Abstract:
Modification of heat transfer surfaces to minimize the
effects of fouling in the dairy industry is investigated in the
current study. Special attention is given to the initial
deposition mechanisms, which are believed to determine the
fouling and cleaning performance of the surfaces studied.
Preliminary results have been obtained for stainless steel
and titanium nitride (TiN) surfaces fouled for 3 minutes
with whey protein and calcium phosphate. Scanning
Electron Microscopy (SEM) images of air-dried, whey
protein fouled samples showed both TiN and stainless steel
surfaces were covered with a thin layer of deposit,
following the topography of the heating surface. X-ray
Photoelectron Spectroscopy (XPS) spectra for the TiN
surfaces fouled with whey protein showed carbon and
oxygen as the main components present. XPS analysis of
the stainless steel surfaces is currently underway. Calcium
phosphate fouling on stainless steel and TiN surfaces
resulted in formation of a crystal matrix on some parts of
the surface, while other parts appeared to have no
deposition. X-ray microanalysis of these crystals yielded a
Ca/P ratio of 1.4. X-ray Diffraction (XRD) analysis is
being undertaken to better identify the phases formed. Also
in consideration is SEM analysis under cryogenic
conditions, and XPS analysis of freeze-dried samples to
eliminate changes taking place during air-drying. Future
experiments will involve fouling of diamond-like carbon
(DLC) surfaces. It is expected that altering the fouling
behavior and therefore deposit adhesion, may influence
cleaning performance, which will be tested in cleaning runs.
At a later stage, similar investigations will be performed
using milk solutions to study the combined effect of
proteins and minerals.
