O. López-Fernández

A Review on the Fermentation of Foods and the Residues of Pesticides—Biotransformation of Pesticides and Effects on Fermentation and Food Quality

Residues of pesticides in food are influenced by processing such as fermentation. Reviewing the extensive literature showed that in most cases, this step leads to large reductions in original residue levels in the fermented food, with the formation of new pesticide by-products. The behavior of residues in fermentation can be rationalized in terms of the physical-chemical properties of the pesticide and the nature of the process. In addition, the presence of pesticides decrease the growth rate of fermentative microbiota (yeasts and bacterias), which provokes stuck and sluggish fermentations. These changes have in consequence repercussions on several aspects of food sensory quality (physical-chemical properties, polyphenolic content, and aromatic profile) of fermented food. The main aim of this review is to deal with all these topics to propose challenging needs in science-based quality management of pesticides residues in food.

Combined determination and confirmation of ethylenethiourea and propylenethiourea residues in fruits at low levels of detection.

In this work, a new method for the determination of ethylenethiourea (ETU) and propylenethiourea (PTU) in fruits and vegetables is presented. Different extraction and purification techniques, including matrix solid phase dispersion (MSPD) and solid-liquid extraction (SLE), followed by a clean-up step by solid phase extraction (SPE), were compared. The determination of ETU and PTU was performed by high performance liquid chromatography with diode array detection (HPLC/DAD) or by gas chromatography with mass spectrometry detection (GC/MS). The effect of several parameters on the extraction, separation and detection was studied. The proposed method based on solid-liquid extraction with acetonitrile, clean-up with Envicarb II/PSA cartridges and subsequent analysis by HPLC/DAD was characterised and applied to the analysis of fruits and vegetables from different countries. Analytes recoveries were between 71% and 94% with relative standard deviations (RSDs) ranging from 8% to 9.5%. Quantification limits obtained for ETU and PTU with the HPLC/DAD method were 7 and 16 μg kg⁻¹ in strawberries (fresh weight), respectively. For apples, they were 11 and 25 μg kg⁻¹, respectively.

Effects of hydrochemistry variables on the half-life of mancozeb and on the hazard index associated to the sum of mancozeb and ethylenethiourea.

&NA; Mancozeb is a dithiocarbamate non‐systemic agricultural fungicide with multi‐site, protective action. It helps to control many fungal diseases in a wide range of field crops, fruits, nuts, vegetables, and ornamental plants. We have investigated the stability profiles of mancozeb in aqueous solutions to determine the effect of pH, temperature and light on the degradation process of mancozeb. In addition, the toxicological risk for humans associated with the joint intake of mancoze7b and its final degradation product, ethylenethiourea (ETU), was calculated and modelled as a function of the experimental conditions. Stability study results showed a very low stability profile of mancozeb in all the aqueous solutions with rapid degradation that varied with experimental conditions. The process followed first order kinetics. The study of the degradation kinetics showed a significant effect of pH*temperature interaction on the degradation process. The results also expressed that light has a greater impact on the stability of mancozeb and the formation of ETU. The current study concludes that mancozeb is unstable in aqueous solutions, particularly at an acid pH, in addition to presenting both severe light and lower temperature sensitivity. The toxicological risk associated with mancozeb degradation increases with time and temperature, being higher at basic pH and in absence of light. HighlightsMancozeb hydrolysis follows a first order reaction model.Mancozeb hydrolysis is controlled by the pH*temperature interaction.ETU and EBIS were the main hydrolysis products.Mancozeb conversion to ETU is minimized at pH 2, 25 °C in presence of light.Risk associated with mancozeb degradation is higher at basic pH in absence of light.

Modelling the isothermal degradation kinetics of metrafenone and mepanipyrim in a grape juice analog

Five photodegradation products of metrafenone (MTF) and six of mepanipyrim (MEP) were identified in synthetic grape juice at 25 °C and the structures of the main reaction products established. The degradation of MTF and MEP was modelled by using three different strategies involving monitoring (a) the disappearance of the parent compound, (b) the conversion of the parent compound into its main structurally related reaction products and (c) the degradation of the parent compound to all intermediates and degradation end-products. The kinetic coefficients of degradation for these fungicides were determined and the corresponding half-lives found to be 20.8 h for MFT and 10.1 h for MEP. The proposed models afford reasonably accurate interpretation of the experimental data. Based on the results, modelling the kinetics of disappearance of the parent compound by itself does not ensure the best fit of the degradation behaviour of the fungicides.