Regulatory Compliance and General Quality Assessment: For all fifteen physicochemical parameters analysed, samples were within the limits of the Turkish Food Codex
12, Codex Alimentarius
19, and EU Directive 2001/110/EC
20. Moisture remained below 20% across all types (15.84–17.06%), consistent with the 13.9–18.0% range reported for Eastern Anatolian honeys by Demir et al.
21 and the 15.91±1.05% mean reported by Gürbüz et al.
22 for Southeastern Anatolian honeys. Free acidity values (22.80–27.76 meq/kg) were well below the 50 meq/kg regulatory limit and comparable to those reported for Turkish multifloral and chestnut honeys in the literature
22,23. HMF values (11.55–21.32 mg/kg) were substantially below the 40 mg/kg maximum, confirming minimal heat exposure and appropriate storage conditions; similar HMF ranges have been reported for fresh Turkish honeys of comparable botanical origin
23. Diastase activity consistently exceeded the 8 DN regulatory minimum across all types (10.54–14.66 DN), in agreement with Aslan and Arık Kibar
24, who similarly reported diastase values above the legal threshold in Turkish pine and flower honeys. Collectively, these findings confirm appropriate post-harvest handling and product integrity across all three honey types.
Moisture, Dry Matter, and Electrical Conductivity: Pine honey's lower moisture content is consistent with the prolonged evaporation associated with honeydew-based production 25. Elevated EC in chestnut and pine honeys relative to flower honey reflects the higher mineral load of honeydew-derived and chestnut-origin products, corroborating findings from comparable Turkish localities. Demir Kanbur et al. 26 reported the highest electrical conductivity values in chestnut honey from Senoz Valley, Rize (a river valley located in the Eastern Black Sea region of Türkiye) compared with highland honeys from the same area, and Saral 27 documented EC values of 0.56–1.12 mS/cm in Artvin chestnut honeys, which is consistent with the 1.249±0.164 mS/cm observed here. That pine honey's EC was statistically indistinguishable from chestnut honey in this dataset may reflect the specific mineralogical profile of the Kastamonu locality 25.
pH, Free Acidity, and Their Mechanistic Relationship: Flower honey had significantly lower pH (4.027±0.275) than chestnut (5.078±0.296) and pine honeys (4.844±0.363), despite comparable free acidity values–an apparent inconsistency that can be explained by differences in buffering capacity among honey types. The higher electrical conductivity of chestnut honey, indicative of a higher mineral load, may confer greater buffering capacity, potentially maintaining a higher pH despite moderate titratable acidity; flower honey's lower mineral-associated buffering reserve may yield a lower pH at similar acidity levels 28. Comparable pH differentials between chestnut and polyfloral honeys have been reported by Akgün et al. 29, who documented higher pH in chestnut honey relative to multifloral and acacia types from Ordu province, and by Gürbüz et al. 22, who reported a mean pH of 4.10±0.73 across mixed-botanical Turkish honeys, which is consistent with the flower honey values observed here. This distinction is functionally relevant: the more acidic environment of flower honey may enhance hydrogen peroxide generation via glucose oxidase activity, a principal antimicrobial mechanism that operates in conjunction with osmotic pressure and phenolic compounds 30; however, as water activity, osmolarity, and phenolic content were not directly measured in the present study, this interpretation should be regarded as mechanistically plausible rather than conclusively demonstrated.
Sugar Composition: Botanical Differentiation and Crystallisation Behaviour: Sugar profiles reflected well-established botanical fingerprints. The highest F/G ratio in chestnut honey (1.620±0.102) indicates the lowest crystallisation tendency among the three types, consistent with Ucurum et al. 31, who reported F/G ratios exceeding 1.3 in both chestnut and pine honeydew honeys relative to multifloral flower types and identified sugar profile and electrical conductivity as key discriminant parameters between honeydew and flower honeys. The markedly elevated maltose in pine honey (7.866±1.273 g/100 g versus 2.156±0.532 in chestnut and 3.313±0.895 in flower) is a recognised biochemical signature of honeydew origin, consistent with the enzymatic processing of oligosaccharide-rich honeydew secretions on Pinus brutia 25,32. This pattern aligns with findings from Ucurum et al. 25, who documented elevated maltose and higher proline and diastase activity as characteristic features of Turkish pine honeydew honeys across 373 geographically distributed samples, and with Aslan and Arık Kibar 24, who similarly confirmed higher diastase and acidity in pine honeys relative to Turkish flower types. Cobanoglu et al. 33 further demonstrated that sugar and phenolic profiles together constitute reliable botanical differentiation markers between Turkish pine and flower honeys. The specific honeydew-producing insect(s) active in the Kastamonu locality were not determined in the present study. The strong negative maltose–F/G correlation (rs ≈ −0.80; Figure 2) is consistent with these botanical patterns, as increasing maltose reduces the relative fructose fraction, a relationship previously documented in comparative studies of honeydew and flower honeys 25,31,32.
HMF and Diastase Activity and Proline: HMF formation proceeds via acid-catalysed fructose dehydration, predisposing lower-pH honeys, such as flower honey, to higher accumulation irrespective of thermal history 34,35. Conversely, the mineral-rich matrix of pine honey confers a buffering effect that suppresses HMF formation, explaining the lowest values in that type. The inverse diastase gradient (chestnut > pine > flower) reflects not only processing history but also botanical differences in enzyme input: chestnut and honeydew honeys receive higher salivary enzyme contributions than most flower types 25-27. Despite the lowest diastase activity in flower honey, all values exceeded the 8 DN legal minimum.
Proline decreased significantly in the order chestnut > pine > flower, yet all samples substantially exceeded the 180 mg/kg authenticity threshold; chestnut honey additionally surpassed the 500 mg/kg type-specific limit 12, consistent with the proline-rich nectars of Castanea sativa reported across Turkish Black Sea localities 22,27.
Multivariate Structure: PCA achieved clear three-way botanical separation, with PC1 driven by HMF, diastase, and F/G ratio, and PC2 discriminating along the maltose–EC axis – a structure paralleling multivariate differentiation reported for Turkish 25 and Greek 36 unifloral honeys, reinforcing cross-regional validity of these parameters as botanical discriminants. The Spearman matrix (Figure 2) captured mechanistically interpretable associations: maltose–F/G (rs ≈ −0.80), EC–free acidity (joint mineral–organic acid influence), and the inverse HMF–diastase relationship. The group heatmap (Figure 5) consolidates these as coherent typological signatures.
Microbiological Quality and Its Relationship to Physicochemical Properties: Yeasts and moulds were below the analytical detection limit (<1.0 log CFU/g) in all 40 samples, while coliform bacteria, sulphite-reducing anaerobic bacteria, and Salmonella spp. were not detected in any sample examined. These findings are consistent with a growing body of evidence documenting the microbiological safety of high-quality honeys across different geographical and botanical origins. Gomes et al. 4 reported the complete absence of faecal coliforms, sulphite-reducing clostridia, and Salmonella in commercial Portuguese honeys, attributing this to the synergistic inhibitory effects of low water activity, acidic pH, and hydrogen peroxide generation. Tornuk et al. 7 similarly reported undetectable yeast and mould counts in artisanal Turkish flower honeys, and Luca et al. 8 comprehensively documented the antimicrobial mechanisms (including osmotic stress, low pH, and hydrogen peroxide generation) that collectively suppress microbial proliferation in honey. Kędzierska-Matysek et al. 37 found that 52% of Polish artisanal varietal honeys contained fewer than 10 CFU/g of total bacteria, with fungal counts below 10 CFU/g in 81% of samples, while Pauliuc et al. 38 reported satisfactory microbiological profiles with no detectable Salmonella or pathogenic Enterobacteriaceae across five botanical honey types from Bucovina, Romania. The absence of a microbiological gradient mirroring the substantial physicochemical differences observed among honey types in the present study is consistent with a threshold effect: although pH, EC, and sugar composition differed significantly, all types maintained inhibitory conditions sufficient to prevent microbial proliferation. Moisture content data (15.8–17.1%) correspond to expected a_w values of approximately 0.55–0.62, based on published reference values for comparable honey types 5. These values provide indirect evidence that water activity suppression was maintained throughout. Once moisture and pH fall within inhibitory ranges, botanical-origin differences in antimicrobial intensity become of limited relevance to routine microbiological safety 8,30.