Processing of phosphocasein dispersions by dynamic high pressure: Effects on the dispersion physico-chemical characteristics and the binding of α-tocopherol acetate to casein micelles

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Dispersions of phosphocaseins (PCs) containing (w/w) 2.5% proteins at pH 6.7 were processed using a ~ 15 L/h homogeniser with a high-pressure valve immediately followed by cooling devices. The effect of dynamic high-pressure (or ultra-high pressure homogenisation, UHPH) at 100–300 MPa and two initial temperatures (Tin = 14 °C or 34 °C) was investigated on (i) casein micelle size distributions, (ii) the turbidity and viscosity of PC dispersions, and (iii) the binding efficiency of α-tocopherol acetate (α-TA) to casein micelles (α-TA:PC molar ratio ~ 1:1). A significant and gradual decrease of casein micelle sizes was observed after UHPH up to 300 MPa at Tin = 14 °C. The decrease in micelle sizes was less extensive after UHPH at Tin = 34 °C. Notably, the binding efficiency of α-TA significantly (p < 0.001) increased after processing, suggesting combined effects of temperature and dynamic high-pressure. Industrial operators in food, cosmetic and pharmaceutical areas are currently interested in developing encapsulating systems to delivery bioactive compounds, generally hydrophobic, unstable and sensitive to light, temperature or/and oxygen. The present study suggests that processing of casein micelle dispersions by dynamic high pressure at ≥ 200 MPa could modify casein micelle organisation with an enhancement of the binding of hydrophobic ligand (α-tocopherol acetate) to the newly UHPH-formed neo-micelles. Here is a potential application for UHPH, a physical technology that offers the added advantage of notably reducing the microbial load of processed samples.