Effect of alkali treatment and natural fermentation on the residue behaviour of malathion and malaoxon during table olive production

Abstract

Pesticide use is indispensable for combating diseases occurring during olive cultivation. However, this has led to challenges of pesticide residues in consumer products as a result of pesticide application errors and the methods used during processing and preservation. This work aimed to identify the effects of table olive processing and preservation techniques on the concentrations of malathion and its degradation product malaoxon. For this purpose, olive trees in an experimental olive orchard were sprayed homogeneously with malathion at a dose of 975 mg L⁻¹ and processed as (i) vacuum-packed, (ii) alkali treated and (iii) directly brined for natural fermentation. The changes in microbial growth, pH-acidity and pesticide (malathion and malaoxon) concentrations were monitored regularly during the experiment. Lactic acid bacteria, yeast and mould growth were not detected in any of the treatments. Mesophilic aerobic bacteria and enterobacteria were the dominant microbial groups in all non-sprayed treatments, but no enterobacteria growth was detected in sprayed treatments. Lower pH values were observed in the brines of natural fermentation treatments of both sprayed and non-sprayed olives. The independent effects of time and processing method and their interactions on malathion and malaoxon concentrations were found significant (p < .05). During the experiments, the highest reduction in malathion concentration was observed in alkali treated samples (95–99%), followed by naturally fermented (77–88%) and vacuum-packed samples (74–76%). Processing factors for all treatments were lower than 1.

Graphical Abstract

Keywords:

• Organophosphorus pesticides
• Liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS)
• alkali
• maximum residue limit (MRL)

Acknowledgements

This work is a part of Abdurahman Luyinda’s Master of Science Thesis. Aysegul YILDIRIM KUMRAL designed and set up the experiments, Abdurahman LUYINDA and Aysegul YILDIRIM KUMRAL performed all of the tests, contributed in writing, reading, and approving the manuscript. Authors especially thank to Prof. Dr. N. Alper Kumral, Gulden Hazarhun and Busra Maden for their kind assistance during pesticide applications and analysis.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Bursa Uludag University Scientific Research Projects Unit under the Grant number FYL-2022-745.