TYPES OF MILK
Standardized milk- This
is made by combining buffalo milk and skimmed milk. The fat percentage is
maintained at 4.5% while the SNF is 8.5%.
Whole milk: Whole milk must contain at least 3.25% milk fat and 8.25% milk solids by weight—which means it derives about 50% of its calories from fat. Because of this relatively high fat content, whole milk is best used only for infants and young children up to age 2.
Reduced-fat milk (2%): This milk contains 2% milk fat. The percentage of milk fat refers to the percentage of fat by weight, and much of milk's weight is water. Once you subtract the water from 2% milk, for example, you're left with a product that contains 20% fat by weight; such milk actually derives 35% of its calories from fat. Drinking 2% milk is a good way to wean oneself from whole milk at first, but is too high in fat as a permanent choice, unless your diet is otherwise very low in fat.
Low-fat milk (1%): One-percent milk gets 23% of its calories from fat. Many people find low-fat milk more appealing and a good compromise.
Skimmed milk/non-fat milk: This type of milk has as much fat removed as
possible. It may not contain more than 0.5% milk fat by weight, and usually contains
less than 0.5 gm of fat per cup, deriving just 5% of its calories from fat.
Skimmed milk has about half the calories of whole milk. It is the best choice
for adults, and is the only type of milk that should be consumed by people on
strict low-fat diets. Unfortunately, skim milk has a very "thin"
flavor and an unappealing bluish cast.
Varieties of
milk
There are many different varieties of milk available for consumption.
The different milks tend to vary according to the way they are
produced, and their fat content. The fat content of milk varies depending on
the product e.g. whole milk has a fat content of about 4% fat, whole
standardised milk, that which is widely available for sale, has a minimum
fat content of 3.5% fat, semi skimmed milk contains 1.7% fat, skimmed milk
contains about 0.1% fat, and in addition there is 1% fat 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
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.
How is it produced?
Natural whole milk is collected from the dairy herd and undergoes
various processing techniques before it reaches the shelf for consumption by
the general public.
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 born 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.
Various pasturisation and heat treatment techniques can be used in
the production of milk which can affect storage capacity.
Much of the milk in the market is now homogenised as well as
pasteurised. Homogenization offers a way to reduce the fatty sensation of whole
milk and prevent the formation of a cream plug.
Semi skimmed milk
Semi skimmed milk is the most popular type of milk with a fat
content of 1.7%, compared to a minimum of 3.5% in whole standardized 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.
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.
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.
The nutritional differences between semi-skimmed and 1% fat milk
are small and dependent mainly on the difference in fat content. 1% fat
milk contains 40% less total and saturated fat than standard semi-skimmed milk.
In addition, it has lower energy content than semi-skimmed and slightly lower
levels of vitamins A and E, but has higher calcium content.
Organic milk
Organic milk comes from cows that have been grazed on pasture that
has no chemical fertilizers, 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.
There is no evidence to suggest that organic milk is any more
nutritious than conventionally produced milk. Although there have been studies
to show that organically produced milk contains higher levels of omega-3
polyunsaturated fatty acids, these are plant derived, short-chain fatty acids
which appear to be of limited health benefit compared to the longer chain
omega-3 fatty acids found in oily fish.
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.
One study has shown that children consuming flavoured milk are not
actually likely to have higher sugar or energy intakes as children consuming
flavoured milk would likely, consume fewer less healthy sweetened drinks.
Flavoured milk is also less likely to cause damage to teeth than
sugary foods and drinks.
Interestingly recent studies have suggested that chocolate
flavoured milk can be used as an effective recovery aid after intense bouts of
exercise.
Heat treated milks
Approximately 99% of milk sold is heat-treated, to kill harmful
bacteria and to improve its shelf life.
Pasteurization
Pasteurization 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).
After this the cold milk that enters the heat exchanger is heated
by the hot milk leaving it, which in turn is partly cooled. Following
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.
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.
There is no legally defined process for sterilising milk but,
commonly, filled bottles are carried on a conveyor belt through a steam chamber
where they are heated to a temperature of between 110-130ºC for approximately
10-30 minutes. Then they are cooled using a cold water tank, sprays or, in some
cases, atmospheric air and then 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
approximately 6 months without the need for refrigeration. Once opened it must
be treated as fresh milk and used within 5 days.
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.
The evaporated milk is poured into cans, which are then sealed. At
this point the cans are moved to a sterilised where they are held for 10
minutes.
A cooling stage follows and the cans are then labelled and packed. 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 sterlised 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. It is
also an alternative to liquid milk which was once traditionally used in these
products.
Untreated (raw) milk
All milk sold from the supermarkets has to be heat-treated
(pasteurised) to kill harmful bacteria.
However, untreated milk can be bought direct from registered
milk production holdings (at the farm gate or in a farmhouse catering
operation) or through a limited number of milkmen in England and Wales.
Sales through other outlets have been banned since 1985 (although
sales by the farmer at farmers markets are allowed). In addition, the milk must
bear the appropriate health warning.
A ban for the sale of raw milk in Scotland has been in place
since 1983.
Raw milk represents only a very small fraction of total milk
consumption. Animal Health Dairy Hygiene has estimated this to be 0.01% of
total cows' milk consumption.
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.
Microfiltration is the most commonly used process and is a
pressure-activated separation process which uses a membrane that is permeable
to substances with a low molecular weight but rejects material with a high
molecular weight.
In the process of microfiltration of skimmed milk, bacteria are
removed using ceramic filters with 1.4 micrometer holes to separate the milk
from the bacteria. After this process, virtually all the bacteria present in
the milk are removed.
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.
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.
Roller drying is an old process
of producing milk powder-this involves spreading the concentrated milk onto
heated rollers. The water evaporates quickly and leaves a thin film of powder,
which is scraped off the rollers. This powder has a cooked flavour and tends to
form lumps when mixed with water.
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.
This process basically results in milk of uniform composition or
consistency and palatability without removing or adding any constituents.
Homogenisation increases the whiteness of milk because the greater numbers of
fat globules scatter the light more effectively.
Most milk available on the market is homogenised at present.
Compiled By:
Hariom Kumar Singhal
Certified Hospitality Trainer (CHT)
9806702315 / 9461085175
