Pulse-Cereal Blend Extrusion for Improving the Antioxidant Properties of a Gluten-Free Flour

Abstract

Extrusion is an interesting technological tool that facilitates pulse formulation into flour mixtures, with tailored fibre content, total antioxidant capacity (TAC) and glycemic index (GI) among other components in final formulas. The gluten-free (GF) market has significantly grown during the last years. GF products have evolved from specialty health foods to products targeted to the general population and not only associated to celiac consumers. This study evaluates how temperature, cereal base (rice/corn) and pulse concentration affect extruded flour properties and which conditions are more efficient to develop a gluten-free flour with high TAC and low GI. Additionally, it evaluated the effect of this optimal formula after the baking process. The results showed an increase of total phenol (TP) and antioxidant activity with extrusion, with a temperature-dependent effect (130 °C ≥ 120 °C ≥ 110 °C), which may imply an enhanced bioaccessibility of phenolics compounds after extraction. Extrusion increased GI in comparison to native flour; however, a dough temperature of 130 °C resulted in a significantly (p ≤ 0.05) lower GI than that observed for 110–120 °C doughs, probably associated to the pastification that occurred at higher temperatures, which would decrease the degree of gelatinization of the starches and therefore a significant (p ≤ 0.05) GI reduction. Corn-lentil flour showed higher antioxidant properties and lower GI index in comparison with rice-lentil blends. The formulation of the optimal blend flour into a baked product (muffin) resulted in a significant loss of antioxidant properties, with the exception of the reducing power (FRAP), although the final antioxidant values of the baked product were in the range of the original native flour blend before any process.

Twin-Screw Extrusion as Hydrothermal Technology for the Development of Gluten-Free Teff Flours: Effect on Antioxidant, Glycaemic Index and Techno-Functional Properties

“…Rice flours (M1 and E1) had the lowest TP values (24.3 and 18.2 mg GAE 100 g −1 respectively). These results agreed with the previous studies reported [ 56 , 88 ], where it was observed that rice flours after extrusion significantly reduced ( p ≤ 0.05) its phenolic content, which may demonstrate that the phenolic compounds in rice flours are more thermally sensitive than in other flours.…”

“…Carbohydrate content was similar in RF to values reported by other authors [ 56 ], and in teff flours, values were slightly higher (81.67 to 81.97 g 100 g −1 ) than those reported by other authors, where teff carbohydrates reached values of 73.1 and 73.6 g 100 g −1 [ 68 ]. A significant reduction of carbohydrates was found, similarly to other authors who have previously reported decreases in carbohydrates after extrusion of cereal matrices [ 69 ].…”

“…The crude protein was analysed before and after extrusion; the native flours had similar values to those found by the authors in previous works with rice [ 56 ] and teff flours [ 17 ], and in the range of those reported by other authors [ 66 ]. Extrusion produced a significant reduction of crude protein content ( Table 2 ); the temperature and shear forces applied during the thermal processing might have favoured the unfolding of the protein structures and enhanced their digestibility [ 67 ].…”

“…Minerals have been considered very stable during extrusion [ 54 , 55 ]. However, the authors have previously observed a decrease in ash content after extrusion in pulses [ 56 ]. This behaviour could be associated to the interaction of minerals with fibre and protein during extrusion [ 57 ], which would explain the limited ash loss from teff, as compared to rice, after the higher content in protein and TDF present in the cereal (WTF and BTF).…”

Comparison and modeling of moisture sorption isotherms of deproteinized rapeseed meal and model extrudate

“…The comparison of the sorption isotherms of raw materials from sour cherry and blackcurrant pomaces and extrudates from the same pomaces with the addition of corn meal showed a reduction of the sorption capacity of the extrudates (Witczak et al, 2020). Rico et al (2021) indicated that the extrusion increased the hydrophobic interaction of proteins with other compounds such as starch and lipids. For example, the proteins and/or amino acids chemically react with reducing sugars at a high temperature which leads to the formation of hydrophobic melanoidins.…”