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.

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.

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 Microbial assessment of potential functional dairy products with added dried herbs

2020 ◽  
pp. 59-63
Author(s):  
Kármen Anita Kiss ◽  
Viktória Kapcsándi ◽  
Rebeka Ligeti ◽  
Erika Hanczné Lakatos
Keyword(s):  
Dairy Products ◽  
Dairy Product ◽  
Raw Milk ◽  
Human Consumption ◽  
Melissa Officinalis ◽  
Active Components ◽  
Mentha X Piperita ◽  
Bulk Milk ◽  
Stable Product

The market of dairy products is a dynamically developing sector of the food industry. Potential, functional dairy products, made by adding herbs or spices, will have antimicrobial and antioxidant effect due to the active biochemical agents of the plant additives. Furthermore, these active components will widen the storage life of food products and enhance their organoleptic properties too. We worked out a technology for creating fresh cheeses using a gentle pasteurizing method by treating the mixture of raw milk and 1.5% fat contained in commercial milk. As herb additives, we used citronella (Melissa officinalis), and peppermint (Mentha x piperita) harvested by us and dried them via Tyndall-method in convective dryer on 40 °C for 5.5 hours per day. The drying period took three days. We bought dried citronella and mint from the supermarket, which were dried by ionizing radiation, to compare the microbiological pollution with the herbs dried by us. The main target of this research was to create a microbiologically stable, potential functional dairy product. However, because of the bad quality of the raw milk and the gentle heat treatment we used for sterilizing bulk milk, or else, cheeses were not safe for human consumption. As a consequence, we need further studies to modify our technology and get a microbiologically stable product.

scholarly journals Sources of psychrotrophic contamination and proteolysis indices in raw milk

2020 ◽  
pp. 35176-35180
Keyword(s):  
Dairy Products ◽  
Principal Component ◽  
Dairy Farms ◽  
Raw Milk ◽  
Raw Material ◽  
Operating Costs ◽  
Human Consumption ◽  
Microbiological Contamination ◽  
Psychrotrophic Bacteria

Storage of raw milk under refrigeration makes it possible to reduce operating costs for production and prevents losses of this raw material by the acidifying activity of mesophilic bacteria. Meantime, storage for prolonged periods may result in decreased quality of dairy products, due to the growth and enzymatic activity of psychrotrophic bacteria. Thus, in this study, we evaluated the presence of psychrotrophic microorganisms, Pseudomonas spp. and Pseudomonasaeruginosa tracing sources of microbiological contamination in the milking process as well as the level of proteolysis of the milk in the expansion tank. The highest contamination (P <0.05) occurred with the psychrotrophic count, with maximum values of 5.11 log CFU•mL-1a value that has hydrolytic potential for K-casein. Some dairy farms were found to have a maximum caseinomacropeptide value of 142.93 mg•L-1, representing loss of quality for the industry and a raw material that is not suitable for human consumption. The points of greatest contamination were udder surface, insufflator, milking bucket and colling system. According to principal component analysis, the values obtained for the microbiological counts were not determinants of the release of caseinomacropeptide.

Proteinase and phospholipase activities and development at different temperatures of yeasts isolated from bovine milk

2011 ◽  
Vol 78 (4) ◽  
pp. 385-390 ◽  
Author(s):  
Priscilla A Melville ◽  
Nilson R Benites ◽  
Monica Ruz-Peres ◽  
Eugenio Yokoya
Keyword(s):  
Dairy Products ◽  
Room Temperature ◽  
Bovine Milk ◽  
Raw Milk ◽  
Pathogenic Potential ◽  
Proteinase Production ◽  
Different Temperatures ◽  
Quality Of Milk ◽  
Means Of Transmission

The presence of yeasts in milk may cause physical and chemical changes limiting the durability and compromising the quality of the product. Moreover, milk and dairy products contaminated by yeasts may be a potential means of transmission of these microorganisms to man and animals causing several kinds of infections. This study aimed to determine whether different species of yeasts isolated from bovine raw milk had the ability to develop at 37°C and/or under refrigeration temperature. Proteinase and phospholipase activities resulting from these yeasts were also monitored at different temperatures. Five genera of yeasts (Aureobasidium sp., Candida spp., Geotrichum spp., Trichosporon spp. and Rhodotorula spp.) isolated from bovine raw milk samples were evaluated. All strains showed one or a combination of characteristics: growth at 37°C (99·09% of the strains), psychrotrophic behaviour (50·9%), proteinase production (16·81% of the strains at 37°C and 4·09% under refrigeration) and phospholipase production (36·36% of the isolates at 37°C and 10·9% under refrigeration), and all these factors may compromise the quality of the product. Proteinase production was similar for strains incubated at 37°C (16·81% of the isolates) and room temperature (17·27%) but there was less amount of phospholipase-producing strains at room temperature (15·45% of the isolates were positive) when compared with incubation at 37°C (36·36%). Enzymes production at 37°C by yeasts isolated from milk confirmed their pathogenic potential. The refrigeration temperature was found to be most efficient to inhibit enzymes production and consequently ensure better quality of milk. The viability of yeasts and the activity of their enzymes at different temperatures are worrying because this can compromise the quality of dairy products at all stages of production and/or storage, and represent a risk to the consumer.

693. A rejection test for raw milk

1958 ◽  
Vol 25 (1) ◽  
pp. 32-51 ◽  
Author(s):  
Peggy B. Taylor ◽  
L. F. L. Clegg
Keyword(s):  
Lactic Acid ◽  
Ferric Chloride ◽  
Technical Assistance ◽  
Milk Proteins ◽  
Raw Milk ◽  
Ph Change ◽  
Yellow Colour ◽  
A Value ◽  
Keeping Quality

The determination of apparent lactic acid has been used as a basis for a rejection test for raw milk. The method consists of precipitation of milk proteins with barium chloride, sodium hydroxide and zinc sulphate, and the addition of ferric chloride to the filtrate to produce the yellow colour of ferric lactate. Lactic acid is not solely responsible for the production of the yellow colour, which, nevertheless, gives a good relationship with keeping quality of milk (measured as hours to the C.O.B. end-point at 22° C.) and the values have been expressed as ‘apparent lactic acid’.The relationship of winter and summer milks to keeping quality has been studied, and a value of 0·03% apparent lactic acid in milk is equivalent to an average keeping quality of 5¾ and 8½ hr. for winter and summer milks, respectively. A value of 0·03% is recommended as the earliest value of apparent lactic acid at which milk could be rejected.The apparent lactic acid in colostrum and late-lactation milk and in milk from cows suffering from mastitis has been determined, and only in late-lactation milk were the values found to be significantly higher than usual in fresh raw milk, and an inverse relationship between yield and apparent lactic acid is suggested.Permanent glass matching disks have been prepared for use in a Lovibond comparator. This permits the intensity of the yellow colour produced with 1% ferric chloride to be determined and the apparent lactic acid in milk estimated.Grateful acknowledgement is made to the management and staff of the Dairy Department of the Reading Co-operative Society and the Farmer's Clean Milk Dairy, Reading, and local milk producers for supplying samples for experiments; to the N.M.T.S. staff in Reading for help in finding suitable farmers, and to the Dairy Husbandry Department of the N.I.R.D. for information about and samples of abnormal and late-lactation milk. Our particular thanks are due Miss Marie Gruber for technical assistance, to Dr N. J. Berridge for the suggestion and help on the work on pH change as an indication of keeping quality (given in the appendix), and to Dr A. T. R. Mattick for the advice given in this work.

scholarly journals Raw milk consumption and health

2015 ◽  
Vol 143 (1-2) ◽  
pp. 87-92 ◽  
Author(s):  
Anka Popovic-Vranjes ◽  
Milka Popovic ◽  
Marija Jevtic
Keyword(s):  
Dairy Products ◽  
Raw Milk ◽  
Cottage Cheese ◽  
Human Consumption ◽  
Microbiological Analysis ◽  
Unpasteurized Milk ◽  
Thermally Processed ◽  
Bacteriological Testing ◽  
Foodborne Outbreaks ◽  
Milk And Dairy Products

Contrary to the safe practices of milk pasteurization or sterilization, which effectively reduce foodborne outbreaks incidence associated with raw milk and dairy products use, outbreaks caused by such products continue to occur. Despite this fact, a worldwide movement advocating for the rights of raw milk and cheese selling and consumption, due to their specific nutritive characteristics, has strengthened significantly in recent years. Traditional agricultural manufacturers from Serbia still sell products related to thermally unprocessed milk, such as cottage cheese and raw cream. In AP Vojvodina during the period of 1981-2010 a total of 179 foodborne outbreaks were reported, where the incriminated cause of the outbreak were milk or diary. In 126 (70.39%) outbreaks, totaling 2276 sick individuals and one casualty, it was confirmed that the incriminated food was from the group of dairy products. In 48 instances (26.82%), bacteriological tests confirmed that milk and dairy products were excluded as the outbreak causes, while in another 5 (2.79%) outbreaks, microbiological analysis of food failed to confirm any relation to the actual epidemiological instances. In some cases, bacteriological testing of incriminated foods was not possible. In the cases of outbreaks associated with the consumption of milk and dairy products, traditional raw milk products were cited as being used. Consumption of unpasteurized milk and cheese represents public health threat. National and international rules ensuring use of safe products for human consumption have to set rules of trade of thermally processed milk and products on the market.

400. Factors influencing the keeping quality of ghee

1949 ◽  
Vol 16 (3) ◽  
pp. 356-362 ◽  
Author(s):  
D. P. Persai ◽  
C. R. Barnicoat
Keyword(s):  
Heat Treatment ◽  
Bacterial Culture ◽  
Storage Life ◽  
Summer Temperature ◽  
Final Temperature ◽  
Marked Influence ◽  
Factors Influencing ◽  
Keeping Quality ◽  
Main Factors

Of the four main factors commonly regarded as influencing keeping properties of ghee, viz. moisture content, acidity, heat treatment and type of bacterial culture used in souring, the heat treatment was found to be the most important.In general, the higher the final temperature (110° C. and higher) attained during evaporation, the better were the keeping properties of the product, providing that the butter had been heated in contact with curd, boiled as rapidly as possible, and given a minimum amount of stirring.The improved keeping properties conferred on ghee heated to 110–150° C. were promoted by antioxidants (apparently phospholipids) extracted from the curd during cooking.Initial acidity and moisture contents had no effect on storage life of ghee at 38° C., and the practice of grading ghee according to its acidity would appear to be of questionable value. Souring of milk to give 2·5–3·0% lactic acid and the accompanying desirable flavour did not detract from the keeping quality of the ghee made from it.The type of bacterial culture used for souring had only slight influence on keeping quality of ghee, but a marked influence on flavour.Storage life of ghee at 38° C. (‘Indian summer temperature’) could be predicted with fair accuracy from its rate of oxidation at 100° C. in a ‘Swift oxidation tester’.

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.

The Abrasive Resistance Study about the Cutting Picker 40Cr of Coal Cutter

2013 ◽  
Vol 387 ◽  
pp. 227-230
Author(s):  
Ning Zhang ◽  
Shu Chen Wang ◽  
Na Shi ◽  
Hao Chen
Keyword(s):  
Heat Treatment ◽  
Wear Resistance ◽  
Service Life ◽  
Labor Intensity ◽  
Surface Wear ◽  
Work Efficiency ◽  
Abrasive Resistance ◽  
Treatment Processes ◽  
Mining Capacity

The cutting pick is primarily used in footing excavation such as coal mining and roadway excavation, so the performance of cutting tooth directly affect the mining capacity, the driving efficiency, and the service life of the tool. The quality of domestic mining pick is lower than that abroad, especially the tooth body wear of the whole shearer picks accounts for half of its overall failure. Thus tooth body 40Cr was treated by various heat treatment processes in this experiment, so as to improve the hardness and wear resistance of cutting tooth, analysis the surface wear scar of morphology, research the wear mechanism, that made for reducing the consumption of cutting tooth, improving work efficiency, and easing the labor intensity of workers undergound.

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