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Application of HACCP to mycotoxin control

Once tasks 1 to 5 have been completed the following will be in place: a HACCP team, a Description and Intended Use table, and a verified Commodity Flow Diagram. This will provide information on a specific commodity from a unique source, and this information is required to complete the hazard analysis. See the case studies in Chapter 3 for examples of implementation, including that of stages 1 to 5.

Task 6 - Mycotoxin hazard analysis and identification of possible control measures

Hazard Analysis

a) Identification of mycotoxin hazard

For a given commodity system in a particular location, the HACCP team need to first consider which, if any, of the mycotoxins known to constitute a food safety hazard are likely to be present.

Over 300 mycotoxins are known, but only a relatively few of these are widely accepted as presenting a significant food or animal feed safety risk. These hazardous mycotoxins are listed in Tables 1 and 2 in Chapter 1. Of these only the following mycotoxins have regulatory limits set by one or more countries: the aflatoxins (including aflatoxin M1), ochratoxin A, zearalenone, patulin, ergot alkaloids, and deoxynivalenol. Guideline limits exist for fumonisin B1 and regulatory limits are likely to be set in the near future. The regulatory limits are taken as the target levels and should be included in the Product Description table. Mycotoxin limits can also be set by the customer in specific contracts and it is possible that these may include mycotoxins not subject to regulatory limits.

The risk of a particular mycotoxin hazard should be estimated using well established data on the relative susceptibilities of commodities to given mycotoxins and the climatic conditions required for the mycotoxins to be produced. The EU has identified the following animal feed ingredients, and their products, as being highly susceptible to aflatoxin contamination: maize, groundnut cake, cottonseed cake, babassu, palm kernel cake and copra cake. The EU has also identified the following foodstuffs as highly susceptible to aflatoxin contamination: dried figs and other dried fruit, groundnuts, pistachios and other edible nuts and cereals. These commodities are specified in the respective EC regulations (1525/98 amending regulation 194/97). Maize grown in temperate climates would be less likely to be contaminated with aflatoxin, but could be contaminated with trichothecene mycotoxins or fumonisin B1. Although published mycotoxin survey data exists for many commodities, it is important that surveillance studies are performed if mycotoxin data is lacking for a particular commodity, or for production in a particular climatic zone.

b) Identification of steps in the Commodity Flow Diagram (CFD) where mycotoxin contamination is most likely to occur

Once the mycotoxin hazard(s) has been identified, each step in the CFD must be considered in turn and the likelihood of mycotoxin contamination occurring must be assessed. Usually published scientific data will be available to act as a guide, but it may be necessary to commission a study to determine, or confirm that the correct steps have been identified. The situation may change from year to year, and season to season, so there will need to be an element of mycotoxin surveillance in the HACCP plan.

An important fact to establish is whether pre-harvest contamination with mycotoxins is likely or whether contamination occurs primarily post-harvest. Mycotoxins produced by Fusarium spp, such as fumonisin B1 are invariably produced pre-harvest, but climatic conditions effect the degree of blight and the resultant level of mycotoxin contamination. Aflatoxins can be produced both pre-harvest and post-harvest and climatic conditions can have a significant bearing: drought stress favours pre-harvest contamination, whereas post-harvest handling during the rainy season favours post-harvest aflatoxin contamination.

It is rarely possible to be certain that pre-harvest mycotoxin levels are below regulatory or target levels in the commodity system, so post-harvest mycotoxin control measures can often only prevent or reduce ADDITIONAL contamination, rather than prevent the hazard completely. Consequently it is often necessary to introduce a segregation step to remove any batches containing an unacceptable level of mycotoxin.

c) Possible Mycotoxin Control Measures

The most effective mycotoxin control measures is to dry the commodity such that the water activity (aw) is too low to support mould growth and/or prevent mycotoxin production. To prevent the growth of most moulds the aw needs to be £ 0.70, which translates to a moisture content of approximately 14% for maize and 7.0% for groundnuts at 20°C (the corresponding moisture content decreases as the temperature increases). Each toxigenic mould has its own minimum water activity for growth and mycotoxin production and these translate into moisture contents for each commodity. These moisture contents are termed 'safe' and would be the critical limit for the control measure.

It is important to specify a target 'safe' moisture content with a maximum as well as an average value, e.g. 14% no part exceeding 15%. If only an average value is specified it may conceal a large range of moisture contents within the batch and the commodity would not be safe from mould growth and mycotoxin contamination. A drying process is required which dries evenly and the critical limits must be set bearing this in mind. Validation of such a CCP must involve moisture determination of multiple samples.

If the commodity is at an 'unsafe' moisture content for longer than 48 hours, then mould can grow and mycotoxins be produced. Hence limiting the time that the commodity spends in the 'unsafe' moisture content window to less than 48 hours is a control measure. This explains why timely sun-drying can sometimes be safer than delayed mechanical drying. Two days on a drying floor with occasional turning can often achieve the target 'safe' moisture content, whereas a back-log at the mechanical drier can result in the critical limit of 48 hours not being met.

Once produced, it is not usually possible to remove mycotoxins, other than by physical separation (grading) techniques. To apply this type of control measure, representative samples of batches of commodity are collected and tested for selected mycotoxins. Only those batches containing less than the critical limit of mycotoxin, as specified in official regulations, are accepted. For some commodities, such as blanched groundnuts, colour sorters may be effective in rejecting individual high-aflatoxin nuts and accumulating low-aflatoxin nuts, and may be classified as a control measure.

There are a few examples where effective chemical detoxification is possible, such as ammoniation of certain animal feed ingredients and refining of vegetable oils. These are control measures that would also be suitable for application at a critical control point for aflatoxin, but only for the specified commodities.

It is essential that GAP, GSP, and GMP pre-requisites are in place, and simply ensuring that this is the case can significantly reduce the risk of the mycotoxin hazard. Examples of procedures which fall within the scope of these pre-requisites include: irrigation, insect control, use of resistant varieties, and use of pallets in store.

Task 7 - Determine Critical Control Points (CCPs)

Determination of CCPs can be achieved using a well designed decision tree, if necessary, to supplement the knowledge and experience of the HACCP team (see Appendix IV). Each step in the CFD is considered in turn, and the questions answered in sequence. It should be noted that it is necessary to be able to answer Yes to Question 1 (Do preventative control measures exist?) before a CCP can be established. The Codex 1997 definition of a control measure is any action and activity that can be used to prevent or eliminate a food safety hazard, or reduce it to an acceptable level.

There are commodity systems, such as the production of apple juice (Case study 5), where control measures are possible at a number of steps, and each is capable of achieving a known percentage reduction in the level of mycotoxin. It is possible, therefore, to calculate the acceptable level of patulin at each step and perform validation. If the risk of the acceptable level of mycotoxin being exceeded is considered to be sufficiently low, then the HACCP team may determine each of the steps as CCPs.

Task 8 - Establish critical limits for each CCP

When the control measure is segregation based on mycotoxin analysis, then the critical limit will often be set at the acceptable level, which in turn will be set at, or below, the regulatory mycotoxin limit. Acceptable levels, and any associated critical limits, can sometimes be set higher than a regulatory limit, provided that a subsequent step can guarantee to attain the acceptable level of hazard in the final product.

For control measures that involve drying to a 'safe' moisture content, the parameter that will be measured, and for which critical limits will be set, will usually be parameters such as the temperature of the drier and the dwell time, e.g. for a continuous flow drier the critical limit for temperature could be 80 +/- 2°C and the critical limit for dwell time could be 20 +/- 1 minute.

Critical limits for chemical detoxification could be the temperature and pressure of the reaction vessel and the dwell time.

Task 9 - Establish a monitoring system for each CCP

The monitoring system must be a scheduled measurement, usually of a basic parameter such as temperature or time, to detect any deviation from the critical limits.

When segregation of acceptable and unacceptable batches is required in the agricultural system, for example at a secondary trader, then rapid testing procedures are needed to test incoming batches.

A number of semi-quantitative immunoaffinity rapid test kits are available which work to a stated target level, eg 5 or 20 µk/kg of the appropriate mycotoxin. Here the critical limit would normally be the presence or absence of a coloured derivative. More traditional mini-column and TLC dilution to extinction techniques can still be useful for segregation of batches at the factory gate, and for these the presence or absence of a blue fluorescent band or spot is the critical limit.

Task 10 - Establish a corrective action

There are two sorts of corrective action. The first is action to regain control. For instance if a critical limit for a moisture content is not attained, then the corrective action could be to check the specification of the drier and effect repairs, or perhaps to increase the temperature setting or the dwell time. The second type of corrective action is to isolate the product produced whilst the CCP was out of control and amend the product disposition, by either discarding or down-grading it, or re-processing it if this is appropriate.

Task 11 - Establish verification procedures

At regular, specified, intervals the complete HACCP plan should be verified by checking that the levels of mycotoxin in the final product are within acceptable levels. If this is found not to be the case, then immediately trouble-shooting should be carried out to identify the step at which the hazard has become out of control. Critical limits may need to be amended, or a new control measure may need to be validated and introduced. Similarly, if a review of deviations and product dispositions indicated an unacceptable degree of control at a particular CCP, then revisions will need to be made.

Task 12 - Establish documentation and record keeping

Standard HACCP documentation and record keeping is appropriate, but the complexity of the records should reflect the sophistication of the step in the commodity system.

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