Determination of Physicochemical Characteristics, Phytochemical Profile and Antioxidant Activity of Various Clover Honeys

This paper reports on some physicochemical and phytochemical characteristics (i. e. pH, electrical conductivity, colour, moisture content, total phenolic content, sugar profile) and in vitro antioxidant activity of honeys harvested from five legume species, red clover (Trifolium pratense), balansa clover (T. michelianum), Persian clover (T. resupinatum), purple clover (T. purpureum) and sanfoin, also known as holy clover (Onobrychis viciifolia), that were grown in enclosed shade houses to ensure that the honeys' characteristics are reflective of a truly monofloral honey. Glucose and fructose, determined via High-Performance Thin-Layer Chromatography (HPTLC) analysis, were found as the main sugars in all investigated honeys with the ratio of fructose to glucose ranging from 1 : 1.2 to 1 : 1.6. The honeys' pH values ranged from 3.9 to 4.6 which met Codes Alimentarius (CA) requirements. The moisture content was found to be between 17.6 and 22.2 % which in some cases was slightly higher than CA requirements (<= 20 %). The honeys' colour values, prior and after filtration, were between 825.5-1149.5 mAU and 532.4-824.8 mAU respectively, illustrating golden yellow to deep yellow hues. The total phenolic content (TPC) of the honeys was determined using a modified Folin-Ciocalteu assay. Their antioxidant activity was captured by the Ferric Reducing-Antioxidant Power (FRAP) assay as well as HPTLC analysis coupled with 2,2-diphenyl-1-picrylhydrazyl (DPPH) derivatisation. The highest total phenolic content was found in red clover honey (45.4 mg GAE/100 g) whereas purple clover honey showed the highest level of activity in the FRAP assay (7.3 mmol Fe2+/kg). HPTLC-DPPH analysis of the honeys' organic extracts demonstrated the presence of various bioactive compounds that contribute to their overall antioxidant activity. This study developed a methodology for producing monofloral clover honeys in a space limited, enclosed production system, which allowed to collate important baseline data for these honeys that can serve as the foundation for their potential future development into commercial honeys, including honeys that can be used for medicinal purposes. image