Milk!
Milk Joke
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When Alan read the note, he felt there must be a mistake. He thought she probably meant 1.5 gallons, so he knocked on the door to clarify the order.
Gloria came to the door, and Alan said, "I found your note to leave 15 gallons of milk. Did you mean 15 gallons or 1.5 gallons?"
Gloria said, "I want 15 gallons. I'm going to fill my bathtub up with milk and take a milk bath."
Alan asked, "Oh, alright, would you like it pasteurized?"
Gloria replied, "No, just up to my waist."
Milk
Milk is an opaque white liquid produced by the mammary glands of female mammals (including monotremes). Mammary glands are highly specialized sweat glands. The female ability to produce milk is one of the defining characteristics of mammals. It provides the primary source of nutrition for newborns before they are able to digest other types of food. The early lactation milk is known as colostrum, and carries the mother's antibodies to the baby. It can reduce the risk of many diseases in the baby. Males of all mammal species retain the breasts that are part of the fundamental mammalian animal structure, hence their nipples. Lactation occurs in males in certain rare circumstances, both naturally and artificially, however, some pharmaceuticals precipitate lactation in males readily.The exact components of raw milk varies by species, but it contains significant amounts of saturated fat, protein and calcium as well as vitamin C. Unfortunately the vitamin C is destroyed by the heat in pasteurization process. Humans are among the few animals who cannot manufacture this vitamin so its presence in the natural milk of their mothers is essential for the health of human infants and vitamin supplements are necessary for human infants fed only pasteurized milk. Aquatic mammals, such as seals and whales, produce milk that is very rich in fats and other solid nutrients when compared with land mammals' milk.
A goat kid feeding on its mother's milk.Humans, as other mammals, can consume mother's milk during their infancy. Some mammals lose the ability to digest milk properly if a long period passes without consumption of it after weaning. In many ethnic groups, people lose the ability to digest milk after childhood (that is, they become lactose intolerant), so many traditional cuisines around the world, such as Chinese cuisine, do not feature dairy products. On the other hand, those groups that do continue to tolerate milk often have exercised great creativity in using the milk of domesticated ruminants, not only of cows, but also sheep, goats, yaks, water buffalo, horses, and camels. For millennia, cow's milk has been processed into dairy products such as cream, butter, yogurt, ice cream, and especially the more durable and easily transportable product, cheese. Industrial science has brought us casein, whey protein, lactose, condensed milk, powdered milk, and many other food-additive and industrial products.
Human milk is fed to infants through breastfeeding, either directly or by expressing the milk to be stored and consumed later. Some cultures, historically or presently, continue to use breast milk to feed their children until as old as seven years.
The term milk is also used for whitish non-animal substitutes such as soy milk, rice milk, almond milk, and coconut milk, and even the regurgitated substance pigeons feed their young, called crop milk, which bears little resemblance to mammalian milk.
Milk History
Holstein cattle, the dominant breed in industrialized dairying today.Milking has its advent in the very evolution of placental mammals. While the exact time of its appearance is not known, the immediate ancestors of modern mammals were much like monotremes, including the platypus. Such animals today produce a milk-like substance from glands on the surface of their skin, but without the nipple, for their offspring to drink after hatching from their eggs. Likewise, marsupials, the closest cousin to placental mammals, produce a milk-like substance from a teat-like organ in their pouches. The earliest immediate ancestor of placental mammals known seems to be eomaia, a small creature superficially resembling rodents, that is thought to have lived 125 million years ago, during the Cretaceous era. It almost certainly produced what would be considered milk, in the same way as modern placental mammals.Animal milk is first known to have been used as human food at the beginning of animal domestication. Cow's milk was first used as human food in the Middle East. Goats and sheep were domesticated in the Middle East between 9000 and 8000 BC. Goats and sheep are ruminants: mammals adapted to survive on a diet of dry grass, a food source otherwise useless to humans, and one that is easily stockpiled. The animals were probably first kept for meat and hides, but dairying proved to be a more efficient way of turning uncultivated grasslands into sustenance: the food value of an animal killed for meat can be matched by perhaps one year's worth of milk from the same animal, which will keep producing milk in convenient daily portions for years (McGee 8-10).
Around 7000 BC, cattle were being herded in parts of Turkey. There is evidence of milk consumption in the British Isles during the Neolithic period. The use of cheese and butter spread in Europe, parts of Asia and parts of Africa. Domestic cows, which previously existed throughout much of Eurasia, were then introduced to the colonies of Europe during the Age of exploration.
Milk Modern production
In the Western world today, cow's milk is produced on an industrial scale. It is by far the most commonly consumed form of milk in the western world. Commercial dairy farming using automated milking equipment produces the vast majority of milk in developed countries. Types of cattle such as the Holstein have been specially bred for increased milk production. According to McGee, 90% of the dairy cows in the United States and 85% in Great Britain are Holsteins (McGee 12). Other milk cows in the United States include Ayrshire, Brown Swiss, Guernsey, Jersey, and Milking Shorthorn. The largest producers of dairy products and milk today are India followed by the United States and New Zealand.Other milk animals
Goat's milk can be used for other applications such as cheese and other dairy products.In addition to cows, the following animals provide milk used by humans for dairy products:
Sheep (the ewe)
Goats (the nanny)
Horses (the mare)
Donkeys
Camels (including the South American camelids)
Yaks
Water buffalos
Reindeers
In Russia and Sweden, small moose dairies also exist. Donkey and horse milk have the lowest fat content, while the milk of seals contains more than 50% fat.
Whale's milk, not used for human consumption, is one of the highest-fat milks. It contains, on average, 10.9% protein, 42.3% fat, and 2.0% lactose, and supplies 443 kcal of energy per 100 grams.
Human milk is not produced or distributed industrially or commercially; however, milk banks exist that allow for the collection of donated human milk and its redistribution to infants who may benefit from human milk for various reasons (premature neonates, babies with allergies or metabolic diseases, etc.).
All other female mammals do produce milk, but are rarely or never used to produce dairy products for human consumption.
Milk Physical and chemical structure
Milk is an emulsion of butterfat globules within a water-based fluid. Each fat globule is surrounded by a membrane consisting of phospholipids and proteins; these emulsifiers keep the individual globules from joining together into noticeable grains of butterfat and also protect the globules from the fat-digesting activity of enzymes found in the fluid portion of the milk. In unhomogenized cow's milk, the fat globules average about four micrometers across. The fat-soluble Vitamins A, D, E, and K are found within the milkfat portion of the milk (McGee 18).Schematic of a micelle.The largest structures in the fluid portion of the milk are casein protein micelles: aggregates of several thousand protein molecules, bonded with the help of nanometer-scale particles of calcium phosphate. Each micelle is roughly spherical and about a tenth of a micrometer across. There are four different types of casein proteins, and collectively they make up around 80 percent of the protein in milk, by weight. Most of the casein proteins are bound into the micelles. There are several competing theories regarding the precise structure of the micelles, but they share one important feature: the outermost layer consists of strands of one type of protein, kappa-casein, reaching out from the body of the micelle into the surrounding fluid. These Kappa-casein molecules all have a negative electrical charge and therefore repel each other, keeping the micelles separated under normal conditions and in a stable colloidal suspension in the water-based surrounding fluid (McGee 19-20).
Both the fat globules and the smaller casein micelles, which are just large enough to deflect light, contribute to the opaque white color of milk. The fat globules contain some yellow-orange carotene, enough in some breeds Guernsey and Jersey cows, for instance to impart a golden or "creamy" hue to a glass of milk. The riboflavin in the whey portion of milk has a greenish color, which can sometimes be discerned in skim milk or whey products (McGee 17). Fat-free skim milk has only the casein micelles to scatter light, and they tend to scatter shorter-wavelength blue light more than they do red, giving skim milk a bluish tint.
A simplified representation of a lactose molecule being broken down into glucose and galactose.Milk contains dozens of other types of proteins besides the caseins. They are more water-soluble than the caseins and do not form larger structures. Because these proteins remain suspended in the whey left behind when the caseins coagulate into curds, they are collectively known as whey proteins. Whey proteins make up around twenty percent of the protein in milk, by weight. Lactoglobulin is the most common whey protein by a large margin (McGee 20-21).
The carbohydrate lactose gives milk its sweet taste and contributes about 40% of whole cow milk's calories. Lactose is a composite of two simple sugars, glucose and galactose. In nature, lactose is found only in milk and a small number of plants (McGee 17). Other components found in raw cow milk are living white blood cells. Mammary-gland cells, various bacteria, and a large number of active enzymes are some other components in milk.
Milk Processing
A milking machine in action.In most Western countries, a centralised dairy facility processes milk and products obtained from milk (dairy products), such as cream, butter, and cheese. In the United States, 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 and raw milk
Pasteurization kills many 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. In many countries it is illegal to sell milk that is not pasteurized. Unfortunately, the heating destroys the vitamin C content and light further destroys other beneficial aspects of milk, being the reason that opaque containers are recommended for storage and transportation.Milk may also be further heated to extend its shelf life through ultra-high temperature treatment (UHT), which allows it to be stored unrefrigerated, or even longer lasting sterilization.
Those preferring raw milk argue that the pasteurization process also kills beneficial microorganisms and other important nutritional constituents. The resulting pasteurized product is said to be less digestible, be less nutritious, and turns rancid (as opposed to ferment) with age. However, unpasteurized milk can harbor harmful disease-causing bacteria such as tuberculosis, brucellosis, salmonella, diphtheria, and escherichia coli. The cows must be maintained in very sanitary conditions and a watchful eye kept as to disease testing and vaccinations for this to be completely safe. Cheeses made with raw milk are regarded as safer as the milk typically had to be heated to some extent anyway to make the cheese, and this would kill many of the dangerous organisms possibly present.
Milk 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 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 (McGee 19). 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 (McGee 19).Milk from Ireland.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. 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 (McGee 23). Creamline, or cream-top, milk is unhomogenized; it may or may not have been pasteurized. Some have suggested that homogenized milk is harder to digest or not so suited to some people as is unhomogenized, it was just for convenience so one didn't have to shake the bottle, and isn't so important as is pasteurization which is done for safety purposes.
Unhomogenized milk has made a small comeback in a few areas, such as the west coast of the United States where Straus Family Creameries, based originally out of Sonoma, sells one line of organic milk with the cream still on top in old-fashioned glass bottles. They still however pasteurize it to prevent harmful microorganisms.
Milk Nutrition and health
The composition of milk differs widely between species. Factors such as the type of protein; the proportion of protein, fat, and sugar; the levels of various Vitamins and minerals; and the size of the butterfat globules and the strength of the curd are among those than can vary.Introduction to Dairy Science and Technology, webpage of University of Guelph For example:Human milk contains, on average, 1.1% protein, 4.2% fat, 7.0% lactose (a sugar), and supplies 72 kcal of energy per 100 grams. Cow's milk contains, on average, 3.4% protein, 3.6% fat, and 4.6% lactose, and supplies 66 kcal of energy per 100 grams
Interestingly, a study has shown that for women currently desiring to have a child, women who consume full fat dairy products may actually slightly increase their fertility, while women consuming low fat dairy products may slightly reduce their fertility through interference in ovulation, however studies in this area are still inconsistent.
Milk Nutritional and physiological detriments
The following issues are often cited as warranting consideration by alternative medicine sites- frequently with limited hard evidence. Note that these claims have a varying degree of validity, and that this section serves to simply catalog claims frequently made by milk detractors-not to endorse these claims themself.Milk contains casein, a substance that breaks down, when digested by humans, into several chemicals including casomorphine, an opiate. Milk products are therefore suspected by some to play a role in behavioral disorders among children, especially with regards to autism.
Some Who even go so far as to promote casein-free diets for everyone. It is also one of the reasons cited by some vegans, for avoiding dairy as well as meat.
Milk Lactose intolerance discussed
Milk that has not received a fat content reduction is rich in saturated fat and cholesterol, which numerous sources have suggested as contributing to an increased risk of atherosclerosis and coronary heart disease when consumed in excessive quantity. Low-fat and non-fat forms of milk may mitigate this risk.Cow milk allergy (CMA) is as an immunologically mediated adverse reaction to one or more cow's milk proteins. Rarely is it severe enough to cause death.
Milk from contaminated or heavily polluted areas can contain high levels of toxic compounds that have bioaccumulated into it. The nuclear power plant disaster at Chernobyl in Ukraine spread a cloud of radioactivity that ended up in the milk supply and many animals had to simply be killed. The contamination spread across many areas of Europe and affected the dairy industries and even milk as far away as the United States had detectable levels of contamination. As well through the principle of bioaccumulation, herbicides and pesticides can accumulate in milk, and organic milk produced without chemicals has become one of the most popular organic products that people choose.
There are some fringe groups debating the amount of calcium from milk that is actually absorbed by the human body. However, calcium from dairy products has greater bio-availability than calcium from vegetable products.
Several studies have shown that men who drink large amount of milk and consume dairy products may increase their risk of developing Parkinson's disease. The reason behind this is, however, not fully understood and it also remains unclear why this is not the case for women.
Several sources suggest a correlation between high calcium intake (2000 mg per day, or twice the US recommended daily allowance, equivalent to six or more glasses of milk per day) and prostate cancer. A large study specifically implicates dairy. A review published by the World Cancer Research Fund and the American Institute for Cancer Research states that at least eleven human population studies have linked excessive dairy product consumption and prostate cancer, however randomized clinical trial data with appropriate controls only exists for calcium, not dairy produce, where there was no correlation.
Controversy surrounding milk and milk production
A number of advocate groups have sprung up protesting that milk presents a health threat. While whole and other fattened forms of milk contain a large amount of saturated fat and cholesterol, factors which are known contributors to the risk of heart disease and many individuals are lactose intolerant, no study has concluded any causal health risk to normal individuals consuming moderate quantities of skim and fat-free varieties of milk.Common claims cited by anti-milk advocates:
White blood cells -- Milk contains varying levels of white blood cells, depending upon the health of the source animals; controversy surrounds whether these are simply somatic cells or, in an alternate form, pus. In the United States, one to seven drops of these cells are in every eight-ounce glass of milk, varying by state, according to guidelines set up by the Food and
Drug Administration and statistics reported by the dairy industry. Only one state out of all fifty, Hawaii, has a cell count lower than the dairy industry's recommendations; seventeen states produce milk that would be illegal to sell based on somatic cell limits in Europe.
No study has ever conclusively demonstrated that the levels of white blood cells found in normal milk actually pose any health risk to normal individuals. The concept of pus in one's milk is somewhat revolting, but evidence for an impact on health is not existent.
Bovine Growth Hormone(rbst) -- Since November 1993, with FDA approval, Monsanto has been selling recombinant bovine somatotropin (rbST)--or rBGH--to dairy farmers. Bovine growth hormone is administered to cattle in order to increase their milk production, though the hormone also naturally fosters liver production of insulin-like growth factor 1 (IGF1). The deposit thereof in the milk of rBGH-affected cattle has been the source of concern; however, all milk contains IGF1. The IGF1 in milk from rBGH-affected cattle does not vary from the range normally found in a non-supplemented cow. Elevated levels of IGF1 in human blood has been linked to increased rates of breast, colon, and prostate cancer by stimulating their growth, though this has not been linked to milk consumption. The EU has recommended against Monsanto milk. In addition, the cows frequently contract an udder infection known as mastitis, partly responsible for the aforementioned prevalence of blood cells in dairy products. Milk from rBGH-affected cattle is banned in Canada, Australia, New Zealand, and Japan due to the mastitis problems. On June 9, 2006 the largest milk processor in the world and the two largest supermarkets in the United States--Dean Foods, Wal-Mart, and Kroger--announced that they are "on a nationwide search for rBGH-free milk."
No study has indicated that consumption of rBST-produced milk increases IGF1 levels, nor has any study demonstrated an increased risk of any disease between those consuming rBST and non-rBST produced milk. The FDA has concluded that no significant difference has been shown between milk derived from rBST-treated and non-rBST-treated cows, nor does any test exist which can differentiate between milk from rBST-treated and non-rBST treated cows.
Milk Lactose intolerance
Lactose is a simple sugar that is present in all milk of the species of origin, and is digested with the help of the enzyme lactase. The production of this enzyme declines significantly after weaning in all mammals, including human beings. Lactose intolerance is the condition in which lactase is not produced in adulthood. With lactose intolerance, the result of consuming too much lactose is excess gas production and often diarrhea. Lactose-intolerant adults can drink about a cup (250 ml or 8 oz) of milk per day without severe symptoms.Most adults in the world are lactose-intolerant (McGee 14: "lactose tolerant adults are a distinct minority on the planet"). Lactose-intolerant adults stop producing significant amounts of lactase sometime between the ages of two and five. A relatively recent genetic change caused some populations (McGee 14: "several thousand years ago"), including many Northern Europeans, to continue producing lactase into adulthood.
