From the Farm to the Processing Plant

To provide the safest and highest quality product to the consumer, the Pasteurized Milk Ordinance (PMO, 2005) provides standardized guidelines. The PMO is a document from the United States Departments of Health and Human Services and Public Health, and the Food and Drug Administration that defines practices relating to milk parlor and processing plant design, milking practices, milk handling, sanitation, and standards for the pasteurization of Grade A milk products. Each state regulates their own dairy industry, but the state's guidelines usually meet or exceed those defined by the PMO. Milk that is shipped between states must follow the PMO regulations.

Milk is obtained from the cow (or goat, sheep, or water buffalo) under sanitary conditions and cooled to 45°F (7°C) within 2 hours of milking. Milk is picked up by a handler who takes a sample and then pumps the milk from farm's bulk tank into the milk truck. A handler may pick up milk from more than one farm, so a truck load may contain milk from several farms when it is delivered to the processing plant. Before the milk can be unloaded at the processing plant, each load is tested for antibiotic residues. If the milk shows no evidence of antibiotics, it is pumped into the plant's holding tanks for further processing. If the milk does not pass antibiotic testing, the entire truck load of milk is discarded and the farm samples are tested to find the source of the antibiotic residues. Regulatory action is taken against the farm with the positive antibiotic test. Positive antibiotic tests are rare, and account for far less than 1% of the tank loads of milk delivered to processing plants.

Milk at the plant is stored at less than 45°F (7°C) and is usually processed within 24 hours, but can held for up to 72 hours (3 days) before processing. Longer holding time allows for growth of spoilage organisms that grow at refrigerator temperatures, called psychrotrophs.

Almost all of the milk in the United States is pasteurized, with the exception of some raw milk cheese production and some states that allow the sale of raw milk. The conditions of the heat treatment used for pasteurization depends on the final product - lower temperatures are used for refrigerated products and higher heat treatments are used for products stored at room temperature. The composition of many dairy products is defined by law, called Standards of Identity, in the United States Code of Federal Regulations (2006).

Processing

In most Western countries, a centralized dairy facility processes milk and products obtained from milk (dairy products), such as cream, butter, and cheese. In the U.S., these dairies are usually local companies, while in the Southern Hemisphere facilities may be run by very large nationwide or trans-national corporations (such as Fonterra).

Pasteurization

Pasteurization is used to kill harmful microorganisms by heating the milk for a short time and then cooling it for storage and transportation. Pasteurized milk is still perishable and must be stored cold by both suppliers and consumers. Dairies print expiration dates on each container, after which stores will remove any unsold milk from their shelves.

A newer process, Ultra Pasteurization or ultra-high temperature treatment (UHT), heats the milk to a higher temperature for a shorter time. This extends its shelf life and allows the milk to be stored unrefrigerated because of the longer lasting sterilization effect.

Microfiltration

Microfiltration is a process that partially replaces pasteurization and produces milk with fewer microorganisms and longer shelf life without a change in the taste of the milk. In this process, cream is separated from the whey and is pasteurized in the usual way, but the whey is forced through ceramic microfilters that trap 99.9% of microorganisms in the milk (as compared to 95% killing of microorganisms in conventional pasteurization). The whey is then recombined with the pasteurized cream to reconstitute the original milk composition.

Creaming and homogenization

Upon standing for 12 to 24 hours, fresh milk has a tendency to separate into a high-fat cream layer on top of a larger, low-fat milk layer. The cream is often sold as a separate product with its own uses; today the separation of the cream from the milk is usually accomplished rapidly in centrifugal cream separators. The fat globules rise to the top of a container of milk because fat is less dense than water. The smaller the globules, the more other molecular-level forces prevent this from happening. In fact, the cream rises in cow's milk much more quickly than a simple model would predict: rather than isolated globules, the fat in the milk tends to form into clusters containing about a million globules, held together by a number of minor whey proteins.^[5] These clusters rise faster than individual globules can. The fat globules in milk from goats, sheep, and water buffalo do not form clusters so readily and are smaller to begin with; cream is very slow to separate from these milks.

Milk is often homogenized, a treatment which prevents a cream layer from separating out of the milk. The milk is pumped at high pressures through very narrow tubes, breaking up the fat globules through turbulence and cavitation.^[26] A greater number of smaller particles possess more total surface area than a smaller number of larger ones, and the original fat globule membranes cannot completely cover them. Casein micelles are attracted to the newly-exposed fat surfaces; nearly one-third of the micelles in the milk end up participating in this new membrane structure. The casein weighs down the globules and interferes with the clustering that accelerated separation. The exposed fat globules are briefly vulnerable to certain enzymes present in milk, which could break down the fats and produce rancid flavors. To prevent this, the enzymes are inactivated by pasteurizing the milk immediately before or during homogenization.

Homogenized milk tastes blander but feels creamier in the mouth than unhomogenized; it is whiter and more resistant to developing off flavors.^[5] Creamline, or cream-top, milk is unhomogenized; it may or may not have been pasteurized. Milk which has undergone high-pressure homogenization, sometimes labeled as "ultra-homogenized," has a longer shelf life than milk which has undergone ordinary homogenization at lower pressures.^[27] Homogenized milk may be more digestible than unhomogenized milk.^[28]

Kurt A. Oster, M.D., who worked in the 1960s through the 1980s, suggested a link between homogenized milk and arterosclerosis, due to damage to plasmalogen as a result of the release of bovine xanthine oxidase (BXO) from the milk fat globular membrane (MFGM) during homogenization. However, Oster's hypothesis has been widely criticized and has not been generally accepted by the scientific community. No link has been found between arterosclerosis and milk consumption.

Medical research

Studies show possible links between low-fat milk consumption and reduced risk of arterial hypertension, coronary heart disease, colorectal cancer and obesity. Overweight individuals who drink milk may benefit from decreased risk of insulin resistance and type 2 diabetes.^[42] One study has shown that for women desiring to have a child, those who consume full fat dairy products may actually slightly increase their fertility, while those consuming low fat dairy products may slightly reduce their fertility.^[43] Milk is a source of Conjugated linoleic acid.

It appears to be effective at promoting muscle growth.

Varieties and brands

Additives and flavoring

In areas where the cattle (and often the people) live indoors, commercially sold milk commonly has vitamin D added to it to make up for lack of exposure to UVB radiation.

Reduced fat milks often have added vitamin A palmitate to compensate for the loss of the vitamin during fat removal; in the United States this results in reduced fat milks having a higher vitamin A content than whole milk.^[72]

To aid digestion in those with lactose intolerance, milk is available in some areas with added bacterial cultures such as Lactobacillus acidophilus ("acidophilus milk") and bifidobacteria ("a/B milk").^[73] Another milk with Lactococcus lactis bacteria cultures ("cultured buttermilk") is often used in cooking to replace the traditional use of naturally soured milk, which has become rare due to the ubiquity of pasteurization which kills the naturally occurring lactococcus bacteria.^[74]

Milk often has flavoring added to it for better taste or as a means of improving sales. Chocolate milk has been sold for many years and has been followed more recently by such other flavors as strawberry and banana.

UHT Milk

Milk preserved by the UHT process is sold in cartons often called a brick that lack the peak of the traditional milk carton. Milk preserved in this fashion does not need to be refrigerated before opening and has a longer shelf life than milk in ordinary packaging. It is more typically sold unrefrigerated on the shelves in Europe and Latin America than in the United States. In Australia it is generally sold unrefrigerated, though some supermarkets also keep small quantities refrigerated.

Glass

Glass milk containers are now rare. Most people purchase milk in bags, plastic jugs or plastic-coated paper cartons. Ultraviolet (UV) light from fluorescent lighting can alter the flavor of milk, so many companies that once distributed milk in transparent or highly translucent containers are now using thicker materials that block the UV light. Many people feel that such "UV protected" milk tastes better.

Spoilage and fermented milk products

When raw milk is left standing for a while, it turns "sour". This is the result of fermentation, where lactic acid bacteria ferment the lactose inside the milk into lactic acid. Prolonged fermentation may render the milk unpleasant to consume. This fermentation process is exploited by the introduction of bacterial cultures (e.g. Lactobacilli sp., Streptococcus sp., Leuconostoc sp., etc) to produce a variety of fermented milk products. The reduced pH from lactic acid accumulation denatures proteins and caused the milk to undergo a variety of different transformations in appearance and texture, ranging from an aggregate to smooth consistency. Some of these products include sour cream, yoghurt, cheese, buttermilk, viili, kefir and kumis. See Dairy product for more information.

Pasteurization of cow's milk initially destroys any potential pathogens and increases the shelf-life ^[76][77], but eventually results in spoilage that makes it unsuitable for consumption. This causes it to assume an unpleasant odor, and the milk is deemed non-consumable due to unpleasant taste and an increased risk of food poisoning. In raw milk, the presence of lactic acid-producing bacteria, under suitable conditions, ferments the lactose present to lactic acid. The increasing acidity in turn prevents the growth of other organisms, or slows their growth significantly. During pasteurization however, these lactic acid bacteria are mostly destroyed.

In order to prevent spoilage, milk can be kept refrigerated and stored between 1 and 4 degrees Celsius in bulk tanks. Most milk is pasteurized by heating briefly and then refrigerated to allow transport from factory farms to local markets. The spoilage of milk can be forestalled by using ultra-high temperature (UHT) treatment; milk so treated can be stored unrefrigerated for several months until opened. Condensed milk, made by removing most of the water, can be stored in cans for many years, unrefrigerated, as can evaporated milk. The most durable form of milk is milk powder, which is produced from milk by removing almost all water. The moisture content is usually less than five percent in both drum and spray dried milk powder.

5. ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k McGee, Harold (1984). "Milk and Dairy Products". On Food and Cooking: The Science and Lore of the Kitchen. New York: Charles Scribner's Sons. pp. 3–53. ISBN 0-684-18132-0.

26. ^ Homogenization of Milk and Milk Products, webpage of University of Guelph

27. ^ "Research Can Lead To Longer Shelf Life For Dairy Products"

28. ^ ^a ^b "Does homogenization affect the human health properties of cow’s milk?"

42. ^ Dairy's Role in Managing Blood Pressure, web page of the US National Dairy Council

43. ^ Chavarro JE, Rich-Edwards JW, Rosner B, Willett WC (May 2007). "A prospective study of dairy foods intake and anovulatory infertility". Human Reproduction 22 (5): 1340–7. doi:10.1093/humrep/dem019. PMID 17329264.

72. ^ "How to Buy Dairy Products", Home and Garden Bulletin 255, USDA, February 1995. Retrieved 16 May 2007.

73. ^ "Yogurt and Other Cultured Dairy Products", National Dairy Council, 2000.

74. ^ Rombauer, Irma S. and Marion Rombauer Becker (1975). The Joy of Cooking (Revised Edition). Bobbs Merrill. pp. 533. ISBN 0-672-51831-7.

76. ^ Got Milk? Make Sure It's Pasteurized

77. ^ Shelf-Life of Pasteurized Fluid Milk as Affected by Age of Raw Milk

References

· McGee, Harold (2004). On Food and Cooking (Revised Edition). Scribner. ISBN 0-684-80001-2.

· Information on milk by Parmalat

· Introduction to Dairy Science and Technology: Milk History, Consumption, Production, and Composition

· Milk

· Milk Notes

Heat Treatments and Pasteurization

This page describes the Purpose of Pasteurization and Pasteurization Conditions used in milk processing. The History of Pasteurization provides background on the implementation and benefits of pasteurization and the rationale for the conditions used.

The Purpose of Pasteurization

1. To increase milk safety for the consumer by destroying disease causing microorganisms (pathogens) that may be present in milk.

2. To increase keeping the quality of milk products by destroying spoilage microorganisms and enzymes that contribute to the reduced quality and shelf life of milk.

Pasteurization Conditions

Minimum pasteurization requirements for milk products are shown in Table 1 below, and are based on regulations outlined in the Grade A Pasteurized Milk Ordinance (PMO). These conditions were determined to be the minimum processing conditions needed to kill Coxiella burnetii, the organism that causes Q fever in humans, which is the most heat resistant pathogen currently recognized in milk. Milk can be pasteurized using processing times and temperatures greater than the required minimums.

Pasteurization can be done as a batch or a continuous process. A vat pasteurizer consists of a temperature-controlled, closed vat. The milk is pumped into the vat, the milk is heated to the appropriate temperature and held at that temperature for the appropriate time and then cooled. The cooled milk is then pumped out of the vat to the rest of the processing line, for example to the bottling station or cheese vat. Batch pasteurization is still used in some smaller processing plants. The most common process used for fluid milk is the continuous process. The milk is pumped from the raw milk silo to a holding tank that feeds into the continous pasteurization system. The milk continuously flows from the tank through a series of thin plates that heat up the milk to the appropriate temperature. The milk flow system is set up to make sure that the milk stays at the pasteurization temperature for the appropriate time before it flows through the cooling area of the pasteurizer. The cooled milk then flows to the rest of the processing line, for example to the bottling station. There are several options for temperatures and times available for continuous processing of refrigerated fluid milk. Although processing conditions are defined for temperatures above 200°F, they are rarely used because they can impart an undesirable cooked flavor to milk.

History of Pasteurization

The process of heating or boiling milk for health benefits has been recognized since the early 1800s and was used to reduce milkborne illness and mortality in infants in the late 1800s. As society industrialized around the turn of the 20th century, increased milk production and distribution led to outbreaks of milkborne diseases. Common milkborne illnesses during that time were typhoid fever, scarlet fever, septic sore throat, diptheria, and diarrheal diseases. These illnesses were virtually eliminated with the commercial implementation of pasteurization, in combination with improved management practices on dairy farms. In 1938, milk products were the source of 25% of all food and waterborne illnesses that were traced to sources, but now they account for far less than 1% of all food and waterborne illnesses.

Pasteurization is the process of heating a liquid to below the boiling point to destroy microorganisms. It was developed by Louis Pasteur in 1864 to improve the keeping qualities of wine. Commercial pasteurization of milk began in the late 1800s in Europe and in the early 1900s in the United States. Pasteurization became mandatory for all milk sold within the city of Chicago in 1908, and in 1947 Michigan became the first state to require that all milk for sale within the state be pasteurized. In 1924 the U.S. Public Health Service developed the Standard Milk Ordinance to assist states with voluntary pasteurization programs. The Grade A Pasteurized Milk Ordinance (PMO), as it is now called, is administered by the U.S. Departments of Health and Human Services and Public Health, and the Food and Drug Administration and defines practices relating to milk parlor and processing plant design, milking practices, milk handling, sanitation, and standards for the pasteurization of Grade A milk products. Each state still regulates milk processing within their own state but dairy products must meet the regulations stated in the PMO for products that will enter interstate commerce.

Initial pasteurization conditions, known as flash pasteurization, were to heat the milk to 155 to 178°F (68.3 to 81°C) for an instant followed by cooling. Pasteurization conditions were adjusted to 143°F (61.7°C) for 30 minutes or 160°F (71.1°C) for 15 seconds to inactivate Mycobacterium bovis, the organism responsible for tuberculosis. However, in 1957 these conditions were shown to be inadequate for the inactivation of Coxiella burnetii which causes Q fever in humans (Enright et al., 1957). New pasteurization conditions of 145°F (62.8°C) for 30 minutes for a batch process, or 161°F (71.7°C) for 15 sec for a continuous process, were adopted in order to inactivate Coxiella burnetii, and these conditions are still in use today.

Updated 2/26/07

The Manufacturing
Process

Milk is a perishable commodity. For this reason, it is usually processed locally within a few hours of being collected. In the United States, there are several hundred thousand dairy farms and several thousand milk processing plants. Some plants produce only fluid milk, while others also produce butter, cheese, and other milk products.

Dairy cows are milked twice a day using mechanical vacuum milking machines. The raw milk flows through stainless steel or glass pipes to a refrigerated bulk milk tank.

a few hours of being collected. In the United States, there are several hundred thousand dairy farms and several thousand milk processing plants. Some plants produce only fluid milk, while others also produce butter, cheese, and other milk products.

Collecting

1 Dairy cows are milked twice a day using mechanical vacuum milking machines. The raw milk flows through stainless steel or glass pipes to a refrigerated bulk milk tank where it is cooled to about 40° F (4.4° C).
2 A refrigerated bulk tank truck makes collections from dairy farms in the area within a few hours. Before pumping the milk from each farm's tank, the driver collects a sample and checks the flavor and temperature and records the volume.
3 At the milk processing plant, the milk in the truck is weighed and is pumped into refrigerated tanks in the plant through flexible stainless steel or plastic hoses.

Separating

4 The cold raw milk passes through either a clarifier or a separator, which spins the milk through a series of conical disks inside an enclosure. A clarifier removes debris, some bacteria, and any sediment that may be present in the raw milk. A separator performs the same task, but also separates the heavier milk fat from the lighter milk to produce both cream and skim milk. Some processing plants use a standardizer-clarifier, which regulates the amount of milk fat content in the milk by removing only the excess fat. The excess milk fat is drawn off and processed into cream or butter.

Fortifying

5 Vitamins A and D may be added to the milk at this time by a peristaltic pump, which automatically dispenses the correct amount of vitamin concentrate into the flow of milk.

A clarifier removes debris, some bacteria, and any sediment that may be present in the raw milk. The milk is then fortified and pasteurized.

Pasteurizing

6 The milk—either whole milk, skim milk, or standardized milk—is piped into a pasteurizer to kill any bacteria. There are several methods used to pasteurize milk. The most common is called the high-temperature, short-time (HTST) process in which the milk is heated as it flows through the pasteurizer continuously. Whole milk, skim milk, and standardized milk must be heated to 161° F (72° C) for 15 seconds. Other milk products have different time and temperature requirements. The hot milk passes through a long pipe whose length and diameter are sized so that it takes the liquid exactly 15 seconds to pass from one end to the other. A temperature sensor at the end of the pipe diverts the milk back to the inlet for reprocessing if the temperature has fallen below the required standard.

Homogenizing

7 Most milk is homogenized to reduce the size of the remaining milk fat particles. This prevents the milk fat from separating and floating to the surface as cream. It also ensures that the milk fat will be evenly distributed through the milk. The hot milk from the pasteurizer is pressurized to 2,500-3,000 psi (17,200-20,700 kPa) by a multiple-cylinder piston pump and is forced through very small passages in an adjustable valve. The shearing effect of being forced through the tiny openings breaks down the fat particles into the proper size.
8 The milk is then quickly cooled to 40° F (4.4° C) to avoid harming its taste.

Packaging

9 The milk is pumped into coated paper cartons or plastic bottles and is sealed. In the United States most milk destined for retail sale in grocery stores is packaged in one-gallon (3.8-liter) plastic bottles. The bottles or cartons are stamped with a "sell by" date to ensure that the retailers do not allow the milk to stay on their shelves longer than it can be safely stored.
10 The milk cartons or bottles are placed in protective shipping containers and kept refrigerated. They are shipped to distribution warehouses in refrigerated trailers and then on to the individual markets, where they are kept in refrigerated display cases.

Cleaning

11 To ensure sanitary conditions, the inner surfaces of the process equipment and piping system are cleaned once a day. Almost all the equipment and piping used in the processing plant and on the farm are made from stainless steel. Highly automated clean-in-place systems are incorporated into this equipment that allows solvents to be run through the system and then flushed clean. This is done at a time between the normal influx of milk from the farms.

Quality Control

The federal Food and Drug Administration (FDA) publishes the Grade A Milk Ordinance which sets sanitation standards for milk production in most states and for all interstate milk shippers. The composition of milk and milk products is specified in Agricultural Handbook 52 published by the United States Department of Agriculture. It lists both federal and state standards. Testing of milk products includes tests for fat content, total solids, pasteurization efficiency, presence of antibiotics used to control cow disease, and many others.

Mastitis Control Programs:
Proper Milking Techniques

AS-1126, March 1997

Charles Stoltenow, DVM, Extension Veterinarian
J. W. Schroeder, Extension Dairy Specialist

Key Points

Proper milking procedure is important.
Milking wet udders will increase mastitis.
Teats, but not the udder, should be washed.
Teats should be clean and dry before the milking machine is attached
Teats should be dipped after milking.

Conclusion

The goal of every mastitis control program is to prevent the introduction of bacteria into a normal and healthy mammary gland. Mastitis prevention must be practiced on every cow at every milking every day. Udder care is essential for the profitable milk producer. Udder care is practiced by reducing the spread of bacteria from cow to cow, eliminating reservoirs for bacteria in and around the barn yard. It only takes a few seconds per cow per milking. Repeating the process will make mastitis prevention a management habit.

Contact your veterinarian or county extension office for additional resources on mastitis prevention and treatment.

Proper hand milking procedures

By Rosalie Sinn (for Heifer Project International)
and Jennifer Stultz

Learning how to milk a goat by hand involves using the proper equipment and procedures. It also involves a personal love for animals, especially the dairy doe, who so willingly shares her bounty with those who care for her.

Equipment needed to properly milk and care for the milking dairy goat includes the following items: a milking stand (optional), a milk bucket (stainless steel or enamel is best but any deep, clean container can be used), two cups (one for examining the milk prior to full milking, one for teat dip), a filter or strainer or clean cloth for straining the milk, a pan for pasteurization, a container for the milk, cool water to cool the milk rapidly, teat dip (may be two percent iodine or a solution of 50 percent bleach and 50 percent clean water), soap and water, clean clothes.

After making sure all the needed equipment is assembled and clean after having been washed with soap and water and air or sun dried, cover items not in use with a clean cloth.

Place some feed in a bucket or in the feed container attached to the milking stand. Wash your hands.

Bring the goat to the milking location and tie her or put her on the milking stand.

If the goat's udder is dirty, wash it with soap and water and dry with a clean towel. If the goat's udder is clean and free of manure and dirt, simply brush away loose hair and/or dirt.

Direct the first milk from each teat into a cup. Examine this milk for any stringy, lumpy milk, or blood in the milk. Do not use the milk if this occurs; it could be an indication of sickness or mastitis. Do milk out the udder and discard the milk, then ask a veterinarian for help/advice.

If the first milk is clear, clean and good, place the milk pail under the goat.

Grasp the teat with thumb and index finger together to trap the milk in the teat. Gently but firmly, bring pressure on the teat with a second finger forcing the milk down further. The third finger does the same and then the little finger.

Massage and gently bump the udder while milking and the doe will let down more milk.

Do not drag, pull or jerk down on the teat. Use a steady pressure and loosen finger grip before squeezing again.This allows the milk back down into the teat for the next squirt. It should take approximately five minutes to milk the doe. The udder will feel noticeably empty and no more milk can be expressed from the orifice (teat end) when finished.

After all milk is out of the udder, dip each teat in a teat cup with dip solution in it. Let the doe stand on the milk stand until the end of the teat is dry and then return her to her pen. This closes the orifice, preventing bacteria from entering the teats and udder which could cause future problems.

Try to milk the doe(s) twice daily, every morning and evening, on a regular schedule. Milking 12 hours apart is ideal and will help maximize production and limit stress on the udder, but this may vary according to personal schedules. It is important to record milk weights per milking as this can indicate health and value of the doe over a period of time.

Spend time getting to know and enjoying each doe on the milk stand and milking can become a special time for the goat as well as the owner.

The dairy cow

Cattle, goats, buffalo, sheep, deer, llamas and yaks are all dairy animals that are kept by humans. The tradition is to milk these animals by hand.

The milking method is basically the same for all peoples, although there are small differences. Thus, for example, the British milk from the right side, and the South Africans from the left side of the animal. In France, where sheep are milked, the milker sits at the back of the sheep. Whatever the method, the animal becomes accustomed to being milked from the same side by the same milker.

Healthy milk requires a healthy animal, and a healthy milker must care for the animal in such a way that both the milk and the animal remain healthy. Let us now consider the dairy cow in particular.

A healthy cow requires food and water, and shelter against heat, rain and cold wind. If the cow is too cold, the food is converted into energy in order to keep her warm, and as a result, she gives less milk. If she is too hot she loses her appetite and also gives less milk. Where there is no natural pasture or trees, food must be provided and kraals and shelters must be erected.

Shade is essential. Kraals must be cleaned regularly and they must also drain well. A wet and dirty kraal is a breeding place for diseases.

Cows must be tested annually for tuberculosis and Brucellosis. Both diseases can be transmitted to humans. All cattle must be inoculated annually against anthrax and botulism, and young animals must also be inoculated against quarter evil. Additionally, all heifers must be inoculated once against Brucellosis. A state veterinarian or animal-health technician can also advise you on diseases such as redwater and gallsickness.

Sticks, beatings, shouting, etc. upset the cow and she will not let down her milk.

A healthy cow that has enough food, shelter and water, will still not be a good milking cow if she is not calm and tranquil. Therefore she must not be beaten or shouted at or handled brutally in any way.

What is the best milking method and which method will give the best production?

It is important to note the following:

· A milker can damage a cow’s teats.

· A cow will not let down her milk if she has been hurried along and hurriedly tied.

· Avoid noise during milking time.

· Dirty milking conditions can cause mastitis.

· If the milking action is too slow, this can cause mastitis.

· All the milk must be expressed if the cow does not suckle the calf.

· Irregular milking times causes a decrease in the volume of the milk.

· Calm and tranquil handling and a brisk and effective milking method will give the best milk production. In addition, rubbing the udder and washing the teats will make the cow let down her milk sooner and make her give more milk. Remember to wash the hands after this, before starting to milk.

· A tranquil cow does not need to be shackled.

· Milk must be expressed from the teat and not pulled out. If the correct milking method is followed, no lubricating ointment is necessary. Milk froth or milk must never be used to smear the teat.

The milker must also pay attention to the appearance of the cow. If the flanks are soiled with dust, mud or manure, they must be brushed down. Long hair around the teats must be cut short. The udder must also be washed clean and dried with a clean cloth.

The correct and best milking method is with the whole hand. The teat is held in the hand and the milk is expressed with the fingers, just as a calf takes the whole teat in its mouth and expresses the milk with its tongue. With this method no lubricating ointment is necessary. Remember: the best hand milker never pulls or stretches the teat.

A bad habit is to take the teat between the fingers and to pull it. This damages the teat and is uncomfortable for the cow, and can even result in mastitis.

To squeeze out milk between the folded-over thumb and the fingers, or between the fingers and a straight thumb, damages the upper part of the teat, and hurts and upsets the cow, thus reducing the milk flow and the production.

Stripping, for which the teat is held between the forefinger and thumb, and then pulled down, should be used only for expressing the first and last spouts of milk. This method requires a good lubricating ointment. A good hand milker will never pull or stretch a teat unnecessarily.

Regular milking times are important because cows become accustomed to being milked at set times. Even half an hour earlier or later can make a considerable difference to the quantities of milk and cream a cow produces.

How important is clean milk for human health?

Milk is one of the best foodstuffs for man, but unfortunately also for the germs that cause diseases in man. Therefore contaminated milk can cause cholera, sore throat, diphtheria, enteric (gastric) fever and polio. How does this happen?

· dirty hands

· dirty and long nails

· manure

· flies

· sores on milkers’ hands

· unhygienic habits such as coughing over milk, spitting on the hands and blowing the nose while milk is being handled.

What is clean and healthy milk?

It is milk obtained from clean, healthy, tranquil cows, that were milked by clean, healthy milkers into clean buckets, in a clean environment, and subsequently kept clean and cold until consumed.

After use, the milk bucket and milk-can must first be rinsed with cold water and then with hot - preferably boiling water in which washing soda has been dissolved (half a cup of washing soda in 10 litres of water). If the water is not up to standard, it can be made reasonably safe by adding two tablespoonfuls of Jik to 10 litres of water. Let it stand for ten minutes before use. After the bucket and can have been thoroughly cleansed, they must be placed upside-down to drip dry. A simple stand can be used for this purpose.

Milk cloths, wash cloths and drying cloths must be washed with soap after each milking, rinsed thoroughly, and left to soak in Jik water so that all germs can be killed. The milk in the milk-can is poured through the milk cloth to keep back any particles of dirt.

Before milking takes place, the following must first be done:

· Milk the first spout of milk from each teat into a mastitis jug or through black silk-stocking fabric. If the teat is mastitic, the milk will either show lumps or be watery. Such milk must not be used.

After milking is completed, the following guidelines are important:

Lubricating ointment becomes badly contaminated when it is fastened onto the shackle. This must never be done.
Treat scabby teats with a teat ointment containing a disinfectant. Do not use Vaseline or an oily ointment, as this collects dust.
The farmer must never wipe the ointment off the nozzle with a dirty finger. It contaminates the ointment, thus exacerbating the mastitis.
A cow that has mastitis must be marked. Such a cow must receive treatment immediately and always be milked last.

DVenter
ELSENBURG / Milk control laboratory

Milking Machine

Dairy cattle are milked by machine. Milking machine design and function is critical for rapid and efficient removal of milk without damage to the teat or gland and with minimal risk for transmitting pathogenic microorganisms that might cause mastitis. The only way for mastitis-causing organisms to enter the teat is through the streak canal. This is the same route by which milk leaves the gland, therefore, anytime that the streak canal is opened to remove milk the gland is susceptible to potential intramammary infection.

Much of the recommended process of milking relates directly or indirectly to control and prevention of mastitis. The physical and functional interface between the teat and the machine are carefully designed to minimize the chances of intramammary infection occurring as a result of milking. Although the milking machine may only account for 5-10% of mastitis cases, proper milking machine function must be maintained over time. Incorrect vacuum or pulsator settings or worn teat cup liners all can enhance the role of the milking machine in contributing to intramammary infection.

The machine includes teat cups that contact the cow’s teats and remove the milk, a claw where milk pools as it is removed from the four teats, vacuum tubes that provide vacuum to the teat cups and a milk tube that removes milk away from the claw, a source of vacuum for the machine, and a pulsator that regulates the on-off cycle of the vacuum. Many milking machines today have an automatic take-off (ATO or detacher) device that removes the machine from the cow when milking is completed. In addition, many milking machine systems are linked to a computer system that both regulates the machine and generates data about the cow and its milk as milking is occurring. The description below is an overview of the milking machine components.

If you consider this arrangement for a moment, you will realize that the teat cup assembly results in two chambers (see below): A) one inside of the liner and B) one between the metal shell and the outside of the liner. A vacuum is pulled in both chambers; the vacuum in chamber A is continuous, while the vacuum in chamber B alternates between atmospheric pressure and the vacuum.

When the teat cup is applied to the teat, the end of the inside chamber is filled by the teat. During the milk phase the vacuum applied inside the liner is constant and keeps a constant negative pressure at the end of the teat, drawing milk (in yellow) from the gland. The vacuum applied to chamber B, between the shell and the thinner walled part of the liner, keeps the liner from collapsing under the vacuum. During the rest phase, the vacuum inside chamber B is monetarily off. Air (in green) enters chamber B instantly reaches atmospheric pressure, colapsing the rubber liner around the teat end, massaging the teat and maintaining blood flow. The lower part of chamber A maintains its vacuum (lower part of right diagram), while the upper part around the teat momentarily loses vacuum. This alternating vacuum-atmospheric pressure in chamber B is controlled by a pulsator.

However, if the constant vacuum were left onto the teat end for an extended period, blood and lymph would accumulate in the end of the teat, causing trauma to the teat. This would be like attaching a vacuum hose to the end of your finger. The area exposed to the hose would turn red with accumulated blood. To prevent teat-end trauma, This alternating vacuum-atmospheric pressure, referred to as pulsation, is important for maintaining teat end health.

A proper pulsation rate, that is the number of cycles of vacuum on - vacuum off (in Chamber B above), or milk phase – rest phase cycles, usually is about 45-60 per minute. The ratio of time that the machine is in milk phase vs rest phase should be between 50/50 to 60/40 (pulsation ratio). In some systems, pulsation ratios are slightly different for teat cups milking the fore quarters vs the rear quarters. This is done because typically the rear quarters are larger and contain more milk than fore quarters. Therefore, rear quarters usually take slightly longer to milk out compared with fore quarters. The adjusted pulsation to rear vs. fore can account for this difference so that the rear quarters milk out faster and all quarters are properly milked out when the automatic take-offs detach the machine.

Teat-end vacuum should be stable and should be approximately 11-12 inches of mercury. Teat end vacuum fluctuations can occur because of several things. Improper vacuum, either because of incorrect vacuum settings, flooded milk lines (see below for high lines), or uneven milkout of quarters, can cause air to leak in between the teat and the rubber liner of the teat cup. This often results in a sucking sound called liner slips. It is not unusual to hear a sucking or squawking noise in any milking operation, but if they are too frequent, it is a sign of something improper in the milking system. The concern about liner slips (liner squawks) with respect to mastitis is that air entering one teat cup can forcefully blow milk from the claw up the other liners and droplet so milk may enter the other teats. This also may occur if the teat cup slips off of one of the teats, or the person putting the machine on the cow allows too much air to be sucked into a teat cup while milk is being removed from the other quarters. If a milk droplet entering another teat is contaminated with a bacterium, then transmission of mastitis-causing pathogens may occur.

After the milk leaves the teat it collects in the collecting bowl of the claw (image to the right). The milk then is drawn from the claw, through the milk hose to the milk line by the same vacuum as inside the liner (same as Chamber A above).

If a milk line is above the cow (high line), then the milk in the milk hose must flow against gravity. If too much milk is flowing through the milk hose and the vacuum is blocked off, the vacuum inside the milk hose/claw/liners can be momentarily reduced (vacuum fluctuations), causing liner slippage on the teats or even for the machine to fall off the cow. If the milk line is lower than the cow (low line), as in a parlor where the people milking the cows are in a pit below the level of the cows, then milk flows away from the claw with gravity. These low line systems result in overall more efficient milk removal.

Many milking systems today are equipped with an automatic detacher (called an automatic take-off or ATO; see resources on the Milking Process). The milking system detects flow rate of milk coming from the gland. When that flow rate drops to a specified level, the vacuum is turned off and a mechanical arm or chain retracts and pulls the machine from the cow's udder. This prevents overmilking of the cow's udder that often happens when humans have to make the decision of when to take the milker off.

Milk in the milk line flows to a pump that pumps it to the milk tank, usually housed in a separate room from where the milking is occurring.

Pump that pumps milk into the bulk tank.

Milking systems today often are controlled by computer systems that record production information, sometimes indicators of mastitis, and other cow information. Milk yield is determined by a milk flow meter.

Obviously, because the milking machine comes into contact with the cow’s teats or milk in the claw can impact up on the teat ends, cleanliness of the machine and hygiene during the milking process are critical for successful control of mastitis during the milking process. After milking, the machine is thoroughly cleaned with hot water, soap, acid and germicide solutions.

Story of Homogenization

Raw milk, as it comes from the cow, is an emulsion- a mixture of milk-fat globules, various solids and water. Over time, the fat globules separate out and rise to the surface as a layer of cream, leaving what is essentially skim milk, down below.In the years before today's processed dairy products, some people found this to be an inconvenience because it meant the milk had to be agitated often to keep the cream mixed in. Enter inventor Auguste Gaulin, a Frenchman who, like Pasteur before him, had a hand in further changing the physical and chemical properties of milk. Gaulin's brilliant invention, an emulsifying or 'homogenizing' machine, patented in 1899, (above, a modern version) broke milk's fat globules into a smaller, more uniform size that resisted separation and rising. Since then, over a hundred patents have been granted to other devices aiming for smaller and smaller particle size while using less and less energy. Homogenization today is usually a two step process. The first stage, similar to Gaulin's early device, pushes milk through small, tapered tubes or pores. As the diameter shrinks and the flow of milk remains constant, pressure builds up and fat globules break apart in the turbulence. The higher the pressure, the smaller the particles. How much pressure? Typically 2,000-3,000 pounds per square inch (psi), although some super homogenizers work at over 1000 times atmospheric pressure- 14,500psi and higher! As the much smaller fat globules begin to reassemble, they include fragments of whey and casein in their walls. Some are completely surrounded by a layer of protein. The tendency is for these new, chemically altered globules to clump together. Stage two of the homogenization process breaks up this unwanted assembly and makes sure everything stays in solution.

Various Manufacturers of Homogenisers

APV Manton Gaulin, APV Rannie, APV Crepaco, Tetra Pak, Tetra Pak Alex, Tetra Alex, Tetra TAM. GEA, FBF, Bertoli, Alfa Laval, Mark, Gaulin, Rannie, Cherry Burrel, Armfield

Ways of spelling Homogeniser

Homogeniser (UK), Homogenizer (US)

milk production

Friday, February 26, 2010