Fractionation of Milk Fat Globule Membranes in butter processing

Bovine milk contains components that are significant to human nutrition and most beneficial if present in infant formulas. Such components are mainly associated with the biological membrane surrounding the milk fat globules, the Milk Fat Globule Membrane (MFGM). MFGM, one of the most complex fractions in milk, contains proteins and polar lipids that form a trilayer structure. Compared to its native form, MFGM structure is disrupted during milk processing, leading to the release of valuable components and affecting associated structural and functional properties. Therefore, novel methods are demanded for the isolation, fractionation and deployment of MFGM. In this thesis, we apply concepts relevant to colloid and surface chemistry to establish new processing methods aimed to maximizing the nutritional and technological value of MFGM components. We propose cream microfiltration prior to the traditional buttermaking to separate fat globules from other dairy constituents, such as proteins, lactose and minerals. Filtered cream fractions were churned, upon which phase inversion facilitated the production of butter (termed here as "ideal butter") and buttermilk, the latter of which was enriched with MFGM fragments but depleted of other dairy components. The microfiltration resulted in a protein separation efficiency of 93% and the filtered cream was found suitable for buttermaking, without affecting negatively the process. MFGM damage was observed under intense processing conditions, leading to losses in polar lipids (up to 20%). Moreover, the pH drastically effected filtration performance given its roles in modulating the electrostatic interactions and in fouling the filtration membrane. The optimisation of the process in relation to shearing forces and other factors, was found critical in defining the structure and possible losses of fat globules and MFGM. MFGM-rich ideal buttermilk powder was surface-active and capable of forming relatively stable food emulsions. Such material is proposed for the formulation of nutraceutical and infant formulas.