Effect of carob protein incorporation on the structure and functionality of low-moisture pea protein extrudates for meat analogues

The growing demand for plant-based meat alternatives is driven by concerns related to environmental sustainability, animal welfare, and human health. Pea protein is widely used in these products due to its balanced amino acid profile and cost-effectiveness; however, when processed via low-moisture extrusion, it often forms dry, porous structures with low water-holding capacity and weak texture, limiting its functionality. To address these limitations, pea protein was blended with carob bean protein, an underutilized by-product of locust bean gum production widely available in the Mediterranean area, at substitution levels of 0, 30, 50, 70, and 100%, and processed using low-moisture extrusion. All formulations were characterized for structural and functional properties (expansion ratio, density, porosity, and mechanical properties) and for protein chemical properties, including free sulfhydryl (SH) and disulfide bond (SS) contents before and after extrusion. The incorporation of 30% carob protein significantly improved water-related functionality, with water holding capacity increasing from 4.48 ± 0.08 to 5.49 ± 0.41 g/g. This improvement was associated with increased porosity (0.52 ± 0.01 to 0.57 ± 0.02) and reduced apparent density (0.168 ± 0.003 to 0.132 ± 0.007 g/cm³), indicating the formation of a more internally aerated structure, despite minimal changes in expansion ratio. At higher inclusion levels (50%), structural densification occurred, characterized by decrease in porosity and increased apparent density, along with enhanced textural strength. However, excessive carob incorporation (70%) reduced water functionality, indicating a loss of performance. Overall, the formulation containing 30% carob protein provided the optimal balance between structure and functionality. In the next phase of the study, we will evaluate these extrudates in meat analogue systems, particularly to assess whether carob protein can reduce or mask beany and grassy off-flavors of pea protein. Sensory analysis of juiciness and overall acceptability combined with volatile compounds profiling will be used to better clarify flavor–structure–function relationships.