Enzymatic activities of curry leaves (Murraya koenigii L.) during storage in chilling temperature

Curry leaves are highly susceptible to chilling injury (CI) under prolonged storage at 4-8 degrees C. CI in plants is a complicated process interconnected through several biochemical reactions especially enzymatic activities. Present study monitored the activities of polyphenol oxidase (PPO), peroxidase (POD), phenylalanine ammonia lyase (PAL), lipoxygenase (LOX), superoxide dismutase (SOD), catalase ( CAT) and glutathione peroxidase (GPX) in curry leaves stored at 4 degrees C under perforated LDPE packaging (100 g package(-1)). Leaves without packaging served as control. Surface colour (L*, a*, and b*), electrolytic leakage, chlorophyll content, total phenolic content (TPC) and total antioxidant activity (TAA) were measured in leaf samples. Samples were analysed every 3 days for 15 days. Prolonged chilling temperature induced CI in curry leaves. Leaf surface colour such as (L* and b*) gradually decreased while leaf redness ( a*) gradually increased, reflecting browning enzymatic activities and chlorophyll degradation. Electrolytic leakage was severe in control leaves. TPC influenced the TAA activities in curry leaves, and the values tended to decrease with time (P<0.05). During the initial storage period (0-8 days), enzymatic activities remained constant but increased markedly during 9-15 days at 4 degrees C. LOX increased in control leaves throughout storage, and as a consequence, PPO, POD and PAL activities were also higher in control. Similarly, SOD, CAT, and GPX were also found higher in control, indicating that prolonged chilling increased reactive oxygen species in control samples. The LDPE package that acted as a barrier between the package and samples and slightly reduced the CI in curry leaves.