Decreased sulforaphene concentration and reduced myrosinase activity of radish (Raphanus sativus L.) root during cold storage

Glucosinolates (GSLs) are sulfur-rich secondary metabolites characteristic of the Brassica vegetables. After disruption of tissue, GSLs are hydrolyzed by myrosinase to produce hydrolysis products, isothiocyanates (ITCs) including sulforaphene (SFE), which is one of the main ITCs in radish roots and has health benefits. The postharvest quality of radish roots for SFE content and myrosinase has not yet been assessed. In this study, we measured the SFE concentration and myrosinase activity in two radish cultivars, namely 'Chungwoon plus' (CP) and 'Taebaek' (TB), during storage at 0 degrees C for 4 months. The SFE concentrations in the CP and TB cultivars were 66.0 and 69.2 mu g/g fresh weight, respectively, at harvest. After 4 months in storage, the concentrations were 12.7 and 41.2 mu g/g fresh weight in the CP and TB cultivars, which represented an 81 and 40% reduction from the SEE concentrations at harvest, respectively. The myrosinase activity decreased from 0.31 to 0.1 in CP and 0.32 to 0.06 U/g fresh weight in TB, respectively. The reduced myrosinase activity decreased the formation of SFE. Our findings suggest that postharvest conditions, even with storage of the radish roots at cold temperature, may play a key role in either the maintenance of SFE or myrosinase activity. The development of specific postharvest technology to improve the freshness of radish roots is required because radish roots are vegetables with health benefits and are often stored long term. (C) 2014 Elsevier B.V. All rights reserved.