WHAT'S ABOUT CREAM ?
Cream can be used in many
foods such as ice-cream, sauces, soups, custard bases and cakes. It is a dairy
product composed of a higher butter fat layer skimmed from the top of the milk
before being homogenized. According to Food Act and Regulations, cream shall be
the fatty liquid prepared from milk by separating the milk constituents through
a separation process in such a manner so as to extract the milk fat content. It
usually come from cow’s or goat’s milk. However, it can also derived from plant
source which will end up as plant cream. The reasons of plant cream is being
produced and consumed is due to the group of people who are lactose intolerance
or milk allergic and also for vegetarians. The cream produced by cattle contains
some natural carotenoids derived from the plants they eat which gives a
pale-yellow tone. Actually, cream is easy to be made. One can get their own
cream by simply heating milk and allowing it to cool completely. Once the milk
is cooled, skim off the fat layer that has risen to the top. The quality of the
milk and its heat treatment determines the fat content in the milk. Most
jurisdictions have their own percentage classifications to determine the grade
of milk. The classifications of cream are depending on their thickness and
applications. For instant, double cream has a very high butterfat content which
is 48% whereas 35% for whipping cream and 18% for light sour cream.
The composition of cream
depends on the type of milk from which it has been produced and also on the fat
content of cream. The compositions of cream containing different levels of fat
and obtained from cow and buffalo milks. The fat content in the buffalo milk is
80% which is higher than in the cow milk which is 50%. Besides, buffalo milk
contains higher protein and lactose amount compared to cow milk. According to
Food Regulations 1985, Regulations 100, cream shall not less than 35 percent of
milk fat. For instant, the composition of table cream consists of 19.3% of fat,
2.7% of protein, 3.6 % of carbohydrates and 73.8 % of moisture.
Composition
of constituents (%) in creams made from buffalo milk and cow milk.
Constituents Source
Cow
milk Buffalo
milk
Fat 55.0 80.0
Protein 1.50 1.80
Lactose
2.20 2.30
Data retrieved from http://dairy-technology.blogspot.my/2014/01/composition-of-cream.html.
Flow chart for preparation of cream.
The milk is
piped into a pasteurizer to kill any bacteria. There are several methods used
to pasteurize milk. The most common is called the high-temperature, short-time
(HTST) process in which the milk is heated as it flows through the pasteurizer
continuously. Milk must be heated to 72° C for 15 s. The hot milk passes
through a long pipe whose length and diameter are sized so that it takes the
liquid exactly 15 seconds to pass from one end to the other. A temperature
sensor at the end of the pipe diverts the milk back to the inlet for
reprocessing if the temperature has fallen below the required standard. Milk is then homogenized to reduce the size of the
remaining milk fat particles. This prevents the milk fat from separating and
floating to the surface as cream. It also ensures that the milk fat will be
evenly distributed through the milk. The hot milk from the pasteurizer is
pressurized to 17,200-20,700 kPa by a multiple-cylinder piston pump and is forced
through very small passages in an adjustable valve. The shearing effect of
being forced through the tiny openings breaks down the fat particles into the
proper size.The milk is then quickly cooled to 4.4° C to avoid harming its
taste. Lastly, the milk passes through a
separator, which spins the milk through a series of conical disks inside an
enclosure. A separator performs the same task, but also separates the heavier
milk fat from the lighter milk to produce both cream and skim milk. Some
processing plants use a standardizer-clarifier, which regulates the amount of
milk fat content in the milk by removing only the excess fat. The excess milk
fat is drawn off and processed into cream.
During
the processing of cream, there are some physical and biochemical changes
occured. Basically, milk contains many natural enzymes such as lipases,
oxidases, proteases and amylases which function as the biological catalysts
capable of producing chemical changes in organic substances. During
pasteurization, the enzymes in milk such as β-lactoglobulin will be
denatured and inactivated as the heat treatment. Besides, milk may be
coagulated by rennin or other enzymes, usually in conjunction with heat. When
milk is pasteurized and continuously refrigerated for two or three weeks before
separation process, it may eventually coagulate or spoil owing to the action of
psychrophilic or proteolytic organisms that are normally present or result from
post pasteurization contamination. Other than that, when the temperature and
the duration of pasteurization of milk are not set correctly will lead to
denaturation of protein in the cream produce. Furthermore, cream is very
susceptible to developing off-flavours. Some flavours, given such names as
“feed,” “barny,” or “unclean,” are absorbed from the food ingested by the cow
and from the odours in its surroundings. Others develop through microbial
action due to growth of bacteria in large numbers. Chemical changes can also
take place through enzyme action, contact with metals (such as copper), or
exposure to sunlight or strong fluorescent light. Besides, the colour of cream
changed from white to pale yellow during pasteurization process. During
separation, the oil in water emulsion of cream can be stabilized.
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