One-step, one-tube derivative spectrophotometric method for screening natamycin in fermented milks

A one-step, one-tube, ultrarapid, simple, sensitive and cost-effective method for the determination of natamycin in fermented milk products (yoghurt, kefir, airan) is proposed here. In this method, samples were extracted with acidified aqueous acetonitrile, while quantification of natamycin in the extracts was based on the intensity of the trough appearing at 322.6 nm when third-order derivative processing of the normal absorption spectrum was carried out. The proposed method was validated according to Commission Implementing Regulation (EU) 2021/808 and exhibited exceptional analytical characteristics, which allowed a limit of quantification of 303 ng g -1 , for all three fermented milk products, to be realized. The method was successfully applied to determine natamycin in fermented milk products purchased from local markets. The results demonstrated the illegal use of natamycin in 85 out of 235 examined samples. Due to its simplicity, rapidity and reliability, the method is highly recommended for routine screening of natamycin in fermented milk products. • Third-order derivative spectrophotometry in natamycin determination • Ultra-rapid and eco-friendly method for screening natamycin in fermented milks • High-reproducibility, high-accuracy and cost-effective procedure • A method suitable for routine analyses due to its high throughput • Extensive use of natamycin in yoghurt has been confirmed