Preserving nutrients in milk via UHT

Preserving nutrients in milk via UHT

Made Astawan, Jakarta, astawan@indo.net.id

Milk is the best food for land mammals because it
contains an almost perfect composition of nutrients, such as
water, protein, carbohydrates, minerals, fat, along with
sufficient amounts of vitamins A, C and D.

Today, unlike decades ago, it is seldom that milk is
consumed fresh, straight from a cow. Generally, in liquid form,
it is processed either via UHT or pasteurization treatment or is
made into a powder form.

Pasteurization basically means heating milk to between 63
and 720 C for about 15 seconds to kill the pathogen bacteria.
Pasteurized milk has to be refrigerated at around 50 to 70 C and
this milk is good for only about 14 days.

Powdered milk, meanwhile, is derived from fresh milk
combined with or without other ingredients, such as fat or
protein, which is dried using the spray or roller dryer method.

This type of long-life milk can be kept for a maximum of two
years if stored correctly. There are three categories of powdered
milk: Full cream milk powder, composite skim milk powder and skim
milk powder.

Finally, there is Ultra High Temperature (UHT) milk. UHT
heats milk at between 1350 and 1450 C for about two to five
seconds to kill all of the microorganisms while at the same time
not disrupting the nutritional ingredients of the milk, including
the color, aroma and taste.

Factors that contribute to the quality of UHT milk
include the cow feed, the composition of the raw milk, and the
milking and packaging process that must be hygienic.

At the factory, processing is conducted using highly
sophisticated sterile tools to minimize milk's contact with
bacteria. Multi-layer packaging is used in the milk cartons to
prevent any bacteria and damaging ultra violet rays from entering
the package.

These safeguards ensure the freshness and quality of UHT
milk as required by international hygienic standards. Besides
being free from bacteria, the UHT process makes it possible for
the milk to be stored for a long time without preservatives and
with no refrigeration, for up to 10 months after production,
which is much longer than pasteurized milk. Once the pack is
opened however, the milk must be stored in a refrigerator for
further use.

Some tips on checking UHT Milk

UHT Milk in cartons can go bad if there is a leak in the
package. An easy way to check this is to see if the pack is
bloated or 'puffed'. This is the result of microbes entering the
damaged pack, fermenting the milk, causing CO2 to be released,
thus causing the pack to bloat.

Avoid consuming UHT milk which appears thick of lumpy -
bacteria which has infected the milk causes coagulation leading
to a break-up of proteins and a decrease of organic acid.

Damage to the product can of course be easily detected by its
smell and taste. One precaution to be borne in mind is storing
UHT milk in very high temperature - above 50 degree centigrade -
as this causes the milk to go sour quickly.

--- the writer is a senior lecturer on Food and Nutrition at the
Bogor Farming Institute (IPB)