Effects of Short-duration Microwave Treatment on Biochemical Properties, Essential Oil Characteristics and Storage Behavior of Foeniculum vulgare Mill. Seeds

Abstract

Foeniculum vulgare Mill. (fennel) seeds were evaluated to determine the effects of short-duration microwave irradiation on biochemical attributes, essential oil characteristics, storage infestation and subsequent field performance. Seeds were exposed to 2.45 GHz microwave radiation for 0–100 s at 10 s intervals and assessed immediately after treatment, after 3.5 months of storage and after field cultivation. Before storage, total phenolic content (TPC) and total flavonoid content (TFC) were highest at 30 s (3.27% and 1.23%, respectively), whereas antioxidant capacity was highest at 40 s (10.28% inhibition). Essential oil content and density declined with increasing exposure, from 1.39% and 0.99 g mL⁻¹ in the untreated control to 0.52% and 0.91 g mL⁻¹ at 100 s. After storage, the highest TPC, TFC and antioxidant capacity occurred at 10, 30 and 40 s, respectively. Red flour beetle infestation decreased as exposure duration increased and was not observed at 50–100 s. Storage significantly reduced essential oil content, oil density and TFC, whereas TPC and antioxidant capacity remained statistically unchanged. In the field experiment, seed yield was highest in the untreated control (398.67 g) and lowest at 100 s (49.00 g). Among harvested seeds, the 40 s treatment produced the highest TPC and antioxidant capacity, while the 30 s treatment produced the highest TFC. Overall, moderate microwave exposures favoured selected biochemical attributes, whereas prolonged exposure reduced essential oil retention and field seed yield.