Amyloid protein fibrils show enhanced ice recrystallization inhibition activity when serve as pickering emulsion stabilizer

Abstract

Ice recrystallization adversely affects the quality of frozen foods. Therefore, food-grade materials with ice recrystallization inhibition (IRI) activity are attracting growing attention. Our previous study has found IRI activity of amyloid protein fibrils (APFs); however, as with most other food-grade IRI active materials, the IRI activity of APFs is moderate and needed to be enhanced. Here, we report that IRI activity is greatly enhanced when APFs serve as Pickering emulsion stabilizer. Adsorption of APFs to the oil-water interface resulted in the formation of microsized Pickering emulsion droplets. The IRI activity resulted from the adsorbed APFs rather than steric hindrance of emulsion droplets because self-induced emulsion droplets without APFs on the surface had no IRI activity. The oil core chemistry does not affect the IRI activity of adsorbed APFs. A structure−activity relationship analysis revealed that IRI activity of adsorbed APFs increases with larger particle size and emulsion droplet number (total number of droplets per unit volume). The enhancement of IRI activity caused by oil-water interface adsorption is reasonably ascribed to enlarged size, crowding of APFs on the surface of emulsion droplets, and enhanced ice adsorption of APFs. Compared with free APFs, adsorbed APFs were more IRI active at higher annealing temperatures and higher unfrozen water contents. Given the amphiphilic nature of most IRI-active materials, the findings of this study shed light on the application of IRI-active materials as emulsifiers to improve the quality of frozen food containing emulsions, such as ice cream and frozen meat paste.