Buckwheat honeys: Screening of composition and properties
Introduction
Buckwheat honey, collected from the little pink flowers by honeybees, is characterised by a dark purple colour, almost black and by a strong animal odour, malty aroma and molasses flavor (Dalby, 2000). In several studies have been reported the high antioxidant properties of this honey (Gheldof, Wang, & Engeseth, 2002), as well as its antibacterial activity, highlighting its efficacy in respiratory tract infection (cough) and wound healing (e.g. burn wounds and venous leg ulcers) (Paul et al., 2007, Ranzato et al., 2012, van den Berg et al., 2008).
Buckwheat unifloral honey is mainly produced in North America (Canada and California), China and in some countries of Europe, such as Poland, Russia, The Netherland and Germany. Because of the quite low cultivation of buckwheat plants, in Italy the monofloral buckwheat honey is difficult to produce and it is usually found as a natural component of multifloral honeys.
The botanical and geographical origin of honey, which influence its quality and price, has been traditionally identified by the analysis of the bee pollen present in the honey, together with organoleptic and physicochemical determinations. However, this information should be enriched with data derived from the sensory profile and bioactive components. Therefore, new analytical methods have also been developed (Anklam, 1998, Ferreres et al., 1991) and among them, the determination of specific markers, such as phenolic compounds, is one of the most promising way for studying the healthy properties and quality of honeys (Gómez-Caravaca et al., 2006a, Gómez-Caravaca et al., 2006b, Tomás-Barberán et al., 2001, Yao et al., 2003.
Besides, the honey volatile fractions have been studied and different authors report that the same volatile components are present in the majority of honeys, although the mutual proportions of these substances can be different (Alissandrakis et al., 2007, Anklam, 1998, Baroni et al., 2006, Piasenzotto et al., 2003, Radovic et al., 2001, Soria et al., 2003). Similarly, certain specific volatile compounds are characteristic of a given floral origin (Cuevas-Glory, Pino, Santiago, & Sauri-Duch, 2007).
Buckwheat honey is produced at different levels of “uniflorality”, following the major or minor diffusion of the corresponding plant. In Italy taking into account the great attention in healthy foods, there is a growing interest for the production of foods made from buckwheat especially for celiacs, therefore farmers are planning more extensive cultivations and consequently the output of buckwheat honey will increase. There is a lack of investigation about this interesting botanical origin so the principal aim of this study was to analyse the quality of 10 buckwheat honeys collected from different producers, prefering those that come from areas where the cultivation is wide as in east Europe. The chemical composition of samples was evaluated by the use of traditional (melissopalynological and physicochemical analysis) and new analytical methods (phenolic and volatile compounds), emphasising correlations among the obtained data and also the presence of possible chemical markers of this honey.
Section snippets
Honey samples
Ten honey samples were bought from beekeepers claiming to produce monofloral buckwheat honeys. Honeys were kept at room temperature (25 ± 2 °C) and in the dark until analysed.
Reagents and chemicals
Unless otherwise stated, solvents and reagents used were of analytical grade and were from Merck (Darmstad, Germany). The standards used for the identification and quantification of phenolic acids and flavonoids were: protocatechuic acid, p-hydroxybenzoic acid, p-hydroxyphenylacetic acid, benzoic acid, apigenin, galangin from
Physicochemical and melissopalynological analysis
Table 2 lists the mean, standard deviations and ranges of the data obtained from the analysis of the different physicochemical parameters.
The electrical conductivity of honey usually shows great variability according to the floral origin and the results obtained for the samples under study varied between 0.33 and 1.86 mS/cm. In particular, the values of samples B-1, B-9 and B-10 (1.02, 1.37 and 1.86 mS/cm, respectively) exceeded the limit allowed for floral honeys (0.8 mS/cm), suggesting the
Conclusion
Since an exaustive characterisation of the buckwheat honey is not yet available, this study proposes a preliminary but comprehensive and detailed evaluation of composition and properties of that botanic origin. Besides the traditional descriptive analyses as pollen spectra and physicochemical proprieties, the aromatic and antioxidant profile were also included in order to improve the monofloral assessment of buckwheat honey.
Indeed volatile compounds, because of their relation to aroma and hence
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