from the storage to the incubation baths.

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