Exploring the potential of the agar-based emulsion gel as a pork fat substitute in sausage with a focus on the digestive behaviors of lipids and proteins in vitro

Abstract

This study evaluated the physicochemical properties and in vitro digestion behavior of the sausages when pork back fat was replaced with a canola-oil-based emulsion gel in a pork sausage model. Three polysaccharides—agar (AG), sodium alginate (SA), and xanthan gum (XT)—were used as gelling agents, whereas isolated soy protein (ISP) and soy lecithin served as natural emulsifiers. Sausages were prepared using three treatments: conventional sausage (CS), sausage with half the pork fat replaced by an emulsion gel (RS50), and all pork fat replaced by an emulsion gel (RS100). In the meat batter incorporated with the AG-SA-XT emulsion gel, lipid droplets were uniformly dispersed into smaller sizes, resulting in reduced cooking loss (P < 0.05) and increased gel hardness (P < 0.05) in RS50 and RS100 compared with CS. Following sausage digestion in vitro, RS50 and RS100 demonstrated slower calcein release than CS (P < 0.05), whereas no significant differences in free fatty acid release were observed among the treatments (P > 0.05). The α-amino group content was higher in RS100 during the gastric phase and in both RS50 and RS100 during the intestinal phase compared to CS (P < 0.05). However, the content of proteins with molecular weight <3 kDa in the digesta showed no significant differences among treatments (P > 0.05). Consequently, adding AG-SA-XT emulsion gel as a pork fat substitute to sausages enhanced the emulsion stability and gel properties, achieved a free fatty acid release comparable to that of pork fat, and improved protein degradation.