Quercetin-associated structural rearrangement and functional modulation of silkworm Pupa protein: Comparison of covalent and non-covalent interactions

Abstract

This study investigated the effects of covalent and non-covalent quercetin interactions at concentrations of 10–160 μmol/g protein on the structure, interfacial properties, and antioxidant performance of silkworm pupa protein (SPP). The results showed that quercetin incorporation substantially altered the functional behavior of SPP, leading to maximum increases of 115.4% in foaming capacity and 32.7% in emulsifying activity index compared with the corresponding controls. A moderate quercetin level (Q40) provided the most favorable interfacial stability in the covalent system, with the ESI increasing from 32 to 46 min, whereas excessive quercetin reduced foam and emulsion stability. Quercetin incorporation also markedly enhanced the antioxidant capacity of SPP, with ABTS radical-scavenging activity increasing by 4.35-fold and 4.08-fold in the covalent and non-covalent SPP-Q systems at Q160, respectively. FTIR and SEM observations suggested that the presence of quercetin altered the structural organization of SPP at both the molecular and microscopic levels, which contributed to the improved functional performance, with more pronounced changes observed under the covalent preparation conditions. Overall, the results demonstrate that quercetin binding can modulate the structural and functional properties of SPP, while the extent of these changes depends on both the binding mode and quercetin concentration.