Effects of extrusion conditions on Fuji Otebo bean powder intended for cookie production

Nowadays, the consumption of pulses, the edible seeds of plants belonging to the legume family, is highly recommended. Pulses need to be cooked before consumption. Extrusion processes can provide new technological performances to pulse powders. The objective of this study was to explore the effects of different extrusion conditions on the physical and chemical properties of Fuji Otebo bean powder intended for cookie production. To study simultaneously the main and interaction effects of feed moisture (20, 27.5, 35%), barrel temperature (70, 100, 130°C), and feed rate (2, 2.5, 3 kg/h), a 3-factor, 3-level Box Behnken experimental design was applied. According to the Response Surface Methodology elaboration, a highly significant effect of feed moisture was observed for slowly digestible and resistant starch levels, with a minor influence of barrel temperature. As expected, feed moisture and barrel temperature each had effects on bean powder pasting properties, studied by a Rapid Visco Analyzer (RVA), as well as on water and lactic acid retention capacities. Feed rate significantly affected only resistant starch of extruded powders. In comparison with raw bean powder, the extruded samples showed lower RVA-final viscosities (mean value of 609, versus 1642 cP for the raw sample) indicating that partial gelatinization of starch occurred during extrusion and confirming the cooking effect of this technology. Extruded bean powder samples were then used in the production of gluten-free cookies by blending bean powder (raw or extruded) with corn starch (70:30). Depending on the extrusion conditions applied, different cookie spread ratio values were obtained (from 5.83 to 6.76), while a value of 6.20 was obtained for raw-bean-powder cookies. The texture parameters of cookies containing extruded powders were in the range of the values obtained for raw-bean-powder cookies and gluten-free references (rice flour, and rice flour blended with corn starch in a ratio of 70:30). The results of this study demonstrated that extrusion modifies the physical and chemical properties of bean powders, however only minor effects were observed on cookies. Accordingly, extruded bean powders present potential opportunities for other food applications (e.g., beverages, baby foods, etc.) where the interaction with liquid plays a key role and rapidly digestible starch is desired.