Processes applied to whole sorghum flour: effects on technological, antioxidant and sensory properties of gluten-free cakes

Although a variety of gluten-free products based on sorghum flour have been developed in Brazil, the sensory attributes of some of these products, can still be improved. Thus, the aim of this study was to apply different pretreatments (roasting, cooking, extrusion) to sorghum flour and evaluate their effect on improving the technological and sensory properties of gluten-free sorghum cakes. As bioactive compounds can be affected by treatments, antioxidant properties were also evaluated. Five cake formulations were produced with BRS305 whole sorghum flours: raw (RSF), toasted (TSF), a blend of toasted and raw (RTSF), cooked (CSF) and extruded (ESF), and a control made with raw rice flour. The formulation containing RSF stood out from the others, exhibiting greater height, less firmness (greater softness), lightest color (among sorghum formulations), greater sensory acceptance and purchase intention, besides higher antioxidant capacity (AC), total phenolic compounds (TPC) and 3-deoxyanthocyanidins contents. The CSF and ESF formulations presented the worst results in almost all characteristics. TSF and RTSF cakes also showed high AC (> 93%) and TPC (> 84%) retentions, even after undergoing two thermal processes (roasting and baking). CSF retained, respectively, 29.2 and 51.6% of AC and TPC, highlighting that the moist heat degrades sorghum bioactive compounds. Thus, pretreatments used in sorghum flour promoted losses in the antioxidant properties of gluten-free cakes and did not improve their physical and sensory characteristics. Therefore, RSF remained the best option for the development of this product, since it involves fewer processing steps, in addition to lower energy expenditure and preparation time.