Prefermentation addition of Lonicera caerulea L. pomace modulates casein aggregation to improve physicochemical properties and nutritional functionality of stirred yogurt.

Driven by sustainable food systems and high-value valorization of agricultural by-products, as well as the development of diversified dairy products, this study incorporated 0.5-2% (wt/wt) Lonicera caerulea L. pomace (LCP) into milk before fermentation to prepare nutrient-fortified stirred yogurt, and evaluated pre-fermentation addition effects on gelation, physicochemical properties, functionality and sensory quality. During fermentation, LCP modulated casein aggregation through noncovalent interactions between proteins and polyphenols/dietary fibers, accelerating the formation of casein micellar aggregates and complex clusters without interfering with final acid-induced gel network generation. After fermentation, dietary fiber and polyphenols in LCP remained stably bound within complex clusters even after stirring. These interactions preserved the continuous structural network and generated a denser, more compact microstructure, endowing yogurt with superior water-holding capacity (WHC), higher cohesiveness and enhanced rheological stability. Notably, the 2% LCP addition delivered an approximate 8% elevation in WHC relative to the control, alongside reduced syneresis and improved physical stability over storage. Furthermore, LCP markedly enhanced the antioxidant activity of stirred yogurt, especially at the 2% addition level, with activity retention exceeding 90% throughout the 21-d storage period, attributed to stable complexation with milk proteins during fermentation. Similarly, protein-polyphenol binding also effectively mitigated LCP-induced astringency in 2% LCP-fortified yogurt, without disrupting the inherent flavor balance or compromising sensory acceptability. This work offers a sustainable approach to develop functional yogurt with superior physicochemical properties, prominent antioxidant activity, and favorable sensory characteristics, while supporting the high-value utilization of Lonicera caerulea L. processing by-products in the dairy industry.