Abstract: In order to investigate the effect of high relative humidity (RH) storage on delaying postharvest yellowing of broccoli heads and to explore its relationship with sugar metabolism, broccoli heads were stored at (4.0 ± 0.5) ℃ in either a dry-fog humidity controlled cold room with 95%–98% RH or a normal cold room with 70%–75% RH for 36 days. Samples were taken at 6-day intervals during the storage period to measure the parameters of interest. The results showed that high RH storage could significantly delay the increase in mass loss rate and yellowing index of broccoli, inhibit the activity of chlorophyllase and Mg-dechelatase (MDCase), and maintain high contents of chlorophyll a, chlorophyll b and total chlorophyll. Meanwhile, compared with low RH storage, high RH storage increased the activity of sucrose-phosphate synthase (SPS), reduced the activity of sucrose acid invertase (SAI), glucokinase (GK) and UDP-glucose pyrophosphorylase (UGPase), and maintained high contents of glucose, fructose and sucrose. These results suggest that high RH storage?can maintain high soluble sugar content by regulating sugar metabolism-related enzyme activity and thereby delaying the yellowing of broccoli heads.

Key words: broccoli, high relative humidity storage, mass loss rate, yellowing, sugar metabolism