Formation mechanism of thermomechanically stabilized whey protein-pectin complexes: Contribution of pectin and protein to complex structure

Abstract

Whey protein pectin complexes (WPPC) processed at the technical scale in the particle size range of 1–40 µm have the potential to be utilized as fat replacers. WPPC are formed via thermomechanical treatment at a specific pH level, which allows for the interaction between the biopolymers. In the pH range of 4.75 to 5.75, whey protein and pectin form coacervates or soluble complexes. The diverse interactions result in WPPC with particle sizes d_3.2 between 0.2 and 40 µm after thermomechanical treatment on a scraped surface heat exchanger. The pectin contributes to the WPPC structure in three distinct forms, dependent on the pH, as determined via mass balance. The pectin is present in three forms: (i) 50–80 % free, (ii) 15–30 % electrostatically stabilized, and (iii) 5–10 % incorporated pectin. Approximately 20 % of the whey protein with particle sizes below 1 µm was electrostatically stabilized. The addition of pectin-degrading enzymes resulted in a multimodal particle size distribution, indicating that pectin is connecting larger aggregate structures. Based on the core-shell model, a revised model for the WPPC formation at the technical scale on a scraped surface heat exchanger is proposed.