Impact of extrusion-induced protein molecular rearrangement on cooking qualities, in vitro digestibility and gluten allergenicity of durum wheat pasta

The cooking quality and digestibility of pasta are influenced by its protein structures. However, how shear forces affect protein molecular structure leading to pasta quality and the allergenicity of pasta is not well understood. This study explored the impact of varying screw speeds (150 rpm and 550 rpm), which directly influence specific mechanical energy (SME) input during extrusion, on protein molecular weight distribution, cooking properties, and starch and protein digestibility in both regular durum wheat pasta and gluten-enriched pasta. Pasta produced at 550 rpm exhibited reduced water absorption and cooking time but significantly increased cooking loss, accompanied by a decrease in disulphide bonds. Size-exclusion chromatography (SEC) and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) results indicated that high screw speed caused the insolubility of glutenins and globulins while increasing the solubility of gliadins. Additionally, these structural changes corresponded to decreased ionic and hydrogen bonding and increased hydrophobic interactions. Although starch and protein enzymic digestibility was decreased with added gluten, the increased screw speed enhanced their digestion. Proteomic mapping by liquid chromatography-tandem mass spectrometry (LC-MS/MS analysis) revealed a reduction in the number of identified proteins and allergens in the digestate of pasta produced at 550 rpm, while the number of identified peptides increased. Additionally, added gluten delayed protein hydrolysis during the gastric phase and offset differences due to screw speed. This understanding aids in optimizing processing and formulations, balancing efficiency with pasta's nutritional and cooking quality.