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Abstract:The antioxidant activities and total phenolic content of 30 samples of acacia honey from Croatian territory were analysed. Phenolics were determined by the modified Folin-Ciocalteu method, antiradical activity by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) method and potential antioxidant activity using the ferric reducing antioxidant power (FRAP) method. In all samples, physicochemical parameters (water content, electrical conductivity, total reducing sugars, sucrose content, acidity, hydroxymethylfurfural content, prolin content, optical rotation, diastase activity and invertase activity) were measured according to Croatian legislation and International regulatory standards. Honey can be considered as a dietary supplement as it contains some important components including α-tocopherol, ascorbic acid, flavonoids and phenolics. The composition and properties of honey are dependent on floral origins, climatic conditions of the produced area, processing and storage methods. The results of physicochemical analyses showed that all the values of investigated parameters are in agreement with the current legislation. Phenolic content ranged from 31.72 mg/kg to 80.11 mg/kg, antiradical activity expressed as IC 50 ranged from 61.28% to 253.47% and antioxidant activity expressed as FRAP value from 6.95 to 142.43. A positive correlation was observed between total phenolic content and antioxidant activity, indicating that phenolic compounds are mainly responsible for the antioxidant power of acacia honey.

AbstractŠarić G., Marković K., Vukičević D., Lež E., Hruškar M., Vahčić N. (2013): Changes of antioxidant activity in honey after heat treatment. Czech J. Food Sci., 31: 601-606.We determined how the antioxidant activity and total phenolic content of honey changed after being subjected to a high temperature. Antioxidant activity was determined using two methods -FRAP (ferric reducing antioxidant power) and DPPH (1,1-diphenyl-2-picrylhydrazyl) assays. Total phenolic content was determined by modified FolinCiocalteu method. The research was conducted on 31 samples of acacia honey and 8 samples of chestnut honey. All measurements were done at two temperatures -at 23°C (room temperature) and after 5 min of heating at 95°C. The obtained results show uneven changes of antioxidant activity and total phenolic content among individual samples, i.e. in some samples antioxidant activity decreased after heating, while in others it increased. The same applies to the total phenolic content. Statistical analysis of the results (t-test) showed no statistically significant differences between the results measured at two different temperatures (P > 0.05) in all three methods used, and in both types of honey. The only statistically significant difference (P < 0.05) was observed when using DPPH method in acacia honey.

Uršulin-Trstenjak N., Levanić D., Primorac L., Bošnir J., Vahčić N., Šarić G. (2015): Mineral profile of Croatian honey and differences due to its geographical origin. Czech J. Food Sci., 33: 156-164.The proportions of twelve minerals were determined in 200 samples of the black locust honey from five Croatian regions during two seasons. The average proportions were dominated by that of K (205.57-428.05 mg/kg), followed by Ca (33.53-329.00 mg/kg) and Na (23.34-218.04mg/kg), which was in percentages as follows: K 31.69-81.34%, Ca 6.51-35.56%, and Na 7.36-23.65%. Melissopalynological and physico-chemical analysis of honey confirmed its general quality requirements and botanical origin. One-factor analysis of variance showed a significant differences between the regions in each season based on the average proportions of macro and micro elements except for Mn and Cd in season 2 (P < 0.05). t-Test enabled an insight into the significance of differences between the seasons within each region based on the average proportions of macro and micro elements. Principal components analysis (PCA) showed that Al (Bjelovar-Bilogora), Fe (Bjelovar-Bilogora and Istria), Cu (Eastern Croatia), and K (Istria) could present mineral substances typical for the black locust honey of each region.

The purpose of this study was to determine the changes in the contents of flavonoids that were the most prevalent in acacia and multifloral honey during one year of storage. Samples were stored in transparent glass containers, at room temperature, on open shelves exposed to light during daytime. Eight individual flavonoids identified and quantified using HPLC-Diode Array Detector (DAD) belongs to three subgroups: flavonols (quercetin, luteolin, kaempferol and galangin), total flavanons (hesperetin and pinocembrin) and total flavones (apigenin and chrysin). Obtained results revealed that multifloral honey had more total flavonoids than acacia samples did. On average from all of the samples, multifloral honey had more of quercetin, hesperetin, luteolin, kaempferol and apigenin than acacia honey did. Content of flavonoids increased in samples between the 1st and 6th month of storage and then started to decrease until the 9th month, when they remained relatively constant all the way until the 12th month of storage. In conclusion, acacia and multifloral honey after one-year of storage still can be a valuable source of flavonoids.