The edible bird's nest hydrolysate-induced formation of drinkable yogurt.

To use fragmented edible bird's nest (EBN), protease-mediated hydrolysis was employed, and these hydrolysates were subsequently incorporated into milk before fermentation for yogurt production. Notably, supplementation with specific EBN hydrolysates induced a fundamental structural transition from conventional set yogurt to a drinkable system. Thus, this study aimed to prepare such drinkable yogurt and investigate the formation mechanism. It was revealed that ≥2 h hydrolysis duration combined with 2.0% hydrolysate incorporation induced transition from set yogurt to drinkable yogurt. Below these thresholds (≤1 h hydrolysis or ≤1.0% dosage), a conventional gel network persisted. Microstructural characterization through confocal laser scanning microscopy revealed the formation of discrete protein microgels within the liquid matrix in drinkable yogurt samples, confirming macroscopic fluidity. Rheological assessments demonstrated significantly lower storage modulus and loss modulus and higher loss factor in the drinkable yogurt samples than in set yogurt. Mechanistic investigations using CN micelle suspensions showed that EBN hydrolysate addition could inhibit aggregation of CN microgels and maintain CN suspension mobility at pH 4.3. Electrophoresis analysis revealed the generation of low-molecular-weight peptides (≤11 kDa) that constituted the predominant fraction in the EBN hydrolysate. Thus, it was inferred that peptides with the molecular weight ≤11 kDa in the EBN hydrolysate inhibited aggregation of CN microgels induced by acidification into a continuous gel, thus enabling production of drinkable yogurt.