Ziziphus spina-christi Fruit Pulp as a Multifunctional Natural Ingredient for Functional Yogurt: Effects on Physicochemical, Technological, Antioxidant, and Antimicrobial Properties

The growing demand for clean‐label functional dairy products has increased interest in plant‐derived bioactive ingredients with antioxidant and antimicrobial properties. This study investigated the potential of Ziziphus spina-christi fruit pulp (NFP) as a natural multifunctional ingredient for yogurt fortification. NFP was characterized for its phytochemical composition, antioxidant activity, and antimicrobial properties, followed by its incorporation into yogurt formulations at 0.5%, 1.0%, and 1.5% (w/w). NFP exhibited considerable bioactive properties, with a total phenolic content of 10.91 ± 0.84 mg GAE g ⁻¹ , total flavonoid content of 2.14 ± 0.05 mg QE g ⁻¹ , and DPPH radical scavenging activity of 63.59 ± 1.43%. The ethanolic extract demonstrated stronger antimicrobial activity than the aqueous extract against the tested microorganisms. Among the tested treatments, yogurt fortified with 1.5% NFP exhibited the highest technological performance, showing the greatest water‐holding capacity (58.51%) and the lowest syneresis value (18.68%). In addition, increasing NFP concentrations resulted in a reduction in total microbial counts during storage, including a concentration‐dependent decrease in yogurt starter culture populations, although viable starter counts were maintained throughout the storage period. Sensory evaluation indicated good consumer acceptance of NFP‐fortified yogurt, particularly at moderate supplementation levels. Response surface methodology (RSM) was applied using NFP concentration and storage period as independent variables, whereas physicochemical, microbiological, technological, and sensory characteristics were used as response variables. Based on the overall desirability function, yogurt containing 1.0% NFP was identified as the optimum formulation. These findings demonstrate that NFP can be successfully valorized as a natural functional ingredient for producing yogurt with enhanced antioxidant capacity, improved texture, and acceptable sensory quality.