Assessment of <i>Gracilaria fisheri</i> agar-based emulsion gel as a functional fat replacer in fish sausages

Seaweeds in the red algal genus Gracilaria (Gracilariaceae) are recognized as primary sources of agar, an important hydrocolloid widely utilized in the food industry. However, agar derived from Gracilaria fisheri (AGF) remains underutilized compared to that from other Gracilaria species due to its relatively low gel strength, which limits its application as a stand-alone gelling agent. Consequently, AGF is more suitable for use as a composite material rather than in its native form. Meanwhile, excessive consumption of saturated fats from meat products has been associated with health risks such as obesity and cardiovascular diseases. To address these challenges, this study developed a novel AGF-based emulsion gel as a functional fat replacer in fish sausages. The emulsion gel, comprising 6% AGF, 4% whey protein isolate, and 10% black seed oil, exhibited syneresis stability and viscoelastic properties suitable for use as a fat replacer in fish sausages. The characteristics of fish sausages containing 8% emulsion gel were compared with control sausages containing 8% vegetable fat. Results showed that sausages with emulsion gel had significantly (p < 0.05) higher water holding capacity (99.60%) and antioxidant activity (45.44%) than the control. Texture analysis revealed significant (p < 0.05) improvements in hardness, gumminess, chewiness, and resilience of the sausages with emulsion gel, while both types showed comparable cooking loss ( < 14%) and oxidative stability. Both formulations maintained oxidative stability, as indicated by low thiobarbituric acid reactive substance levels ( < 1mg MDA kg−1), below the rancidity threshold. Scanning electron microscopy revealed a more cohesive and uniform network structure in sausages containing the emulsion gel. Overall, the findings demonstrate that AGF-based emulsion gel serves as an effective fat replacer with added antioxidant benefits, offering a promising strategy for developing healthier meat.