(Jrt)
Milk
The milk is a drink usually whitish color produced by mammals (including Monotreme). The ability of females is a defining characteristics of mammals. The milk is produced by cells secreting glands in the udder. The milk secreted in the first days after parturition called colostrum.
The primary function of milk is to feed the offspring until sevree, ie able to digest other foods. In most human civilizations, the milk of animals (mammals themselves) domestic (cow, sheep, goat, horse, driver, camels, camels, buffalo) is commonly consumed.
By analogy, it also uses the term to describe several milk beverage consistency and / or similar appearance and produced based plants, like soy milk, coconut, rice, almond, oats or Pistachio yet.
History
The milk is a phenomenon that occurred during the evolution of placental mammals. The exact time of its appearance remains unknown, but the immediate ancestors of modern mammals like much to Monotreme, including the platypus. Today these animals secrete a substance similar to milk from glands located on the surface of their skin, but they lack the nipple that allows their offspring to drink after hatching their eggs. Similarly, the marsupials, the closest cousins of placental mammals secrete a substance similar to milk from a body resembling a nipple in their pockets. Now the first known ancestor of placental mammals appeared to be eomaia, a small creature that looked superficially to rodents and believed she lived there are 125 Ma, during the Cretaceous. It is almost certain to produce what would be considered milk, the same way that modern placental mammals.
We know that the milk of animals has been used in food as soon as they began to be domesticated. That cow's milk which was used first in the Middle East. Goats and sheep were domesticated in the 9th century BC. AD, it is ruminantia, ie mammals that have adapted to survive through a system of dry grass, a power source unnecessary to humans and easily stored. It is likely that has begun to keep these animals for their meat and skin, but raise them for their milk has proved to be a more efficient way to convert food waste pastures; also the nutritional value of an animal killed for its meat may be offset by the value of milk produced by the same animal, which will continue to provide - and daily - for years.
In the 7th millennium BC. AD, there were herds of cattle in parts of Turkey today, and the traces of milk were found on fragments of pottery from this period. There is evidence that we consumed milk in the British Isles to the Neolithic. The use of cheese and butter spread in Europe and some parts of Asia and Africa. The domestic cows, which already existed in much of Eurasia, were then introduced in the colonies of Europe at the time of the great explorations.
Science
Milk is a liquid matte white, slightly viscous, whose composition and physical and chemical characteristics vary significantly among animal species, and even in races. These characteristics also vary during the lactation period, and in trafficking.
Physics
Cow's milk has an average density equal to 1032. It is a mixture very complex and unstable. It contains a high proportion of water, approximately 87%. The rest is dry, which represents 130 g per liter, 35 to 45 grams of fat. The other main components are the organic components (lactose carbohydrates, lipids, proteins, vitamins), the mineral components (Ca, Na, K, Mg, Cl) and water. Milk contains the various groups of nutrients. The organic substances (Carbohydrate, lipids, proteins) are present in quantities roughly equal and release all the energy. These nutrients are broken down into components builders, protein and energy components, carbohydrates and lipids. The milk also contains functional elements, mineral ions (Ca, P, K, Na, Mg, ...), vitamins and water.
On the physical level, it is both a solution (lactose, minerals), suspension (raw nitrogen) and emulsion (fat).
Chemistry
The pH of milk is slightly acidic (pH between 6.4 and 6.8 for cow's milk). It is somewhat basic for human milk with a pH between 7 and 7.5. The acidity of milk increases with time. In fact, lactose will be broken down into lactic acid, which will be an indicator of the degree of conservation. This is done using the degree Dornic (° D).
Biology
Milk also a biological environment: it contains blood cells and breast (around 250 000 per ml) and micro-organisms (around 15 000 per ml).
Biological composition
Casein is the most abundant protein milk. It is a polypeptide complex as a result of the polycondensation of different amino acids, which are the main leucine, proline, glutamic acid and serine.
Phosphorus is attached as phosphates. Joins the calcium phosphate and casein given for the complex phosphocaseinate calcium to form a colloid. It also magnesium, potassium and sodium but it is, at least for cow's milk, low trace. Milk is among the animals fluids, one of those that contain the largest concentration of citric acid is an anticoagulant and it opposes the precipitation of proteins.
The lipid concentration varies from 10 to 500 g / l depending on the species. They are mainly (99%) triglycerides.
The principal sugar of milk is lactose, whose sweetness is six times lower than sucrose. It may cause some intolerances.
The protein micelles have a diameter of about 0.1 microns. Overall, there is more of carboxyl groups as amines, this explains that the milk is naturally acid (6.6
Arguments in favor
The milk is generally considered a food's comprehensive nutritional point of view. It contains almost all vitamins (with the notable exception of vitamin C and, for skimmed milk, vitamins A and D). Fat dairy are rich in saturated fatty acids and contain trans fatty acids.
Arguments against
A growing number of scientific studies consider cow's milk as a food that could be harmful to human beings: they believe their protein and calcium are hardly absorbed by the human species, as adapted to new small only .
Asian populations consume some dairy products, without apparent consequences for health. Japan holds the world record for longevity: 84 years for women, 77 years for men and especially in life expectancy in good health aged 73 on average. The Japanese island of Okinawa, hosting an exceptional number of centenarians, has repeatedly been the subject of scientific studies and books declining regime without meat and milk. However, these results qualify taking into account all formed by food (contributions of unsaturated fatty acids from a regime based on fatty fish ,...) and lifestyle of Japanese citizens.
Studies challenge cow's milk and its benefits against osteoporosis. These arguments have been compiled by the science journalist Thierry Souccar who reviewed the studies published to date and concludes that there is no evidence that dairy products make stronger bones. According to him, casein milk, its calcium and certain hormones it contains could actually contribute to the emergence of some serious diseases (type I diabetes in children, multiple sclerosis, cancer and osteoporosis that milk is supposed to prevent).
Religion
In the Christian religion, the prohibition of consuming fatty foods the day of fasting, led cooks to substitute dairy products by the food scarce. Thus the Middle Ages, in some recipes, milk animal is replaced by almond milk. In Britain, milk Ribot of Breton "laez ribod" which means milk Barrat, is a little milk that you drink on Friday.
Regulation
In France, regulatory level:
"The name" milk "without identifying the species of animal origin, is reserved to cow's milk. While milk from a female other than the dairy cow must be designated by the term "milk" followed by an indication of the species from which it comes: "goat milk", "milk sheep", "d milk 'donkey' and so on. See "
Read also Royal Jelly
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