Etephon degradation in grapes

Ethephon (2-chloroethylphosphonic acid), is an ethylene-releasing agent used as growth regulator and ripening agent for many crops. For table grapes, Ethephon is mainly used to accelerate the ripening process and to improve the color uniformity in red varieties. The European Commission has fixed the residue concentration at 1.00 mg/kg, but some retailers set own limits of e.g. 1/3 of the MRL. Mediterranean growers, cannot comply with the 1/3 of EU MRL, despite the fact that they strictly adhere to the recommended application doses and the pre-harvest intervals established in the framework of Good Agricultural Practices (GAP). The pre-harvest interval after the application is 21 days (T+21). The main reason for this study conducted by ANALYTICA ALIMENTARIA was to know the degradation process of Ethephon in table grapes under real production conditions, in order to handle the production and commercialization of table grapes in a safe way for all parties. Ethephon was applied as the grapes started to ripen at concentrations related to the commercially recommended dose of 1 l of Ethephon per 1,000 l of water and per hectare defining this dose as 100%. Data on the plant development, such as climatic conditions, berry size, brix degrees, color evolution and number of bunches per tree. was collected weekly for a period of 28 days. Moreover, leaves and fruits were sampled and analyzed for Ethephon residues. The Ethephon concentration was measured in the laboratory twice by the LC/MS-MS; SOP LC 027 2014-03 (QuPPE) method and the average was taken.