How to detect pesticides throughout the supply chain

“Accurate sampling and analysis in an accredited laboratory are the key points to identify if a commodity actually contains pesticides over the MRLs. By accurate sampling and analysis, we measure the level of pesticides in our supply chain and we are able to work on preventive or corrective actions to limit the negative health effects. Cutting back on pesticides is as apparent as it is necessary. This does not mean that we will see more insects in our installations and products. Significant advances are made on alternative methods killing insects in natural ways.”

Untitled-1

Peter de Weert

International Pest Control Manager
Control Union

There are several points in the supply chain where pesticides are applied. It is very common to fight plant diseases, weeds and harmful insects with chemicals on field level but there are even more cases when post-harvest pesticide applications are made: in the warehouse, during transit, in the silos, in fumigation chambers and more.

Next to analysis of traces in foodstuffs, control of pesticides in general has already for long time been under scrutiny of important global organizations. Already in 1992 the Kyoto Protocol not only negatively assessed the greenhouse gas effect of pesticides but its impact on human health as well. This was further underlined by various important global protocols through the years and for example by WHO, in the 2014 WHO and FAO ‘International Code of Conduct on Pesticide Management’ in which it is stated that pesticides are among the leading causes of death by self-poisoning, in particular in low- and middle-income countries and that as they are intrinsically toxic and deliberately spread in the environment, the production and distribution of food supply chains. Therefore, use of pesticides requires strict regulation and control. Regular monitoring of residues in food and the environment is also required. An extra dimension to this is given by the fact that pesticides are at all not accepted in biological produced commodities an ever-growing industry.

As recent as Friday 7-9-2018 The European Union has announced that they will ban the world’s most widely used insecticides from all fields due to the serious danger they pose to bees. The ban on neonicotinoids, is expected to come into full force by the end of 2018 and will mean they can only be used in closed greenhouses.

Bees and other insects are vital for global food production as they pollinate three-quarters of all crops. The plummeting numbers of pollinators in recent years has been blamed, in part, on the widespread use of pesticides. The EU already banned the use of neonicotinoids on flowering crops that attract bees, such as oil seed rape, in 2013.

Accurate sampling and analysis in an accredited laboratory are the key points to identify if a commodity actually contains pesticides over the MRLs (Maximum Residue Limit).

Sampling
Usually takes place when a commodity changes ownership and accordingly changes storage or means of transportation, for example when unloading a ship to trucks. During this transfer, representative samples may be taken using special tools and following ISO or GAFTA sampling rules. Independent surveying companies are appointed to draw the samples. Sampling points must be carefully selected in order to acquire samples that are representative of the transferred commodity. The amount of increments is also very important. If for example only one side of a conveyor belt, or only a specific part of a stockpile is sampled, major differences and / or discrepancies can occur in the final analysis. Samples taken are divided to smaller units leading to a sample size that is convenient for lab analysis. For example, out of a cargo of wheat weighing 5.000 metric tons, only a sample of few grams will finally reach the lab and will be used for analysis. It is evident that proper sampling and sample division are very important to determine actual quality parameters

Analysis
In 2016 the European Authority for Food Safety (EFSA) analyzed samples originating from countries outside the EU and found these samples to have a significantly higher MRL (maximum residue level) exceedance rate compared to food produced in the EU and EEA countries. To be specific 7.5 % of the samples produced in third countries exceeded the legal limit compared to 1.4 % of samples within the EU and EEA provenance. Wheat was specifically mentioned as one of the commodities where levels above MRL were frequently found, specifically traces of chlormequat.

An extensive range of accredited analyses for identifying mycotoxins, dioxins, heavy metals and pesticides (fungicides, herbicides and biocides) are available. There are over 1000 pesticides which can be found on cereal commodities by proper analysis! Without getting to specific the most commonly used methods remain solvent extraction and solid-phase extraction. The QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) approach is being increasingly used for the development of multi-class pesticide residues methods in various sample matrices. MS detectors-triple quadrupole (QqQ), ion-trap (IT), quadrupole linear ion trap (QqLIT), time-of-flight (TOF), and quadrupole time-of-flight (QqTOF)-have also been established as powerful analytical tools sharing a primary role in the detection/quantification and/or identification/confirmation of pesticides and their metabolites. Recent developments in analytical instrumentation have enabled coupling of ultra-performance liquid chromatography (UPLC) and fast gas chromatography (GC) with MS detectors, and faster analysis for a greater number of pesticides.

The QuEChers method is most relevant in a commercial and practical point of view. In this method the sample is homogenized and centrifuged with a reagent and agitated for just 1 minute. The reagents used depend on the type of sample to be analyzed. Following this, the sample is put through a dispersive solid phase extraction cleanup prior to analysis by gas-liquid chromatography or liquid-liquid chromatography.
Samples prepared using the QuEChERS method can be processed more quickly using a homogenization instrument. Such instruments can homogenize the food sample in a centrifuge tube, then agitate the sample with the reagent of choice, before moving the extracted sample for centrifuging. By using such an instrument, the samples can be moved through the QuEChERS method very quickly.

Some modifications to the original QuEChERS method have to be introduced to ensure efficient extraction of pH-dependent compounds (e.g., phenoxyalkanoic acids), to minimize degradation of susceptible compounds (e.g., base and acid labile pesticides) and to expand the spectrum of matrices covered.

By accurate sampling and analysis, we measure the level of pesticides in our supply chain and we are able to work on preventive or corrective actions to limit the negative health effects. Cutting back on pesticides is as apparent as it is necessary. This does not mean that we will see more insects in our installations and products. Significant advances are made on alternative methods killing insects in natural ways.
-Heat treatment of production lines and empty silos is a very successful method as above 50C no insects survive.
-Controlled atmosphere on products in bulk or in packages, in chambers and silos is another successful alternative to pesticides as below 1% oxygen no pests survive.

Food quality and safety are the top objectives for the milling industry. Furthermore, there is a responsibility for all of us to work towards a sustainable and safe supply chain.

We also suggest you to read our previous article titled "Measuring particle sizes and optimizing processes".

Check Also

The Stone-Age Taste of Flat Bread

“Since mills in the Middle East are confronted with fluctuating cereal qualities, just as elsewhere, …