Abstract

This study explored a sustainable pH shift process to transform unhatched eggs (infertile; INF and dead-in-shell; DIS) into valuable protein isolates (PPI). The optimal solubilization pH was determined as pH 2 and pH 12, with a precipitation pH of 5 for protein isolation. PPI quality varied based on egg type and process. Protein content was higher in DIS egg PPI than INF one. Alkaline process achieved superior protein recovery, lipid reduction, and cholesterol elimination compared to acid process, particularly in DIS egg. Despite higher lipid and cholesterol content in INF egg PPI, the alkaline process yielded lower cholesterol level. Oxidative stability, measured by TBARS, was well maintained or improved in all PPI, with DIS egg PPI showing significant reduction. The pH shift process lowered purine content, particularly hypoxanthine and xanthine in DIS egg, and altered mineral profiles, but both PPI were still good mineral sources. Heme protein, which causes the brown color in DIS eggs, was reduced in both PPI. Essential amino acids and functional protein groups were retained in both PPI. This research highlights the pH shift process as an innovative and sustainable method to upcycle hatchery by-products, reducing waste and creating value-added protein ingredients for the poultry industry.