Milk

A glass of milk

Milk most often means the nutrient fluid produced by the mammary glands of female mammals (including monotremes such as the Australian platypus). It provides the primary source of nutrition for newborns, before they are able to digest more diverse foods. It can also be used to mean the white juice of a coconut and the processed meat of the coconut in, more or less, liquid form. Coconut milk lacks the rich nutritional values of animal milk but is often used in place of animal milk in cookery, especially in varieties of Thai curry and in Polynesian cooking.

Human breast milk is often fed to infants through breastfeeding, either directly or by the female expressing her milk to be saved and fed later.

Non-animal "milk" substitutes are made from soybean manufacturing processes soya milk.

Composition and nutrition

The composition of milk varies greatly among different mammals.

• Human breast milk is thin and high in lactose, its primary sugar.
• Cow's milk, in contrast, is lower in sugar and higher in protein, and is composed of about 3.5% to 6.5% milkfat, 4% to 8.5% milk solids and about 88% water. Its main protein (80%) is casein.

The milk of some mammals, particularly cows, goats, water buffalo, horses, donkeys and sheep is collected for human consumption directly and after pasteurization in more regulated counties, or it is processed into dairy products such as cream, butter, yoghurt, ice-cream, gelato, cheese, casein, lactose, dried milk or parts of milk, and many other food-additive and industrial products.

In Russia and Sweden, small moose dairies exist[1] (http://www.cnn.com/2004/WORLD/europe/06/23/sweden.moosecheese.ap/index.html). Donkey and horse milk have the lowest fat content, while the milk of seals contains more than 50% fat. [2] (http://www.havemilk.com/content/contentid/1706#contentbyspecies)

Lactose in milk is digested with the help of the enzyme lactase produced by the bodies of infants. In humans, production of lactase falls off towards adulthood (depending on the person's ethnic origin), in many cases to the point where lactose becomes indigestible, leading to lactose intolerance a gastrointestinal condition that afflicts many.

There is some controversy over whether consumption of cow's milk is good for adult humans. While milk is often touted as healthy for its significant amount of calcium, required for healthy bone growth and nerve function, there is some research to suggest that proteins in milk interfere with the use of its calcium to form bones. However breeds of cattle produce milk that is significantly different from that of others as do different mammals' from others. Such factors as the lactose content, the proportion of and size of the butterfat globule and the strength of the curd, formed by the human enzymes digesting the milk, can differ from breed to breed and mammal to mammal.

Milk has also been linked in a small number of studies to osteoporosis, cancer, heart disease, obesity and high blood pressure yet in countries where dairy products are plentiful and cheap, New Zealand and Australia, have no particular indications of those diseases.

Curdling

When raw milk is left standing for a while, it turns sour. This is the result of fermentation: lactic acid bacteria turning the milk sugar into lactic acid. This fermentation process is exploited in the production of various dairy products such as cheese and yogurt.

Pasteurized cow's milk, on the other hand, spoils in a way that makes it unsuitable for consumption, causing it to assume a disgusting odor, which alone may induce vomitting in sensitive persons, and pose a high danger of food poisoning if ingested anyway. The naturally-occurring lactic acid bacteria in raw milk, under suitable conditions, quickly produce large amounts of lactic acid. The ensuing acidity in turn prevents other germs from growing, or slows their growth significantly. Through pasteurization, however, these lactic acid bacteria are mostly destroyed, which means that other germs can grow unfettered and thus cause decomposition.

In order to prevent spoilage, milk can be kept refrigerated and stored between 1° and 4° Celsius. 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. Sterilized milk, which is heated for a much longer period of time, will last even longer, but also lose more nutrients and assume a still different taste. The most durable form of milk is milk powder which is produced from milk by removing almost all water.

Cow's milk

Cow's milk is produced and distributed on an industrial scale for human consumption and for processing into dairy products.

Distribution

Prior to the widespread use of plastics, milk was usually commercially distributed to consumers in glass bottles. In the UK, milk was delivered daily by a milk man who travelled round his local milk round on an electric milk float. In New Zealand in some urban areas milk is still delivered to customers' homes.

Glass containers are rare these days and most people purchase milk in plastic jugs or bags or in waxed-paper cartons. Ultraviolet light from fluorescent lighting can destroy some of the proteins in milk, so many companies that once distributed milk in transparent or highly translucent vessels are starting to use thicker materials that block the harmful rays. Many people feel that such "UV protected" milk tastes better. But few people have ever tasted fresh, unprocessed, milk straight from the cow.

Varieties and brands

Cow's milk is generally available in several varieties. In some countries these are:

• full cream (or "whole" in North America),
• semi-skimmed ("reduced fat" or "low fat"), and
• skimmed.

Milk in the U.S. is sold as

• "skim" (very low fat),
• "1/2 percent" (low fat),
• "1 percent" (low fat),
• "2 percent" (reduced fat), and
• "whole" varieties.

Full cream, or whole milk, has the full milk fat content (about 3-4% if Friesian- or Holstein-breed sourced). Skimmed milk has all of the fat content removed and then some is returned for semi-skimmed milk that has about half the milk fat returned (1.5-1.8% fat content in some countries, 2-2.5% in others). Skimmed milk has almost all the milk fat removed (about 0.1% fat content). The best-selling variety of milk is semi-skimmed; in some countries full-cream (whole) milk is generally seen as less healthy and skimmed milk is often thought to lack taste. However whole milk is the best for frothing for drinking with coffee. Whole milk is recommended to provide sufficient fat for developing toddlers who have graduated from breast milk or infant formula.

There are many well-known brands of milk

• Anchor
• Dairy Farmers
• H.P. Hood
• Leche Caparra
• Leche Suiza
• Lucerne
• Mainland
• Parmalat
• Pauls (a subsidiary of Parmalat in Australia)
• Pura
• Shamrock Milks
• Tenuvah

Milk is the state drink of Minnesota and Pennsylvania.

See also

• bovine somatotropin
• almond milk
• raw milk
• rice milk
• soy milk

External links

Wikibooks Cookbook has a section about:   Milk

• Boning Up on Osteoporosis (http://www.ars.usda.gov/is/AR/archive/mar03/osteo0303.htm)
• Horse milk (http://www.drafthorsejournal.com/features/horsemilk/horsemilk.htm)
• Not Milk (http://www.notmilk.com/)

cy:Llaeth da:Mælk de:Milch et:Piim es:Leche eo:Lakto fr:Lait it:Latte he:חלב nl:Melk ja:乳 nds:Melk pl:Mleko pt:Leite ro:Lapte fi:Maito sv:Mjölk tt:Söt simple:Milk