Dairy Processing - November/December 2023 - 65

EQUIPMENT
Reverse osmosis provides
the tightest membrane available
in liquid separation, meaning
only water can pass through
the membrane, while all
other material is removed.
Nanofiltration removes a range
of minerals from liquid, allowing
only the liquid and specific
monovalent ions to pass through
the membrane. Ultrafiltration
separates skim milk into two
different streams, which allows
water, salts, lactose and acids to
pass through the membrane in
either direction while keeping and
concentrating proteins and fat.
Finally, microfiltration uses the
most open kind of membrane. It's
used to remove spores, bacteria
and fat globules from the liquid
and also for fractionation of
skim milk.
A custom-designed
filtration plant from
GEA, built to utilize
a range of filtration
applications.
Each of these processes
have different applications.
Ultrafiltration assists with protein
concentration and protein
standardization and boosts the
yield of white cheese and other
fermented products. Alternatively,
reverse osmosis allows processors
to efficiently reclaim water from
milk or whey before the evaporation stage, increase total
solid content through solids recovery or reduce the volume
of milk or whey. Reverse osmosis is also beneficial for its
sustainability, as it is beneficial in waste recovery.
Nanofiltration has specific uses, such as reducing
the mineral content and volume of whey and permeate,
concentrating lactose prior to crystallization or evaporation,
and producing quality lactose-free milk products.
Of the four processes, microfiltration is considered an
emerging processing technology that extends milk's shelf life
by using semipermeable membranes to keep out undesirable
microbes. Microfiltration helps improve the quality of milk,
whey powder and high-value dairy ingredients to produce
extended shelf life (ESL) milk, cheese milk and lactosereduced
or lactose-free milk.
Microfiltration also offers an alternative to
At-machine display to monitor filtration systems.
DAIRYPROCESSING.COM | NOV-DEC 2023 65
high-temperature ultra-pasteurization, which is another
method for extending the shelf life of milk.
PROPER CLEANING
Commercial milk filtration systems are able to run
continuously. Although today's filtration systems are highly
effective, they still require oversight to ensure they are
working at peak performance.
It's important that filtration system are cleaned thoroughly
and regularly to remove trapped debris and maintain sanitary
filtering conditions. Microfiltration, specifically, can introduce
bacteria that are resistant to pasteurization into fluid milk if
equipment is not cleaned properly, as was recently discovered
by researchers at Cornell University, Ithaca, NY.
In their research, the Cornell researchers examined
whole milk and skim milk processed using microfiltration,
pasteurization and then refrigerated at 38 degrees Fahrenheit,
43 degrees and 50 degrees for 63 days. Analysis showed
significant differences in bacterial concentrations for the
microfiltered milk held at different temperatures, but no
difference in milk with different fat levels. The results were
published in the Journal of Dairy Science in September.
In addition to proper cleaning, membrane fouling can
also be a concern. When deposited materials build up on the
membrane surface, filtration efficiency is reduced. In dairy,
common materials that build up along the membranes are
lactose, whey solids and mineral salts. Membrane fouling
can be found in both ultrafiltration and microfiltration and
can impact the quality of product by reducing pressure in
the filter.
For filtration systems to be most effective, they need
regular maintenance. Without it, systems could see a
significant drop in pressure over time. This not only reduces
the efficacy of the system, it also requires more energy. This
could lead to longer system shutdowns, resulting in a drop
in productivity.
GEA
http://www.DAIRYPROCESSING.COM
Dairy Processing - November/December 2023

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