Analysis of the influence of different factors on the quality of a curd-whey mixture during pumping

- A centrifugal pump can replace a rotary lobe pump for pumping curd-whey mixtures without quality losses.
- Larger, softer curds have to be pumped at low volume flows.
- Comminution is lower and independent of volume flow for pumping smaller, harder curd.
- Low amounts of curd fines are generated by pumping of curd-whey mixtures.

High stresses lead to comminutions of curd during pumping of curd-whey mixtures. There are three factors that could have an effect on this comminution, which were tested in this study. Two different types of curd were produced and tested, and each had different dimensions and textural properties. The effects of volume flows were tested in accordance with the volume flows used in the cheese industry (3.2-4.7 m3 h−1). Two types of pumps - a rotary lobe pump and a centrifugal pump with a vortex-type impeller - are tested. The particle size distribution of the curd, the characteristic parameters of the distribution and the concentration of curd fines were measured and calculated to evaluate the pumping process.With an increasing volume flow and, in particular, the pumping of larger, semi-hard curd, the median of the particle size distribution is reduced by 0.61 mm. The comminution of small, hard curd was low (<0.20 mm) and independent of the tested volume flows. No differences between pumps regarding all of the measured parameters were observed. Due to the small amount of curd fines uprising during pumping (<0.28 g l−1), no factor shows a significant influence on the evaluated parameters.