Milk
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Milk
Transcript of Milk
MILK
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 milk or 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.
Semi skimmed milk
• Semi skimmed milk is the most popular type of milk in the UK with a fat content of 1.7%
Skimmed milk• Skimmed milk has a fat content of between 0.1-0.3 %.
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
• The lower level of fat in skimmed milk reduces its calorie (energy) content. For this reason it is not recommended for children under the age of 5 years as they need the extra energy for growth. However it is ideal for adults who wish to limit their fat or calorie intake.
• Skimmed milk has a slightly more watery appearance than other types of milk and has a less creamy taste due to the removal of fat.
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.
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”.
Flavoured milk• The flavoured milk market is one of the fastest growing dairy sectors.• 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.
• Flavoured milk is less likely to cause damage to teeth than sugary foods and drinks.
Heat treated milks
Approximately 99% of milk sold in the UK is heat-treated, to kill harmful bacteria and to improve its shelf life.
Pasteurisation• Most of the milk consumed in Europe,
Scandanavia, the USA, Australia and New Zealand is pasteurised.
• Pasteurisation is the process whereby milk is heated with the purpose of killing potentially harmful micro-organisms such as certain pathogenic bacteria, yeasts and moulds which may be present in the milk after initial collection. This helps to protect against any food bourne illness that can occur through consumption of raw (unpasteurised) milk.
• Following pasteurisation, the milk is rapidly cooled and is then stored in a refrigerator in order to preserve its shelf life.
• Pasteurisation is the most popular method of heat treatment. It is a relatively mild form of treatment, which kills harmful bacteria without significantly affecting the nutritional value or taste of the milk.
• The basic process for whole milk involves heating the milk to a temperature of no less than 71.7ºC for a minimum of 15 seconds (max 25 seconds). This process is known as High Temperature Short Time (HTST).
• The cold milk that enters the heat exchanger is heated by the hot milk leaving it, which in turn is partly cooled. After heating, the milk is cooled rapidly to below 6ºC using chilled water on the opposite side of the plate. This process also extends the keeping quality of the milk.
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.
• First the milk is pre-heated, sterilised, then homogenised and poured into glass bottles or plastic cartons, which are closed with an airtight seal.
• The bottles are put on a conveyor belt and pass through a steam chamber where they are heated to a temperature of between 113-130ºC for approximately 10-30 minutes. Then they are cooled and crated.
• The sterilisation process results in a change of taste and colour and also slightly reduces the nutritional value of the milk, particularly the B group vitamins and vitamin C.
• Unopened bottles or cartons of sterilised milk keep for several months without the need for refrigeration. Once opened it must be treated as fresh milk and used within 5 days.
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.
• 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.
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.
• The evaporated milk is then homogenised to prevent it separating under storage and then it is cooled.
• As a result of processing, evaporated milk possesses a characteristic cooked flavour as well as a characteristic colour.
• The shelf-life of canned evaporated milk is commonly stated as one year stored at ambient temperatures, though in practice the product will keep for longer.
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.
• The heat treatment used consists of holding standardised milk at a temperature of 110-115ºC for one to two minutes.
• The milk is then homogenised, the sugar added and the sweetened milk is then evaporated at low temperatures (between 55-60ºC). The concentration of the condensed milk is now up to 3 times that of the original milk.
• The milk is then cooled rapidly to 30ºC and packaged.• Sweetened condensed milk is commonly used in the
sugar confectionary industry for the production of toffee, caramel and fudge.
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. • The milk is then homogenised to standardise and evenly
distribute the fat molecules, where it then undergoes the pasteurisation process before being chilled down quickly to 5ºC or less.
• Microfiltration adds an extra level of cleanness which can extend shelf life up to 45 days when stored at temperatures of up to 7ºC and an average 7 days once opened.
• Filtered milk is available in whole, semi skimmed or skimmed milk varieties.
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.
• Skimmed milk powder can be mixed easily with water; however whole milk isn’t easily reconstituted due to its higher fat content.
• Whole milk powder contains all the nutrients of whole milk in a concentrated form with the exception of vitamin C, thiamin and vitamin B12. Skimmed milk powder contains hardly any fat and therefore no fat soluble vitamins. However, the protein, calcium and riboflavin content remain unaffected.
• If stored correctly, skimmed milk powders can be kept for up to one year. Once they are reconstituted, they must be treated as fresh milk.
Homogenisation
• Homogenisation of milk involves forcing the milk at high pressure through small holes. This breaks up the fat globules in order to spread them evenly throughout the milk and prevent separation of a cream layer.
Calcium• Calcium has many important functions in
the body but most importantly in children and adolescents is the development of healthy bones, teeth.
• Calcium requirements increase dramatically from about the age of 11 years in what is known as the pre-pubertal growth spurt.
• A lack of calcium can lead to poor mineralization of bones and low bone mineral density (a measure of bone strength). This can lead to many problems including permanent bone deformities and diseases of the bone such as osteoporosis (where bones are weak and break easily) in later life.
• Dairy products are good providers of calcium and many other nutrients important to good bone health and of increased demand during childhood and adolescence e.g. phosphorous, magnesium and protein.
• Other foods containing dietary calcium include fish with edible bones, green leafy vegetables, nuts, bread etc.
• However significantly greater quantities of these foods are required in order to provide the same amount of calcium as dairy foods. This is because the calcium in dairy foods is more easily absorbed than from other foods and is therefore a very valuable provider of calcium for children and teenagers.
• Consumption of 3 portions of dairy foods every day (3-A-Day) e.g. a glass or 200ml milk, a matchbox sized (30g) piece of cheese and a pot (150g) yogurt will go a long way to helping this age group meet their daily calcium requirement.
1. How easy is it to buy milk and milk products?2. How expensive are milk products to buy?3. How should milk be stored? What are the
advantages to a caterer for using UHT and dried milk products?
4. Explain the versatility of milk. Include the different varieties, ease of preparation and cooking.
5. Discuss the different uses of milk.6. Discuss the nutritional value of milk.
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