Characterization of a novel Taylor-Couette ultraviolet reactor for
non-thermal pasteurization of milk
Disinfection of milk by a novel UV reactor based on TaylorCouette vortex flow was evaluated as part of an effort to develop nonthermal processing technology for pasteurizing milk. By using Bacillus
subtilis endospores and bacteriophages as model microbes, it was
demonstrated that level of inactivation was dependent on the flow-pattern
of the milk passing through the reactor. The transition from laminar wavy
vortices(WV) to laminar modulated wavy vortices (MWV) achieved 4.5
log pfu reduction of Salmonella phages. Turbulent wavy vortices (TWV)
achieved 5.8 log reduction of bacillus subtilis endospores PS 346. The
stability of the generated Taylor-Couette vortices could be enhanced by
increasing the viscosity of the milk although this did not translate to
higher levels of microbial UV inactivation. Tryptophan and cystiene
provided protection to the microbes by absorbing UV photons. Although
the actual UV dose required to inactive Escherichia coli in milk was
comparable to the efficacy of other reactors, only a 1 log cfu reduction in
numbers could be achieved under optimal operating conditions. The
results from this study would suggest to re-design Taylor Couette reactor
to decrease that force of the flow rate and to generate stable vortices that
could support efficient mixing, hence higher level of microbial
inactivation.