The impact of κ-carrageenan on the pea protein gelation by high pressure processing and the gelling mechanisms study

The transition toward sustainable and health-conscious diets has intensified plant-based proteins, particularly pea protein. This research explored the gelation mechanisms of pea protein with kappa-carrageenan by high-pressure processing (HPP) as an alternative to traditional thermal methods. Suspensions containing 15% pea protein with 0.1-1% kappa-carrageenan were subjected to HPP at 100-600 MPa for 5-30 min. Increasing kappa-carrageenan concentration reduced the pressure required to obtain good gels, rendering HPP more energy efficient. Pea protein gels with 1% kappa-carrageenan at 600 MPa demonstrated a 27-fold increase in compressive strength compared to 15% pea protein alone by HPP and over 5 times the strength of heat-induced counterparts. Gel textures could be tailored by modulating HPP conditions and kappa-carrageenan concentrations. Fourier transform infrared spectroscopy, confocal laser scanning microscopy, and scanning electron microscopy characterized protein unfolding, phase separation, and network formation to study the gelation mechanisms. Results revealed that HPP induced protein tertiary structure unfolding, facilitating phase separation and uniform submicron kappa-carrageenan particle distribution in the protein matrix. This, along with a more compact protein network induced by HPP, enhanced gel strength, compensating for limited cysteine in pea protein for disulfide bonds. Higher pressures intensified protein unfolding and aggregation, with kappa-carrageenan particles evenly distributing into smaller particles, further strengthening gel structures. Conversely, heating-induced gelation caused more random protein aggregation, leading to coarser and weaker gel networks. This research highlights HPP's effectiveness over traditional heating methods in preparing strong pea protein gels with minimal kappa-carrageenan and provides preliminary insights into tailoring HPP and kappa-carrageenan for desirable gel textures.