Guideline No. 7
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Processing studies are used to support a raw commodity MRL proposal and in some cases the setting of a processed commodity MRL. These guidelines give advice on when processing studies should be provided to support the MRL.
There is an increasing need for information about the effects of storage, peeling, washing, cooking and food processing on the fate of agricultural and veterinary chemical residues in foods/animal feeds both from a regulatory and public concern perspective. Consequently in some situations residue levels determined from processing studies allow a more realistic estimation of dietary intake of residues resulting from the use of an agricultural or veterinary chemical.
It should be noted, however, that for many pesticide products no data will be required since residues in raw agricultural or animal commodities are not significant or are non-detectable. In such cases MRLs in the processed foods are covered by the entries for the raw agricultural/animal commodities.
It is intended that this guideline should be in harmony with those used in other countries such as European Union (EU), the United States and Canada, where processing studies are also conditionally required, and with Codex.
Data from relevant studies conducted in other countries, along with appropriate argument, will normally be acceptable for Australia. Completed processing studies conducted overseas should be submitted with an application for registration.
This guideline gives only general advice on when, and what type of processing study may need to be carried out. In some situations it may be necessary to produce a protocol in consultation with the National Registration Authority. Further detailed information about the conduct of processing studies can be obtained from Codex4, EU1 and the US EPA guidelines2.
Processing studies may be required in the following situations:
- when the theoretical maximum daily intake (TMDI) exceeds the acceptable daily intake (ADI) so as to determine the level of residue in the consumed food relative to the raw commodity and thus calculate a processing factor (relative concentration or reduction of residues) to allow a better estimate of actual daily intake of residues;
- when there is a possibility that processing may convert residues into a metabolite that has toxicological significance;
- when it is evident that residue levels in the processed food/feed will be greater than in the raw agricultural commodity and hence there is a need to set MRLs for various processed foodstuffs; and
- when the commodity contains residues above the limit of quantitation and processing studies are mandatory, e.g. wheat;
It is expected that processing studies will be required when significant (>0.1 mg/kg) residues are present in the following raw commodities: cereals, oil seeds, citrus, grapes, apples, potatoes and dried fruit and sugarcane.
The decision on whether processing studies (rather than reasoned argument) are necessary to support an MRL proposal for a particular crop/animal commodity will depend on a combination of factors.
- The importance of the level of intake of the processed product in the human or animal diet should be considered when considering whether to do processing studies for TMDI calculations. When the commodity is not widely consumed the impact on the TMDI could be small and a processing study not warranted. In most instances a processing study on one commodity in a group can be extrapolated to cover a range of foods. The importance of the processed product to the human diet can be determined from national dietary surveys conducted by the Australia New Zealand Food Authority (survey last done in 1983). In the case of animal diets, consultation with appropriate animal nutrition experts may be required.
- Physicochemical properties
of the active ingredient can be used to assist in determining whether
residues in processed commodities might be higher than those in raw
agricultural commodities. The likely behaviour of the active ingredient
and/or its metabolites can be drawn from the:
- octanol/water distribution coefficient - e.g. when log Kow is greater than 3 it is probable the residue will be concentrated in oil;
- hydrolysis stability - e.g. when stable to hydrolysis the residue is not readily degraded by storage;
- heat stability - e.g. residue not readily degraded by cooking;
- solubility behaviour - e.g. good water solubility indicates residues may concentrate in juices including wine.
- The level of residues
in the raw commodity. Processing studies are not usually necessary to
support the proposed MRL if:
- the commodity is mainly eaten raw;
- there are no significant (below 0.1 mg/kg) or toxicologically-active residues;
- there is adequate evidence that residue levels in processed foods/feeds will not exceed the level in a raw agricultural commodity.
The process for deciding what data is appropriate to support a proposed MRL is provided in Figure 1. It must be read in conjunction with the accompanying guideline notes.
Processing studies should only be conducted on commodities containing weathered (aged) residues. Using fortified samples is generally not acceptable unless the raw commodity residue consists entirely of a surface residue. If processing results in alteration of the residue, then a radiolabelled processing study to determine the nature of the residue in the food/feed should be carried out on one of the major food processing procedures that involves the use of heat. It will not be necessary to carry out a radiolabel study on every crop/crop group.
When designing a residue program, all raw commodities that are processed should be considered. Lists of commonly processed animal and crops commodities that should be considered are given in Tables 1 and 2.
Processing trials should be considered for all raw commodities which are processed. Applicants who are in doubt about a particular situation should consult with the APVMA before conducting the study(s).
The number of studies needed will depend on the use pattern proposed and the number of crop and livestock species involved. Data should be developed for representative foods. One study per crop or animal or no more than two studies per crop or animal group is generally sufficient, although if the processed products play an important part in dietary intakes additional studies may be required (if in doubt consult with APVMA prior to conducting trials).
Where the raw commodity undergoes a number of processes (e.g. cereals) the initial major primary processed products should be examined first (e.g. flour, bran). Studies on secondary processed and cooked products will only be required if there is reason to believe residues in those commodities could be higher than those occurring in primary processed products. When a number of similar crops are to be included on the label, studies on one representative from each crop group will normally be acceptable.
Studies conducted overseas to determine processing factors will be acceptable provided the processing methods are similar to those used in Australia. Normally the processes and cooking techniques used in Australia are not significantly different from those used in Europe and North America.
Table 1. Commonly processed animal commodities
|Cattle||Cooked edible offal; cooked meat; pasteurised milk; meat meal|
|Sheep||Cooked edible offal; cooked meat, meat meal|
|Pig||Cooked edible offal, cooked meat, meat meal|
|Poultry||Cooked edible offal, cooked meat, cooked eggs, meat meal|
If the label contains more than one animal species then data on one species will normally be sufficient.
Table 2. Commonly processed crop commodities
|Raw commodity||Primary processed food||Secondary processed food||Raw commodity||Primary processed food||Secondary processed food|
|Canola||oil(a)||Potato||chips, dried, boiled|
|Cereals (small grain)||Rice||polished, flour|
|Wheat/rye||flour, bran wheat germ||bread,||Safflower||oil(a)|
|Cotton seed||oil(a)||Sugarcane||raw sugar juice||refined sugar,|
|Berries (currant strawberry)||jam, juice||Sunflower||oil(a),meal|
|Citrus (orange)||juice, pulp, peel||Vegetables|
|Pome (apple)||juice, dried, sauce||Root & tuber (carrots)||juice, cooked|
|Stone (plum, peach)||preserved, jam, dried||Bulbs (onions)||peeled,|
|Sub tropical||juice, preserved||Brassicas (cabbage)||inner & outer leaves|
|Tropical (pineapple)||juice, preserved||Stem (asparagus)||cooked preserved,|
|Grapes||juice, dried,||wine||Legumes (peas)||whole,
|Mungbeans||sprouts||(tomatoes)||juice, preserved, cooked|
|Mustard seeds||powder||Leafy (lettuce); (spinach)||inner & outer leaves cooked|
- If it is likely that a higher residue will be present in refined oil than in raw oil, studies should also be conducted on the refined oil.
- If the label contains a wide range of fruit crops, one study containing a fruit juice (e.g. apple), a preserved fruit (e.g. peach), a cooked fruit (e.g. peach), a jam (e.g. strawberry) and a dried fruit (e.g. prune) will normally be sufficient.
The technology used in processing studies should correspond as closely as possible to the actual conditions in common usage (in the home or commercially). Extended periods of storage should be considered as a processing practice. Where more than one process can occur, then data should be produced for the worst case situation. It is not expected that studies using every conceivable type of processing or cooking will be needed, but a limited number using typical conditions is desirable.
Data from processing studies will allow:
- recognition of reductions and concentrations of residues;
- estimation of transfer factors;
- recognition of significant alterations in residues.
The appropriate MRL can normally be set by multiplying all available raw commodity results for the crop/animal by the relevant transfer factor (from processing study) and the estimated residue levels evaluated in the normal manner.
Reporting of Results
A full laboratory report including all relevant data should be written using the standard format for residue reports (see Residue Guideline No. 11; Reporting of residue trials). The report must include a full description of the processing practice used.
 Lundehn JR. Guidelines for the Establishment of Community Maximum Residue Levels (MRLs) of Plant Protection Products in Food and Feedstuffs of Plant and Animal Origin - Final Report. For the Commission of the European Communities, Directorate-General for Agriculture. January 1993.
 US Environmental Protection Agency (US EPA). Pesticide Assessment Guideline: Residue Chemistry Subdivision O PB83-153981. October 1982; Technical Guidance, December 1989; Addendum on data reporting PB88-117270. November 1987; Standard Evaluation Procedure PB88-243209, July 1988.
 Health and Welfare Canada, Health Protection Branch. Guidelines for Developing Pesticide Residue Data in Foods as Consumed. July 22 1988.
Correspondence from Chief, Joint FAO/WHO Food Standards Programme. Codex
Alimentarius Commission. August 1993.