Impact of roasting on the physicochemical, functional properties, antioxidant content and microstructure changes of Algerian lentil (Lens culinaris) flour

Abstract

The effect of roasting on the physicochemical and functional properties of Algerian whole lentil (Lens culinaris) flour was investigated. Whole milk absorption capacity and skim milk absorption capacity as functional properties were reported for the first time on the lentil flour. Lentil seeds were roasted at 150 °C for 30 min and ground to flour, which were then extracted with aqueous methanol (80%). The phenolic contents of the extracts (phenolics, flavonoids, tannins, anthocyanins, flavonols, carotenoids and lycopene) were quantified and the antioxidant activity was evaluated by the DPPH free radical scavenging activity to determine the impact of the roasting. Similarly, the changes on the microstructure were evaluated by the scanning electronic microscopy. The results showed that the roasting treatment had different impacts on all properties studied. Roasting treatment affect positively the physicochemical properties (conductivity, browning index and A420) except the moisture content, which decreased significantly. For functional properties, dispersibility, water absorption capacity, hydrophilic/lipophylicy ratio, whole milk absorption capacity, emulsifying activity, foaming stability and swelling capacity were improved after roasting, whereas oil absorption capacity, emulsion stability, foaming activity decreased significantly. After roasting, the flavonoids, tannins and flavonols increase significantly; nonetheless, phenolics, anthocyanins, carotenoids, lycopene contents and the antiradical activity against DPPH° were significantly reduced. Lentil flour did not show significant changes in microstructure after roasting. Based on these results, the positive impacts of roasting outweighed the negative impacts, therefore, roasting of lentils can be applied to produce flours with improved functional properties and important bioactive molecule content and can be used in the formulation of food products.