Demineralisation and recovery of whey proteins from commercial full-fat salty Cheddar whey using size-exclusion chromatography

Extraction of the whey proteins from salty whey would add value to milk waste streams. Size-exclusion chromatography (SEC) is a non-invasive method to screen proteins, based on molecular size. Here, compositional analysis of commercial salty whey showed total solids (TS), ash, and protein contents were 12.3 ± 0.1 %, 8.92 ± 0.01 %, and 0.9 ± 0.1 %, respectively. Prior to SEC, salty whey pH (5.5) was adjusted to pH 4.6, 7.0 and 9.0. This adjustment was associated with protein losses through aggregation. Following SEC, a substantial amount of whey protein (82–100 %) and salt (>99 %) was recovered/removed. SEC samples exhibited similar ranges of conductivity (1.8 × 102 – 2.4 × 102 μS.cm−1) and NaCl (0.005–0.009 %). SEC protein and salt fractions were characterised for particle size, and zeta potential, and subjected to sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS-PAGE) and Fourier transform infrared (FTIR) spectroscopy. Generally, demineralisation resulted in decreased conductivity and particle size, whereas zeta potential was pH-dependent. FTIR analysis showed modifications and/or rearrangement of whey protein secondary structure after SEC. This work suggests that SEC can be used to demineralise and recover WPs from salty whey.