Incorporating air-classified quinoa flour in high-moisture-extruded meat analogues: digestive insights.
Abstract
High-moisture extrusion and formulation-induced structural differences are associated with differences in dynamic gastric disintegration and subsequent intestinal protein hydrolysis in meat analogues; however, the underlying mechanisms remain unclear. This study compared the in vitro digestive behaviours of high-moisture-extruded meat analogues incorporated with 20% air-classified quinoa flour (QF) (MA-20QF), QF-free analogues (MA-0QF) and cooked chicken. Samples were subjected to dynamic gastric digestion (240 min) followed by static small intestinal digestion (120 min). Gastric-emptied digesta collected at 60 and 180 min were further digested in the intestinal phase. Gastric pH, solid and protein retention, particle size, protein degradation, degree of hydrolysis (DH) and peptide molecular weight distribution were analysed. QF incorporation reduced structural anisotropy, weakened textural properties and accelerated gastric acidification (ΔpH = 0.2784/min for MA-20QF, 0.2491/min for MA-0QF and 0.2431/min for chicken; R2 > 0.995). During gastric digestion, meat analogues exhibited slower solid and protein emptying than chicken and retained larger particle sizes. After 240 min, meat analogues fragmented into 10-100 μm particles, whereas chicken fragmented into 5-10 μm particles. DH followed the order of MA-20QF > chicken > MA-0QF. Furthermore, gastric digesta collected at 180 min exhibited higher DH in the subsequent intestinal phase than that collected at 60 min. Although gastric digestion predominantly produced peptides with a molecular weight of 1000-5000 Da for all samples (>93%), intestinal digestion drove extensive hydrolysis. Cooked chicken generated the largest proportion of <1000-Da peptides, followed by MA-20QF and MA-0QF. Overall, formulation-induced matrix structure and gastric pre-processing were associated with differences in gastrointestinal proteolysis, highlighting the importance of formulation strategies in modulating the digestive behaviour of plant-based meat analogues.