Enrichment of Rapeseed Honey with Combined Polyphenol-Rich Dry Extracts from Mandarin Peels and Clove Buds

Enriching honey with plant additives allows for increasing its antioxidant potential in an additive-dependent manner and at the same time shaping new sensory properties, increasing consumer acceptability. Known spices and by-products from fruit processing can also be used to produce such additives. Combined dry extracts of clove buds and mandarin peels were used to enrich antioxidant properties and to flavor rapeseed honey. Four different extracts combining both raw products were produced by ultrasound-assisted extraction using 50% vol. ethanol and converted into powder by vacuum concentration followed by lyophilization. The obtained extracts were evaluated for antioxidant activity (FRAP and DPPH assays) as well as total polyphenols content. Phenolic HPLC-DAD profiles were compared and selected polyphenols (syringic acid, ellagic acid, hesperidin and eugenol) were quantified. The dry extracts were incorporated into rapeseed honey (0.25% w/w) during the creaming process. No significant changes in color and texture were visually noted; whereas, some changes (p < 0.05) in titrable acidity and electrical conductivity were observed. A significant increase (p < 0.05) in antioxidant activity (from 4 to 6-fold) and the beneficial enrichment with well-known bioactive compounds (mainly eugenol and hesperidin) was observed for all produced flavored honeys. Moreover, tested properties of the enriched honeys remained stable during 6 months of storage. The two honeys with the most improved antioxidant activity showed better sensory characteristics and consumer acceptability compared to pure rapeseed honey, but slight extract type-dependent differences were noted. It was shown that the proposed sustainable technological process using waste mandarin peels can lead to the development of a new product referred to as "plant-enriched honey" with increased health-promoting value belonging to the functional food segment.