Thyme essential oil-loaded electrospun nanofiber membranes as active packaging: effects on physicochemical quality and antioxidant-related compounds of autumn olive (Elaeagnus umbellata) fruit during shelf life

This study aimed to assess the effects of thyme oil-loaded nanofiber (NF) membranes used as an active packaging component on the selected postharvest quality attributes and bioactive compound retention of autumn olive ( Elaeagnus umbellata ) fruit during shelf-life period (21 ± 1 °C and 75 ± 5% RH) for 12 d. Quality parameters, including weight loss, soluble solids content (SSC), titratable acidity (TA), vitamin C, total phenolics (TPC), total flavonoids (TF), and antioxidant activity determined by DPPH and FRAP assays, were evaluated. Thyme oil-free control membranes were compared with NF membranes prepared with nominal thyme oil loadings of 50 and 100 mg (50 mg NF and 100 mg NF) on days 4, 8, and 12. Both NF treatments significantly reduced weight loss on day 12. NF-treated fruit had lower SSC and TA than the control at all sampling dates, indicating moderated physicochemical changes rather than preservation of the initial acidity. Vitamin C was better retained only in the 100 mg NF treatment, whereas the 50 mg NF treatment did not differ from the control. Both NF treatments resulted in higher TF values on days 8 and 12 and higher FRAP values at all sampling dates, whereas TPC was higher only in the 100 mg NF treatment on day 4. The higher DPPH and FRAP values indicate greater antioxidant capacity of the fruit extracts rather than reduced oxidative stress in fruit tissues. The 100 mg NF treatment was generally associated with higher values of the measured bioactive compounds and antioxidant activity. In the multivariate analyses, vitamin C, TPC, TF, DPPH, and FRAP were strongly and positively associated, partly reflecting their common decline during shelf life, and NF-treated fruit, particularly 100 mg NF fruit, were more closely associated with these variables than control fruit at each sampling date. Under the tested conditions, thyme oil-loaded nanofiber membranes may be a candidate active packaging approach for retaining selected physicochemical attributes and antioxidant-related compounds of autumn olive fruit during shelf life; their effects on firmness, color, microbial decay, sensory quality, and marketable shelf life remain to be determined.