Effect of β-sitosterol and oil phase on gel properties, microstructure and sensory characteristics of pea protein/carrageenan emulsion gels as solid fat substitutes

In this study, pea protein isolate (PPI)/κ-carrageenan (CG) emulsion gels were formulated with various oil phases (sunflower seed oil, SFO; cocoa butter, CB; palm stearin/SFO, PST/SFO) and β-sitosterol (β-Sit) concentrations (0%, 5%, 10%, 15%, 20% w/w) to mimic the textural and melting properties of animal solid fat. The potential application of these emulsion gels as solid fat substitutes in reduced-fat sausage was also evaluated. Confocal laser scanning microscopy and polarized light microscope images revealed an increase in mean droplet diameter and crystal size of the emulsion gels at higher β-Sit concentration. Compared to CB and SFO samples, PST/SFO emulsion gels exhibited more numerous, smaller crystals and a more homogeneous protein network structure. Texture analysis showed the hardness of the three emulsion gels progressively increased and the springiness reduced with rising β-Sit concentrations. Among the oil phases, PST/SFO emulsion gels with 20% β-Sit exhibited texture properties and melting behavior most akin to pork back fat (PBF). Scanning electron microscopy showed that the replacement of PBF with PST/SFO emulsion gels at higher substitution ratios resulted in a rougher structure with increased amounts of gel particle aggregates and voids of sausages although the texture property and gel strength were enhanced. Overall, sensory perception revealed that sausages with ≤75% fat replacement remained highly acceptable. This study offers a novel approach to developing animal fat substitutes with adjustable texture and crystallization characteristics based on PPI/CG emulsion gels.