Cleaning is an important unit operation
in food processing for
removal of fouling deposits to ensure not only optimal operability
of process equipment but also product safety and quality. In modern
large-scale processing plants, cleaning is commonly achieved by cleaning-in-place
(CIP) operation, which, however, consumes large amounts of water,
energy, and chemicals. Because of their unique interfacial physicochemical
properties, this study incorporated microbubbles (MBs) into water
as a novel cleaning agent for the prerinse step of CIP operation,
aiming to enhance its cleaning efficiency. MB-infused water (MB water)
was introduced into bench-top spinning disc apparatus to clean milk
deposits fouled on a stainless-steel surface. A computational fluid
dynamics model was built to predict the contact frequency of MBs with
deposits under swirl flow and further identify the cleaning conditions
that provided maximum MB–deposit contact. MB–deposit
attachment was visualized by microscopic imaging. A series of cleaning
experiments were conducted at 25–55 °C and a Reynolds
number (Re) of 3380–5403, and incorporation of MBs into water
with 1431 bubbles/mL proved effective in increasing the cleaning efficiency
at 25 °C and a Re of 4392 and 5403 by 27 and 31%, respectively.
However, increasing water temperature and decreasing Re and bubble
density were found to make the effect of MBs on cleaning insignificant.
The findings of this study can serve as the groundwork for developing
an MB-assisted CIP system to improve the environmental performance
of food manufacturing.
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