Heat-induced protein aggregation influences protein partitioning during microfiltration of whey in the production of whey protein isolate

This study was designed to investigate the effects of heat treatment and selective thiol blocking using N-ethylmaleimide (NEM) on protein partitioning during microfiltration (MF) of whey. Clarified sweet whey was subjected to five treatments: untreated control (CTRL), pH-adjusted (CTRL pH ), pH+NEM (T NEM ), pH+heat (T Heat ), and pH+NEM+heat (T NEM+Heat ). Significant differences (P<0.05) were observed in protein permeation and retention. Compared to CTRL, protein content in the permeate was 22% and 16% lower in T Heat and T NEM+Heat , respectively. Conversely, protein retention in the retentate was 22% and 16% higher in the same treatments. These results confirm that disulphide bond-mediated aggregation reduces protein permeation during MF. The findings provide new insight into how thiol reactivity and thermal treatment influence protein transmission. This scientific insight supports the development of targeted strategies (e.g., reduced- or non-thermal processing) to increase protein yield and processing sustainability in the production of value-added whey streams and whey protein ingredients.