A dairy company contacted Tetra Pak after encountering difficulties caused by creaming in its 18% fat UHT cream. The dairy, whose products sell in 13,000 food stores in Europe, had just installed a new line complete with a new homogenizer. But 12 days after packing, a solid cream plug was visible in the top of the packages.
The homogenizer had been installed with the same running conditions as the old one. Nobody had considered that it was more efficient than the old machine and that this might lead to creaming.
“Cream is a difficult product that is prone to over-homogenization, and customers quite often come to us in order to get support,” says Tetra Pak food technologist Pavlos Kouroutsidis.
“A customer that is used to homogenizing milk might think that a little extra pressure is just beneficial for product quality, but for cream it is the opposite.”
This is because products with a high fat content, like cream, contain limited natural membrane to cover the newly created free surface area. If cream is homogenized at excessive pressures, the end result will be fat aggregation and free fat leaking out, causing premature creaming and eventually cream plug formation.
The dairy, which risked losing its contract with a large supermarket chain due to the cream plugs, called out Tetra Pak to troubleshoot the process. Two main causes quickly emerged.
One was over-homogenization. Here the solution was to find a new sweet spot for optimum product quality and stability by lowering the pressure from 135 to 110 bar.
Kouroutsidis explains: “In these cases it’s very important to measure the fat globule size distribution directly after homogenization, which is something Tetra Pak offers free of charge.”
In addition, the counter pressure was too high, with a 10 bar back pressure after stage one even though stage two was set to 0 bar.
Correlating this line pressure with extra shear results in too much shearing on the fat globules. This can damage them after homogenization, causing free fat dispersion and more agglomeration in the package.
Tetra Pak therefore recommended the removal of stage two.
Together the actions improved product stability, with no visual creaming after 12 days – and the customer was able to resume deliveries with minimal disruption and no long-term loss of business.