Walnut oleosome and protein co-structured cold-set emulsion gels: linking protein concentration and oil content to gel stiffness, deformation resistance, and digestive behavior.

This study aimed to develop glucono-δ-lactone (GDL)-induced cold-set emulsion gels derived from walnut oleosomes (WOL) and walnut protein concentrates (WPC). The effects of varying WOL content (0-20%) and WPC concentration (4-8%) on rheological, textural, microstructural, and digestive properties of the WOL/WPC-based emulsion gels (WEG) were systematically investigated. Rheological analysis demonstrated that increasing the WPC concentration from 4% to 8% enhanced the storage modulus by approximately 4-fold but simultaneously reduced the flow strain of WEG. In contrast, increasing WOL content from 0% to an equivalent of 20% walnut oil (WO) led to a moderate increase in gel strength by approximately 20%, while simultaneously enhancing the flow strain by 6-fold. Large amplitude oscillatory shear tests confirmed the pronounced strain-stiffening behavior and superior deformation resistance of WEG samples with high WOL content. WOL-rich emulsion gels exhibited enhanced springiness and hardness; however, higher WPC concentration led to a more pronounced enhancement in hardness but slightly reduced springiness. Microstructural observations revealed that the emulsion gels formulated with 20% WO and 6% WPC possessed a denser network with uniformly entrapped oleosomes. Increasing both WPC and WOL content restricted water mobility and significantly improved water-holding capacity. Furthermore, WEG exhibited improved free fatty acid release profiles during in vitro digestion compared with free WOL emulsions.