Effect of low-temperature dissociation time on the separation of β-casein by hollow fiber membranes: Purity, structural and functional characterization

This investigation focuses on examining an integrated approach employing hollow fiber membrane filtration combined with dialysis washing filtration. By systematically varying the low-temperature dissociation time following the addition of deionized water to dilute casein obtained through 50 °C microfiltration membrane separation, the β-casein (β-CN) to whey protein ratio in the permeate samples was modulated. Comparative analyses were conducted to evaluate β-CN purity, structural properties, and physicochemical-functional attributes across samples prepared with different dissociation periods. The optimal β-CN purity (70.96 %) was achieved following 36 h of dissociation treatment. The high-purity β-CN preparations exhibited superior functional performance, demonstrating enhanced foaming capacity and emulsification properties. Specifically, the emulsion activity index reached 20 m 2 /g and 70 % emulsion stability, whereas foaming capacity attained 113.70 % and 49.25 % foam stability. Throughout the low-temperature dissociation process, the particle size of the β-CN increased gradually, and the average particle size peaked at 86.67 nm at 48 h. This investigation seeks to optimize the β-CN isolation process while establishing technical parameters for industrial-scale production of β-CN across multiple purity grades. Meanwhile, a comprehensive evaluation was conducted to systematically characterize the physicochemical properties and functional performance of β-CN preparations with varying purity levels.