Rapid and label-free Raman detection of azodicarbonamide with asthma risk

• Ag-coated Au nanoparticles are synthesized as high SERS active substrate.
• The asthma risk azodicarbonamide in food product is determined by SERS.
• The portable Raman based assay is label-free, rapid and suitable for onsite sensing.

Azodicarbonamide (ADA), a dough conditioner and bleaching agent of flour, is widely applied as a new flour fortifier in some certain countries. However, it is banned in Australia and Europe because of its toxicity and asthma risk for human beings. Surface-enhanced Raman spectroscopy (SERS) with ultrahigh sensitivity can offer the intrinsic fingerprint information of trace sample. Herein, based on the synthesis of the silver-coated gold nanoparticles (Au@Ag NPs), using a portable Raman spectrometer, a simple, rapid, ultrasensitive and inexpensive approach for label-free SERS detection of azodicarbonamide in flour and flour product is reported. The limits of detection (LOD) for azodicarbonamide in water, flour, steamed bread are 0.1 μM (11.6 ppb), 10 μM (1.16 ppm) and 20 μM (2.32 ppm), respectively, which are below the FDA's tolerance level of 45 ppm in flour. Therefore, this SERS-based method of azodicarbonamide detection offers great practical potential for the effective on-site assessments of food safety.

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