Regularly pasteurized milk is heated at 72 degrees for 15 seconds and this is referred to as high-temperature, short time (HTST) pasteurization. This milk is sold cold and must be stored cold. Ultra-high temperature (UHT) milk is heat treated at 90°C for 2 seconds. This milk does not have to be stored cooled in unopened containers, and it can be stored for several months at room temperature. Once opened it must be put in the refrigerator. Extended shelf-life (ESL) or ultra-pasteurized milk is produced by thermal processing using conditions between those of HTST and UHT pasteurization. This milk has a refrigerated shelf-life of more than 30 days.
Raw milk has not been treated beyond body temperature (38.5°C in the cow). Pasteurized milk has been heat treated to between 62°C and 80°C and this heat treatment has changed various aspects of the milk. There are changes in the protein fractions and bacterial composition of the milk and the changes are dependent upon the time and the length of the heat treatment, as well as impacted by other treatments such as homogenization. In general, as the temperature increases from 40 to 80°C and as the time of the heat treatment increases there are similarly increasing elimination of bacteria including potential disease-causing bacteria, and proteins become denatured and enzymes (that are proteins) are no longer active. The heat treatment protein denaturation results in that allergen causing epitopes on proteins are exposed which leads to milk allergies. The whey proteins are particularly heat sensitive and there are large changes in their three-dimensional structure.
All proteins have a complex three-dimensional structure. Through the heat treatment the structure becomes increasingly linear, in essence, they break open. The open breaking of the original structure results in that new parts of the protein become exposed and these exposed parts are more likely to cause allergic reactions than the intact protein.
In the beginning of the 20th century as the urban population increased and people moved away from the traditional farming communities the milk was started to being transported at environmental temperature into the cities and towns. This resulted in that various bacteria, including disease-causing bacteria could grow in the milk during transportation and storage. The high levels of bacteria in the milk lead to rapid spoilage of the milk and many foodborne disease outbreaks. Furthermore, tuberculosis in humans was linked to bovine tuberculosis in dairy cows, and people were sick and died in tuberculosis. Thus around World War II milk was heat treated (pasteurized) to prevent and reduce tuberculosis in humans and to increase the shelf-life of the milk. This was good for the milk industries as this enabled the milk to be transported longer and over larger distances, and be sold for longer periods of time. In the 20th century most European and North American countries have succesfully managed to eradicate tuberculosis from the bovine population.
Fat in milk in found in fat droplets. Fat in milk is surrounded by a thin membrane. In cow milk, these fat droplets are quiet large. When the milk stands for some time, the fat separates out to the surface of the milk. The dairy industry employs a system of homogenization, whereby the milk fat fraction is pressed through microfilters at high pressure to create smaller size droplets. By breaking down the droplets results in disruption of the original fat membrane
Goat milk, as compared to cow’s milk has naturally smaller fat droplets and it is thereby naturally homogenized.
The intact larger milk fat droplets clump together and separate out from the milk and fat always rises to the surface of water because they are more buoyant. Through the homogenization the milk fat droplets are reduced in size and number and they can not form large clusters that rise to the surface and thereby they remain in emulsion and distributes throughout the milk.
The pasteurization of milk used to make cheese results in the destruction of various bacteria and enzymes. This influences the ripening of the cheese. The ripening of pasteurized milk cheese takes place through the bacteria that are added to the milk in the cheese making. This bacteria composition of added cultures is not as rich and varied as the original milk flora. Cheese made from pasteurized milk is more neutral in taste, simpler and more constant and this is therefore preferable for the large scale industry. Farmhouse cheese has a much more rich and varied flavour, and is therfore preferred by many cheese lovers.
QUESTIONS ABOUT MILK, ITS COMPOSITION
Most milk that we drink today comes from cows, goats, sheep, yak, or camels. These ruminants have been bred and domesticated by humans for over 10,000 years. The ruminants can be kept on land that is not suitable for other plant production. Since they are feeding mainly of forage such as grass, hay and leaves, they are not competing with food resources for humans. This creates a symbiotic system, where the humans assure that the animals have forage, water and protection, while the animals provide valuable proteins and other nutrients for the humans in the form of milk and meat. In organic production a major part of the forage consists of nitrogen-fixing plants such as clover and lucerne that are important for fixing nitrogen from the air and bringing it into the soil, which is very important for a nutrient-rich soil.
Many adult consumers may experience problems with digesting the sweet, whole milk. This is mainly linked to the genetic background of the consumer and their milk consumption patterns. Children have naturally high levels of the enzyme lactase in their digestive systems to digest the lactose of milk (= milk sugar), whether it comes from the mother or from a ruminant. As children ages and when milk consumption decreases, the lactase enzyme may decrease and create an inability to digest the lactose present, and this results in bloating and gastric distress. This is what we refer to as lactose intolerance (which is different to an allergy to milk). In people with a Caucasian background (= white people) there is less lactose intolerance, due to several mutations and adaptation on a milk diet.
In sour, fermented dairy products, such as yogurt, kefir and cheese, the lactose has to a large extent been broken down into lactate = lactic acid. People with true lactose intolerance may therefore find that they have a higher tolerance for these fermented products.
Cows, goats and sheep are ruminating herbivores. A ruminant is a mammal that has a very special stomach. The ruminants are specially adapted to deriving their nutrition from plants fibers (cellulose). Omnivours and carnivours can not digest plant fibers. The digestion-system of the ruminant consists of four compartments. The abomasum corresponds to the stomach of us humans. In young mammals, like calves, it is mainly used for digestion of the milk. The rumen, reticulum and omasum are compartments in front of the abomasum, which are used for forage digestion. The rumen content (40-60 Liters in a cow) is a large soup of bacteria and forage particles. The ruminal bacteria are the ones that are doing the actual breaking down of the cellulose (fibers). The ruminants regurgitates the forage 50-60x per minute to chew on the forage and break it down further and to mix it with huge quantities saliva and digestion enzymes. This rhythmic process is called rumination. A ruminant lies for hours between eating, simply ruminating her feed. The trillions of bacteria growing on the digested forages will be used as a protein source by the animal. The ruminant will be able to create proteins from fibers, and this makes these animals exceedingly fit to live on plant material that provide little value for us omnivours and carnivours.
Milk production varies tremendously between breeds of cows and between farms. Various breeds have different milk production potential. Through breeding for 1000s of years, the best milk producing cows have been selected. In the last 100 years the milk production of our dairy cows has increased four to five times. In the 1900s an average cow would produce approximately 2,000 Kg milk per year. Today, in most conventional dairies the production lies between 9,000 to 13,000 Kg per year. There are dairy cows that produce 14,000 Kg per year, and the highest producing breed is the Holstein. This high level of production requires that the cow can eat huge quantities of feed to support milk production and this can not be achieved through forage alone.
Through breeding and feeding, the cow of today produces milk with higher protein and fat content than in the 1900s. This is mainly achieved through the diet of the cows. The high milk production requires that that the cow consumes high levels of nutrients and energy. The cow can not extract sufficient energy and nutrients from the forage alone to support a milk production above 20 liters per day. Various forms of concentrates such as grains, soy proteins and fats are added to the diet to support the milk production. The concentrates in the diet presents a challenge to the cow’s metabolism, as she was not created to eat grain. Unfortunately these concentrate supplements influences the fatty acid profiles of the milk fat. High concentrate diets can also lead to ruminal acidosis and displacement of the abomasum. This metabolic conditions affects her overall health and production. There are some breeds that are more suitable to an all forage diet such as grass and hay and these can produce a milk with a better fat composition. .
Mammals produce highly specific and unique milk depending on the needs of their offspring. The milk may vary in fat, milk sugars and protein levels depending on the age and even illnesses of her baby. Milk fat has also been adapted to the environmental conditions, f.i. hot or cold environments. Milk proteins vary between species, but also between breeds within a species.
Milk is about 87% water. In the milk there is approximately 3-4% proteins, 4-6% milk fats and 4,7-5% lactose. There are some variability between different breeds in milk composition and also between individual animals. The lactose content is fairly constant among breeds, milk fat varies extensively (Jersey and Guernsey are high and Holstein is low), and protein varies somewhat among breeds.
The fatty acid composition of milk is favorable in cows that are grazing solely on pastures. The fatty acid composition of the milk obtained from cows that are eating fresh growing grass on pastures has been shown to be associated with health promoting effects. Cheese and butter obtained from pastured cows can be recognized through that it has a a) a low melting point making it smooth and creamy and b) a more yellow color due to beta-caroteens in grass.
Milks contain over 400 different fatty acids (FA) and they all have the same basic structure: a chain of carbon atoms (C) bonded to two hydrogen atoms (H). The number of carbons in the chain can vary and those with more than 12 carbons are called long chain. If the chain of carbons has only single bonds, the fatty acid is said to be saturated, whereas the presence of at least one double bond makes it an unsaturated fatty acid. A long chain fatty acid chain with multiple double bonds are called polyunsaturated fatty acid (PUFA). PUFA are further grouped based on the location of the double bonds, not only the number of double bonds. In nature we find f.i. Omega-3, Omega-6 or Omega-9 FA (n3, n6 or n9).
Several n3 and n6 FA are considered essential, because humans must get them from the diet. However, in many Western diets, the n6 FA are too high in relation to the n3 FA. N3 FA are important for brain development, cognitive functioning and vision. The alpha linoleic acid (ALA)(C18:3 n3) is common in plants and cows grazing on pastures and at high altitudes obtain more of these from the forage. Organically produced milk has been shown to have higher levels of the n3 FAs compared to conventional milk, while the ratio of n6 to n3 FA also is improved in organic milk, especially in forage based diets.
Conjugated linoleic acid (CLA) are naturally occurring isomers of linoleic acid present in ruminant fats and dairy products. It is an 18-carbon fatty acid with 2 double bonds. The “conjugated“ indicates that the two double bonds are only separated by one carbon atom. There are two forms, the cis- and the trans- position, indicating that the hydrogen atoms are located on the same side (cis-) or on opposite sides (trans-) of the carbon atom. The bio-active CLA (c9,t11 CLA) is commonly found in milk. The conjugation structure of the CLAs in milk can be used to evaluate various cow ratios.
Fat-soluble vitamins absorb best when consumed with higher-fat foods. The body can store these vitamins in the liver and body fat. There are four vitamins that are fat soluble Vitamin A, D, E and K.
Vitamin A is actually a collection of compounds known as retinoids that are important for vision and immunity. Vitamin A can be found in butter, fish liver oil and liver. Pro-vitamin A compounds called caretonoids can be found in plants such as carrots and spinach.
Vitamin D is produced naturally in the skin exposed to the sun. Vitamin D aids in bone health/development and immunity. There are several types of this vitamin. Vitamin D3 (cholecalciferol) is found in animal fats and vitamin D2 (ergocalciferol) is found in plants such as mushrooms. Dairy products are sometimes fortified with vitamin D.
Vitamin E includes eight different types, with the two main kinds being tocopherols (the most abundant form) and tocotrienols. Vitamin E is very important for a good functioning immunity. Vitamin E is also an antioxidant that protects cells from free radicals that can cause cell damage. Vitamin E is most abundant in seeds, vegetable oils, and nuts.
Vitamin K has a variety of types. The two most common groups are vitamin K1 (phylloquinone), found in plant sources (greens) and vitamin K2 (menaquinone), found in animal sources and is also produced in the colon through the microbiota. Vitamin K1 plays a major role in blood clotting, whereas K2 is important for heart health and bone health and calcium homeostasis in the blood. Vitamin K-2 are found in butter, eggs, liver, and fermented dairy products as well as fermented soy (natto). Vitamin K is not stored as well in the body as vitamin A or D, and therefore one can experience a vitamin K deficiency very quickly.
Traditional cheese has always been made from cows grazing on pastures in the summer times or consuming hay (dried grass) in the winter times. Most conventional milk and conventional cheese is made from milk from cows that eat fermented grass and maize as silage. The milk from cows consuming hay has different properties from the milk from cows consuming silage. The hay milk is free from Clostridia, which are bacteria that can negatively influence the ripening of the cheese. Field-dried hay is different than under-roof-dried hay, which is dried inside under more controlled conditions, and thereby can a consistent higher quality be achieved. Many traditional mountain cheeses are hay milk cheeses, and also the all famous Emmental cheese can only be made from cows fed grass or hay.
Organic cows produce less milk than conventional cows. Farmers must use organically produced feed, has requirements for pasture and concentrates, and different requirements for veterinary treatments. A large majority of conventional dairies do not provide pasture access to the cows, but they are housed in free-stalls without pasture access. There are national and regional differences in both the organic and the conventional farming systems. In the majority of organic farms cows are grazed or fed fresh grass inside. The pasture access has a positive influence on the fatty acid composition of the milk. .
The whey protein are highly digestible and has a very good amino acid profile. Body builders and weight lifters specifically use the whey protein supplements to build up muscle mass.
QUESTIONS ABOUT MILK AND ANTIBIOTICS
Many cows are treated with antibiotics for mastitis, which is an infection of the udder. Most mastitis types are treated with antibiotics to facilitate healing and alleviate pain and disease in the cow. All forms of antibiotic use can create resistance, in the bacteria causing disease and also in other bacteria present in the body of the animal. This present problems for curing mastitis and can also pose a threat to other humans and animals, since the overall levels of antimicrobial resistant bacteria increase in our food production and environment. The direct risk to humans from antibiotic treatment of dairy cows seems lower than some other form of antibiotic use in food animal production such as in-feed antibiotics to chicken and pigs.
If an animal has a very acute form of mastitis of certain bacteria, then it is sometimes necessary to treat a cow with antibiotics. Alternatives to antibiotics are not just different treatment strategies for disease, but it involves a completely different strategy to prevent disease. A holistic animal health system needs to be present that reduce the stress on the animals, improves the feed and management so that diseases are less likely to develop. Furthermore, using breeds and selecting single animals that are more disease-resistant are important components of such a preventive health approach.
There are many farms where extremely little or no antibiotics are used. In US-Organics, there is a certification programs in dairy for ‘no antibiotics’, called NOP. European organic farms may treat sick animals with antibiotics. It is important to realize that even on conventional dairies, no milk is sold to humans during or after antibiotic treatments, until a safety period (a milk with-holding time) has been fulfilled to assure that there are extremely little or no antibiotics in the milk. For organic dairies the with-holding time for milk is twice as long than for conventional dairies.
QUESTIONS ABOUT THE RISKS OF RAW MILK
In the conventional food supply, great attention has been paid to reduce microbial hazards in food. The dairy farmer has certain obligations to deliver good milk to the creameries. However, this milk may still contain harmful bacteria, which would be destroyed through pasteurization and therefore be safe once it reaches the consumer. A farmer that sells raw milk therefore need to take extra measures to assure that the risks of contamination of the raw milk is minimal. In many countries milk directly sold on the farm or in milk vending machines are signposted with a label that heat treatment of the milk is necessary. In Germany, there is a federal system for the sale of state controlled raw milk. You need to carefully select your source of raw milk to assure yourself that the farmer is a professional raw milk producer who knows how to do this with minimal risk.
Due to that doctors fear that those with a compromised immune system are at greater risk for food-borne disease, doctors will many times recommend certain groups of people such as young children, elderly and pregnant women to not consume raw milk or products thereof. However, raw milk is not necessarily more dangerous than many other raw products that we consume, such as vegetables, eggs, nuts or similar. Scientific studies indicate that the people that they consider ‘high risk groups’ are exactly the group of people that will benefit the most from raw milk products. You as a consumer need to educate yourself as to the risks and benefits, and communicate with your dairy producer about the zoonotic risks of his milk.
Tuberculosis was a dreaded infectious disease in Europe a century ago that killed many people, especially children. In the 1930s, pasteurization of milk became a major tool to reduce the risk of tuberculosis. Nowadays we have virtually eliminated tuberculosis from our production animals through veterinary control programs, and most European countries are declared ‘officially free’ from bovine tuberculosis. Some countries, such as the United Kingdom, are still working on complete eradication of the disease. In Germany, already in the 1930s, they recognized the value of raw milk, and they set up a system called ‘Vorzugsmilch’, certified high quality safe raw milk. This milk was also sold as ‘Child milk or health milk’. Pasteurization was initially not intended as a permanent measure to assure the safety of milk. However, it resulted in easier production, transportation and extended shelf life, and therefore the sale of raw milk was not re-introduced after the tuberculosis and brucellosis threat were eliminated. Today, you can still get sick from tuberculosis, but it is not necessarily only through food, you can get infected by other people. Migration may contribute to that tuberculosis infected people come to Europe and it is important that farm animal workers are free from tuberculosis, otherwise they can transmit it to the animals.
There are many bacteria that are risks in raw milk, similar to other raw food. The most common bacterial challenges in milk in Europe are Campylobacter spp., verotoxin-producing Escherichia coli (VTEC), Listeria monocytogenes and Salmonella spp. Other hazards could include Mycobacterium bovis (tuberculosis bacteria) and Brucella spp., and these risks are higher in certain areas such as the UK for tuberculosis and Southern Europe for brucellosis. Coxiella burnetti, which causes Q-fever, may possibly be transmitted by milk, but it is more likely to be infected in the environment of infected animals. Most bacteria that are foodborne disease hazards can be reduced by having a high level of biosecurity on the farm, good animal husbandry and milking hygiene. As a raw milk drinker, your most important precaution is to source your milk from a dairy where they have set up a farm food safety program for the raw milk, which includes regular controls of their raw milk, checking that their milking hygiene is working, and at regular intervals screen for the most common pathogens. The risks from raw milk are most likely not greater, and many times smaller, than risks from other food commodities. The risks of eating a raw, nutritionally wholesome food needs to be put in relation to the benefits.
These are acronyms for certain types of the coliform bacteria called Escherica coli (E. coli or EC). E. coli lives in the intestines. There are many types of E. Coli, and most types do not cause disease. Some types, however, can cause disease, and thereto they get a pathotype (pathological type) name. Enterohemorrhagic E. coli (EHEC) can invade the intestinal mucosa and thereby damage the cells, leading to a bloody diarrhea. Shiga-toxin producing E. coli (STEC), and related verotoxin (shigalike-toxin) producing E. coli (VTEC) are E. coli that produces toxins that can damage not only the intestinal cells, but they can invade the body and cause damage to organs inside the body. The E. coli are also characterized by proteins that they have on their cell membrane, and some of these are called O – fimbriae and other are called H – flagellae. For example, EHEC, E. coli O157:H7 is renown for serious disease when it causes kidney failure and death. E. coli O157:H7 was first described in the 1980s when it caused a large outbreak through an American hamburger chain and it was for a long time referred as the hamburger disease. Since than, these VTEC has regularly been associated with minced meat outbreaks. Also STEC have been linked to cattle, and only a small number of bacteria can cause disease. In the last decades new mutations of STEC have been related to food outbreaks and not only in animal products.
Most bacterial diseases and many parasites have zoonotic potential, in that they can be spread from animals to humans, and vice versa. Many viruses are more linked to a particular type of animal. Zoonoses can spread in many ways, such as direct transmission from animal to man such as through the air (influenza), through bites and saliva (rabies) or through consumption of meat, eggs or milk. Zoonosis can also spread through vectors such as insects (borrelia). Animals can sometimes carry disease, without being affected, and shed the disease-causing agent in milk or eggs, such as Salmonella. Thus, it is not a requirement that the animal is sick from a zoonosis, to be called a zoonotic agent. Diseases that travel from humans to animals are sometimes called ‘reverse zoonosis’ and examples of such could be tuberculosis. For many zoonotic diseases, there have been active eradication programmes, such as Tuberculosis, Brucellosis and Trichinellosis. For other zoonosis, where eradication is not realistic, there are control programmes, such as those for Salmonella and Campylobacter in poultry and pig production. For all zoonotic agents, there are measures taken to reduce the risks for humans.
There are risks for zoonotic disease through raw milk consumption. The magnitude of those risks are many times exaggerated by the medical and food safety community. However, it is important that you, as a consumer, educate yourself regarding the risks, and purchase raw milk from farmers that show professionalism and attention to the safety of their milk, since it will be consumed without any further risk reduction measures such as heat-treatment.
The presence of a potentially harmful bacteria in milk does not necessarily mean that you will get sick from the milk or be infected. Our gastro-intestinal system has been developed to deal with many potential hazards in the food we consume, including harmful bacteria. We have a very well-developed immune system, and there is no other organ in the body where there are more immune cells than the gastro-intestinal tract. Furthermore, in our gastro-intestinal tract we have trillions of good bacteria that are forming a community (a microbiota) and many times those bacteria can keep the harmful bacteria in balance. The risk of becoming sick from a pathogen (harmful bacteria) depends on the number of bacteria consumed, how disease-causing or aggressive the particular strain is, how good the immune system is of the human, the microbiota, and many other factors. Today we have very good methods for detecting bacteria even at extremely low levels, such as taken samples of milk filters on the dairies and using highly refined testing systems (such as RT-PCR).
The generally accepted golden methods to estimate microbial risk in food safety is called a Quantitative Microbial Risk Assessment (QMRA).
QUESTIONS ABOUT HEALTH CLAIMS
Our modern western civilization has experienced an increased frequency of asthma and allergies. This has partly been attributed to the so called ‘hygiene hypothesis’, which states that a lack of early childhood exposure to infectious agents, symbiotic microorganisms (such as the gut flora or probiotics), and parasites increases susceptibility to allergic diseases leading to a unbalance in the immune system.
Raw milk consumption is found to be a single factor that can protect against allergies and asthma. The mechanisms for this has not been sufficiently researched, but it is reasonable to believe that the microflora in raw milk may prove a more natural exposure to many of the bacteria in the environment and improve the immune function. Furthermore, it is also necessary for our immunity to at regular basis be challenged by potentially disease-causing bacteria and virus, so that we can mount a good defense to these. Thus, elimination of all disease-causing bacteria and viruses and parasites from our environment and food may actually be counter-productive to keeping us healthy.
There are numerous epidemiological studies and even laboratory studies in mice that are supportive of that raw milk protects against allergy and asthma. Studies have been done in over 10 countries, and have shown a strong association between early childhood consumption of raw milk and reduced asthma, hay fever and allergies. In many of these studies children grew up on farms and drank raw milk or children that grew up in villages and drank raw milk, have reduced asthma symptoms. Within the well-protected group of farm children, comparisons have been made between those that received heat-treated farm milk versus those that drank farm milk raw. Farm children drinking raw milk had less asthma, hay fever and allergies compared to the ones that drank heat-treated milk, comparable with the control group of farm children drinking homogenized and pasteurized shop milk. Therefor, a range of researchers accept that raw milk consumption is a single factor, protective for the diseases mentioned. Furthermore, it has been shown that mothers that drink raw milk during pregnancy had lower risk of allergies and asthma in their children.
In the statistical analysis of these epidemiological studies, it has been shown that there is a raw milk effect that is separate from and additional to the farm environment effect. These studies have shown that the farm environment, the behavior of the pregnant mother are also protective against asthma and allergies. Critics of these studies refuse to recognize the sound statistical analysis performed, or simply disregard these components of the studies. There seem to be an additive effect. If the mother works in the stables, if the child is vaginally born, breast fed and drinks raw milk, then the newborn is highly protected against allergies and asthma. Furthermore, being born in larger families, and not being the first-born is also protective against allergies.
