Effects of freeze-drying and vacuum-drying on the quality, total phenolic contents,and antioxidant activities of bee honey in northern Thailand

Abstract

Weaimed to evaluate the effect of freeze-drying and vacuum-drying on moisture, water activities (aw), total soluble solid (TSS), hydroxymethylfurfural (HMF), diastase activity, total phenolic content(TPCs), and antioxidant activities(ABTS, DPPH, FRAP, ORAC)of longan (Dimocarpus longanLour.) blossomhoneyand Siam weed (Chromolaena odorataLour.) honey. The fresh longanblossomhoneyand Siam weed honeywere collected from a local apiarist in Northern Thailand. Freeze-dryingat 0.013 kPa, −54°C for 72 h or vacuum-dryingat 2.5 kPa at 60°C for 12 h was applied to dehydrate fresh honey. The moisture of freeze-driedsamples was 10.10% for longan blossomhoneyand 11.50% for Siam weed honey, and the awof both freeze-driedhoneyswas 0.43. Freeze-andvacuum-driedproduced more TSS than fresh honeydid(p≤0.05).However, the amounts of TSS derived freeze-dryand vacuum-drywere not significantly different. Freeze-driedhoney contained the highest HMF and the lowest diastase activity regardless of honey origins (p≤ 0.05).Drying processes significantly increased the TPCs levels of honey (approximately 2 folds by freeze-drying method). The antioxidant activity of dried honey was significantly higher than that of fresh honey. It was observed that the freeze-dryingmethod tended to better preserve the antioxidant activity of honey compared to vacuum-drying methods in both typesof honey.The results indicated that drying processes significantly affect the quality of dried honey, including TSS, HMF, diastase activity, TPCs, and antioxidant activity. In this study, freeze-drying emerged as the relatively low temperature drying method that canpreserve the quality of honey, especially in termsof TPCsandantioxidant activity.