NMR Profiling of European Oak Honeydew Honeys: Saccharide Diversity and Geographical Differentiation

Although European oak honeydew honeys have a similar botanical origin, it is unclear if their chemical composition reflects their geographical origin. Sixty samples from Bulgaria, Germany, Greece, Italy, North Macedonia, Romania, Serbia, and Spain were analyzed using semiquantitative ¹³C nuclear magnetic resonance (NMR) spectroscopy. The protected designation of origin (PDO) Strandzha honey was compared to honey from other regions in Bulgaria. The profiles included 25 identified constituents, 21 saccharides, and 16 reproducible unidentified signals. Statistical analysis differentiated country groups through combinations of variables rather than a single marker. A decision tree based on nigerose, fructose, melezitose, panose, sucrose, and one unidentified signal summarized the main differences among the countries. Strandzha honeys exhibited a unique regional profile characterized by higher glucose levels and lower concentrations of several minor saccharides and unidentified signals. Two coordinated saccharide networks revealed that minor sugars fluctuate in linked groups rather than independently. This pattern has not been previously described in European honey. Conventional honeydew-associated indicators varied across the dataset. However, 1-kestose was present in all samples. Nevertheless, its specificity to oak honeydew origin remains unresolved. While extended ¹³C NMR profiling may support geographical characterization, independent validation is required before it can be used for authentication.