Stability and molecular interactions in cold-induced hazelnut protein-chlorogenic acid gel

Phenols have been demonstrated to enhance protein gelation but their stability is often compromised in heat-induced gels. This has prompted the development of cold-induced gels. The objective of this study was to enhance the gel properties of hazelnut isolate protein (HPI) through the incorporation of transglutaminase (TGase), glucono-δ-lactone (GDL), and chlorogenic acid (CA). It also aimed to investigate the biofunctional role of CA.

In comparison with heat-induced gels, cold-induced gels exhibited a higher prevalence of disulfide (25.51%) and hydrogen bonds (35.88%). Transglutaminyl transferase also facilitated the formation of ε-(γ-glutamyl)lysine interpeptide bonds, enhancing the gel properties of cold-induced gels significantly. The gel strength increased by about 3.9 times, the water-holding capacity increased by approximately 2.8 times, and storage modulus increased by about 2.5 times. The resulting gels were more compact and stable, which reduced protein digestibility. It was observed that the interaction between HPI and CA in cold-induced gels was significantly enhanced, thereby enabling CA to improve the gelation capability of HPI more effectively, particularly in TGase-induced formulations. Chlorogenic acid displayed strong thermal stability in cold-induced gels; findings from in vitro digestion simulation also indicated that the CA present in HPI exhibited effective sustained release properties within the gastrointestinal tract.

The present study offers novel approaches to the utilization of HPI in food applications and presents innovative strategies for developing HPI gel foods characterized by enhanced gel properties and rich active compound content. © 2025 Society of Chemical Industry.