Elsevier

LWT

Volume 107, June 2019, Pages 199-207
LWT

Authentication of phacelia honeys (Phacelia tanacetifolia) based on a combination of HPLC and HPTLC analyses as well as spectrophotometric measurements

https://doi.org/10.1016/j.lwt.2019.03.009Get rights and content

Highlights

  • Authentication of phacelia honeys.

  • HPLC and HPTLC fingerprint analysis for the classification of honey samples.

  • Spectroscopic techniques to characterize the botanical origin of honey.

  • The use of chemometric methods allowed for identification of pure phacelia honey.

Abstract

The growing interest in the quality of honey affects customer preferences and consumption trends. Generally, monofloral honeys are more expensive than multifloral honeys, and the price strictly depends on its botanical origin. The increasing popularity of a variety of monofloral brands has led to the increasing number of adulterations and therefore for the need to develop new analytical methods for assessing honey authenticity. The purpose of the present study was to develop a method for the authentication of phacelia honeys on the basis of HPLC and HPTLC analyses and spectrophotometry. The results obtained by spectrophotometric analysis indicated significant differences only between one sample and remaining ones of phacelia honeys. The application of HPLC and HPTLC methods allowed the complete differentiation of Phacelia tanacetifolia honey samples in context of content of other plants pollen. Thus, honeys containing more than 45% pollen from Phacelia tanacetifolia appear to exert more similarities in their respective chromatograms, while the chromatograms of two samples (Ph1 and Ph9), which derived from honey containing majority of pollen from other plants, differed significantly. Therefore, the combination of HPLC and HPTLC fingerprints supported by spectrophotometric measurements seems to be a suitable method for the classification of honey samples.

Introduction

Honey is a very popular food product in all parts of the world. A sweet taste, a pleasant aroma, good nutritional properties and antibacterial and antioxidant activity are its characteristic features. It allows for its inclusion into the “minimally processed” food category (Kuś et al., 2014). The composition of honey depends on the type and species of the plant from which bees collect the nectar. The main ingredients of honey are sugars (primarily glucose and fructose) and water. Honey also contains a cocktail of low-molecular-weight compounds (organic acids, amino acids, proteins, polyphenolic compounds and minerals), which significantly contribute to the honey biological activity being also responsible for its aroma, taste and colour. Honeys are offered as multifloral (produced by bees using nectar from many flower sources) or monofloral (from the nectar of one flower spices) ones, and their botanical origin affect the quality and price.

In this paper we are presenting the chemical composition of non-sugar factions of monofloral phacelia honeys. It is produced by honeybees by collection of nectar from Phacelia tanacetifolia alongside with these of other plants. This honey has a light beige or white colour, mild aroma and soft taste. Phacelia tanacetifolia is an herbaceous, flowering annual of the Hydrophyllaceae family. This plant gives high quality nectar and pollen that are very attractive to bees. It is on the list of the world's top twenty honey plants. Furthermore, many of the benefits of Phacelia tanacetifolia (for example, quick growth, rapid flowering, good growth in dry soil and climate adaptability) have made beekeepers more likely to produce phacelia honey (Adgaba et al., 2016; Farkas & Zajacz, 2007).

The available literature clearly indicates that honey is the product most susceptible to fraud in the food industry. Therefore, the control of the quality of honeys is of great importance (Jasicka-Misiak, Poliwoda, Dereń, & Kafarski, 2012; Soares, Amaral, Oliveira, & Mafra, 2017; Trifković, Andrić, Ristivojević, Guzelmeric, & Yesilada, 2017). Honey authentication began with melissopalynological analysis. In recent decades, new methods based on the identification of natural products, such as phenolic compounds, have been implemented (Karabagias et al., 2014). Polyphenols were found in individual varieties of honey in different contents and compositions. Unfortunately, the determination and identification of such compounds in honey is challenging because these occur there at low concentrations. Therefore, the described results are strongly dependent on the isolation and kind of analytical method applied for their identification (Pyrzyńska & Biesaga, 2009; Ciulu, Spano, Pilo, & Sanna, 2016; Kečkeš et al., 2013). High-performance liquid chromatography (HPLC) is the most commonly technique used for quantitative and qualitative method analysis of this class of compounds (Badjah Hadj Ahmed et al., 2016; Pascual-Maté, Osés, Fernández-Muiño, & Sancho, 2017). The technique used equally as frequently for studying low-molecular-weight compounds is high-performance thin layer chromatography (HPTLC) (Locher, Neumann, & Sostaric, 2017). These methods allow the construction of phenolics profiles, which indicate the differences and similarities between honeys. In recent decades, accumulation of the large amount of data available by various analytical methods requires the use of statistical methods to classify the botanical origin of honey. The most common statistical techniques that have been used to authenticate honey are hierarchical cluster analysis, principal component analysis and discriminant analysis (Kečkeš et al., 2013; Karabagias et al., 2014; Kuś et al., 2014; Zieliński, Deja, Jasicka-Misiak, & Kafarski, 2014).

Therefore, the aim of this study was to determine the characteristic phenolic HPLC and HPTLC profiles obtained for phacelia honey samples and to investigate their correlation with pollen analysis data and thus their authentication. In addition, selected parameters are presented, such as: the total phenolic and flavonoid contents (TPC and TFC), antioxidant activity (DPPH and ABTS test) and colour characteristics. These parameters are known to correlate with pro-health properties of honey (Parker, Byrne, & Hemsworth, 2016; Piljac-Žegarac, Stipčević, & Belščak, 2009).

Section snippets

Chemicals and materials

All chemicals used for the analyses were of analytical purity grade. Methanol, dibasic sodium phosphate heptahydrate (Na2HPO4 x 7H2O), 85% phosphoric acid, chloroform, ethyl acetate and formic acid were purchased from POCH S.A. (Gliwice, Poland). The standards: chrysin (5,7-dihydroxy-2-phenyl-4H-chromen-4-one), galangin (3,5,7-trihydroxy-2-phenylchromen-4-one), apigenin (5,7-dihydroxy-2-(4-hydroxyphenyl)-4H-1-chromen-4-one), pinocembrin (5,7-dihydroxy-2-phenyl-2,3-dihydro-4H-chromen-4-one),

Total phenolic and flavonoid contents, antioxidant activity and colour intensity

Table 1 presents the predominant plant sources of all tested honeys. As seen from the Table nearly all of them could be classified as phacelia brand. Samples ascribed as Ph1 and Ph9 (declared by producers as phacelia honeys) contained significant amounts of pollen from other plants (Ph1: Phacelia 38.9%, Salix 32.3%, Fagopyrum 10.1%, Brassicaceae 9.3%; Ph9: Brassica napus 40.3%, Phacelia 39.5%). Thus, these are typical examples of honeys obtained when bees feed on more than one source. This set

Conclusion

This research suggests that the exact classification of honey could be made either by spectrophotometric measurements but as well by HPLC and HPTLC analysis. The best solution, however, is to use several complimentary methods. The use of two different chromatographic methods provided complimentary information that was useful for the classification and differentiation of phacelia honey. These methods distinguished pure honeys containing the highest phacelia pollen content from honeys containing

Declarations of interest

The authors declare there is no conflict of interest.

Funding

This study was funded by No. 2014/2015/15/B/NZ9/02182.

Acknowledgements

This work was supported by The National Science Centre of Poland in the frame of Grant NO: 2014/15/B/N29/02182.

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