Chemical modification of grass pea (Lathyrus sativus L.) protein through phosphorylation and deamidation methods: A comparative study on structural and techno-functional properties

The restricted techno-functional characteristics of grass pea protein isolate (GPPI) limit its use in food systems. This research investigates how treating GPPI with phosphorylation (2% sodium trimetaphosphate, pH 11.5) and deamidation (0.13 M acetic acid, 121 °C, 10 min) affects its structure and techno-functional properties. FTIR, XRD, fluorescence spectroscopy, and FESEM analyses confirmed successful modifications, revealing changes such as altered hydrogen bonding and increased surface exposure to functional groups. The analysis of the secondary structure using circular dichroism (CD) spectroscopy showed that the amounts of α-helix and β-sheet decreased, while the amounts of β-turn and random coil increased in both phosphorylated (PGPP) and deamidated (DGPP) samples, suggesting structural unfolding. The zeta potential significantly increased in PGPP (31.65 ± 0.68 mV) and DGPP (37.34 ± 0.89 mV) compared to GPPI (25.78 ± 0.53 mV). Notable improvements were observed in the techno-functional properties of PGPP and DGPP. DGPP exhibited the highest foaming capacity (92 ± 0.86%), foaming stability (73.33 ± 1.24%), emulsifying activity index (92 ± 0.81 m²/g), and emulsifying stability index (74 ± 2.16 min). These findings highlight phosphorylation and deamidation as particularly effective approaches for improving GPPI techno-functional properties and expanding its potential applications in food formulations.