An investigation on Trakya region Oak (Quercus spp.) honeys of Turkey: their physico-chemical, antioxidant and phenolic compounds properties

Abstract

Abstract Objective The purpose of this study was therefore to investigate various physicochemical properties, phenolic composition and antioxidant capacities of the oak honey, large quantities of which are produced in the Thrace region of Northwest Turkey. Methods Hunter color values (Lab), optical rotation, electrical conductivity, moisture and ash were measured as physicochemical determinants. Sugar, proline content, mineral, phenolic acids, total phenolic flavonoids contents were evaluated as chemical parameters. Ferric reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging were used as antioxidant determinants. Results The results determined that dark-colored honeys (mean 24.95±8.35 L) have proline levels (649.82±203.90 mg/kg), total phenolic content (TPC) (67.29±13.10 mgGAE/100 g) and total flavonoid content (TFC) (10.14±4.78 mgQE/100 g), a high ratio of fructose/glucose (1.65±0.18). Rutin (11.14±8.50 μg/g), p-coumaric acid (6.97±5.80 μg/g) and protocatechuic acid (6.12±4.39 μg/g) were the major phenolic components, and quercetin was also detected in varying amounts in all samples. Potassium (2523±0.28 mg/kg), calcium (63.40±3.20 mg/kg) and magnesium (38.88±0.65 mg/kg) were the major minerals in the honeys. Conclusion Our results showed that physicochemical properties, phenolic compounds, antioxidant capacity, sugar and mineral contents successfully distinguish the geographical origins of oak honey. These findings will contribute to a more accurate evaluation of oak honey in the literature.