What’s in your Dubai chocolate? Nuclear scientists test pistachios for toxins
For the uninitiated, Dubai chocolate is a candy bar filled with pistachio and tahini cream and crispy pastry recently popularized by social media influencers. While it’s easy to dismiss as a viral craze now past its peak, the nutty green confection has spiked global pistachio demand, and growers and processors are ramping up production. That means more pistachios need to be tested for aflatoxins—a byproduct of a common crop mold.
An FSCL staff member uses a sensor that can detect contaminants in food. (Photo: B. Maestroni/IAEA)
Nuclear science can help: Pistachios are routinely tested for aflatoxin contamination to ensure safety, but the conventional, lab-based testing process is time-consuming and expensive. A recent news article from the International Atomic Energy Agency explains how a technique developed in a nuclear science laboratory could help pistachio growers and handlers around the world detect the toxins “faster, cheaper, and more effectively than ever before, making the consumption of pistachios safer for everyone.”
It’s not the first time nuclear-derived techniques have helped ensure pistachio yields and quality. U.S. pistachio growers plagued by infestations of the navel orangeworm moth rely on the sterile insect technique (SIT) in combination with other integrated pest management techniques to minimize the use of pesticides in tree nut orchards.
SIT works by rearing insects by the thousands—for navel orangeworm moths, that happens in a USDA facility in Phoenix, Ariz.—and irradiating them to render them sterile. The sterile insects are released by airplane over targeted crops. Their attempts to breed with wild moths are unsuccessful, which reduces the pest population.
Infestations of the navel orangeworm in pistachio orchards damage the nuts and can make them more susceptible to aflatoxin contamination, according to the American Pistachio Growers.
So what are aflatoxins? Aflatoxins are mycotoxins produced by some Aspergillus molds, which are common crop fungi. According to the U.S. Food and Drug Administration, regularly eating foods with aflatoxins can increase liver cancer risk, cause birth defects, and lead to kidney and immune system problems, while eating food contaminated with a large amount of aflatoxins can cause acute poisoning and even death.
Pistachios are especially susceptible to aflatoxins because as the nut ripens its shell splits open, exposing the nut (technically, it’s a drupe) to insects and mold spores. Contamination “can be aggravated post-harvest due to inappropriate storage conditions,” the IAEA said.
That’s why pistachio testing is so rigorous. According to the IAEA, no more than 10 micrograms of aflatoxin is permissible per kilogram of pistachios, which it notes is “akin to about a single grain of sugar in a 100 kg sack.”
Testing in the U.S.: The United States is one of the world’s top pistachio-producing countries, with orchards in California, Arizona, and New Mexico. Turkey and Iran are also top producers.
The U.S. Department of Agriculture’s Agricultural Marketing Service regulates aflatoxin testing for pistachios grown in and imported to the United States in USDA or USDA-approved labs. The majority of those labs rely on a high-performance liquid chromatography technique.
Conventional testing techniques for aflatoxins are expensive and require skilled technicians, which, according to the IAEA, makes them hard to use in field operations or in countries with limited laboratory resources.
The new nuclear technique: At the joint Food and Agriculture Organization/IAEA Food Safety and Control Laboratory (FSCL) in Seibersdorf, Austria, in 2023, a team developed a technique to detect aflatoxins in “low-resource settings.” In its work developing radiometric and related analytical techniques to control toxins like aflatoxin, the IAEA strives to make techniques cheap and accessible for use in member states that lack extensive laboratory infrastructure.
With the new technique, a sample can be placed on a ceramic test surface with electrical conductors and a sensor that can detect four types of aflatoxins. The sample is inserted in a potentiostat, which detects a current when aflatoxins are present and sends a small electrical signal. That signal can be recorded using a mobile phone, according to the IAEA. The technique has been validated using conventional liquid chromatography–tandem mass spectrometry and can detect aflatoxins at concentrations that are 150 times lower than the allowed limit.
“It’s faster, cheaper, and doesn’t require an entire lab,” FSCL head Christina Vlachou was quoted as saying in the IAEA’s news article. “That means it can be used in the field, even during emergencies, and in countries that need it most.”
More than just pistachios: The IAEA and the UN’s FAO launched Atoms4Food in October 2023 as a flagship initiative to help boost food security and tackle growing hunger around the world. Food safety and control is one of the seven assessment services the Atoms4Food initiative.
Food safety experts in the IAEA’s FSCL are working to apply the technique to detect contaminants in other food products, including corn and fruit juices.
