Collet and cooking extrusion change the soluble and insoluble β-glucan contents of barley

• Extrusion at high moisture, as in cooking extrusion, increased soluble β-glucan.
• Extrusion at low moisture, as in collet extrusion, lowered soluble β-glucan.
• Higher soluble β-glucan content implied higher slowly digestible starch content.
• High soluble β-glucan extrudates can be used to develop slowly digestible foods.

This study investigated the effects of extrusion types (collet and cooking) and parameters (moisture content, screw speed and temperature) on the β-glucan content of barley and the impact of β-glucan content on starch digestibility. The results demonstrated that extrusion significantly reduced the total β-glucan (TBG) content of barley as a raw material, but the differences in TBG from extrudates obtained using different extrusion parameters were not significant. Extrusion at high moisture content, as in cooking extrusion, increased SBG, whereas extrusion at low moisture content, as in collet extrusion, lowered SBG. The regression coefficients revealed that the most significant extrusion parameters affecting SBG and IBG content in barley extrudates were feed moisture content for collet extrusion and screw speed for cooking extrusion. The in vitro digestion analysis demonstrated that collet and cooking extrudates containing high amounts of SBG revealed the highest slowly digestible starch (SDS) content. In conclusion, different extrusion types and parameters exhibited more pronounced effects on the SBG and IBG content than on the TBG content, and higher SBG content implies higher SDS content.