Chestnut-plum? Vine and clover? Tawłowo-linden? Wait a minute… In fact, how do we know what kind of honey we are dealing with? Honey-lovers usually encounter such problems. And as we know, the road from a honey-amateur to an expert in bee specialties is a long one and not always a bed of roses. Hence, the Pszczelarium comes with help, which knows a bit about honey and other bee products and is very willing to share this knowledge.

As usual, in hopeless cases, science comes to the rescue, and in this particular case it is melisopalinology, which deals with the botanical and geographical origin of honey, determined on the basis of solid particles contained in honey - most often pollen of melliferous plants. For the record, just a few words about the pollen itself - these are the male reproductive cells of plants. Okay, but how to extract this pollen from honey and, above all, what the pollen analysis itself looks like. Below we present the commonly used research methodology proposed by J. Louveaux, Anna Maurizio and G. Vorwohl (1978).

Methodology

The first stage of the analysis involves the careful taking of honey samples. To do this, carefully peel off the wax layer and examine the frame under a strong light source to identify cells that do not contain pollen - only from such cells we collect honey for further research. To convert honey into a laboratory sample, we first need to liquefy it at 40°C, and if it is contaminated, strain the honey through a fine sieve. In the next step, weigh 10 g of honey, which should then be dissolved in 20 ml of warm distilled water. The obtained solution is centrifuged for 10 minutes in a laboratory centrifuge (approx. 2500 rpm). After centrifugation, the pollen will be at the bottom of the tube. In the next step, decant (i.e. simply pour off) the upper part of the solution. If the sugars contained in the honey are not sufficiently separated from the pollen, we add 10 ml of distilled water to the obtained sediment and repeat the process.

In the next step, we prepare a microscope preparation. For this purpose, we transfer the clean pollen after the centrifugation and decanting process to a glass slide and, using a glass rod, spread the preparation on the surface of 20 X 20 mm. After drying, we cover the preparation with liquefied glycerol gelatin and a coverslip, carefully so as not to create air bubbles.

Fig. 1. Photos of pollen taken with an optical microscope. A - Parthenocissus quinquefolia pollen (vintage ivy); B - Tilia pollen (linden); C - Robinia pollen ("acacia"); D - Aesculus (chestnut). Source: PalDat - A palynological database. https://www.paldat.org (12/16/2022)

Microscopic analysis of pollen allows to determine the botanical and geographical origin of honey. Botanical origin is directly related to the concept of honey quality. During the identification and counting of pollen grains, the person conducting the analysis refers to the data contained in the literature and databases, including: PalDat - Palinological Database, which is the world's largest collection of information on pollen from plants from around the world. The methodology of melisopalinological preparation and analysis proposed by J. Louveaux et al. (1978) recognizes that the real percentage of individual pollen content in honey must contain as many as 1200 counts of individual pollen grains per sample. In the case of honeydew honeys (poor in pollen grains), depending on the degree of accuracy, we count from 50 to 600 grains.

Fig. 2. Photos of pollen taken with a scanning microscope (SEM). A - Parthenocissus quinquefolia pollen (vintage ivy); B - Tilia pollen (linden); C - Robinia pollen ("acacia"); D - Aesculus (chestnut). Source: PalDat - A palynological database. https://www.paldat.org (12/16/2022).

Interpretation of test results

An important aspect during the melisopalinological analysis is the separation of wind-pollinated plants or plants devoid of nectar, including: Gramineae (wild grasses - about 192 species in Poland), Cyperaceae (sedges), Rumex spp. (knotweed), Cannabis (hemp) , Quercus (Oaks), Amaranthus (Amaranth); pollen of conifers (Abies, Pinus, Picea, Juniperus, Larix, Taxus), Betula spp. (birch), Fagus spp. (beech), Carpinus spp. (hornbeam), Populus spp. (poplar), Alnus spp. (alder ), Corylus spp. (hazel), Papaver spp. (poppy), Plantago spp. (plantain) or Thalictrum spp. (rue-tail), which are not relevant for honey production. The following frequency classes are used for pollen analysis: "dominant pollen" - more than 45% of counted grains, "secondary pollen" - 16 - 45%, "important minor pollen" 3-15%, "minor pollen" <3%). If 1200 grains are counted, pollen frequencies can be expressed to within 1%. Mono-plant honey is usually considered to contain dominant pollen. However, it is worth paying attention to a few aspects that are the proverbial "exception to the rule".

Some plants show an overproduction of pollen in relation to nectar. The most extreme case of pollen overrepresentation is Myosotis spp. (forget-me-not). Castanea sativa (chestnut) pollen also overproduces nectar and only honeys containing 90% or more of Castanea pollen can be considered single-plant quality honeys.

Fig. 3. Myositis (forget-me-not). Wikipedia Commons by Sedum Tauno Erik.

Plants such as Robinia (commonly known as acacia), Tilia (linden), Rosmarinus (rosemary), Lavandula latifolia (broad-leaved lavender), citrus or Medicago (alfalfa) stand in opposition to plants that overproduce pollen. In their case, the range of 10-30% is considered a high frequency of occurrence.
A good practice leading to the assessment of the type of honey is also the use of auxiliary tests that facilitate the diagnosis of the type of honey. For example, acacia or tupelo honeys contain a lot of fructose - which also translates into their long-term crystallization; honeydew honeys are characterized by high electrical conductivity, and also contain many honeydew elements, which consist of spores and fungal hyphae (honeydew ellements/pollen ellements ~3), and additionally, they have an increased content of pollen from plants that do not contain nectar.

Analysis of the quality of Warsaw meads

Due to the high variety of honey in the city, Warsaw meads clearly differ from their traditional counterparts. Instead of classic ingredients such as Brassica napus (rapeseed) or Fagopyrum esculentum (common buckwheat) nectar, we will find in them the nectar of melliferous plants such as Parthenocissus (grapevine), Spiraea (meadowsweet), Aesculus (chestnut) or Echium (viper). The nectar of these plants makes the taste and aroma of honey herbal-mint, and maybe even slightly citrus? It's hard to judge, it's best to try it yourself 🙂

An additional curiosity is that city honeys are pesticide-free and, contrary to the predictions of many honey lovers, they are free of heavy metals and aromatic hydrocarbons - but that's a topic for another post.

Pollen analysis results

Test method: Microscopic pollen analysis method according to the Regulation of the Minister of Agriculture and Rural Development of January 14, 2009 (Journal of Laws No. 17, item 94) point VI.

Normative value according to PN-88/A-77626 "Bee honey": For linden honey not less than 20% of Tilia pollen. Description below.

no
 Pollen types of nectar-producing plants Mean sum of grains from 2 analyses Percentage of pollen
1
 Parthenocissus - grapevine 96.0 29
2
 Tilia - linden 56.5 17
3
 Spiraea - meadowsweet 42.5 13
4
 Aesculus - chestnut tree 26.5 8
5
 Robinia - robinia ("acacia") 20.5 6
6
 Trifolium type - clover type 12.5 4
7
 Another 80.0 24
Together 334.5 100
Table 1. A fragment of the result of the pollen analysis of Wilanów honey - 2022, performed by Honeylab Teper & Was .

Opinion and interpretation: Taking into account the uncertainty of the method, estimated at 5%, honey can be considered linden honey.

Literature:

Louveaux, J., Maurizio, A., & Vorwohl, G. (1978). Methods of melissopalynology. Bee world, 59(4), 139-157.

https://www.paldat.org/ - 12/16/2022