Archive Article: 1997/12/13

13 December 1997

MITES, mice and mycotoxins. There were enough horror stories at last months quality assurance and traceability in grain storage symposium to keep the consumer press busy for days, had they been there.

Chairman Mike Kelly of independent pest consultancy the Acheta Partnership, co-hosts with the RASE, kicked off by describing the sea change in grain storage and pest control fuelled by quality assurance.

"The food industry, whether of its own accord, or probably from external pressure, has been upgrading its standards, which are now being pushed down the line to the farming community, the last bastion of old habits."

Alistair Tucker of British Bakeries, home of the Hovis loaf, went on to describe how food scares were now "like open warfare" and were bound to appear on the front pages of the tabloids. So the best defence was to present a whiter than white case.

"We spend a lot of time on our back foot, trying to convince people what was wrong has been put right," he said. An assurance scheme, on the other hand, shows things are being done right, right from the start.

He believed that all wheat for breadmaking would ultimately be assured wheat, and that biscuit and cake makers would follow suit. While he couldnt give a timescale, he did think it might be sooner than many anticipated.

One of the tenets of the Assured Combinable Crops Scheme is that a crop in the store should be treated just like a crop in the field. Just as you would check the growing crops for inputs, so you should check regularly that stored crops are in good condition, he said.


But even the most committed supporters of QA might have their best intentions thwarted if pesticide resistance in insects and mites develops. And Ken Wildey of the Central Science Laboratory believes it is.

Of the mite strains collected in surveys of farm and commercial grain stores, plus animal feed mills and oilseed stores between 1987 and 1995, high percentages survived exposures of 14 days to 8ppm of pirimiphos-methyl (Actellic), twice the maximum approved dose.

"In the 1970s and 80s, we were accused of scaremongering, but time has caught up with us," he announced. "Weve never seen mite infestations like this before."

Organophosphates are naturally poor pesticides in terms of mite control, said Dr Wildey, but more reliance has been placed on them now that organochlorine products such as Lindane (gamma-HCH) are no longer available for use on grain. "We need something completely different, such as a new chemical group to control mites," he added.

In the same surveys, phosphine resistance was also detected in a number of beetle strains, such as the saw-tooth grain beetle. Resistance here was at an earlier stage which should still allow control to be achieved in practice, he added. No need for excitement, he said. Yet.

But, for mites, given that no chemical alternatives are currently approved for admixture with grain, failure to control strains resistant to organophosphate pesticides is likely to add to existing contamination problems in cereal-based foodstuffs.

Mites are enough of a cause for concern in terms of the scale and frequency of their presence alone. An estimated 21% of cereal-based products purchased retail are contaminated with mites, and an alarming 15% of baby foods. One particular worry is the allergenic consequence of contamination; a clinical study is currently monitoring the health effects of such a challenge, said Dr Wildey.

"The study glosses over the question whether customers know theyre there, far less whether they want them there. And I wont mention research in the United States which suggests that mites might be able to replicate scrapie-carrying prions." He also casually mentioned that the poultry red mite, one of the predatory mites detected in food on the supermarket shelves, is a blood sucking ectoparasite!

Next, Keith Scudamore of KAS Mycotoxins, an independent consultant, gave an update on these unseen contaminants, the toxic products of fungal infections such as cereal moulds.

Mycotoxins are generally present only at very low levels, but they are very toxic, explained Mr Scudamore. The difficulty is deciding just how important they are. In sufficient quantity, mycotoxins in cereals undoubtedly do cause illness and death in less developed countries where there are high levels of contamination by mould, he said. But in the UK the problem was one of quality, not toxicity.

However, the Food Advisory Committee advises that all attempts should be made to minimise levels of ochratoxin A (OTA) in the human diet, and aflatoxin B1 in animal compounds.

Aflatoxin control

Aflatoxin control, introduced in animal feed in 1980 and in nuts and dried figs in 1992, is likely to be extended to cereals under a new EC ruling by the end of 2000. The irony is that, although this mycotoxin is one of the most potent liver carcinogens known to man, its unlikely to be present in home-grown cereals, as UK temperatures are normally too low for their development, said Mr Scudamore.

On the other hand, OTA is more likely to be found in UK-grown and stored cereals, but isnt covered by legislation. Some nations are very strongly pressing for OTA testing in a range of commodities, including cereals. This could cause some problems to the UK trade, since 2-5% of UK cereals – about a million tonnes – would exceed the probable limit.

Under the new rules, throughout the food chain the onus will be on the owner to ensure grain doesnt contain the specified toxins above set limits. This, said Mr Scudamore, could lead to possible conflict and raises questions about whether testing should take place on loading or emptying the grain store.

As far as prevention is concerned, rate of drying after harvest is one of the most important factors, he stressed. Moulds can form within two or three days, so mycotoxins have the potential to occur wherever a bulk of grain is drying slowly. He didnt consider it good practice to mix clean with infected grain to reduce the load artificially.

Quality assurance in grain storage faces some serious threats, writes Tia Rund.

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