Detection of adulteration in Chinese monofloral honey using 1H nuclear magnetic resonance and chemometrics

Incidents of fraud are emerging on the domestic Chinese honey market, especially where lower value rape honey is mixed with high-value acacia honey. In this study, we use a combination of H-1 NMR spectroscopy combined with chemometric techniques to detect and quantify adulteration of acacia honey with cheaper rape honey. The honey H-1 NMR spectroscopy was split into three regions i.e. the aliphatic (0.00-3.00 ppm), carbohydrate (3.00-6.00 ppm) and aromatic (6.00-9.50 ppm) regions, to investigate which region provided the best qualitative and quantitative indicators in terms of rape honey adulteration in acacia honey. Results showed that the highest prediction accuracy for rape honey addition is 89.7 % using canonical discriminant analysis (CDA), determined from compounds located in 0.00-6.00 ppm spectral range. Orthogonal projection to latent structures discriminant analysis (OPLS-DA) was used to further discriminate samples of pure acacia honey adulterated with different amounts of rape honey. A partial least squares model (PLS) established a linear fit between the actual and predicted adulterant concentration with an R-2 value up to 0.9996. When the content of rape honey added was less than 100 g/kg, the purity of acacia honey could still be estimated using H-1 NMR spectroscopy and chemometric methods.