Abstract:

Phospholipase A1 (PLA1) was used for enzymatic modification of egg yolk to prepare egg yolk powder with high emulsifying properties in the present study. The optimal reaction conditions of PLA1 for maximizing the release of free fatty acids from egg yolk were determined by single factor and orthogonal array methods as follows: reaction temperature 55 ℃, reaction time 4.5 h, enzyme amount 1500 U/g, initial pH 6.0, and substrate concentration 200 g/L. According to the particle size distribution of egg powder measured using laser particle size analyzer, no obviously destructive effect of PLA1 on the structure of egg yolk was observed. The emulsifying capacity, emulsifying stability and thermostability of PLA1-modified egg yolk powder were enhanced by 75%, 389% and 132%, respectively, when compared with common egg yolk powder. Color change of egg yolk powder before and after modification measured using Chroma Meter (Ultra scan XE, Hunter Lab) indicated that PLA1 treatment resulted in increases of L* value from 86.04 to 87.87 and b* value from 38.82 to 54.22 but a decrease of a* value from 5.23 to 0.11.

Key words: egg yolk powder, molecular modification, enzyme, thermostability, emulsifying properties