According to European food law, no foreign substances may be added to honey as it constitutes natural foodstuff. However, various studies in the recent past have indicated that a high rate of adulteration can be observed in honey. One of the most common forms of adulteration is the inadmissible addition of industrially produced sugar syrup, which is much cheaper than natural bee honey. To detect sugar syrup in honey, the NRZ-Authent develops and establishes non-invasive methods with minimal sample preparation. These efforts aim to provide efficient and conveniently applicable methods for official food control authorities, supplementing the currently available methodologies.
NIR spectroscopy (NIR: near-infrared) offers a promising approach to evaluate the authenticity of honey. This non-destructive analysis method can be used as a cost-effective and time-saving screening method which often provides results in less time than many other analytical approaches. To assess its suitability, a study was carried out to evaluate the feasibility of NIR spectroscopy to detect honey adulteration with sugar syrup. NIR spectra of a total of 14 authentic honeys, 4 syrups and 224 adulterated samples generated thereof were acquired. To gain a deeper understanding of the resultant data, principal component analysis (PCA) was performed. In this process, information from many variables is combined into a few so-called principal components. The samples were then mapped onto the first two principal components: Pure honey and sugar syrup samples were easily separated from each other in the PCA plot, while the various honey-sugar syrup mixtures lay between these two groups.
Using further chemometric analyses, calibration models based on the NIR spectra were derived and then validated with a defined sample set. One of the models achieved a coefficient of determination (indicating the agreement between measured and predicted values) of 0.95, and is therefore able to predict the sugar syrup content in the honey samples investigated in this study based on an NIR spectroscopic measurement with very good approximation. These results indicate that NIR spectroscopy can likely be developed as an important tool for the detection of honey adulteration by sugar syrup addition.