FSU scientists develop new tests to detect nut allergens in processed food
By Libby Fairhurst
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 nutritious little nuggets 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 current edition of the Journal of the Science of Food and Agriculture. FSU's Shridhar Sathe, the D.K. Salunkhe Professor of Food Science, and Kenneth Roux, a professor in the department of biological science, conducted the research with assistance from graduate students Mengna Su, Yanhong Wei and Mahesh Venkatachalam, and from Susan Teuber, an associate professor at University of California-Davis.
"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-sensitizing 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 labeling 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 lab 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.
"Development of specific, robust, sensitive and reproducible assays for tree nut detection will help protect sensitive consumers who must rely upon accurate labeling, as well as food industry and regulatory agencies who monitor the presence of trace quantities in both food and feed," said Sathe. He cautioned that "continued and vigorous research is now urgently warranted" to expedite preparation of the techniques for commercial use.
The study was funded in part by FSU's department of nutrition, food and exercise sciences in the College of Human Sciences, the Council for Faculty Research at FSU, the Almond Board of California and the United States Department of Agriculture.