Development of a novel dual-enzyme modification method for the functionality improvement of egg yolk powder

Abstract

Spray dried egg yolk powder (EYP) is a kind of food ingredient with high nutritional value. However, its low solubility and insufficient emulsifying properties restrict its applications in the food industry. In this study, a new method of dual enzymatic hydrolysis (phospholipase and protease) was proposed to improve the functional properties of EYP including emulsifying properties, solubility, rehydration time and so on. The optimal conditions were determined to be 50 U/g (phospholipase A1 (PLA1)) and 250 U/g (neutral protease). Under these optimal conditions, the solubility of HYP (hydrolyzed EYP) treated by dual enzyme (61.30%) was significantly higher than that of unhydrolyzed EYP (16.49%) or HYP treated by single PLA1 (23.97%). Meanwhile, the emulsifying stability index (ESI) of HYP (hydrolyzed EYP) treated by dual enzymes was about 16/1.4 times larger than unmodified EYP/single PLA1 modified HYP. The increasing electronegativity and decreasing surface hydrophobicity/surface tension of HYP could be responsible for the above results. Scanning electron microscopy (SEM) revealed that dual-enzyme hydrolysis could promote the formation of fine HYP with pore structure, enabling it to rehydrate more effectively. In addition, the usage of protease could improve the radical scavenging activity of dual enzyme modified HYP by releasing antioxidant peptides. This study could provide new insights to promote the techno-functionality of EYP, thus optimizing its utilization as a high-performance emulsifier in the food industry.