Multi-scale structural changes of starch and proteins during pea flour extrusion

Abstract

Dehulled yellow pea flour (48.2% starch, 23.4% proteins, d.b.), was processed by a twin-screw extruder at various moisture contents MC (18-35% w.b.), product temperature T (115-165 °C), and specific mechanical energy SME (50-1200 kJ/kg). Structural changes of extruded pea flour were determined at different scales by measurements of density (expansion), crystallinity (X-ray diffraction), gelatinisation enthalpy (DSC), starch solubility in water and protein solubility in SDS and DTE (SE-HPLC). Foam density dropped from 820 to 85 kg/m with increase in SME and T (R ≥ 0.78). DSC and XRD results showed that starch was amorphous whatever extrusion conditions. Its solubility in water augmented up to 50%. Increasing temperature from 115 to 165 °C decreased proteins soluble in SDS from 95 to 35% (R = 0.83) of total proteins, whereas the proteins soluble in DTE increased from 5 to 45% (R = 0.75) of total proteins. These trends could be described by sigmoid models, which allowed determining onset temperatures for changes of protein solubility in the interval [125, 146 °C], whatever moisture content. The SME impact on protein solubility followed similar trends. These results suggest the creation of protein network by SS bonds, implicating larger SDS-insoluble protein aggregates, as a result of increasing T and SME, accompanied by creation of covalent bonds other than SS ones. CSLM images suggested that extruded pea flour had a composite morphology that changed from dispersed small protein aggregates to a bi-continuous matrix of large protein aggregates and amorphous starch. This morphology would govern the expansion of pea flour by extrusion.

Functional and physical properties of naked barley-based unexpanded extrudates: effects of low temperature

“…However, the a values of the extrudates were higher than those of the formula flour. Similar results were obtained by Kristiawan et al [31] in the extrusion of pea flour. It can be concluded that some components of the blends changed during the extrusion process.…”

“…It can be concluded that some components of the blends changed during the extrusion process. Kristiawan et al [31] also found that L and a were correlated with protein aggregations by covalent bonds in the samples.…”

Palatable Noodles as a Functional Staple Food Made Exclusively from Yellow Peas Suppressed Rapid Postprandial Glucose Increase

“…Dehulled yellow pea (Ohtsuya Inc., Tokyo, Japan), unshelled pea (Toyota Tsusho Foods Corp., Tokyo, Japan), chickpea (Bob's Red Mill Inc., Milwaukee, OR, USA), and lentil (Beans Market Inc., Shizuoka, Japan) sold in Japan for food use were purchased. We then used these legume flours to prepare noodles using extrusion molds [16]. Briefly, 50% water was added to the legume flour, kneaded, extruded at 120 • C, and then air dried.…”

In Vitro Antioxidant Activity Optimization of Nut Shell (Carya illinoinensis) by Extrusion Using Response Surface Methods

“…The increase in phenolic content with barrel temperature has been ascribed to the formation of Maillard reaction products [42]. The effect of extrusion on bioactive compounds depends on the physical and chemical characteristics of the product and the extrusion conditions [43,44].…”