Monday, May 6, 2013

Veggies that glow in the dark?

You must have heard the old joke that one advantage of irradiated food is that you can find it during a power outage.

Unfortunately, this sort of misunderstanding about food irradiation is common.  The food doesn't become radioactive and it doesn't glow in the dark.  Appropriate use of irradiation can prevent sprouting in potatoes or can be used for disinfestation.

The subject has come to prominence again with the stated intention of the New Zealand government to permit the import from Australia of irradiated tomatoes and peppers.

Exposure of vegetables to low levels of ionising radiation kills insects, rendering the vegetables safe for importation to New Zealand without the need to use chemicals such as methyl bromide**. New Zealand agriculture could be severely affected if certain insect pests were able to enter and establish in the country.

What effect could this irradiation have on the nutritional quality of the food and the health of consumers?  There are some very minor changes in the food - levels of the vitamin thiamine are slightly reduced, but not sufficiently to result in thiamine deficiency (and there are other sources of thiamine besides imported tomatoes and peppers).  Indeed, the changes in food are so minor as to make it difficult to determine whether food has been irradiated or not. 

Opponents of irradiation claim that the minor changes that occur in the food show that the process should not be permitted.  However, they neglect the changes induced by other processing methods.  Who could argue that a canned peach is the same as a fresh one?  In fact, careful study shows that all the chemical changes produced by irradiation can also be detected when foods are processed by more conventional means.

Other arguments are that unscrupulous food manufacturers will use irradiation to defraud the consumer by covering up spoilage.  This is plain nonsense.  If spoiled bacon, for example, were irradiated at sufficiently high dosage, microbiological testing would give low or zero microbial counts.  But the bacon would still be spoiled and a taste test would show this. 

Irradiation is the most extensively studied form of food preservation, and the weight of expert opinion is that irradiated foods are safe for human consumption.

A number of years ago, a European supermarket put irradiated foods on the shelves alongside similar foods not treated.  The irradiated foods were labelled, so that there was no attempt to deceive the consumers.  However, consumers appeared to select the irradiated foods in preference for the non-irradiated.

The issue is not about safety, but about consumer perception.


**  Methyl bromide was formerly used extensively in many countries to disinfest a wide range of agricultural materials in many countries.  Unfortunately, it is also an ozone-depleting compound and was phased out in most countries between 1995 and 2005.

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