Elsevier

Food Chemistry

Volume 272, 30 January 2019, Pages 66-75
Food Chemistry

Physicochemical properties and phenolic content of honey from different floral origins and from rural versus urban landscapes

https://doi.org/10.1016/j.foodchem.2018.08.035 Get rights and content

Highlights

  • Urban multi-floral honeys had a higher total phenolic content than rural honeys.

  • Heather honey had the highest total phenolic content of all Irish honeys.

  • Irish heather honey had a higher total phenolic content than Manuka honey.

  • Irish heather honey had similar physiochemical characteristics to Manuka honey.

Abstract

The composition of honey influences how beneficial it is to human health. This study evaluated the physiochemical properties and total phenolic content (TPC) of single vs. multi-floral Irish and selected international honeys, and whether properties varied according to hive location. Oilseed rape honey had the lowest TPC of Irish unifloral honeys. Heather honey had the highest TPC, similar to Manuka honey (Mean ± SD = 68.16 ± 2.73 and 62.43 ± 10.03 respectively), and the TPC of ivy honey was approximately half that of heather. Urban multi-floral honeys contained higher TPC (28.26 ± 13.63) than rural honeys (20.32 ± 11.54). Physiochemical properties varied according to floral origin, and whether hives were in urban or rural sites. Irish heather honey had similar physiochemical characteristics to Manuka honey. This first examination of Irish honey confirms that TPC and physiochemical properties vary with honey type and hive location, and suggests that Irish heather honey should be examined for potential health benefits.

Introduction

Honey produced by honey bees (Apis spp.) can promote many beneficial biological processes in humans, including: antioxidant (Aljadi and Kamaruddin, 2004), antibacterial (Gomes, Dias, Moreira, Rodrigues, & Estevinho, 2010), antidiabetic (Bobiş, Dezmirean, & Moise, 2018), anti-inflammatory (Shah & Amini-Nik, 2017) and antimicrobial activity (Gomes et al., 2010), as well as radical scavenging (Meda, Lamien, Romito, Millogo, & Nacoulma, 2005), and wound healing (Efem, 1988). Of these, food antioxidants have been shown to reduce oxidative stress and thus prevent oxidative damage (Pisoschi & Pop, 2015), and are thus of great interest for promoting human health and wellbeing. The constituents of honey that are responsible for antioxidant effects are flavonoids, phenolic acids, ascorbic acid, catalase, peroxidase, carotenoids, and products of Maillard reactions (Gheldof & Engeseth, 2002). Phenolic acids and flavonoids have been comprehensively researched in honey (Dimitrova et al., 2007, Ferreira et al., 2009, Kečkeš et al., 2013, Khalil et al., 2011, Pyrzynska and Biesaga, 2009) and can be used to assess honey quality. Several studies have shown that antioxidant activities are strongly correlated with the concentration of total phenolics. This was confirmed for seven single origin Italian honeys (Rosa et al., 2011), four types of Romanian honeys (Mǎrghitaş et al., 2009) and seven types of Slovenian honeys (Bertoncelj, Dobersek, Jamnik, & Golob, 2007). A study of Portuguese honeys demonstrated that the phenolic content of honey is not only responsible for its antioxidant properties, but also for its anti-microbial effects (Estevinho, Pereira, Moreira, Dias, & Pereira, 2008).

It is widely agreed that the botanical origin of honey has the greatest influence on its phenolic content and thus antioxidant activity, and some floral honeys are perceived to have a higher quality than others. For example, some-single origin honeys (i.e. from a single plant taxa, e.g. Manuka honey (Leptospermum scoparium) from New Zealand and heather honey (Calluna/Erica spp.) from northern Europe) have a higher retail price than blended honey (a mixture of two or more honeys) (National Honey Board, 1991). The purity of the honey also plays a role in its quality and Manuka honey has varying UMFs (Unique Manuka Factors) whereby the designated factor, price and potential health benefits correlate positively (Beitlich, Koelling-Speer, Oelschlaegel, & Speer, 2014).

In this study, we focus on honey produced in Ireland. The main feature of the Irish honey market is that most of the production comes from small private producers: according to the Federation of Irish Beekeepers, there were 2800 registered beekeepers in Ireland in 2014 and the average number of hives per beekeeper was three (Federation of Irish Beekeepers, 2015, personal communication). Given the maritime (relatively cool and damp) climatic conditions of Ireland, the production of honey is limited, and the majority of Irish beekeepers only harvest honey once a year. Despite this, trade in honey increased in value and tonnage in Ireland between 2009 and 2013. Within these years Ireland imported seven times more honey than it exported (Central Statistics Office, 2013). Increasing consumer preferences for products based on honey has led to the expansion of the honey market, resulting in a greater number of varieties of honey and varieties of honey-based foods. This has also led to increased demand for single-origin honeys (such as heather and ivy (Hedera spp.)) particularly those with perceived health benefits. Being able to identify particular characteristics in honey which are associated with honey’s health benefits, and rapidly assessing these characteristics in Irish honey could help beekeepers to market their honey appropriately and increase its commercial value.

The main aim of this study was to investigate the chemical composition (in terms of total phenolic content) and physiochemical parameters (honey electrical conductivity, moisture, pH, total sugar and colour) of different types of Irish honey and compare these with international honeys. In addition, microbial contamination and microbial stability of Irish multi-floral honey was assessed. The comparison of Irish single-origin honeys (heather, ivy and oilseed rape (Brassica rapa) and multi-floral honeys has to our knowledge never previously been made, nor has a comparison of honey from urban vs. rural hive sites. In addition, the relationship between total phenolic content and physiochemical parameters was assessed to enable rapid assessment of Irish honey quality. Results confirmed that total phenolic content (TPC) could be used to differentiate between honey types. Urban multi-floral honeys had a higher TPC than rural multi-floral honeys. Irish heather honey had the highest TPC of all Irish single origin honeys, and had a higher TPC than Manuka honey. It was illustrated that honey colour correlates with electrical conductivity and with TPC, although ivy honey was an exception to this. While ivy was the darkest Irish honey analysed, its TPC was less than that of heather and Manuka honeys. To our knowledge this is the first time that ivy honey and Irish honey have been comprehensively researched.

Section snippets

Sample collection

One hundred and thirty-one Irish honey samples from Apis mellifera were collected directly from beekeepers between 2013 and 2015, from 78 locations across Ireland (Fig. 1). The majority (124) of samples were multi-floral honeys (55 from urban and 69 from rural locations), three were heather (Erica and/or Calluna spp.) honeys, two were ivy (Hedera spp.) honeys and two were oilseed rape (OSR) honeys. Honeys were classified according to landscape context (urban/rural) (Dijkstra & Poelman, 2014) or

Total phenolic content

The total phenolic content (TPC) of Irish multi-floral honeys (including urban and rural honeys) ranged from 2.59 to 81.10 mg of gallic acid equivalent (GAE)/100 g of honey, (n = 124, Mean ± SD = 23.84 ± 13.07) (Fig. 2(a)). This TPC range is similar to the ranges typically found for European honeys (Kús et al., 2014, Mǎrghitaş et al., 2009). A large proportion of the samples (over 85%) were within the range of 10–50 mg GAE/100 g of honey, (n = 106, Mean ± SD = 23.66 ± 8.62). The variation in

Conclusion

Our findings confirm that the differences in phenolic profiles of honey can be attributed to the floral origin of the honey. Multi-floral honeys from different landscapes (i.e. containing different land uses and therefore a different composition of floral resources) and single origin honeys were demonstrated to contain different phenolic contents. Irish heather honey had the highest TPC of the three Irish single origin honeys whilst OSR honey had the lowest. This study has also confirmed that

Acknowledgements

Financial support was provided by the Irish Research Council, Ireland (Postgraduate Scholarship, S. Kavanagh) and Dublin City University, Ireland (Career Enhancement Award, B. White). The beekeepers of Ireland are gratefully acknowledged.

References (48)

  • I.K. Karabagias et al.

    Botanical discrimination of Greek unifloral honeys with physico-chemical and chemometric analyses

    Food Chemistry

    (2014)
  • S. Kečkeš et al.

    The determination of phenolic profiles of Serbian unifloral honeys using ultra-high-performance liquid chromatography/high resolution accurate mass spectrometry

    Food Chemistry

    (2013)
  • P.M. Kús et al.

    Antioxidant activity, color characteristics, total phenol content and general HPLC fi ngerprints of six Polish uni fl oral honey types

    LWT – Food Science and Technology

    (2014)
  • A. Meda et al.

    Determination of the total phenolic, flavonoid and proline contents in Burkina Fasan honey, as well as their radical scavenging activity

    Food Chemistry

    (2005)
  • A.M. Pisoschi et al.

    European journal of medicinal chemistry the role of antioxidants in the chemistry of oxidative stress: A review

    European Journal of Medicinal Chemistry

    (2015)
  • K. Pyrzynska et al.

    Analysis of phenolic acids and flavonoids in honey

    TrAC Trends in Analytical Chemistry

    (2009)
  • A. Rosa et al.

    Antioxidant profile of strawberry tree honey and its marker homogentisic acid in several models of oxidative stress

    Food Chemistry

    (2011)
  • S. Silici et al.

    Total phenolic content, antiradical, antioxidant and antimicrobial activities of Rhododendron honeys

    Food Chemistry

    (2010)
  • V.L. Singleton et al.

    Analysis of total phenols and other oxidation substrates and antioxidents by means of Folin-Ciocalteu reagent

    Methods in Enzymology

    (1999)
  • J.M. Stephens et al.

    Phenolic compounds and methylglyoxal in some New Zealand Manuka and Kanuka honeys

    Food Chemistry

    (2010)
  • M.O. Adenekan et al.

    Physico-chemical and microbiological properties of honey samples obtained from Ibadan

    Journal of Microbiology and Antimicrobials

    (2010)
  • J.M. Alvarez-Suarez et al.

    Honey as a source of dietary antioxidants: Structures, bioavailability and evidence of protective effects against human chronic diseases

    Current Medicinal Chemistry

    (2013)
  • H.A. Alzahrani et al.

    Antibacterial and antioxidant potency of floral honeys from different botanical and geographical origins

    Molecules

    (2012)
  • N. Beitlich et al.

    Differentiation of manuka honey from kanuka honey and from jelly bush honey using HS-SPME-GC/MS and UHPLC-PDA-MS/MS

    Journal of Agricultural and Food Chemistry

    (2014)
  • Cited by (0)

    View full text