14C-dimethoate residues in olive oil during oil processing

An olive tree was treated twice in the field with 14C-dimethoate (237.7 muCi, 2.4 g) and 14C residues were determined in the olive fruits at harvest. The fruits were crushed and pressed to extract the crude oil, then refined by neutralization, bleaching and deodorization. The crude oil contained 14.1% of the total 14C in the olive fruits. Neutralization resulted in a reduction of 14C by about 50% of the total 14C residues in oil. Bleaching and deodorization processes further reduced the 14C residues and the refined oil contained 31.6% (which corresponds to 4.4% of 14C residues of the total 14C in olive fruits) of the total 14C in the crude oil. Industrially extracted crude oil was fortified with 14C-dimethoate at 1.8 mg kg-1 (0.02 muCi) level and subjected to the same refining process. A sharp decrease in the amount of 14C was observed by neutralization and the amount of 14C remaining in the refined oil was about 7.3% of the total 14C in the crude fortified oil. The data suggest that the 14C residues in the aged and the fortified oil amples were not of the same nature. The terminal 14C residue in the refined oil obtained from the field experiment did not contain dimethoate and/or its oxon.