Lactiplantibacillus plantarum JLAU103 fermented walnut-milk dual-protein yogurt: Physicochemical property, volatile flavor profile, antioxidant activity, and isolation of neuroprotective peptides targeting Aβ1-42 oligomers

Walnuts are nutrient-dense with diverse physiological functions. This study developed a walnut-milk dual-protein yogurt (WY) using Lactiplantibacillus plantarum JLAU103, investigating its refrigerated storage (4 °C) properties, microstructure, volatile profile, sensory traits, antioxidant activity, and isolating antioxidant peptides. The WY exhibited excellent storage stability over a 21-day period, maintaining an optimal and stable pH range of 4.48–4.78 and titratable acidity of 63.3–72.66 °T. Compared with the MY control, WY showed markedly reduced syneresis, enhanced water-holding capacity, and superior textural and viscosity properties, while sustaining viable L. plantarum JLAU103 populations above 10 7  CFU/mL. Rheological and microstructural analyses showed WY had higher elastic (G′)/viscous (G″) moduli and a denser protein network, enhancing gel stability. WY contained 200 volatile compounds, with higher aldehydes/furans (key for nutty/roasted aromas) and better sensory acceptability than MY. Ultrafiltration fractionated WY proteins into <3 kDa (superior antioxidant) and 3–10 kDa fractions; the <3 kDa fraction was purified to sub-fraction B1, which exhibited strong radical scavenging (ABTS + : 15.86 %, DPPH: 53.48 %, •OH: 48.21 %) and Fe 2+ chelating (98.23 %) capacities. Nano-LC-MS/MS identified 1972 peptides in B1, 10 peptides with predicted antioxidant activity via BIOPEP-UWM. Peptide GPYHFR bound Aβ 1-42 oligomers (−7.7 kcal/mol), showing potential to mitigate memory impairment. This study provides a theoretical/technical basis for high-quality functional walnut fermented dairy products and walnut bioactive peptide exploitation.