Co-folding of buckwheat protein and shellac for develop W/O/W emulsions: enhanced encapsulation and gastrointestinal protection of Lactiplantibacillus plantarum

Probiotic viability during gastrointestinal transit is critical for their functional efficacy but is compromised by acidic pH and enzymatic degradation. This study developed a buckwheat protein–shellac (BW–SH) co-folded complex to stabilize W/O/W double emulsions for protecting Lactiplantibacillus plantarum during gastrointestinal transit. Co-folding with shellac not only enhanced BW’s functionality as an emulsion stabilizer but also facilitated the formation of a pH-driven BW–SH complex through hydrogen bonding and hydrophobic interactions, as confirmed by UV, fluorescence, and FTIR spectroscopy. The optimized BW–SH complex (BWS-1, pH 9) exhibited a fibrillar morphology (TEM) and a highly negative ζ-potential (−61.4 ± 1.17 mV). pH-shifting with shellac effectively improved the emulsifying activity and stability of BW. Double emulsions stabilized by the BW–SH complex achieved a higher encapsulation efficiency (95.56%) and viable cell count (7.5 log CFU/mL, vs. 4.0 log CFU/mL for free cells) after in vitro gastrointestinal digestion, demonstrating that the oil layer and BW–SH interfacial adsorption synergistically protected the probiotics. Microscopic imaging further revealed pH-dependent structural retention, with gradual disintegration correlating with sustained probiotic viability. Overall, this study provides a scalable strategy for probiotic delivery using grain protein–shellac hybrids, addressing key challenges in functional food and nutraceutical applications. • BWS complexes stabilized W/O/W emulsions with improved structural integrity. • Shellac co-folding markedly increased L. plantarum survival during GI digestion. • pH 9–driven BWS complexes exhibited fibrillar morphology and high ζ-potential. • BWS emulsions achieved high encapsulation and sustained probiotic release.