Changes of Antioxidant Activity and Phenolic Content in Acacia and Multifloral Honey During Storage
Goran Šarić1*, Ksenija Marković1, Nikola Major1, Marina Krpan1, Natalija Uršulin-Trstenjak2, Mirjana Hruškar1 and Nada Vahčić1
1Laboratory for Food Quality Control, Faculty of Food Technology and Biotechnology, Pierottijeva 6, HR-10000 Zagreb, Croatia
2Polytechnic of Varaždin, Križanićeva 33, HR-42000 Varaždin
Article history:
Received October 17, 2011
Accepted July 4, 2012
Key words:
antioxidant activity, phenolic compounds, honey, storage
Summary:
Total flavonoid and total phenolic content were studied in acacia and multifloral honey for 12 months in 6-month intervals. DPPH (1,1-diphenyl-2-picrylhydrazyl) and FRAP (ferric reducing antioxidant power) methods were used to determine total antioxidant activity in honey samples during the same period of time. Samples were stored in transparent glass containers at room temperature, on shelves exposed to natural light during daytime and in the dark during nighttime. Two types of honey from four different regions in Vara`- din county, Croatia, were investigated: monofloral – acacia (Robinia pseudoacacia L.) and multifloral. Of the total of 40 samples, there were 20 of each type of honey (5 from each region). The goal of this study is primarily to demonstrate the changes in the antioxidant activity of the two investigated types of honey during one year of storage, and not to make comparisons between them. According to the obtained data, the rate of decrease in the content of total flavonoids and phenolics was determined and changes in the antioxidant activity in honey samples were measured. After one year of storage, total phenolic content decreased by 91.8 % in acacia honey, and by 88.6 % in multifloral honey. Total flavonoid content also decreased in both types of honey, by 45.6 % in acacia honey and by 43.8 % in multifloral honey. During the same period, an increase from 12.20 to 16.73 mg/mL (i.e. by 37.1 %) was recorded in the IC50 values in multifloral honey, while in acacia honey this increase was from 44.64 to 407.01 mg/mL (i.e. by 811.7 %). Decrease in the antioxidant activity measured by FRAP method was also bigger in acacia honey than in multifloral honey (by 428.0 and 72.5 %, respectively), which corresponds well with the results obtained by DPPH method. Simple correlations were made to determine how each of the investigated parameters affects the others. The analysis of variance was used in order to determine the influence of the region, honey type and storage time on different parameters of antioxidant activity as well as on the total phenolic and total flavonoid content in honey samples.
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