Influence of lactose on the rheological properties of reconstituted casein micelles concentrates

Abstract

Despite increasing demand for lactose-reduced and lactose-free dairy products, little is known about the influence of lactose on the flow behaviour of casein micelles. Therefore, we investigated the rheological influence of lactose on reconstituted casein micelles over a wide concentration range of casein and lactose (wCasein = 2.9–13.4%, w/w; wLactose = 0–15%, w/w). Analysis of the relative viscosity curves with the Ostwald-de Waele model shows that the flow consistency index and the flow behaviour index as well as thixotropic effects depend on the lactose-casein mass ratio. In the range of small ratios, the relative viscosity hardly changes with increasing lactose, while at a mass ratio close to 1, the shear thinning effect changes strongly leading to maximum values of flow consistency and flow behaviour index n. With excess lactose, the shear thinning effect decreases again, which we explain with a decreasing voluminosity of the casein micelles.