Level and fate of chlorpropham in potatoes during storage and processing.

Chlorpropham (isopropyl 3-chlorocarbanilate) is a pesticide used to control sprouting of potatoes during long-term storage. The objective of the present study was to establish the total chlorpropham residue balance (residues in unwashed and washed whole tubers, peeled tubers, peels, boiled and pureed tubers, and washing and cooking waters) for two potato varieties after uniform application as a function of storage time under different typical storage conditions (in a basement, storehouse, and refrigerator) in Lithuania. Chlorpropham concentration on washed and unwashed tubers decreased from approximately 15 mg kg(- 1) after storage for 28 d to approximately 9 mg kg(- 1) after storage for 85 d. Peel concentrations decreased from approximately 50 mg kg(- 1) at 5 d after treatment to approximately 20 mg kg(- 1) at 85 d after treatment. The average concentration in the two varieties of peeled tubers in the three storage facilities was 1 mg kg(- 1). Chlorpropham concentrations in the wash water decreased from 3.5 to 1.0 mg L(- 1) when the storage time increased from 28 to 85 d. The cooking water concentration similarly decreased, from > 0.2 mg L(- 1) at 28 d after treatment to > 0.1 mg L(- 1) at 85 d after treatment. The results of this study show that chlorpropham concentrations in tubers under these typical conditions were below the recently revised levels that are acceptable for residues in whole potatoes (30 mg kg(- 1)) and peels (40 mg kg(- 1)). Also, despite fluctuating conditions during storage, chlorpropham treated tubers did not sprout, as compared to untreated tubers, which sprouted.