The influence of microwave cooking on the nutritional composition and antioxidant activity of the underutilized perah seed

Abstract

Background. Perah seed is one of the most underutilized oilseeds, containing high nutritional values and high percentage of α-linoleneic acid, which may have a high potential in food and pharmaceutical applications. The main objective of this study was to evaluate the influence of microwave (MW) cooking on the proximate composition and antioxidant activity of perah seeds. Material and methods. In this study, the proximate composition and amygdalin concentration of MW irradiated perah seeds were determined. The total phenolic content (TPC), Maillard reaction products (MRPs) and antioxidant activity of methanol (PME), 70% methanol in water (PMW), ethanol (PEE), 70% ethanol in water (PEW) extracts and methanol extract of oil (PMO) were evaluated during MW cooking. The antioxidant activity was evaluated using multiple assays, namely DPPH radical scavenging activity, ß-Carotene bleaching assay, and reducing power. Results. Microwave cooking did not significantly increase crude lipid and carbohydrate content, and the amounts of other nutrients such as ash, crude protein and fibre remained almost unchanged. As evaluated by HPLC, the amygdalin concentration in the seeds was reduced by MW cooking. The TPC, MRP and antioxidant activity of the solvent extracts of perah seeds increased significantly with increasing roasting time. Of all the extracts, PMW at all MW cooking times displayed the highest antioxidant effectiveness. However, thermal treatment significantly reduced the antioxidant properties of PMO. The values for TPC, MRP and antioxidant effectiveness of the samples were ranked in the following order: PMW > PEW > PME > PEE > PMO, in both control and microwaved samples. Conclusions. In determining the overall quality of the products, MW cooking time was found to be a critical factor. Solubilization of phenolic compounds and formation of MRPs during MW cooking could have caused the increase in antioxidant activity of the perah seeds.