Abstract: The purpose of this study was to determine the impact of ultrasound-induced lipid crystal rearrangement and whey protein concentrate (WPC) cross-linked with glutamine transaminase (TG) as emulsifier on the in vitro digestibility of emulsified lard and to investigate the change in unadsorbed protein concentration among different formulations of emulsified lard. Particle size, zeta-potential, free fatty acid profile and microstructure of emulsified lard were investigated to evaluate its in vitro digestibility. The results showed that ultrasound and TG treatments had different impacts on emulsified lard. Ultrasound treatment decreased the unadsorbed protein concentration and stability of the emulsion compared with the nontreated control, while TG treatment rendered the emulsion more sable. Moreover, the ultrasound-treated sample exhibited significantly larger average droplet size and increased release of free fatty acids (P < 0.05), and its zeta-potential was also much lower than the control. In the presence of TG cross-liked WPC, the droplet size of the emulsion became smaller and significantly less free fatty acids were released during digestion when compared with the ultrasound-treated sample (P < 0.05). Overall, ultrasound treatment rendered emulsified lard more digestible, while TG treatment slowed down the digestion of emulsified lard.

Key words: emulsified lard, ultrasound, transglutaminase, in vitro digestion