How the wasp is helping to fight boar taint

A great deal of research is being done into getting rid of the smell of the male pig - or boar taint as it is known. The latest idea is to use wasps to sort out the meat that smells too bad.

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John-Erik Haugen

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For animal welfare reasons, a ban on castrating boars is on the cards. But before this can happen, we need to overcome the problem of boar taint, which is proving to be a bigger problem than we first thought. It has also been discovered that, whatever may have been done in advance, the slaughterhouses always have to perform a final quality control on the slaughter line.

The solution is rapid measurement methods

In both Norway and the EU there is a strong lobby to ban the castration of boars. In Norway, the Storting voted to ban the castration of boars with effect from 2009. The problem is that the meat from a mature boar can have boar taint. Even after four years intensive research in the Norwegian Boar Programme (2005-2008), no overall solution to the problem has been found. The decision to ban castration has therefore been postponed indefinitely.

The unpleasant smell in boar meat is caused by high levels of the substances skatole and androstenone. The boar programme has been looking at various measures for reducing boar taint. One idea is to breed pigs that become sexually mature later and so do not have such a prominent smell. Another measure is to increase the amount of easily digested fibre in the feed, to inhibit the bacteria in the intestine that create skatole. More recently immune castration has come into the picture, with the development of a vaccine that prevents male pigs from becoming sexually mature.

But whatever solution is finally arrived at, the slaughterhouses will still need to carry out continuous quality control during slaughtering, to sort out the worst stinkers. Such methods need to be rapid and cheap and to measure both skatole and androsterone.

“Nofima Mat has done a lot of work on this in recent years and has become a world leader in this field. So far we have found two rapid methods with potential for practical use. There is a spectroscopic method based on gas sensors and a biosensory method that uses living insects,” explains John-Erik Haugen, a Senior Research Scientist at Nofima Mat.

Boar taint head bangers

In his work on developing a good biosensory method, Haugen has been inspired by insects’ sense of smell and their ability to learn. He has been in contact with the British company Inscentinel Ltd, which uses bees to sniff out both explosives and narcotics, and the Department of Agriculture in the USA, which uses wasps to combat pests on plants.

“Out of the methods we have worked with, our results so far show that the ichneumon wasp is best suited for checking pork by smell,” says Haugen.

Training is based on classic Pavlovian methods; the wasps are exposed to the substances that cause boar taint at the same time as they are given food in the form of sugar water. Once they have learnt the smell, they will indicate its presence by beginning to head bang, which is their natural behavioural response.

“The biggest problem with these wasps is their short lifespan. They live only 3 to 4 weeks, but because training them takes only a few minutes and the technology is so simple, this method would be very cost effective,” says Haugen.

Needs adapting to industrial conditions

Once the wasps have been trained, 6 to 8 of them are placed inside a chamber in a detector box. The box has an inbuilt web camera and a fan that passes the odour through the wasp chamber. These wasps are solitary and do not interact with other wasps. This means that they do not influence each other’s behaviour.

“We have shown that the wasps are able to recognise skatole and androstenone individually from a mix of odours. Before this can be applied in practice, the wasps must also be able to distinguish between different concentrations of the boar taint substances. The strategy is to train them to the human threshold levels for these odours. Our preliminary results show that this is actually possible,” explains Haugen.

The wasps manage to sort out samples with boar taint, based on the human threshold levels for detecting skatole and androstenone. As quality assurance, it works extremely well. By using several wasps at the same time, 100% correct classification can be achieved.

The large boar project has now finished and its research funding has been used up. It is therefore uncertain how research will be carried forward.

“We now have methods that we know work and all that remains is to adapt them to industrial conditions. Now it is important for the industry to get on board,” concludes the senior researcher.

The project is financed by Norges forskningsråd, Foundation for Research Levy on Agricultural Products and EU.

Raw materials and process optimisation  

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