Crucial role of remaining lactose in whey protein isolate powders during storage

- Protein lactosylation favoured protein aggregation in the dry state.
- Small variation of lactose content affects the ageing-induced changes of WPI powder.
- The control of lactose content in a WPI powder is crucial for storage stability.
- Storage-induced changes are greatly limited for a WPI powder with 0.1 w/w % lactose.

This study aimed to investigate the effect of lactose on the ageing-induced structural changes through a varying lactose content in whey protein powders. In this scope, four powders differing in their lactose content (0.1-16 w/w %) were stored at 40 °C and 60 °C for up to 3 months and sampled periodically. A small variation in lactose content of WPI powders was found to affect the level of structural and functional changes during powders ageing. At a higher lactose content (2.6 w/w %), proteins were more rapidly lactosylated and aggregated, with a higher rate than the control WPI powder; whereas at a lower content (0.1 w/w %) the rate of lactosylation and aggregation was considerably limited. These results highlighted the great contribution of the Maillard reaction during ageing of WPI powders. Reducing lactose content in the WPI powders is a promising way to extend their stability among storage.