Ovalbumin (OVA) and lysozyme (LYZ) are the predominant globular proteins in egg white and play a crucial role in influencing thermal stability and colloidal behavior. In this study, the thermal and conformational stability of OVA and LYZ under various physicochemical conditions including pH (5–9), protein concentrations (5, 10, and 20%), heating rates (2.5, 5, and 10 °C/min), sugars (sucrose and glucose), and salts (NaCl, KCl, and CaCl₂) was systematically investigated using differential scanning calorimetry (DSC), aiming to elucidate their behavior within colloidal and gel-forming systems. The denaturation temperatures (T_d) of OVA and LYZ in water (5% w/v, 5 °C/min) were 80.22 °C and 77.46 °C, respectively. The T_d of LYZ and OVA decreased with protein concentration, heating rate, and CaCl₂. OVA thermal stability was improved with increasing pH, but the stability of LYZ was decreased. Sugars enhanced the thermal stability of OVA and LYZ. In contrast, NaCl and KCl increased OVA stability but reduced LYZ stability. LYZ exhibited nearly 100% reversibility during the second heating cycle in water. Sugars maintained reversibility at approximately 90% for LYZ. However, the presence of salts diminished the reversibility. In contrast, OVA was completely denatured in water and sugar and salt solutions.

With the growing demand for functional dairy products, integrating dual-animal proteins presents a promising strategy to enhance both nutritional value and functional properties. This study aimed to elucidate the impact of egg white supplementation on the stability, physicochemical attributes, sensory quality, and shelf-life of yogurt. Yogurt samples were prepared by fermenting milk supplemented with 0%, 5%, 10%, 15%, 20%, and 25% egg white, and subsequently evaluated for physicochemical parameters, microstructure, rheological behavior, water-holding capacity, and sensory profiles using an electronic nose and electronic tongue. Results showed that 5% egg white significantly improved yogurt stability after one day of refrigeration, whereas 10% supplementation yielded texture comparable to the control but with enhanced protein content, water retention, gel strength, and microstructural uniformity. Over 14 days of cold storage, a gradual decline occurred in physicochemical and structural parameters across all samples; however, flavor profiles remained largely stable, with no adverse effects on sensory quality except for a mild increase in acidity. These findings highlight egg white as a functional ingredient capable of improving yogurt stability and textural quality without compromising flavor, offering new opportunities for the development of high-protein, dual-animal protein fermented dairy products in the functional food industry.