Effect of roasting pulse seeds at different tempering moisture on the flour functional properties and nutritional quality

Abstract

Knowledge on the functional and nutritional properties of wet roasted pulses can increase the utilization of processed pulses as ingredients in food products. This study investigated the effects of tempering different pulse [chickpea (CP), green lentil (GL), navy bean (NB) and yellow pea (YP)] seeds to 20 or 30% moisture prior to roasting (160℃ for 30 min) on the functional properties and nutritional quality of their resulting flours. The surface charge of each pulse remained the same (p > 0.05) after wet roasting and there were no significant (p > 0.05) differences between the different raw pulse flours. The oil holding capacity (OHC) of GL (~2 g/g) was not improved by wet roasting (p > 0.05) whereas the other pulses generally had better OHC for one or both of the tempering moistures used prior to roasting. Foaming properties of all pulses decreased after heat treatment with the exception of both foaming capacity (107%) and stability (~71%) for GL tempered to 20% moisture prior to roasting (p > 0.05). Raw GL had inferior foaming properties compared to the other raw pulse flours (p < 0.001). Emulsion properties of the wet roasted pulses were similar to those of the control (raw flour) for each pulse. Solubility decreased with roasting regardless of the tempering moisture (p < 0.05) whereas in general the in vitro protein digestibility increased. Small improvements (2.4–6.9% increase) in the in vitro protein digestibility-corrected amino acid score were found for GL and NB tempered to 20% moisture before roasting and roasted YP at either moisture content (p < 0.05). Wet roasting increased (p < 0.05) the rapidly digestible starch content, more so with a tempering moisture of 30%. Overall the results from this study will allow for the utilization of wet roasted pulses as ingredients based on their functional properties and protein quality.