Fabrication and characterization of industrially stable whey protein nanogels via thermal denaturation and calcium interaction

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Colloidal nanogels based on whey protein isolate (WPI) hold significant promise for the food industry due to their nutritional value and functional properties. However, fabricating an industrially stable nanogel, particularly at high protein concentrations, has proven challenging. Addressing the need for stable WPI nanogels, this study explored the thermal denaturation of whey protein across a broad range of concentrations (3–11%, w/w on protein basis), paired with varying calcium levels (0–20 mM). It focused on elucidating the controlled aggregation mechanisms and assessing the stability of these nanogels under several common food processing conditions such as blending with food salts, pH adjustment, thermal sterilization, and spray-drying. The results revealed that controlled aggregation of WPI into nanogels primarily occurred through disulfide bond formation when subjected to denaturation with a limited amount of calcium. However, an excess of calcium induced complete aggregation into macroscopic gels. Once formed, these self-assembled nanogels exhibited resilience to a wide pH range (pH3-7). They also demonstrated exceptional stability under typical industrial processing and food formulation conditions, such as simulated milk ultrafiltration (SMUF), and remained stable through ultra-high temperature thermal sterilization (140 °C) and spray drying. In conclusion, this study not only advances our understanding on the mechanisms behind the formation of calcium induced protein denaturation but also provides significant insights into developing stable whey protein nanogels, addressing a crucial need of stable high-protein food products.