What is milk? Milk is a white liquid produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals before they are able to digest other types of food. Early- lactation milk contains colostrum, which carries the mothers antibodies to the baby and can reduce the risk of many diseases in the baby.
What is milk? Milk derived from cattle species is an important food with many nutrients. The precise nutrient composition of raw milk vary by species and by a number of other factors, but it contains significant amounts of saturated fat, protein and calcium as well as vitamin C. Cows milk has a pH ranging from 6.4 to 6.8, making it slightly acidic.
History In 1856, Gail Borden received the first United States and English patents for condensed milk. Gail Borden patented a method for making condensed milk by heating it in a partial vacuum. In 1861, Gail Borden opened a condensed milk plant and cannery in Wassaic, New York.
History In 1863, Louis Pasteur invented pasteurization, a method of killing harmful bacteria in beverage and food products. In 1891, the first U.S. milk processing plant to install pasteurization equipment was the Sheffield Farms Dairy in Bloomfield, New Jersey. They used a German-made pasteurizer. In 1908, Chicago became the first major American city to pass a law requiring commercial milk to be pasteurized milk.
History In 1878, Doctor Gustav De Laval invented the continuous centrifugal cream separator. In 1884, Doctor Hervey Thatcher of Potsdam, New York invented the first glass milk bottle called Thatchers Common Sense Milk Jar, which was sealed with a waxed paper disk. Victor Farris was the inventor of the paper milk carton. In 1932, plastic-coated paper milk cartons were introduced commercially. In 1964, the all plastic milk container was commercially introduced.
Sources Aside from cattle, many kinds of livestock provide milk used by humans for dairy products. These animals include: Camel Donkey Goat Horse Reindeer Sheep Water Buffalo (Carabao) Yak
Components Lipids including phospholipids and also fatty acids Proteins Caseins - Special types of proteins found in milk that are bound to each other by calcium and or phosphorus ions. Carbohydrates including lactose, glucose, galactose, and other oligosaccharides. Vitamins A, B6, B12, C, D, K, E, thiamine, niacin, biotin, riboflav in, folates, and pantothenic acid Mineral Salt forms of potassium, sodium, magnesium, calcium, phosphates, chlorides, and citrates. Traces of sulfates and carbonates are found. Iron is present in small amount. Iodides are also found in small amounts.
Which milk are available? Whole milk Natural whole milk is milk with nothing added or removed. Whole standardised milk is whole milk standardised to a minimum fat content of 3.5%. Whole homogenised milk is identical in fat and nutrient content to whole standardised milk however it has undergone a specific process known as “homogenisation” which breaks up the fat globules in the milk. This spreads the fat evenly throughout the milk and prevents a creamy layer forming at the top.
Which milk are available? Semi-skimmed milk Semi skimmed milk is the most popular type of milk in the UK with a fat content of 1.7%, compared to a minimum of 3.5% in whole standardised milk and 0.1% in skimmed milk. Skimmed milk Skimmed milk has a fat content of between 0- 0.5% and an average fat content of 0.1%. Skimmed milk therefore has nearly all the fat removed. It contains slightly more calcium than whole milk and lower levels of fat soluble vitamins, particularly vitamin A, as this is lost when the fat is removed.
Which milk are available? 1% fat milk The EU regulations for milk classification previously divided milk into three categories defined by the fat content; whole, semi-skimmed or skimmed. Prior to 2008, any milk that contained a different fat content was defined as a „milk drink‟. On the 1st of January 2008 new regulations came into force to facilitate consumer choice. Now any milk with a fat content other than those laid out can also be considered as „milk‟, provided that its fat content is clearly indicated on the packaging in the form of „….% fat‟. However, these milks cannot be described as whole, semi-skimmed or skimmed. Following this change in regulation 1% fat milk is now offered to consumers who like the taste of semi- skimmed, but want to enjoy milk with a lower fat content.
Which milk are available? Organic milk Organic milk comes from cows that have been grazed on pasture that has no chemical fertilisers, pesticides or agrochemicals used on it. The producers must register with an approved organic body and are subject to regular inspection. Once the cows have been milked, the milk is treated in exactly the same way as regular pasteurised milk.
Which milk are available? Jersey and Guernsey milk Channel Island milk is produced from Jersey or Guernsey breeds of cow and has a particularly rich and creamy taste. It tends to be slightly higher in calories and fat than regular whole milk and also has a higher content of fat soluble vitamins - particularly vitamin A which is important for the promotion and maintenance of healthy growth and development. Jersey and Guernsey milks tend to have a visible cream line and are commonly found in supermarkets as “breakfast milk”.
Which milk are available? Flavoured milk The flavoured milk market is one of the fastest growing dairy sectors. There are a wide variety of flavours and consistencies to cater for all ages and tastes with a choice of long-life (i.e. Ultra Heat Treated or sterilised) or fresh flavoured milk. Most flavoured milk products are produced using reduced fat milk varieties and usually have a fat content of around 1%. The most popular flavours are chocolate, strawberry and banana however more sophisticated flavours such as peach, mocha or products made with real Belgian and Swiss chocolate have been developed for the more adult market. In comparison with plain milks, flavoured milks tend to have slightly higher sugar content, however studies have suggested that they are still a favourable option for children and teenagers as they provide a wide range of beneficial nutrients.
Which milk are available? Heat treated milks Approximately 99% of milk sold in the UK is heat- treated, to kill harmful bacteria and to improve its shelf life. Sterilised milk Sterilised milk is available in whole, semi skimmed and skimmed varieties. It goes through a more severe form of heat treatment, which destroys nearly all the bacteria in it. Firstly the milk is pre-heated to around 50oC, then homogenised (see below for a brief outline of homogenisation), after which it is poured into glass bottles which are closed with an airtight seal.
Which milk are available? UHT milk UHT or ultra heat treated milk is a form of milk that has been heated to a temperature of at least 135ºC in order to kill off any harmful micro-organisms (e.g. harmful bacteria) which may be present in the milk. The milk is then packaged into sterile containers. All milk that is available for sale to consumers through supermarkets and milkmen must be pasteurised i.e. heated to 71.7ºC in order to make it safe for consumers and improve its shelf life. However UHT milks have a longer shelf life as a result of the higher temperatures to which they are heated and the packaging used to store them. UHT milk is available in whole, semi skimmed and skimmed varieties.
Which milk are available? Evaporated milk Evaporated milk is a concentrated, sterilised milk product. It has a concentration twice that of standard milk. The process of producing evaporated milk involves standardising, heat treating and evaporating the milk under reduced pressure, at temperatures between 60ºC and 65ºC. Condensed milk Condensed milk is concentrated in the same way as evaporated milk, but with the addition of sugar. This product is not sterilised but is preserved by the high concentration of sugar. It can be made from whole milk, semi skimmed or skimmed milk.
Which milk are available? Untreated (raw) milk All milk sold via the supermarkets and milkmen has to be heat-treated (pasteurised) to kill harmful bacteria. However, untreated milk can be bought direct form a limited number of farm distributors in England and Wales. Filtered milks Filtered milk goes through an extra, fine filtration system, which prevents souring bacteria from passing through. The nutritional content of the milk is unaffected but the shelf life is increased. The processes involved include, microfiltration, ultrafiltration and nanofiltration.
Which milk are available? Dried milk powder Milk powder is produced by evaporating the water from the milk using heat. The milk is homogenised, heat treated and pre-concentrated before drying. There are a number of ways to produce dried milk powder including spray drying and roller drying. In the most commonly used spray drying process, the concentrated milk is introduced into a chamber (usually as a fine mist) through which hot air is circulating. The droplets of milk soon lose their water and fall to the floor as fine powder. Skimmed milk powder can be mixed easily with water; however whole milk isn‟t easily reconstituted due to its higher fat content.
Milk Processing Clarification – is the process of removing undesirable foreign matter and bacteria from the milk. Separation – is the process of dividing the milk into its component parts mainly skimmed milk, cream, and other effluents for further individual processing and to maximize product variety and yield, also determines which process each would undergo. Standardization – is the industrial adjustment of milk or cream fat content to a precisely specified or desired value. Pasteurization – is the process of heating liquids or foods to kill microorganisms (such as Brucella, Campylobacter, E. coli O157:H7, Listeria, Mycobacterium bovis, Salmonella, and Yersinia) that can cause disease. It was developed by Louis Pasteur in 1864.
Milk Processing Methods for Milk Pasteurization High Temperature Short Time Treatment. Milk is pasteurized at 161 F for 15 seconds. Low Temperature Long Time Treatment. Milk is pasteurized at 145 F for 30 minutes. Flash Pasteurization. This type of pasteurization, which involves high temperature for 3 to 15 seconds followed by cooling and packaging, is used for drink boxes and other liquids that can be stored for long periods of time without refrigeration. Ultrapasteurization. Heating milk or cream to 280 F for 2 seconds can extend the refrigerated shelf life of milk from 60 to 90 days. Ultra-High Temperature Pasteurization. Heating milk to 280 to 302 F for 1 or 2 seconds followed by packaging in airtight containers allows storage without refrigeration for up to 90 days.
Milk Processing Homogenization – allows milk manufacturers to combine the cream and milk so that it does not separate. The main goal behind milk homogenization is to reduce the size of the fat molecules in milk because smaller molecules tend to stay suspended in the body of the liquid. Only large globules float to the top. Fortification – is the process of introducing additional vitamins and minerals to the milk to improve product quality.