Effect of microwave roasting on chemical and bioactive compounds of pistachio (Pistacia vera L.) kernels

Abstract

SummaryIn the present study, the effect of microwave roasting on the total phenolic quantities, antioxidant activities, phenolic constituents, fatty acids and tocopherol amounts of the pistachio kernel and oil was revealed. The moisture, oil, total phenolic amounts and antioxidant capacity value of raw and roasted pistachio nuts were assessed as 31.13%, 28.58%, 34.79 mgGAE/100 g and 0.75%–3.18%, 56.91%, 18.80 mgGAE/100 g and 2.26%, respectively. The raw pistachio nut contains 1.90 gallic acid, 0.22 3,4‐dihydroxybenzoic acid, 0.87 (+)‐catechin, 0.15 1,2‐dihydroxybenzene, 0.15 rutin trihydrate, 0.16 resveratrol, 0.1 quercetin, 0.19 kaempferol and 0.24 mg/100 g isorhamnetin. In addition, microwave‐roasted nuts contained 0.75 gallic acid, 0.62 3,4‐dihydroxybenzoic acid, 0.83 (+)‐catechin, 0.47 1,2‐dihydroxybenzene, 0.21 syringic acid, 0.17 caffeic acid and 0.17 mg/100 g quercetin. The raw and roasted pistachio nut oils contained 74.12% and 71.16% oleic, 13.76% and 15.23% linoleic, 8.16% and 8.92% palmitic and 2.09% and 2.10% stearic acids, respectively. The oil samples of the raw and roasted kernels contained 8.15 and 0.00 α‐tocopherol, 63.78 and 7.60 β‐tocopherol, 8.72 and 7.40 ɣ‐tocopherol and 5.61 and 6.77 mg g−1 δ‐tocopherols, respectively. The total phenolic quantity of the pistachio kernel roasted by microwave decreased significantly. Phenolic compounds of the pistachio kernel showed partial differences depending on microwave heating. Differences were monitored in the fatty acid profiles of Pistachio kernel oils. β‐tocopherol quantity of the oil of the pistachio kernel heated by microwave significantly decreased.