Characterization of Paraffin-Waxed Apples by Raman Spectroscopy

Inexpensive industrial paraffin wax is often coated on the surface of apples to keep them fresh; however, this material is toxic and harmful to human health. Currently, convenient and effective methods to detect paraffin wax residues on the surface of apples are unavailable. Here a Raman spectroscopy-based technique is reported to identify industrial paraffin-waxed apples, and a quantitative detection model was established. An 8 × 8 point scan with an area of 0.16 mm² was conducted to construct a three-dimensional map of the concentration distribution of industrial paraffin wax on the surface of waxed apples before and after washing, as well as for apple flesh 1 mm below the peel. Results demonstrated that the industrial paraffin wax did not penetrate into the flesh and that peeling the apples provides an effective means to eliminate the toxic industrial paraffin wax. This study provides a practical approach to identify fruits coated with industrial paraffin wax.