Lower ultrafiltration temperature improves membrane performance and emulsifying properties of milk protein concentrates

Abstract

Functionality of milk protein concentrates (MPC) can be influenced by process modifications that influence mineral partition and particle size. This work investigated the effect of processing temperature on functionality of MPC obtained by ultrafiltration (UF) of skim milk using polyethersulfone membrane. Skim milk was concentrated five times by UF operated at 15, 30 or 50 °C. Results indicated that the casein micelle size remained unchanged during UF at 15 and 30 °C, and decreased significantly from 92.7 to 83.6 nm at 50 °C, along with the reduction in net negative charge. Operating temperature also influenced the extent of calcium removal in permeate (24.9–16.6%) with minimal changes in protein structure. UF at high temperature (50 °C) reduced membrane performance due to fouling. Proteins and calcium were identified as the major foulants. Overall, operating UF at 15 °C gave better membrane performance as evidenced by better flux, less membrane fouling and shorter time required to reach a 5× concentration, as compared to that operated at 30 or 50 °C. Moreover, no changes in heat stability and solubility of the MPCs were observed while the emulsifying properties were better for MPC obtained at 15 °C.