Looking at the colour of a honey, smelling its aroma and tasting it can tell us a great deal about its characteristics. But some aspects cannot be assessed simply by looking at a jar or relying on taste. Physicochemical analyses make it possible to measure specific properties of honey and provide information about its composition, its state of preservation and the processes it may have undergone.

Among the most commonly measured parameters are moisture, HMF, free acidity and electrical conductivity. These four measurements provide very different kinds of information and, above all, their values become meaningful when interpreted in relation to the characteristics of the honey being analysed. Let us look at what they mean and what they can tell us.

Moisture: how much water does honey contain?

Honey begins with a raw material that contains far more water. As bees transform nectar into honey, they progressively reduce its water content until a much more concentrated product is obtained. Measuring moisture therefore means determining the percentage of water present in the honey, a particularly important parameter for its preservation, because a high water content can encourage the activity of yeasts naturally present in honey and increase the risk of fermentation.

European legislation establishes, for honey in general, a water content of no more than 20%, with different limits for certain specific types of honey. In practice, however, lower moisture levels are normally preferred in order to obtain a honey that remains more stable over time. Below 18%, the risk of fermentation is considerably reduced, while higher values require greater attention.

This also explains why the legal limit should not be interpreted as a threshold above which honey ferments and below which the problem disappears. Stability depends not only on the amount of water present, but also on the presence and concentration of osmophilic yeasts, temperature and storage conditions.

We will return to this subject when discussing fermentation and phase separation, two phenomena closely related to the composition and stability of honey and which deserve a more detailed look of their own.

HMF: a trace of time and temperature

HMF stands for hydroxymethylfurfural, a compound formed through the degradation of sugars. Its concentration in honey tends to increase over time and, above all, with exposure to heat. For this reason, HMF is one of the parameters used to assess the state of preservation of honey and any thermal stress it may have undergone.

Fresh, properly stored honey is generally expected to have a low HMF content, while higher values may be associated with ageing or significant exposure to elevated temperatures. European legislation generally sets a maximum limit of 40 mg/kg, with a different threshold for honeys declared as originating from regions with tropical climates and blends of such honeys.

The HMF value therefore adds information that observation or tasting cannot provide directly: a kind of trace left by time and by the temperatures to which the honey has been exposed during storage.

Acidity: honey contains more than just sugars

When we think of honey, sweetness is probably the first characteristic that comes to mind, but its composition is actually far more complex. Alongside glucose and fructose, honey contains many other substances, including organic acids, which occur naturally and contribute to its characteristics.

Free acidity, expressed in milliequivalents per kilogram (meq/kg), allows this component to be quantified. European legislation generally establishes a maximum free acidity of 50 meq/kg for honey, while actual values can vary naturally between different honeys depending, among other factors, on their origin and composition.

An abnormal increase in acidity may also be associated with fermentation. This is a good example of how different analytical parameters can be connected: moisture gives us an indication of the amount of water present and therefore of conditions that may favour fermentation, while acidity can help reveal the effects of a fermentation process that may already be under way.

Electrical conductivity: what can it tell us about the origin of honey?

Of these four parameters, electrical conductivity is probably the least intuitive. In simple terms, it measures the ability of a honey solution to conduct an electric current, a property that depends on the presence of ionisable substances, including mineral salts and organic acids. Conductivity can therefore provide useful information for characterising honey and can vary considerably depending on its origin.

European legislation uses this parameter to distinguish, with certain exceptions, honeys with values of up to 0.8 mS/cm from honeydew and chestnut honeys and their blends, for which a value of at least 0.8 mS/cm is established.

Here it is particularly important not to confuse this threshold with a measure of quality: higher conductivity does not mean that a honey is better, just as lower conductivity does not mean that it is worse. The value provides information related to its composition and, together with other analytical parameters, can contribute to characterising the product.

A practical example: the analysis of our Forest Flower Honey

All these parameters become easier to understand when we look at a real analysis. Tests carried out on our Miele di Fiori di Bosco – Forest Flower Honey, which received an Ape d’Oro award at the Mieli dei Parchi della Liguria 2025 competition, produced the following results:

A moisture content of 17.3% is not only below the general 20% limit established by European legislation, but also below the 18% level that, in beekeeping practice, represents an important reference point for honey stability and for reducing the risk of fermentation. Free acidity, at 12.2 meq/kg, and HMF, at 2.6 mg/kg, are also well within their respective general limits of 50 meq/kg and 40 mg/kg.

The electrical conductivity value of 1.00 mS/cm is particularly interesting. Our Forest Flower Honey comes from the combination of different flowering plants found in the environment surrounding our apiaries, including chestnut. A value of this kind is therefore useful when interpreting the honey's overall characteristics, but it would be incorrect to use it on its own to draw conclusions about its origin: a single conductivity value is not sufficient to determine the botanical origin of a honey, which requires a more comprehensive assessment.

An analysis is not a report card

Moisture, HMF, acidity and conductivity therefore describe different aspects of the same product. Moisture tells us how much water is present; HMF can provide information about thermal history and storage; acidity measures a natural component of honey and can help highlight possible alterations; and conductivity provides useful information about the composition and characterisation of the product.

The most important point is not to turn these numbers into a ranking. A physicochemical analysis does not give honey a score; it allows us to describe some of its characteristics through objective measurements. Honey composition depends on its origin, the flowering plants available, the environment and many other factors. For this very reason, the different parameters become fully meaningful only when they are interpreted together and considered in relation to the honey being examined.

Behind an apparently simple jar lies a product far more complex than it may seem. And it is precisely this complexity that makes it so interesting to go beyond colour, aroma and taste and discover what a laboratory analysis can tell us as well.