Surface modifications to increase dairy production run length : a thesis presented in partial fulfilment of the requirements for the degree of Master of Chemical Engineering at Massey University, [Manawatū], New Zealand.
Fouling is the build-up of undesired deposits on surfaces. In the dairy industry, fouling
is mainly seen in heat exchangers where dairy fluid is heated or concentrated. It is one
of the primary reasons for restricted run length, causing financial losses from downtime,
the use of cleaning chemicals and reduced product quality.
Fouling is a complex process and is due to number of factors including the properties of
the heat transfer surface. A silica based coating is known to alter the surface properties.
This study was carried out to investigate the effect of a silica based coating on fouling
by whole milk in a falling film evaporator.
Seven independent trials were conducted. In each trial, a control run was carried out
followed by a full cleaning of the equipment and then either another control run or a
coating run with pasteurized milk from the same batch. There was a six hour interval
between the start of the control run and start of the coating run. Since prolonged milk
storage may have some effect on fouling rate, control-control runs were carried out to
see the effect of prolonged storage. The results obtained from control-control runs were
used in analysing the effect of the coating on fouling rate.
All coating trials showed consistently lower fouling rate as compared with
corresponding control trials. The Pearson’s correlation coefficient of 0.83 showed a
strong effect of coating on the fouling rate. Further, a regression analysis gave a p-value
of 0.033, indicating that, at the 96.7% level of confidence, coating reduced the fouling
rate. The extent of reduction in fouling rate varied from trial to trial. It was estimated
that the coating had the potential to increase the run length by a maximum of 34% under
the conditions these experiments were carried out.