Twin-Screw Extrusion of Oat: Evolutions of Rheological Behavior, Thermal Properties and Structures of Extruded Oat in Different Extrusion Zones

Abstract

Further investigation of material properties during the extrusion process is essential to achieve precise control of the quality of the extrudate. Whole oat flour was used to produce low moisture puffed samples by a twin-screw extruder. X-ray diffraction (XRD), Scanning electron microscopy (SEM), infrared spectroscopy (FTIR), thermal analysis, and rheological experiments were used to deeply characterize changes in the structure and cross-linking of oats in different extrusion zones. Results indicated that the melting region was the main region that changed oat starch, including the major transformation of oat starch crystal morphology and the significant decrease of enthalpy representing the starch pasting peak in the differential scanning calorimeter (DSC) pattern (p < 0.05). Moreover, the unstable structure of the protein increased in the barrel and then decreased significantly (p < 0.05) after being extruded through the die head. The viscosity of oats increased in the cooking zone but decreased after the melting zone. A transformation occurred from elastic-dominant behavior to viscoelastic-dominant behavior for oats in the melting zone and after being extruded. This study provides further theoretical support for the research of the change of materials during extrusion and the development of oat-based food.

Effects of enzymatic extrusion on the structure and physicochemical properties of oat flour and its application in oat milk production

“…Starch granules of various sizes were bound together and irregular non-starch components were attached to the surface of starch. The microstructure of OOF was similar to that reported by Dar et al (2018) and Zhou et al (2022). In EEOF-0½, large irregularly shaped aggregates with rough surfaces were observed, which may be due to the high temperature, high shear and mixing action of the extruder that agglomerated the gelatinised starch granules (Bian et al, 2022).…”

“…At the same shear rate, the viscosity of OOF was the greatest, followed by EEOF‐0‰, while the viscosity of the enzymatic extruded sample was the smallest, and the viscosity tended to decrease with the increase of α‐amylase concentration. The mechanical action of high pressure and high shear, together with the hydrolysis of α‐amylase, lead to the degradation of starch macromolecules, resulting in a lower viscosity of extruded samples (Zhou et al ., 2022).…”

“…(2018) and Zhou et al . (2022). In EEOF‐0‰, large irregularly shaped aggregates with rough surfaces were observed, which may be due to the high temperature, high shear and mixing action of the extruder that agglomerated the gelatinised starch granules (Bian et al ., 2022).…”

“…The samples were measured from 4° to 40° (2θ) at a scan rate of 4° min −1 using Cu‐Kα radiation (Wu et al ., 2020). Diffraction patterns were analysed, and relative crystallinity (RC) was determined based on the calculus of crystallinity area (Ac) and amorphous area (Aa) in the diffractogram as follows using MDI Jade 6.0 software (Zhou et al ., 2022; Liu et al ., 2023):…”

The Principle of Steam Explosion Technology and Its Application in Food Processing By-Products

“…In both technologies, the material is placed in a high-temperature and high-pressure confined environment [29]. High pressure in the system is released instantaneously, and the water vapor present in the pores of the material expands, causing physicochemical changes inside the material [30].…”