Objective of the study

Processing studies have the following objectives:

• To obtain information about breakdown or reaction products which require a separate risk assessment.
• To determine the quantitative distribution of residues in the various processed products, allowing the estimation of processing factors for products which may be consumed.
• To allow more realistic estimates to be made of the chronic or acute dietary intake of pesticide residues.

Processed food means the product, resulting from the application of physical, chemical or biological processes to a “primary food commodity” intended for direct sale to the consumer, for direct use as an ingredient in the manufacture of food or for further processing. Examples of processing are: food preparation, e.g. cleaning and peeling; cooking; juicing; brewing and vinification; canning; milling and baking; oil production; and drying.

The processing factor for a specified pesticide residue, commodity and food process is the residue level in the processed product divided by the residue level in the starting commodity, usually a raw agricultural commodity.

The following processing studies may be conducted:

1. Determination of the nature of the residues in processed commodities.

The specific objective of studies of the nature of residues is to establish whether or not breakdown or reaction products of residues in the raw commodities are formed during processing which may require a separate risk assessment.

2. Determination of the magnitude of residues in processed commodities.

The specific objective of studies to estimate the magnitude of residues in processed commodities is to determine the quantitative distribution of residues in the various processed commodities used as food or feed, and to estimate processing factors accordingly.

Further information on effects of processing and/or household preparation on residues can be found in Chapter 3.7 of the JMPR Procedure Manual.

Worked examples on this topic are provided in Chapter 10 of the JMPR Training Manual.

Circumstances in which the study is required

Processing studies are required if significant residues occur in plants or plant products which are processed. “Significant residues” normally means residues >0.1 mg/kg in raw agricultural commodities (RAC). If the pesticide concerned has a low ARfD or ADI, consideration has to be given to conducting processing studies with analyses for residues

Processing studies are normally not required if:

• no residues above the limit of quantification occur;
• the plant or plant product is normally only eaten raw, e.g., head lettuce;
• only simple physical operations such as washing and cleaning are involved;
• the pesticide or metabolite has a water solubility < 0.01 mg/L.

Test conditions

1. Determination of the nature of the residues in processed commodities.

A set of three representative hydrolysis situations simulating the relevant processing operations is generally investigated. The effects of processes other than hydrolysis, e.g., oxidation, reduction, enzymatic or thermal degradation, may also have to be investigated if the properties of the pesticide or its metabolites indicate that such processes may produce toxicologically significant degradation products.

2. Determination of the magnitude of residues in processed commodities.

The procedures to be used in processing studies should always correspond as closely as possible to those that normally occur in practice. Thus products of household preparation, e.g., cooked vegetables, should be produced using the equipment and preparation techniques normally used in households, whereas industrial items such as cereal products, preserves, fruit juices or sugar should be produced by procedures representative of commercial food technology.

Test substance

1. Determination of the nature of the residues in processed commodities.

The studies should be conducted with one or more radio-labelled forms of the relevant substance.

2. Determination of the magnitude of residues in processed commodities.

Samples of the raw agricultural commodities (RAC) used in processing studies should contain quantifiable residues (i.e. = limit of quantification (LOQ)), but preferably up to at least 0.1 mg/kg or 10 times the LOQ, so that processing factors for the various processed products can be determined.

Only RACs containing incurred residues shall be used for processing (i.e. residues in a commodity resulting from specific use of a pesticide, consumption by an animal or environmental contamination in the field, as opposed to residues from laboratory fortification of samples).

Typical endpoints of the study

• Identification of any new metabolites, specific to processing;
• Residue levels of the pesticide (and relevant metabolites) in processed commodities, expressed as mg a.i./kg substrate;
• Processing factors.

Testing guidelines

The following testing guidelines may be used for processing studies:

• OECD Guidelines for the Testing of Chemicals. Test No. 507: Nature of the pesticide residues in processed commodities – high temperature hydrolysis. 

• OECD Guidelines for the Testing of Chemicals. Test No. 508: Magnitude of the pesticide residues in processed commodities.

• OECD Series on Testing and Assessment No 96. Guidance document on magnitude of pesticide residues in processed commodities. Available at: http://www.oecd.org/chemicalsafety/testing/seriesontestingandassessmentotheregpesticideresiduechemistry.htm

• USEPA-OCSPP Harmonized Test Guidelines. Test No. OPPTS 860.1520. Residue Chemistry Test Guidelines – Processed food/feed.

• European Commission. Guidelines for Residue Data – Processing studies. (Technical Guidelines - Appendix E)