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A BLAST of electric current is the best way to find out if packaged food is
likely to go mouldy, according to researchers in Australia. They say the
technique could save the food industry millions of pounds.

Food is likely to go off if its wrapping is damaged, since even the tiniest
of holes can allow bacteria in. To look for leaks in food packages,
manufacturers traditionally pump in dyes or gases. But these techniques destroy
the packaging and invariably spoil the food inside.

Now Karlo Jolic and colleagues at Swinburne University of Technology in
Hawthorn, Victoria, have found a way of finding holes without damaging the
packaging. They took a thin aluminium collar and put it around one end of a
sausage-shaped plastic package of food. The end to be tested for holes was
dipped into a steel container of salty water. They then set up an electric
circuit by connecting the collar to the container through an alternating-voltage
generator and a resistor.

In packages without any holes, the voltage across the resistor was high. But
when Jolic pricked the packaging with a hole half a millimetre wide, the voltage
dropped immediately. According to Jolic, the new technique is significantly more
sensitive than existing detection methods.

鈥淚t sounds really cool,鈥� says Nancy Tregunno of the Guelph Food Technology
Centre in Ontario. 鈥淏ut a big thing in testing is speed.鈥� If the technique
proves too slow, it won鈥檛 become popular, she says.