Quality control of cheese samples for the presence of natamycin preservative – A natural deep eutectic solvent (NADES) based extraction coupled with HPLC

Abstract

A new protocol for the determination of natamycin – an antifungal agent used as a food preservative - in cheese samples – is described. This new method is based on a natural deep eutectic solvent (NADES) green extraction procedure. High-performance liquid chromatography (HPLC) was used for detection and quantification. NADESs with different molar ratios were evaluated for efficient and selective extraction. NADES made of thymol and nonanoic acid (1:1) revealed to be the best extracting solvent. All significant analytical parameters - pH, temperature, NADES volume, time for sonication were optimized using Plackett-Burman (PB) and central composite design (CCD) - response surface methodology (RSM). Optimum conditions for extraction were pH 7, temperature 25°C, NADES volume 4.5 mL for 20 mL sample, and sonication time 10 mins. The developed method has a satisfactory linearity of 2–80.4 mg/kg, limits of detections (LOD), and limit of quantification (LOQ) of 0.45 and 1.45 mg/kg respectively. Under optimized conditions, the sample preparation procedure takes 12 mins. The method was found selective due to the unique and representative features of DESs. Furthermore, the extracts are analyzed by HPLC which provides a second very effective separation step, assuring the selectivity of the method. Validation of the method confirms the robustness and reproducibility of the NADES-based extraction coupled with the HPLC method demonstrating the effectiveness of NADES. The findings of this work contribute to the field of food safety and quality control, offering a novel and efficient approach to the detection of natamycin in cheese samples.