Treatment with Thyme Essential Oil Delays Loss Reductions in Postharvest Chinese Flowering Cabbage

Leaf yellowing is the primary indicator of deterioration in the quality of Chinese flowering cabbage. In this study, Chinese flowering cabbage (Brassica rapa var. Parachinensis), a perishable, freshly cut vegetable, was treated with 0.5 ppm thyme essential oil and stored at 15 °C with 90% relative humidity (RH), with the aim of exploring its preservation effect. Compared with the control group, the treatment postponed the yellowing and chroma decline of leaves by 24% and 60%, respectively, inhibited the degradation of chlorophyll by 62% and the increase in relative conductivity by 62%, and sustained high contents of vitamin C (0.238 mg/g), soluble solids (8.5%), soluble sugar (2.658 mg/g), and soluble protein (5.294 mg/g) after 7 days of storage. Moreover, the rising activity of peroxidase (POD) during treatment was slowed during storage, alleviating lignification, while the activity of catalase (CAT) was dramatically enhanced in the late storage stage, avoiding oxidative damage and improving storage quality. Overall, thyme essential oil treatment significantly delayed the senescence of Chinese flowering cabbage and demonstrated considerable potential as a natural preservative.