Effects of roasting on the functional and pasting properties of chia seed maize composite flour

Abstract

Undernutrition continues to be a global challenge, particularly in vulnerable populations such as children, the elderly, and individuals recovering from illness. This study investigated the effect of roasting of chia seeds on the functional and pasting properties of chia seed maize composite flour, and aimed to improve the nutritional quality of maize based porridges to combat undernutrition. Seven flour formulations (F1 F7) were developed by blending Maize flour (MF) with raw chia seed flour (rCSF) and roasted chia seed flour (RCSF) in various proportions (0%, 5%, 10%, and 15%) respectively. Functional properties evaluated included water absorption capacity (WAC), oil absorption capacity (OAC), foaming capacity (FC), bulk density (BD), emulsion activity (EA), and emulsion stability (ES), while pasting properties were analyzed using a Rapid Visco Analyzer. Results indicated that the inclusion of chia seed, especially in roasted form, significantly improved most functional properties (p < 0.05). Compared to the control (F1: 100% MF), WAC increased from 136.50 g/g to 223.50 g/g in F7 (85% MF + 15% RCSF), a 63.7% improvement. Similarly, OAC rose from 171.50 g/g in F1 to 188.25 g/g in F7 (a 9.8% increase), while FC increased from 8.75% to 14.25% (a 62.9% rise). EA and ES also improved substantially, with EA rising from 21.20% in F1 to 57.24% in F7 (an increase of 170%) and ES from 25.25% to 62.60% (a 148% rise). Bulk density, however, remained statistically unchanged across all formulations. In terms of pasting properties, the inclusion of chia seeds led to notable reductions in peak viscosity (PV), final viscosity (FV), breakdown (BDV), and setback (SBV) resulting in smoother and more digestible porridges, ideal for populations with difficulty swallowing. PV decreased from 2096.00 cP in F1 to 1144.00 cP in F7 (a 45.4% reduction), indicating reduced starch granule swelling due to fiber and lipid interactions from chia. Similarly, FV dropped from 3930.50 cP in F1 to 2214.00 cP in F7. The pasting temperature increased from 77.45°C in F1 to 81.10°C in F7, while peak time rose from 5.43 to 6.27 minutes, reflecting slower gelatinization associated with chia addition. Formulation F7 (85% maize, 15% roasted chia) exhibited the best nutritional properties, offering a higher energy density and better nutrient retention, making it suitable for undernourished individuals, particularly children and those in recovery. These findings underscore the potential of roasted chia seed flour to develop energy dense, nutrient rich porridges that effectively address undernutrition.