Development of hen egg-based protein beverages with high nutritional value

Physical stability is a prerequisite for any emulsion-based beverage. This study aimed to optimize beverage emulsion (BE) rich in whole egg, whey protein isolate (WPI), and soyabean oil in the presence of polygalactose derivative as adsorbing hydrocolloids (AH) and partially hydrolyzed starch as non-adsorbing hydrocolloids (NAH). All formulations were optimized for stability, particle size, polydispersity index (PDI), and zeta potential (ζ). A central composite design was applied to investigate the impact of WPI concentration, hydrocolloid concentration, oil volume, and pH as independent factors on particle size, PDI, and ζ of emulsions. The optimum conditions were met upon formulating BE with 1 whole egg, 9.28 g WPI, 11.24 g AH, 5.58 mL oil at pH 7. Two optimal formulations were obtained for BE stabilized with NAH at pH 3 and 7, at which droplets had the highest electrical charge. Noting that, less amount of NAH (7.5 g) was required at pH 3 than at pH 7 (13.56 g). Oil content (3 mL) and WPI concentration (16 g) for both NAH formulations were similar. The size, polydispersity index (PDI), and zeta potential of AH-stabilized emulsion were 762 nm, 0.69, and - 32.05 mV, respectively, while for NAH emulsion, they were 150.02 nm, 0.40, and - 28.53 mV at pH 7; and 248.39 nm, 0.41, and 27.1 mV at pH 3, respectively. No conspicuous gravitational separation was observed after 20 days of storage at 4 °C. Hence, both hydrocolloids are appropriate to stabilize protein-enriched BE at neutral pH; however, physical stability was also achieved at acidic pH for NAH-stabilized emulsions.