Pre-treatment of whey protein concentrate using calcium sequestering salts and high-pressure homogenisation to modify component partitioning during microfiltration

Whey protein concentrate (WPC) undergoes microfiltration (MF) to produce whey protein isolate (WPI), generating a lower value MF retentate as a co-product. Higher-than-expected protein retention in the retentate, attributed to protein aggregation, has been shown to limit WPI yield. Strategies to reverse or reduce aggregation would be expected to increase protein transmission during MF. This study investigated the effects of pre-treating WPC with 5 mM trisodium citrate (TSC), a calcium-binding salt and high-pressure homogenisation (HPH) at 650 bar, both individually and in combination, on protein transmission during MF. A WPC solution (2.4% protein) was pre-treated with TSC, HPH, TSC followed by HPH (TSC + HPH), or HPH followed by TSC (HPH + TSC). Microfiltration was performed using a 1000 kDa polyethersulfone membrane. Processing time, component partitioning and chemical composition in feed, retentate and permeate were analysed. Protein profiles were assessed using SDS-PAGE and RP-HPLC, in addition to whey protein denaturation. Data were obtained from three independent trials, with all analyses conducted in triplicate. Treatment significantly reduced processing time and increased protein permeation (P < 0.05). Processing time decreased by 6.4–11.0%, with TSC and HPH having the strongest effects. Compared with the control, protein retention in MF retentate from pre-treated samples decreased by 7.5–11.5%, with HPH + TSC showing the greatest effect, while permeate protein content increased by 5.45–9.64% (P < 0.05). SDS-PAGE confirmed lower levels of protein aggregation, particularly in HPH + TSC, coinciding with the lowest sedimented protein level (43.4%). Trisodium citrate pre-treated samples showed significantly lower (P < 0.05) calcium and magnesium levels, providing evidence that cations are involved in mediating protein aggregation. The results indicate that WPC treatment can modify protein permeation, improving the yield of WPI while also generating an MF retentate further enriched in polar lipids, supporting more sustainable dairy processing.