Commercial honey processing generally involves controlled heating (to destroy yeast and delay granulation) combined with fine straining or pressure filtration. There has been concern that the processing of honey may reduce the antioxidant capacity of honey. This study examined the impact of heat and filtration on the antioxidant capacity of clover and buckwheat honeys during storage. Processed and unprocessed clover and buckwheat honey was stored in clear glass, amber glass, and polyethylene bottes and stored at room temperature under both natural laboratory lighting and in the dark (3 samples per condition). Additional samples were stored for 6 months at 4 degrees Celsius and -20 degrees Celsius. Antioxidant capacity of the honeys was determined by oxygen radical absorbance capacity (ORAC). Processing clover did not significantly impact antioxidant capacity; however, processing lowered the antioxidant capacity for buckwheat honey, by 33.4%. Antioxidant capacity of all honey samples was reduced after 6 months storage, with no impact of storage temperature or container type. Processed and raw honeys showed similar antioxidant capacity after storage.

Previous research has indicated that a acute honey consumption (i.e., a single dose) can raise the phenolic concentration of the plasma. This study examined the effects of chronic honey consumption to determine if increases in total plasma phenolic content and plasma antioxidant capacity could be sustained over the long term. Twenty-five subjects (13 Males and 12 females) consumed 1.5 grams of honey per kilogram of body weight (~4-10 tablespoons) for 28 days. Subjects were randomly assigned either a honey with a high phenolic content (HA) or a lower phenolic content (LA). Total plasma phenolics were measured on day 1 and 29 at 5 different time points: immediately after honey consumption and then again 1.5 hr, 3 hr 6 hr and 24 hour post-consumption. The results indicated that the phenolic content of the plasma on day 29 was significantly higher than baseline (i.e., day one) in both honey groups, suggesting that chronic honey consumption can increase the antioxidant capacity of the plasma.

This study examined the acute effects of consuming buckwheat honey (dissolved in water) compared to black tea, black tea with sugar, or black tea with buckwheat honey on serum oxidative status and lipoprotein oxidation. Twenty-five healthy men consumed each of the five beverages in a blind, randomized fashion. Antioxidant capacity of human serum samples was measured using a variety of methods including the oxygen radical absorbance capacity (ORAC) assay, ex vivo susceptibility of serum lipoprotein to Cu(2+)-induced oxidation, and the thiobarbituric acid reactive substances (TBARS) assay. The results showed that black tea with honey had the highest phenolic content and thus antioxidant potential, followed by tea alone, tea with sugar and honey alone. However, buckwheat honey produced the greatest increase in serum antioxidant capacity (demonstrating the inconsistency between the antioxidant potential of a food and its actual effect on serum antioxidant capacity). Ex vivo serum lipoprotein oxidation and TBARS values were not significantly altered after consumption of any of the five beverages.

The effects of consuming 1.5 g/kg body weight of corn syrup or buckwheat honey on the antioxidant and reducing capacities of plasma. Forty subjects were randomly assigned to one of four groups: (1) corn syrup, (2) low phenolic content buckwheat honey, (3) high phenolic content buckwheat honey, (4) water. Following consumption of the two honey treatments, plasma total-phenolic content increased (P < 0.05) as did plasma antioxidant and reducing capacities (P < 0.05). In contrast, corn syrup had no significant effect. These data support the concept that phenolic antioxidants from processed honey are bioavailable, and that they increase antioxidant activity of plasma. It can be speculated that honey consumption could augment the body’s defenses against oxidative stress. Given that the average sweetener intake by humans is estimated to exceed 70 kg per year, the substitution of honey for traditional sweeteners could result in an enhanced antioxidant defense system in healthy adults.

The objective of this study was to quantify and characterize the antioxidants and some of the isolated phenolic compounds and/or fractions of honeys from seven different floral sources (acacia, buckwheat, clover, fireweed, Hawaiian Christmas berry, tupelo, and soybean). Chromatograms of the phenolic nonpolar fraction of the honeys indicated that most honeys contain similar types but quantitatively different phenolic contents. The primary flavinoids identified were the flavanones pinobanksin, and pinocembrin and the flavones chrysin and galangin. A linear correlation between phenolic content and ORAC activity was demonstrated (R(2) = 0.963, p < 0.0001). Honeys were separated by solid-phase extraction into four fractions to identify the relative contribution of each fraction to the antioxidant activity of honey. Antioxidant analysis of the different honey fractions suggested that the water-soluble fraction contained most of the antioxidant components, including protein; gluconic acid; ascorbic acid; hydroxymethylfuraldehyde; and the combined activities of the enzymes glucose oxidase, catalase and peroxidase. Of these components, a significant correlation could be established only between protein content and ORAC activity (R(2) = 0.674, p = 0.024). These results suggest that the antioxidant capacity of honey is a product of the combined activity of a wide range of compounds including phenolics, peptides, organic acids, enzymes, Maillard reaction products, and possibly other minor components.

In this study honeys from seven different floral sources (acacia, buckwheat, clover, fireweed, Hawaiian Christmas berry, tupelo, and soybean) were analyzed for in vitro antioxidant capacity and total phenolic content. Antioxidant capacity was measured by the oxygen radical absorbance capacity (ORAC) assay and by monitoring the formation of conjugated dienes as an index of the inhibition of copper-catalyzed serum lipoprotein oxidation. ORAC values for the honeys ranged from 3.0 micromol Trolox equivalent/g for acacia to 17.0 micromol Trolox equivalent/g for buckwheat and all were significantly higher than the sugar analogue (p < 0.05). A linear correlation was observed between phenolic content and ORAC activity of the investigated honeys (p < 0.0001, R (2) = 0.9497). The relationship between the ORAC activity and inhibition of lipoprotein oxidation by the honeys yielded a correlation coefficient of 0.6653 (p = 0.0136). This work shows that honey may serve as a source of dietary antioxidants and a healthy alternative to sugar.