Effects of different table olive processing methods on the residues of malathion and malaoxon a degradation product

The control of pests and diseases involved in olive fruit cultivation has made the use of pesticides indispensable. However, the errors made while applying these pesticides and the effect of the different steps of olive processing cause pesticide residues in the final consumer products. This study aims to examine the effects of table olive processing methods on the residues of malathion being allowed and widely used in Turkey and malaoxon its degradation product. For the olive fruits used in the experiment, some of the trees were sprayed homogeneously with a commercial malathion formulation at a dose of 975 mg/L (legal dose allowed in Turkey and European Union countries) 7 days before harvest. The olive fruits, having been grouped as-sprayed and non-sprayed after harvest, were treated in three different ways as follows; - (i) packaged in vacuum polyethene bags and stored in a refrigerator (4℃), (ii) brined after debittering with a caustic solution, and (iii) directly brined for natural fermentation. Both (ii) and (iii) were left for fermentation at 20°C in a dark environment for 60 days. During the experimental period, changes in microbial groups (total mesophilic aerobic bacteria, lactic acid bacteria, yeast-mold, and enterobacteria growth), acidity-pH, and malathion and malaoxon concentrations were monitored at 0, 1, 3, 5, 7, 15, 30, and 60 days. Lactic acid bacteria and yeast-mold growth was not observed in any of the samples during the fermentation processes. No growth of mesophilic aerobic bacteria and enterobacteria was detected in the sprayed samples, except for the samples treated with caustic solution. The effects of fermentation period and processing methods both as separate and combined on the change in malathion and malaoxon concentrations during processing were found to be statistically significant. The most significant decrease in malathion concentrations was observed in alkali treated samples (%95,17-98,55), and followed by naturally fermented (%76,81-88,41) and vacuum packed samples (%74,40-75,85).