Pollen analysis of Australian honey

Bioactivities and Phenolic Profiles of Honeys Derived from Plants of the Goldfields, Esperance and Wheatbelt Regions of Western Australia

The aim of this study was to examine a collection of 79 honeys derived from plants endemic to several Western Australian unique bioregions for bioactivity and physicochemical characteristics. For physicochemical analyses, total phenolic content, high performance thin layer chromatography (HPTLC) fingerprints, pH, Brix, colour and hydrogen peroxide generation were examined. Brix (82.6±1.3) and pH (4.34±0.24) values were within expected ranges, whereas hydrogen peroxide levels determined using an o-dianisidine/horseradish peroxidase assay were relatively low, ranging from 0-244 μM. Antibacterial activity determined by the broth microdilution assay showed that Moort (Eucalyptus platypus) and Yate (Eucalyptus occidentalis) honeys had the highest overall activity with mean minimum inhibitory concentrations of 24.8 % and 25.1 % (w/v) honey, respectively. Yate honey also had the highest overall antioxidant activity (4.38±0.58 mmol Fe2+ /kg of honey), followed by Mallee honeys from various eucalypts, as determined by FRAP (Ferric reducing antioxidant power) and DPPH⋅ (2,2-Diphenyl-1-picrylhydrazyl) assays. This study identified new sources of honeys with potentially useful therapeutic properties from bioregions within Western Australia.

An investigation of the suitability of melissopalynology to authenticate Jarrah honey

This study reports on the analysis of eleven Jarrah (Eucalyptus marginata) honeys, of which nearly half (n = 5) were re-classified as Blackbutt (E. patens) honey on the grounds of the predominant flower pollen identified by melissopalynology. Based on a comprehensive analysis of the honeys' physico- and phytochemical characteristics and antioxidant activity data, taking into account pH, electrical conductivity, refractive index and Brix values as well as moisture content, individual fructose and glucose content and derived fructose to glucose ratio alongside total phenolic content and antioxidant activity determined by the DPPH assay, no statistically significant difference was found amongst the eleven honeys classified by pollen analysis into two honey groups, ‘Jarrah’ or ‘Blackbutt’. This study therefore draws into question the value of melissopalynology as an analysis tool to authenticate Jarrah honey.

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Case study on Jarrah (Eucalyptus marginata) honey, presenting comprehensive physico-chemical, phytochemical and bioactivity data.

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The investigated honey samples can be considered as chemically equivalent although nearly half of them were reclassified as either Blackbutt (Eucalyptus patens) or multifloral honeys on the basis of melissopalynology.

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Findings challenge the value of melissopalynology for the authentication of honey harvested from botanically diverse areas.

Identification of pollen taxa by different microscopy techniques

Melissopalynology is an important analytical method to identify botanical origin of honey. Pollen grain recognition is commonly performed by visual inspection by a trained person. An alternative method for visual inspection is automated pollen analysis based on the image analysis technique. Image analysis transfers visual information to mathematical descriptions. In this work, the suitability of three microscopic techniques for automatic analysis of pollen grains was studied. 2D and 3D morphological characteristics, textural and colour features, and extended depth of focus characteristics were used for the pollen discrimination. In this study, 7 botanical taxa and a total of 2482 pollen grains were evaluated. The highest correct classification rate of 93.05% was achieved using the phase contrast microscopy, followed by the dark field microscopy reaching 91.02%, and finally by the light field microscopy reaching 88.88%. The most significant discriminant characteristics were morphological (2D and 3D) and colour characteristics. Our results confirm the potential of using automatic pollen analysis to discriminate pollen taxa in honey. This work provides the basis for further research where the taxa dataset will be increased, and new descriptors will be studied.

Japanese Honeybees (Apis cerana japonica Radoszkowski, 1877) May Be Resilient to Land Use Change

Simple Summary

Pollinators are threatened globally by growing urban sprawl and agriculture. The Western Honeybee (Apis mellifera) readily adapts to whatever food is available, so people have made it the most widely distributed pollinator across the world. Previous research has suggested that the Western Honeybee may be less resilient to land use change outside of its natural range. This study examines a different honeybee species—the Japanese Honeybee (Apis cerana japonica). Unlike the Western Honeybee, this species is found almost exclusively in its natural range in Japan. Consequently, it may be better adapted to its local food sources and therefore more resilient. Working in southern Japan, in the Nagasaki and Saga prefectures, we looked at the nectar and pollen that the Japanese Honeybee feeds on. Their food intake was then examined in relation to local land use composition. We found minimal impact of increasing urban sprawl on the forage of the Japanese Honeybee. This goes against previous studies on the Western Honeybee elsewhere in the world. Though in need of a direct comparison with Western Honeybee, these preliminary results could be due to differences in urban green infrastructure in Japan, or due to an adaptation by the Japanese honeybee to its surroundings.

Abstract

Pollinators are being threatened globally by urbanisation and agricultural intensification, driven by a growing human population. Understanding these impacts on landscapes and pollinators is critical to ensuring a robust pollination system. Remote sensing data on land use attributes have previously linked honeybee nutrition to land use in the Western Honeybee (Apis mellifera L.). Here, we instead focus on the less commonly studied Apis cerana japonica—the Japanese Honeybee. Our study presents preliminary data comparing forage (honey and pollen) with land use across a rural-urban gradient from 22 sites in Kyushu, southern Japan. Honey samples were collected from hives between June 2018 and August 2019. Pollen were collected and biotyped from hives in urban and rural locations (n = 4). Previous studies of honey show substantial variation in monosaccharide content. Our analysis of A. cerana japonica honey found very little variation in glucose and fructose (which accounted for 97% of monosaccharides), despite substantial differences in surrounding forage composition. As expected, we observed temporal variation in pollen foraged by A. cerana japonica, likely dependent on flowering phenology. These preliminary results suggest that the forage and nutrition of A. cerana japonica may not be negatively affected by urban land use. This highlights the need for further comparative studies between A. cerana japonica and A. mellifera as it could suggest a resilience in pollinators foraging in their native range.

Cataloguing the small RNA content of honey using next generation sequencing

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Plant miRNAs are present in Australian polyfloral and Leptospermum scoparium honey.

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Sequencing shows that honey contains a diverse range of small, non-coding RNAs.

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Honey RNA comes from different phylogenies including invertebrates and prokaryotes.

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Unique small RNA profiles can provide insight into honey production conditions.

Honey adulteration is a problem that effects the global honey industry and specifically, has been discovered in the Australian market. Common methods of adulteration include dilution with sugar syrup substitutes and the mislabelling of the floral and geographic origin(s) of honey. Current authentication tools rely on the molecular variability between different honeys, identifying unique chemical profiles and/or DNA signatures characteristic of a particular honey.

Honey is known to contain plant miRNAs derived from its floral source. To explore the composition and variability of honey RNA molecules, this is the first study to catalogue the small RNA content of Australian polyfloral table honey and New Zealand Leptospermum scoparium honey using next generation sequencing. The data shows that in addition to miRNAs, honey contains a variety of small non-coding RNAs including tRNA-derived fragments. Moreover, the honey small RNAs are derived from a range of phylogenetic sources, including from plant, invertebrate, and prokaryotic species. The data indicates that different honeys contain unique small RNA profiles, which suggests a novel avenue in developing molecular-based honey authentication tools.

Development of an HPTLC-based dynamic reference standard for the analysis of complex natural products using Jarrah honey as test sample

In this paper, we describe a novel approach to the development of a reference standard for the quality control of complex natural products, which will assist in the assessment of their authenticity and purity. The proposed method provides a template for the selection of samples, which can be pooled to obtain a reference standard. A shortfall of such an approach is, however, that the pooled sample is static in nature and therefore unable to capture difference in processing conditions or natural variations triggered by geographical or climatic impacts over time. To address this, the paper also outlines the development of a dynamic reference standard, which allows for ongoing adjustments to future variations. The method employs High-Performance Thin Layer Chromatography (HPTLC) derived extract profiles processed by multivariate analysis. The development of the dynamic reference standard is illustrated using honey, a complex natural matrix, as an example.

Pollen DNA metabarcoding identifies regional provenance and high plant diversity in Australian honey

Accurate identification of the botanical components of honey can be used to establish its geographical provenance, while also providing insights into honeybee (Apis mellifera L.) diet and foraging preferences. DNA metabarcoding has been demonstrated as a robust method to identify plant species from pollen and pollen-based products, including honey. We investigated the use of pollen metabarcoding to identify the floral sources and local foraging preferences of honeybees using 15 honey samples from six bioregions from eastern and western Australia. We used two plant metabarcoding markers, ITS2 and the trnL P6 loop. Both markers combined identified a total of 55 plant families, 67 genera, and 43 species. The trnL P6 loop marker provided significantly higher detection of taxa, detecting an average of 15.6 taxa per sample, compared to 4.6 with ITS2. Most honeys were dominated by Eucalyptus and other Myrtaceae species, with a few honeys dominated by Macadamia (Proteaceae) and Fabaceae. Metabarcoding detected the nominal primary source provided by beekeepers among the top five most abundant taxa for 85% of samples. We found that eastern and western honeys could be clearly differentiated by their floral composition, and clustered into bioregions with the trnL marker. Comparison with previous results obtained from melissopalynology shows that metabarcoding can detect similar numbers of plant families and genera, but provides significantly higher resolution at species level. Our results show that pollen DNA metabarcoding is a powerful and robust method for detecting honey provenance and examining the diet of honeybees. This is particularly relevant for hives foraging on the unique and diverse flora of the Australian continent, with the potential to be used as a novel monitoring tool for honeybee floral resources.

A New Approach to Inform Restoration and Management Decisions for Sustainable Apiculture

Habitat loss has reduced the available resources for apiarists and is a key driver of poor colony health, colony loss, and reduced honey yields. The biggest challenge for apiarists in the future will be meeting increasing demands for pollination services, honey, and other bee products with limited resources. Targeted landscape restoration focusing on high-value or high-yielding forage could ensure adequate floral resources are available to sustain the growing industry. Tools are currently needed to evaluate the likely productivity of potential sites for restoration and inform decisions about plant selections and arrangements and hive stocking rates, movements, and placements. We propose a new approach for designing sites for apiculture, centred on a model of honey production that predicts how changes to plant and hive decisions affect the resource supply, potential for bees to collect resources, consumption of resources by the colonies, and subsequently, amount of honey that may be produced. The proposed model is discussed with reference to existing models, and data input requirements are discussed with reference to an Australian case study area. We conclude that no existing model exactly meets the requirements of our proposed approach, but components of several existing models could be combined to achieve these needs.

Cluster Analysis Classification of Honey from Two Different Climatic Zones Based on Selected Physicochemical and of Microbiological Parameters

The geographical origin of honey affects its composition, which is of key importance for the health-promoting properties and safety of the product. European regulations clearly define the physicochemical requirements for honey that determine the microbiological quality. On the other hand, legislation abolishes microbiological criteria. In the study 40 honey samples originating from two different climatic zones were analyzed. The water content, pH, water activity analysis and the microbiological quality of honey samples have been tested using the reference plate method (total viable count, yeast and molds, lactic acid bacteria, Bacillus spp.). The cluster classification showed that total viable count of bacteria could be used as a measure alternative to the count of Bacillus spp. and 70% of honeys from the tropical climate zone had different microbiological quality than honeys from the temperate climate zone but still under the level 3.0 log cfu/g. The study has revealed that geographical origin of honey may significantly affect the quality and safety of honey. It was considered that water content can be the most informative and handy marker of the microbiological quality of honeys. Analysis of lactic acid bacteria showed temperate climate zone honeys as a source of beneficial bacteria in the diet.

Interactions between the introduced European honey bee and native bees in urban areas varies by year, habitat type and native bee guild

European honey bees have been introduced across the globe and may compete with native bees for floral resources. Compounding effects of urbanization and introduced species on native bees are, however, unclear. Here, we investigated how honey bee abundance and foraging patterns related to those of native bee abundance and diversity in residential gardens and native vegetation remnants for 2 years in urbanized areas of the Southwest Australian biodiversity hotspot and assessed how niche overlap influenced these relationships. Honey bees did not overtly suppress native bee abundance; however, complex relationships emerged when analysing these relationships according to body size, time of day and floral resource levels. Native bee richness was positively correlated with overall honeybee abundance in the first year, but negatively correlated in the second year, and varied with body size. Native bees that had higher resource overlap with honey bees were negatively associated with honey bee abundance, and resource overlap between honey bees and native bees was higher in residential gardens. Relationships with honey bees varied between native bee taxa, reflecting adaptations to different flora, plus specialization. Thus, competition with introduced bees varies by species and location, mediated by dietary breadth and overlap and by other life-history traits of individual bee species.

Pollen diversity in honeys of the Czech Republic in the 2019 season

Honeybees are important pollinators. As a side product of pollination, honeybees produce honey, as a natural sweetener. The source of honey depends on the hive location. In specific conditions honeybees produce monofloral honey, but more common are polyfloral kinds of honey. In this study honey from the Czech Republic in the 2019 season was evaluated by melissopalynology analysis. The common botanical taxa in the Czech Republic were determined and season impact to pollen taxa was compared for dominant pollen taxa. The taxonomic distribution of pollen in Czech honey was stable during the year. The average number of species was 11.52 taxa per sample. The dominant pollen source in Czech honey was the Brassicaceae family. The high pollen content in honey was confirmed also in the Rosacea family (fruit tree), Ubelliferacae family and Myosotis genus. During the year the pollen taxa were equally distributed in honey. Seasonal effects were confirmed only in Salix genus, Ubelliferacae family and Phacelia genus. Seasonal effects correspond with the blooming season and honeybee handling in the hive was also confirmed. High variability during the season and hive location was confirmed for other taxa.

Use of kinetic data to model potential antioxidant activity: Radical scavenging capacity of Australian Eucalyptus honeys

Antioxidant activity of honeys may be beneficial in wound healing processes by protecting cells against lipid oxidation. The DPPH assay assesses the efficacy of antioxidant molecules to reduce DPPH^• to DPPHH. Studies determining EC₅₀ are limited by single time-point determinations of antioxidant effect and can miss vital information about the rate of antioxidant response. Acquisition of kinetic data allows determination of the radical scavenging capacity (RSC) of honeys. The purpose of this study was to determine the RSC of 53 honeys from 16 species of Australian Eucalyptus trees and four samples of New Zealand manuka (Leptospermum scoparium) honey. Whereas honeys could not be differentiated based on EC₅₀ values, significant differences were observed for RSC, supporting collection of kinetic data for honey analysis. The greatest RSC was observed for New Zealand manuka (4.6 ± 0.3 × 10^-5 mg.mL^-1.min^-1), grey ironbark (E. paniculate; 3.4 ± 0.2 × 10^-5 mg.mL^-1.min^-1) and river red gum honeys (E. camaldulensis; 3.2 ± 0.2 × 10^-5 mg.mL^-1.min^-1).

Eucalyptus honey: Quality parameters, chemical composition and health-promoting properties

Eucalyptus honey is an important unifloral honey commercialized worldwide and much desired by consumers due to the medicinal properties attributed to it because of the plant from which it is produced. In general, eucalyptus honey has been classified as being rich in pollen grains from the eucalyptus tree as well as having physicochemical characteristics that, in a way, have made it stand out from other honeys. Similar to other types of honey, eucalyptus honey can suffer contaminations and adulterations that compromise its quality, safety and authenticity. Thus, detailed knowledge of the composition and properties of this monofloral honeys is of great importance. With this background, the aim of this review is to present and discuss recent data regarding the physicochemical characteristics, chemical and health-promoting properties of eucalyptus honey as well as microbial contamination, authenticity, processing and adulteration.

Establishing authenticity of honey via comprehensive Romanian honey analysis

Assessing the authenticity of honey is a serious problem that has gained much interest internationally because honey has frequently been subject to various fraudulent practices, including mislabelling of botanical and geographical origin and mixing with sugar syrups or honey of lower quality. To protect the health of consumers and avoid competition, which could create an unstable market, consumers, beekeepers and regulatory bodies are interested in having reliable analytical methodologies to detect non-compliant honey. This paper gives an overview of the different approaches used to assess the authenticity of honey, specifically by the application of advanced instrumental techniques, including spectrometric, spectroscopic and chromatographic methods coupled with chemometric interpretation of the data. Recent development in honey analysis and application of the honey authentication process in the Romanian context are highlighted, and future trends in the process of detecting and eliminating fraudulent practices in honey production are discussed.

Effects of essential amino acid supplementation to promote honey bee gland and muscle development in cages and colonies

There is growing concern about the impact of poor nutrition on honey bee health. With caged bee experiments and whole-colony field experiments, we examined the effects of supplementing bees with essential amino acids (EAA), or a control treatment of nonessential amino acids (NAA). Caged bees fed EAA developed significantly greater head weights than controls, weights that were similar to nurse bees. Caged bees fed EAA developed significantly greater thorax weights than controls, weights that were similar to foragers. Higher head and thorax weights may respectively reflect increased glandular development in nurse bees and higher flight muscle mass in forager bees. In our field study, 29% of the pollen collected by our honey bee colonies came from eucalyptus trees. Amino acid analyses revealed no EAA deficiencies for the bee-collected polyfloral pollen or for monofloral eucalyptus pollen. Colonies fed 29 g EAA supplement may have slightly increased individual bee growth and brood rearing, but this effect was not significant. A clear colony result was a correlation between nurse bee physiology and brood development: 17% increase in nurse bee weight corresponded to 100% more capped brood cells (R² = 0.38). We suggest that colony supplementation should target nurse bee nutrition. Nurse bees eventually become forager bees. Hence, increased glandular development may support colony brood development and greater flight muscle mass may assist colony foraging.