Microbiology of milk and milk products pdf

As with pasteurised milk, it is also vital to ensure that raw milk cannot recontaminate the UHT-treated milk. Certain very heat-resistant spores of mesophilic bacilli, classified as Bacillus sporothermodurans 11 are able to survive UHT processes and may subsequently grow in the final product. However, this organism has been shown not to be pathogenic 12 and does not seem to cause any detectable changes to the product. Thermoduric Bacillus stearothermophilus are able to survive UHT processes and cause flat-sour spoilage 3.

Some of these processes are now being applied on a commercial scale in North America and Europe. Microfiltration, usually using ceramic membrane filters, can be used in combination with a minimum HTST pasteurisation process to remove significant numbers of bacteria from milk, and give a substantial extension to shelf life over conventional pasteurised milk The fat is separated from the milk before filtration and is heat treated separately before being added back to the milk after processing.

Milk produced by this method is on sale in several countries, and is said to have a shelf life of at least 20 days. Bactofugation is a centrifugation process that is also able to remove bacteria including endospores from milk. It has been used in the cheese industry for some years to minimise contamination with the spores of lactate-fermenting clostridia that cause 'late blowing'. The centrifugate produced by the process contains most of the microbial cells present initially in the milk, and this can be sterilised separately and then recombined with the treated milk, which is conventionally pasteurised, to restore its composition.

A shelf life of 30 days or more is claimed for milk treated in this way. Microwaving refers to dielectric heating due to polarisation effects at a selected frequency band MHz to GHz in a nonconductor. It has been in commercial practice for milk pasteurisation for quite a long time as it provides the desired degree of safety with minimum quality degradation.

Plate counts of raw milk undergoing continuous-flow microwave pasteurisation, at MHz, were negative while the temperature reached was Other methods that have been applied to milk processing include irradiation, high-pressure processing, ultra sound treatment, ultra high-pressure homogenisation UHPH , and pulsed-electric field PEF. Psychrotrophic spoilage organisms may well be present on fillers, and these can then contaminate the milk and cause a significant reduction in shelf life.

Microorganisms may also be present in the packaging, especially in poorly cleaned re-usable bottles, and this may also compromise the shelf life of the milk. For UHT-processed milk, aseptic filling into sterile containers is necessary for the maintenance of commercial sterility.

Aseptic filling is not generally used for pasteurised milk, although it would be expected to have a significant influence on shelf life. Spoilage may result from either the growth of psychrotrophic thermoduric organisms that survive pasteurisation, or post-pasteurisation contamination by psychrotrophs. The latter is considered to be by far the most common cause of spoilage Of these, the spore-formers are most important in spoilage, since the other species are not generally psychrotrophic and are unable to grow in refrigerated milk.

Several Bacillus spp. This produces small particles that stick to surfaces. Bitter taints may also be produced as a result of spoilage by Bacillus spp.

These organisms are thought to originate from the raw milk, and the level of contamination has been shown to vary with the season, the highest numbers of spores being present between April and September Initially, Enterobacteriaceae, such as Enterobacter, Cronobacter, and Citrobacter, predominate, but Gram-negative psychrotrophs, principally pseudomonads, but also Alcaligenes, Klebsiella, Acinetobacter and Flavobacterium, are more important in terms of eventual spoilage.

Although these organisms may only contaminate the product in low numbers, they have a competitive advantage over Enterobacteriaceae at low temperatures and may grow rapidly to high levels Spoilage by Gram- negative psychrotrophs usually takes the form of off-flavours, often described as unclean, fruity, rancid or putrid, formed as a result of proteolytic and lipolytic activity. Ropiness and partial coagulation may also occur occasionally.

The time for spoilage to occur depends on the numbers and composition of the initial microflora, and the storage temperature Milk produced with good hygienic practices in a modern facility should have a shelf life of more than 10 days at refrigerated storage temperatures.

Under conditions of mild temperature abuse, Enterobacteriaceae may predominate and cause acid clotting or the development of 'faecal' taints.

At still higher temperatures, souring by LAB is possible. Yeast and mould are also indicators of post-process contamination. Their presence and growth contribute to fruity and yeasty flavours in milk 2, 3. Spoilage caused by survival of heat-resistant Bacillus spores is rare, unless very large numbers of spores are present initially, although reports of sterility failure caused by B.

Post-process contamination usually occurs as a result of a failure in the integrity of the aseptic filling system, or, more likely, as a result of packaging defects, such as pinholes or faulty seals.

The product may then become contaminated with a variety of environmental organisms and the type of spoilage will be dependent on the nature of the contaminant. A particular problem associated with UHT-processed milk is spoilage by heat- resistant, extracellular, proteolytic and lipolytic microbial enzymes. These will have been produced by psychrotrophic organisms growing in the raw milk prior to processing, particularly pseudomonads, Acinetobacter, and Achromobacter, which are then able to survive the thermal process, even though all viable cells have been destroyed.

In the course of the long shelf life that these products are given, proteolytic enzymes can cause bitter flavours and gelation, whilst lipases cause the development of rancid flavours Pasteurisation and improvements in veterinary medicine have seen a very large reduction in the incidence of such traditionally milkborne diseases.

However, raw milk may still contain a very wide range of pathogens, including Salmonella spp. Pathogens may be present even in hygienically produced milk of generally good microbiological quality.

In short, raw milk is a potentially hazardous product, the microbiological safety of which cannot be assured without the use of pasteurisation or an equivalent process. Recent milk-associated outbreaks of infectious intestinal disease in the UK have been shown to be caused mainly by unpasteurised or inadequately pasteurised milk products Therefore, their presence indicates that the process has not been carried out effectively, or that post-process contamination has occurred.

For example, an outbreak of salmonellosis in Kentucky in was associated with pasteurised milk, but an investigation of the dairy concerned showed that pasteurisation temperatures were inadequate, and could have been as low as An outbreak caused by Salmonella braenderup in the UK in was also associated with pasteurised milk, and on this occasion the pasteuriser was found to be poorly designed and incorrectly operated, probably resulting in the application of an inadequate heat treatment In , one of the largest outbreaks of salmonellosis in US history occurred in Illinois.

Investigations at the dairy plant involved revealed no evidence of inadequate pasteurisation, and the outbreak strain was not found to be abnormally heat resistant Although the cause of the outbreak has never been completely explained, the investigation did discover a possible cross-connection between raw and pasteurised milk, which may have been the source of contamination In , an outbreak of salmonellosis in Lancashire, caused by a multiresistant strain of S.

This outbreak was also linked to defective pasteurisation of milk at a dairy on a local farm It is very important that contamination of the post-pasteurisation plant is not allowed to occur and effective precautions and monitoring procedures, based on HACCP principles, are necessary to prevent this.

Campylobacter spp. Nonetheless, outbreaks of campylobacteriosis associated with pasteurised milk have occurred. For example, a large outbreak in the UK in caused by Campylobacter jejuni was estimated to have affected at least 2, schoolchildren, and was associated with free milk provided in schools. Although conclusive evidence was absent, it seems likely that raw milk may have bypassed the pasteurisation process A more recent outbreak in involved 75 people and was linked to the consumption of unpasteurised milk procured thorough a cow leasing program Birds are known to be an important reservoir of Campylobacter infection, and the tendency of some birds to peck through the foil tops of doorstep-delivered milk bottles is becoming recognised as an important source of infection in parts of the UK.

Some individual cases have been attributed to this cause, and, in one instance in , the organism was isolated from the beaks of jackdaws and magpies as well as the contaminated milk More recently, an outbreak thought to be associated with bird-pecked milk was reported An outbreak of listeriosis in Massachusetts during resulted in 49 cases, 14 of whom subsequently died.

The investigation failed to reveal any evidence of inadequate pasteurisation a process of However, samples of raw milk taken from farms supplying the plant were found to be positive for L. So far, investigations have found nothing wrong with its pasteurisation process Furthermore, in a survey of pasteurised milk conducted in Spain, L. The explanation offered for both these findings was that the organisms might have been protected during heat treatment within leucocytes in the milk.

However, this effect has not been conclusively demonstrated, and L. For these reasons, it is currently accepted that existing pasteurisation processes are adequate to inactivate the organism in milk.

Therefore, effective HACCP-based controls to prevent post-process contamination are critical, particularly the cleaning and sanitising of all milk- contact surfaces. Adequate temperature control is also important.

For this reason, raw milk is a high-risk food for this serious intestinal pathogen, and there have been a number of small outbreaks of infection associated with its consumption. However, E. Despite this, there have been outbreaks associated with pasteurised milk. In , an outbreak in Scotland affected over people and was associated with consumption of pasteurised milk from a local dairy.

The outbreak strain was eventually recovered from cows on one of the farms supplying the dairy, from a bulk milk tanker, and from a pipe transferring milk from the pasteuriser to the bottling machine Whether this outbreak was the result of faulty pasteurisation or post-process contamination was unclear, but, in either case, the raw milk is likely to have been the original source of the organism.

In , a serious outbreak occurred in Cumbria in the north-west of England, which was also associated with pasteurised milk from a local dairy.

There were at least 60 confirmed cases involved, and the cause was thought to be a fault in the operation of the pasteuriser 41, The first general outbreak of verocytotoxin-producing E. It was thought to be due to the consumption of a particular kind of organic milk from a small dairy. Environmental and microbiological investigations at the suspected dairy did not confirm the presence of the outbreak strain, but the outbreak stopped once the dairy was closed and thoroughly cleaned However, since the infective dose of this pathogen is thought to be very low probably fewer than cells , effective pasteurisation and the prevention of post-process contamination are critical to ensure product safety.

Three different strains of Y. Therefore, the presence of the organism in pasteurised milk is likely to be the result of post-process contamination. There have been several Y. In , an outbreak affecting 36 children was associated with the consumption of contaminated chocolate milk. It was thought that the organism was introduced to the product during mixing of chocolate syrup with pasteurised milk, without any subsequent heat process Another outbreak in was the largest foodborne yersiniosis outbreak ever recorded in the USA, and was also associated with pasteurised milk.

It is thought that several thousand people may have developed illness, although the organism was not isolated from milk or environmental samples at the dairy.

It was found that surplus milk was used to feed pigs and that the crates used to transport this milk were stored on the ground at the farm and could have become contaminated with pig faeces.

Since pigs are a well known reservoir for Y. Measures should therefore be taken to prevent post-process contamination as with L. This may be because Staph. The organism is also known to be inhibited by the presence of competing species. Nevertheless, an outbreak in California affecting school children was associated with chocolate-flavoured milk. The cause was thought to be growth of Staph. In June and July , a very large outbreak of staphylococcal food poisoning was reported in Japan, associated with consumption of pasteurised low fat milk.

The outbreak was unusual in that the thermal processes had destroyed staphylococci in milk but Staphylococcus enterotoxin A SEA had retained enough activity to cause intoxication. As has already been mentioned, psychrotrophic Bacillus spp.

Concerns have been expressed that some psychrotrophic strains of B. Even so, B. Evidence linking MAP to a chronic inflammatory bowel condition in humans, called Crohn's disease, is becoming increasingly compelling. Concerns have been raised that MAP might be able to survive pasteurisation if present at levels above cells per ml, especially if clumps of cells are present, and that pasteurised milk may therefore be a vehicle for Crohn's disease On the basis of new heat-resistance studies, many UK dairies have increased pasteurisation times to from 15 to 25 seconds A survey of the level of contamination of pasteurised milk by MAP over a 17 month period, in - , revealed a mean of 1.

The potential public health impact of this situation is, however, still uncertain given that an association with Crohn's disease in humans remains unproven However, raw milk has been implicated in outbreaks of hepatitis and poliomyelitis. Some viruses, including poliovirus, are completely inactivated by pasteurisation, but this seems not to be the case with others, such as FMDV, if the virus is naturally present rather than inoculated.

Feed contaminated by aflatoxin B1 as a result of the growth of Aspergillus flavus or Aspergillus parasiticus has been shown to give rise to the presence of aflatoxin M1 in the milk of dairy cows consuming it. However, only a small percentage 0. Aflatoxins are persistent compounds and are not greatly affected by milk processing, and could therefore be present in pasteurised, packaged milk.

However, recent surveys suggest that contamination of the milk supply is very limited and well within acceptable levels McKinnon C.

The effect of udder preparation before milking and contamination from the milking plant on bacterial numbers in bulk milk of eight dairy herds. Journal of Dairy Research, , 57, Doyle M. Food Microbiology: Fundamentals and Frontiers. Washington, ASM Press. Boor K. Managing microbial spoilage in the dairy industry, in Food Spoilage Microorganisms. Blackburn C. Meer R. Psychrotrophic Bacillus spp. Journal of Food Protection, , 54 12 , Wolfson L.

Antibacterial activity of the lactoperoxidase system: a review. Journal of Food Protection, , 56 10 , Ternstrom A.

Classification of the spoilage flora of raw and pasteurised bovine milk, with special reference to Pseudomonas and Bacillus. Journal of Applied Bacteriology, , 75 1 , Mackey B. The heat resistance of Listeria monocytogenes. Letters in Applied Microbiology, , 6 3 , Effect of low-temperature storage on the bacteriological quality of raw milk. Food Microbiology, , 4 4 , Hotchkiss J. Addition of carbon dioxide to dairy products to improve quality: a comprehensive review.

Jay J. Petterson B. Bacillus sporothermodurans, a new species producing highly heat-resistant endospores. International Journal of Systematic Bacteriology, , 46, Hammer P.

Brussels, IDF. Eckner K. Potential for the low-temperature pasteurisation of dairy fluids using membrane processing. Journal of Food Protection, , 54 10 , Ahmed J. Microwave pasteurisation and sterilisation of foods, in Handbook of Food Preservation, Ed. Rahman M. Moseley W. Pinpointing post-pasteurisation contamination. Journal of Food Protection, , 43, Schroder M. Origins and levels of post pasteurisation contamination of milk in the dairy and their effects on keeping quality.

Journal of Dairy Research, , 51 1 , Champagne C. A, Griffiths M. Psychrotrophs in dairy products: their effects and their control. Phillips J. Factors contributing to the seasonal variation of Bacillus spp. Journal of Applied Bacteriology, , 61 4 , Journal of Dairy Research, , 49 4 , Reviews of the progress of dairy science: enzymes of psychrotrophic bacteria and their effects on milk and milk products.

Journal of Dairy Research, , 46 3 , Bryan F. Epidemiology of milk-borne disease. Journal of Food Protection, , 46 7 , Djuretic T. General outbreaks of infectious intestinal disease associated with milk and dairy products in England and Wales: to CDR Review, , 7 3 , R Adams D. Salmonellosis from inadequately pasteurised milk: Kentucky. Morbidity and Mortality Weekly Report, , 33, Safety of pasteurised milk. Lancet, , 2 , Ryan C. Massive outbreak of antimicrobial- resistant salmonellosis traced to pasteurised milk.

Bradshaw J. Thermal resistance of disease-associated Salmonella typhimurium in milk. Journal of Food Protection, , 50 2 , Lecos C. Of microbes and milk: Probing America's worst Salmonella outbreak. Dairy and Food Sanitation, , 6 4 , Defective pasteurisation linked to outbreak of Salmonella typhimurium definitive phage type infection in Lancashire. CDR Weekly, , 8 38 , , Lind L. Salmonella typhimurium infection associated with raw milk and cheese consumption Pennsylvania, , MMWR Weekly, , November 9 , 56 44 , Mazurek J.

A multistate outbreak of Salmonella enterica serotype typhimurium infection linked to raw milk consumption - Ohio, Journal of Food Protection, , 67 10 , Jones P. Campylobacter enteritis associated with the consumption of free school milk.

Journal of Hygiene, , 87 2 , Centres for Disease Control and Prevention. Outbreak of Campylobacter jejuni infection associated with drinking unpasteurised milk procured through a cow leasing program — Wisconsin, Hudson S. C, Russell K. Jackdaws and magpies as vectors of milkborne human Campylobacter infection. Epidemiology and Infection, , 2 , Stuart J. Outbreak of Campylobacter enteritis in a boarding school associated with bird pecked bottle tops.

Fleming D. Pasteurised milk as a vehicle of infection in an outbreak of listeriosis. New England Journal of Medicine, , 7 , Garayzabal J. Listeria monocytogenes in pasteurised milk. Canadian Journal of Microbiology, , 32 2 , Northolt M. Listeria monocytogenes: heat resistance and behaviour during storage of milk and whey and making of Dutch types of cheese.

Netherlands Milk and Dairy Journal, , 42 2 , Upton P. Outbreak of Escherichia coli O infection associated with pasteurised milk supply. Lancet, , , Outbreak of verocytotoxin producing Escherichia coli O infection in North Cumbria. CDR Weekly, , 9 11 , CDR Weekly,, 9 12 , Eurosurveillance editorial team. Outbreak of verocytotoxin-producing E.

Eurosurveillance Weekly, , 8 20 , Wang G. Survival and growth of Escherichia coli OH7 in unpasteurised and pasteurised milk. Journal of Food Protection, , 60 6 , 3. Lovett J. Thermal inactivation of Yersinia enterocolitica in milk. Applied and Environmental Microbiology, , 44 2 , Black R. Epidemic Yersinia enterocolitica infection due to contaminated chocolate milk. New England Journal of Medicine, , 2 , Aulisio C.

C, Lanier J. Yersinia enterocolitica associated with outbreaks in three southern states. Journal of Food Protection, , 45, Evenson M. Estimation of human dose of staphylococcal enterotoxin A from a large outbreak of staphylococcal food poisoning involving chocolate milk.

International Journal of Food Microbiology, , 7 4 , Asao T. An extensive outbreak of staphylococcal food poisoning due to low-fat milk in Japan: estimation of enterotoxin A in the incriminated milk and powdered skim milk. Epidemiology and Infection, , 1 , Langeveld L. Consumption by healthy adults of pasteurised milk with a high concentration of Bacillus cereus: a double-blind study. Journal of Food Protection, , 59 7 , Psychrotrophic strains of Bacillus cereus producing enterotoxin.

Journal of Applied Bacteriology, , 69 1 , Grant I. Letters in Applied Microbiology, , 28 6 , Applied and Environmental Microbiology, , 68 5 , — Viruses pathogenic to man in milk and cheese, in Behaviour of Pathogens in Milk. IDF Bulletin No. Frobish R. Long-Bradley P. Aflatoxin residues in milk of dairy cows after ingestion of naturally contaminated grain.

Journal of Food Protection, , 49 10 , Ryser E. Public health concerns, in Applied Dairy Microbiology. The removal of water from fresh milk gives advantages in terms of reduced storage and transport costs, convenience in use, and, in some cases, a useful extension to shelf life.

Concentrated milk is intended to be reconstituted by the consumer, by dilution with water, to give a similar composition to that of fresh milk. It gives little benefit in terms of keeping quality or convenience, and has not become an important product.

Bulk condensed milk is an important source of milk solids in confectionery, bakery products, ice cream, concentrated yoghurt and other products, and is manufactured in large quantities for this purpose. It may be made from whole, skimmed, or reduced fat milks, depending on the end use. Most bulk condensed milk is made by evaporation, and the degree of concentration is usually within the range 2. The keeping quality is limited because it is not sterilised during or after processing.

Sweetened condensed milk may be made from whole or skimmed milk either in bulk as a food ingredient, or in small cans or tubes for direct sale to the consumer. After evaporation, sufficient sugar is added, usually as sucrose or glucose, to prevent most microbial growth. The sugar concentration in the aqueous phase known as sugar ratio, sugar number or sugar index of retail products is usually in the range of For bulk, whole milk products the sugar index is about 42; this is because the product is stored refrigerated for fairly short periods.

The product is packed in hermetically sealed metal containers for retail trade, and milk cans, barrels, steel drums or bulk tanks for industrial purposes. Significant quantities of bulk sweetened condensed milk are used in the confectionery, bakery and prepared food industries. Evaporated milk is similar in composition to bulk condensed whole milk, but is usually heat processed and canned to give a 'commercially sterile' product.

It normally contains at least 7. Most evaporated milk is sold directly to consumers for use in home cooking. Dried milks are manufactured as food ingredients in large quantities, and with widely varying compositions, depending on their end use. Both dried whole milk and skimmed milk powders are produced, but there is also a range of products with specific characteristics for particular applications in food processing e. Sugar used in sweetened condensed milk may be an additional source of yeasts and moulds and bacterial spores, including thermophilic spores.

In each case, the initial steps of milk storage, transport, separation and standardisation are the same as those used for fresh milk. The first key stage is therefore the pasteurisation or pre-heating process. Much higher processes are used in some instances. Condensed milk is also subjected to processes more severe than milk pasteurisation, with the exact process being determined by the nature of the product required.

This pre- heating helps to increase viscosity and improve other characteristics. These processes may be less controlled than conventional pasteurisation, but it is important that a safe minimum process is always applied.

As with fresh milk, most vegetative bacteria will be destroyed during heating, but some thermoduric types and bacterial endospores are likely to survive all but the most severe processes. The second common process in the manufacture of all types of concentrated milk products is the removal of water, usually by evaporation.

The most common type of evaporator used in the dairy industry is the falling film evaporator, which is both energy-efficient and readily controllable. The vacuum, however, is greater in the lowest temperature effect, so that the milk flows from high to low temperature. This process is very efficient and produces milk at the required concentration without a second pass. The temperatures within the lower temperature effects of the evaporator are low enough to permit the growth of thermophilic and some mesophilic spores, and quite high numbers may develop in the effects during prolonged production runs.

The growth of thermophiles must be controlled, by limiting the length of production runs, effective plant cleaning and sanitation, and ensuring that adequate standards of plant hygiene are applied. It is then concentrated at a low temperature, followed by standarisation, homogenisation and pasteurisation before packaging. Pasteurisation is usually done at Unless skimmed milk is used, homogenisation is also usually carried out at this stage. A pre-heating process is then applied, using a continuous heater or a 'hot well'.

Temperatures of These processes will greatly reduce the number of vegetative bacterial cells in the milk, but they are not under the same degree of control as conventional pasteurisation. Therefore, a further HTST pasteurisation step should be applied to eliminate this hazard. The preheated milk is then concentrated in a vacuum-pan or in a multiple-effect evaporator at a temperature range of It is also likely that post-process contamination could occur during standardisation or packaging.

The process is depicted in Figure 2. Production of condensed milk 2. For bulk, sweetened condensed milk, sugar can be added before concentration at varying levels depending on the end use. This material is not usually microbiologically stable and has a limited shelf life. In the production of sweetened condensed milk for retail sale, sugar generally sucrose is added during the later stages of evaporation. However, some osmophilic yeasts and moulds are able to grow in the product, and may cause spoilage.

Evaporation is carried out at a temperature of around A high standard of hygiene during the later handling and filling stages is necessary to prevent contamination. A particular problem with sweetened condensed milk is its high viscosity, and 'sticky' nature, which makes cleaning processing equipment difficult. This high viscosity means that positive- displacement, plunger-type fillers are needed to fill the product. These are complex and difficult to clean and may become heavily contaminated with micrococci and yeasts if not properly maintained.

Because of this, the milk has to be stabilised to prevent coagulation during processing and to minimise 'age thickening' during storage. Stabilisation is achieved by the addition of permitted salts, including phosphates, citrates and bicarbonates, which are used to maintain the pH of the milk at 6. Only a few bacterial spores are likely to survive such a process.

Condensation is usually performed at a temperature lower than After evaporation, the milk is homogenised, cooled and stored. It is then standardised, and further stabilising salts may also be added at this point. It is important to ensure that cooling is rapid and sufficient to minimise any microbial growth during this procedure. The milk is then filled into cans, hermetically sealed, and sterilised using batch retorts or continuous sterilisers.

Retorted canned milk is commercially sterile, and only extremely heat-resistant spores of organisms such as Bacillus stearothermophilus are likely to survive. Aseptically filled evaporated milk may become recontaminated during filling, unless stringent hygiene procedures equivalent to those used in filling other UHT milk products are used.

Production of evaporated milk 2. Most dried milk powders are now spray- dried, and drum and roller dryers are little used. Therefore, only spray drying will be considered further. Before evaporation and drying, the milk is standardised, if required, and heat- treated. Vegetative bacteria, including Enterobacteriaceae and Listeria monocytogenes 3, 4 have been shown to survive the drying process, and therefore all raw milk should receive a process at least equivalent to pasteurisation.

Skimmed milk may also be subjected to low, medium and high heat processes to give varying degrees of protein denaturation as required. UHT heating units result in products that have excellent microbiological quality, which is important when dried milk is to be used as an ingredient in baby food. As the drying process does not kill all vegetative bacterial cells, effective cleaning and hygiene procedures are required to ensure that the heat-treated milk does not become recontaminated.

The current practice is to link the evaporation plant and dryer as a single integrated unit. Two systems of spray drying are used: jet or nozzle dryers, and rotary atomiser dryers. Each dryer produces powders with specific characteristics. In the case of jet dryer systems, milk is fed to a high-pressure pump, then pumped under pressure to a series of jets or nozzles within the drying chamber. Hygienic milk Lesson 1. Butter is a milk product made by the separation of milk and subsequent churning of the cream.

Milk Microbiology. It is not surpris- ing, therefore, that the microbiology of milk and milks products remains a priority interest for everyone associated with the dairy industry. Keywords: raw milk, microbiological quality, marketing channels, Sudan.

Milk and dairy products are consumed worldwide and considered as relevant sources of nutrition in humans and animals, not only the newborns. There is mounting evidence that the consumption of fermented dairy products such as cheese and yoghurt is associated with a reduced risk of type II diabetes.

Milk allergy is often mistakenly believed to be lactose intolerance, which is when the body is unable to digest the found in dairy products. The differences in the flavour and aroma of the various dairy products are due to additional fermentation products that may be present in very low concentrations.

Not only do individual consumers use liquid milk for beverages and cooking, but food manufacturers use vast quantities of milk powder, concentrated milks, butter, and. Read Paper. Milk has been an important food for man since the domestication of cattle and the adoption of a pastoralist agriculture.

The Milking Equipment 4. But according to the results found after doing the microbiological analysis of milk and milk products in Vellore area. Milk is a good source of nutrients and edible energy, not only for mammals but also for numerous microorganisms that thus can grow in milk.

The unhygienic handling practices in traditional camel milk production and in the informal camel milk Microbiology Handbook Dairy Products. The past twenty years have seen rapid growth of dairy industry in our country. Treatment for milk allergy typically depends on the symptoms present and their severity.

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Remember me on this computer. Enter the email address you signed up with and we'll email you a reset link. Need an account? Click here to sign up. Download Free PDF. Nobin Zx. Douglas Robinson. A short summary of this paper. Copyright 0 by John Wiley and Sons, Inc. All rights reserved. Published simultaneously in Canada. N o par1 of this publication may be reproduccd, stored in a retrieval system or transmitted in any form or by any means. MA Bennett 1. Chambers 2. Boor and Steven C.

Murphy 3.