Validation of analytical methods for the detection of beeswax adulteration with a focus on paraffin

Beeswax adulteration in the apiculture sector represents a growing problem worldwide due to the lack of clearly defined purity criteria, the absence of official quality (authenticity) controls, and the inconsistency of the analytical methods used for adulteration detection. Although beeswax authentication is implemented in other regulatory sectors (pharmaceutical and food industry), the classical physico-chemical analytical methods used for determination of beeswax purity exhibit inconsistencies for the detection of adulterants. In this study, an inventory was made on a comprehensive set of analytical methods and the corresponding purity criteria used for the detection of the most common beeswax adulterants (paraffin, stearin and/or stearic acid) from existing legislations and scientific literature. The selected analytical methods (classical physico-chemical, and advanced instrumental, i.e. chromatographic and spectroscopic analytical techniques) were weighted by three independent experts against two criteria: feasibility and analytical performance in detecting targeted adulterants. Classical methods for which measurement data were available (melting point and acid/saponification/ester values for paraffin-adulterated vs. non-adulterated beeswax samples) were retained and further validated by a receiver operating characteristic (ROC) analysis. These methods were also validated by generating the corresponding calibration curves for paraffin detection using paraffin-beeswax mixtures containing different proportions of paraffin (ranging from 5 to 95%, w/w). The results of the ROC analysis revealed that a tentative detection of paraffin in beeswax can be achieved by a combination of at least two physico-chemical methods. However, for a reliable detection of the most common adulterants in beeswax, physico-chemical methods should be complemented with advanced analytical tools. i.e. GC-MS, HTGC-FID (MS) and/or FTIR-ATR spectroscopy, depending on the expected adulterant.