Tests for nuts

Thursday, 13 January, 2005


Scientists at Florida State University subjected walnuts, cashew nuts and almonds to radiation, roasting, pressure cooking, blanching, frying and microwave heating in an effort to make them safe for allergy sufferers.

In the end, the nuts refused to surrender their allergens, but the research yielded sensitive techniques that detect minute traces of the nuts - potentially fatal to allergic consumers - in seemingly nut-free processed foods. The study, 'Impact of gamma-irradiation and thermal processing on the antigenicity of almond, cashew nut and walnut proteins', is published in the Journal of the Science of Food and Agriculture.

"Globally-popular almonds, walnuts and cashews are the tree nuts most often implicated in permanent and sometimes fatal food allergies, and currently there are no de-sensitising treatments available," said Sathe. Vulnerable individuals must scrupulously avoid all contact with the offending tree nuts, an increasingly difficult feat since they are widely used in a variety of bakery, confectionery and snack foods.

"Improper food labelling and cross-contamination during commercial processing pose serious threats to sensitive consumers while often leading to expensive food recalls," Sathe said.

The researchers had previously identified the specific tree nut proteins relevant to human allergies. They then aimed, through irradiation alone or in combination with other thermal treatments, to induce changes in the protein structures to reduce or eliminate allergenicity and antigenicity.

Yet the antigenicity of the tree nut proteins remained mostly unchanged throughout the irradiation and thermal processing, dashing hopes that the treatments would render the healthy snacks safer for wider consumption and more profitable for growers and industry.

However, the bad news in turn generated some very good news - precisely because the irradiation and thermal procedures likely to be encountered during commercial processing did nothing to alter the tree nut protein antigenicity.

Now laboratory tests originally used on unprocessed cashew nuts, almonds and walnuts to detect antigenic proteins could be reliably applied to detect minute traces in already-processed food products as well.

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