Effect of heat treatment and pH on the efficiency of micro-diafiltration for the separation of native fat globules from cream in butter production

A buttermilk that is rich in functional components from milk fat globule membrane (MFGM) is of great interest to industry and consumers. However, isolation of such components is challenging because of the complexes they form with proteins. In this contribution, we describe a process, the ideal butter process, for separating milk fat globules and proteins in cream prior butter making to enhance MFGM deployment. First, raw and pasteurized bovine creams were micro-diafiltered with water using a tubular ceramic membrane. A 1.4 µm pore size was selected for the membrane to separate proteins and fat globules. Two trans-membrane pressures (0.4 and 0.6 bar) were used to determine the permeate flux and protein mass flow needed in the evaluation of the filtration efficiency. Compared to pasteurized cream, raw cream led to shorter filtration time. Pasteurization induced protein adsorption on the surface of fat globules, thus decreasing separation efficiency. Furthermore, pH was found to fluctuate during the diafiltration, owing to the decrease of buffering capacity by cream in the course of protein and mineral permeation and subsequent equilibration process of colloidal phosphates with serum phase. A relatively higher filtration pH increased filtration efficiency and protected fat globules from coalescence, given the increased osmotic pressure (electrostatic repulsion). Overall, the protein content in cream decreased by ~ 80% upon microfiltration. Despite the reduced protein concentration in the filtered creams, no negative effects were observed during churning into butter, which resulted in low-protein content buttermilk (~ 80% protein reduction). Hence, the ideal butter process can be used to facilitate MFGM isolation and better handling of process streams.