Fabrication of meat-mimicking emulsion gels using oligochitosan-decorated hemoglobin and gelatin as a fat replacer.

Hemoglobin (Hb) can be employed to adjust the color of emulsion gels, thereby compensating for deficiencies in appearance and flavor when used as an animal fat substitute. However, the inherent instability of heme restricts its broader application as a food ingredient. In this study, transglutaminase-catalyzed glycosylation was applied to prepare oligochitosan-modified Hb complexes (OMHC), which were incorporated into emulsion gels to produce meat-colored oil-in-water systems. Glycosylation between oligochitosan and Hb was confirmed by polyacrylamide gel electrophoresis and validated through free amino group analysis. Increasing the oligochitosan-to-Hb ratio from 2:1 to 3:1 resulted in the highest grafting degree, reaching 41.82%. Compared with untreated Hb, OMHC significantly improved the emulsifying capacity, thermal stability, and pH stability of the emulsion gels. The effects of OMHC concentration (0, 0.3, 0.6, 1.2, and 1.8 wt%) were systematically investigated. OMHC addition increased the gel's a* value from -0.79 to 2.68 and b* value from 5.85 to 18.02, producing a natural yellowish-red hue. Rheological analysis revealed that higher OMHC concentrations elevated gelation onset temperature and enhanced gel strength, as indicated by an increase in G' at 20 °C. Fourier transform infrared spectroscopy confirmed hydrogen bonding between OMHC and gelatin, while microscopic observations demonstrated the formation of a uniform, dense gel network. These findings highlight the potential of OMHC to stabilize Hb and advance the application of meat-colored emulsion gels as saturated fat replacers in both processed meat products and plant-based alternatives.