Determining the Authenticity of Ghanaian Honeys Using Stable Isotope Ratio Analysis (SIRA)

Honey is a high-value food product that is vulnerable to adulteration with exogenous sugars, posing challenges for food authenticity and consumer protection. This study applied Stable Isotope Ratio Analysis (SIRA) to assess the authenticity of honey collected from three major honey-producing regions of Ghana (Volta, Bono and Bono East). A total of 28 honey samples were analysed by elemental analysis-isotope ratio mass spectrometry (EA-IRMS) to obtain carbon (δ¹³C), nitrogen (δ¹⁵N) and sulphur (δ³⁴S) isotope composition. Honey authenticity was evaluated according to AOAC Official Method 998.12 by comparing δ¹³C values of bulk honey and the corresponding protein fraction. The δ¹⁵N and δ³⁴S values in honey protein were used to investigate environmental and regional variability. Samples without detectable C4 adulteration exhibited δ¹³C_protein values consistent with C3 floral sources, whereas several samples showed Δδ¹³C values more negative than -1.0‱, indicating the presence of C4-derived sugars above the AOAC adulteration threshold. Calculated C4 sugar contents ranged from 8 to 12% in moderately adulterated samples to as high as 78-79% in severely adulterated samples, confirming substantial dilution with C4 sugars. Nitrogen and sulphur isotope ratios provide additional information on environmental and regional variability among the sampled regions. Principal Component Analysis revealed that the first two principal components (PC1 and PC2) accounted for 83.8% of the total variance 83.8% of the total variance and showed separation between samples with detectable C4 adulteration and those without, while highlighting regional isotopic differences. These results demonstrate that stable isotope analysis is an effective tool for detecting C4 sugar adulteration in honey and that the combined use of carbon, nitrogen and sulphur isotopes can provide additional information on environmental and regional variability. These findings provide preliminary isotopic data on honey collected from three major honey-producing regions of Ghana and support the application of the stable isotope approach for honey authenticity assessment and quality control.