Enzymatic browning in relation to permeation of oxygen into the kernel of postharvest areca nut under different storage temperatures

Abstract

Previous study indicates that kernel of areca nut is susceptible to enzymatic browning caused by phenolic oxidation, which involves the ingression of oxygen into interior tissue. However, the reason for permeation of oxygen into the interior of areca nut and its possible influencing factors (e.g., temperatures) are little known. In the present study, we set three storage temperatures (25, 10, and 5°C) and investigated the effects on kernel browning and related physic‐biochemical and tissue morphological changes. The results showed that the most severe kernel browning was observed in areca nut stored at 25°C, followed by 5°C. Comparatively, a slower browning development was found in areca nut stored at 10°C. More serious kernel browning at 25 and 5°C might be attributed to increased membrane permeability and aggravated tissue damage in view of morphological observations on pericarp, mesocarp, and kernel shell. Higher lignin content and phenylalanine ammonia‐lyase activity were observed in mesocarp of areca nuts stored at 25 and 5°C as compared to 10°C, indicating that mesocarp lignification could facilitate the permeability of oxygen. Furthermore, the data showed that storage at 25 and 5°C induced the higher polyphenol oxidase activity while accelerating the decline in total phenolic content in areca nut kernel, which could contribute to higher occurrence of enzymatic browning reaction compared to that at 10°C. These results suggest that natural senescence at 25°C and severe chilling stress at 5°C could be influencing factors triggering the permeation of oxygen, leading to internal kernel browning in areca nut.

Effects of Postharvest Storage Temperature on Physical Characteristic, Phenolic Compounds, and Antioxidant Activity of Cocoa Pod Husk

“…This showed that the cocoa pod tissue did not undergo significant morphological changes at 30 °C. The results obtained were similar to studies on the storage of areca nuts (Pan et al, 2021), reporting that between temperature variations of 5, 10, and 25 °C, the storage temperature of 10 °C did not cause significant morphological changes in areca nuts, while at 25 and 5 °C, lignification occurred in the areca bean mesocarp tissue. An increase in lignin content was caused by natural aging and cold stress, respectively.…”

Research Progress on Processing Technology of Refined Betel Nut in China: A Review

“…However, as a tropical fruit, the betel nut can experience a chilling injury when stored below 14 • C [83]. Storage at 25 or 5 • C increased polyphenol oxidase (PPO) activity and reduced the total phenolic content in the kernel [86]. Another study has shown that a storage temperature of 10 • C was better than 4 • C [87].…”

tert-Butylhydroquinone alleviates postharvest endocarp browning of longan fruit by regulating antioxidant metabolism

“…Mounting evidence suggests that sustained accumulation of ROS is the main factor that causes postharvest endocarp browning of longan fruit. Excessive amounts of ROS accelerate lipid peroxidation in membranes, resulting in the breakdown of cell structure and the following disruption of enzyme-substrate compartmentalization, which allows the interaction between polyphenol oxidases (PPOs) that located in cytoplasm and their phenolic substrates from vacuoles (Pan et al 2021;Yan et al 2022). The browning reactions are then triggered, PPOs catalyze continuous oxidation steps and form redox-active quinones, which subsequently react with amino acids, polyphenols, and proteins, and converted into brown polymers, melanin (Zhang et al 2021).…”