Structure-property relationships in agar-soy protein emulsion gels: effects of oil type and droplet size

This study investigated agar-soy protein isolate emulsion gels, focusing on the effects of oil type and droplet size on their structural organization and physicochemical properties. Emulsion gels were prepared using canola oil, rice bran oil, or eugenol in micro-sized and nano-sized forms, and their properties were evaluated in comparison with pork fat. Nano-sized emulsions produced finer, more homogeneous networks, while micro-sized emulsions showed higher mechanical strength. Rice bran oil nano-sized gels exhibited balanced strength, high water-holding capacity, and low syneresis, indicating enhanced network compactness and stability. These effects may be associated with differences in interfacial characteristics and droplet-matrix interactions depending on oil type. Eugenol-based gels showed structure-dependent behavior, where micro-sized gels enhanced hardness and freeze-thaw resistance, whereas nano-sized gels exhibited reduced structural integrity. Thermal analysis confirmed the absence of triglyceride melting transitions, although rice bran oil nano-sized gels showed the highest transition enthalpy. FTIR analysis suggested size-dependent differences in molecular organization within the gel network, reflecting variations in interfacial structuring and lipid domain distribution. These findings highlight the potential of combining droplet size control with oil phase characteristics to design structured emulsion gel systems for plant-based applications.