Moisture and pH Meters

Moisture and pH meters are instruments such as refractometers, moisture analysers, hygrometers and pH meters that measure the water content and acidity of bee products. The most important for a beekeeper is the refractometer, which measures honey moisture: moisture largely determines whether honey will ferment. A pH reading does not decide quality on its own, but it helps to monitor processing and storage conditions for acidic products such as royal jelly and honey.

Why is moisture measured in bee products?

The first factor determining the shelf life of bee products is water content. Honey with too much water ferments, damp pollen goes mouldy, and if the storeroom air is humid, even dry products take up water.

• Honey: In the Turkish Food Codex the upper moisture limit for most honeys is 20 percent. For safe storage, below 18 percent is the target.
• Dried pollen: Fresh pollen is very moist; the aim of drying is to bring moisture down to a level at which mould and yeast cannot develop. The end point of drying should be determined by measurement, not by guesswork.
• Royal jelly: A naturally watery product; its water content is one of the quality criteria measured in the laboratory. The international standard (ISO 12824) defines a moisture range for fresh royal jelly.
• Air in the store and extraction room: Ripe honey is in equilibrium with air at about 60 percent relative humidity; if the room is more humid than that, exposed honey absorbs water.

How is honey moisture measured? The refractometer

A refractometer (refractive index meter) measures how much light is bent as it passes through a drop of honey. The more sugar and the less water the honey contains, the greater the refraction; the instrument shows this directly as percent moisture. On hand refractometers made for beekeeping, the scale is usually marked in honey moisture.

How do you use a refractometer?

1. Check the calibration: Check the setting with the calibration liquid supplied with the instrument or a sample of known moisture; correct it with the adjustment screw if necessary.
2. Mind the temperature: The reading depends on temperature. Instruments with automatic temperature compensation (ATC) balance out small differences; even so, the instrument and sample should be at room temperature.
3. Take a representative sample: Take samples not from a single cell but from different parts of the frame and the hive, or from a well-mixed bucket.
4. Use a crystal-free sample: Crystallised honey gives a false reading; warm a small sample gently in a closed tube until the crystals dissolve, then measure once it has cooled.
5. Close the prism and read: The honey should spread in a thin layer without air bubbles. Read the value at the boundary between the light and dark fields.
6. Clean it: Wipe the prism with a soft cloth moistened with lukewarm water and dry it. Do not scratch the prism or immerse the instrument in water.

Capped comb and moisture

When bees have ripened honey, they cap the cells with wax. Honey in capped comb is usually dry enough; but in a humid climate and during a heavy flow, even capped honey can have high moisture. With partly capped frames, measuring with a refractometer before deciding is the safest approach.

How is moisture measured in pollen and other products?

• Moisture analyser: An instrument that weighs the sample, dries it by heating and calculates moisture from the weight loss (the thermogravimetric method). It is the most practical tool for measuring the moisture of dried pollen.
• Oven drying: The standard laboratory method; the sample is dried under set conditions and weighed. The water content of royal jelly is also measured in the laboratory by methods of this kind.
• Grain and nut moisture meters: Because they are calibrated for other products, they are not reliable for pollen.

Ambient humidity: the hygrometer

A hygrometer (humidity meter) shows the relative humidity of the air; most models also measure temperature (a thermo-hygrometer). It is a cheap but very useful tool for the extraction room, bottling room and store.

• Extraction and bottling room: If humidity is high, run a dehumidifier; do not leave honey standing uncovered.
• Honey store: Aim for dry, cool and stable conditions.
• Dried pollen store: A package opened in a humid environment absorbs moisture quickly.
• Humidity inside the hive: Temperature and humidity inside the hive can also be tracked with sensor-based hive monitoring systems; this topic is covered separately on the hive sensor pages.

What is pH, and what does it tell you about bee products?

pH is the scale that shows how acidic a solution is; 7 is neutral and below 7 is acidic. Bee products are naturally acidic:

pH is not a measure of quality or purity on its own. In Türkiye, the quality criteria for honey in the Turkish Food Codex Communiqué on Honey include not pH but free acidity, measured in the laboratory. A pH that deviates markedly from normal can be a clue to suspected fermentation or blending, but the verdict comes from laboratory analysis.

How do you use a pH meter?

1. Calibrate: Calibrate a glass-electrode pH meter at the start of each measuring day with at least two buffer solutions (usually pH 4 and pH 7 for acidic products).
2. Prepare the sample: Because honey and royal jelly are thick, they are measured not directly but in a solution made by diluting a weighed sample with distilled water in a set ratio. If you want to make comparisons, use the same ratio every time.
3. Measure: Immerse the electrode in the solution and wait until the reading stabilises.
4. Rinse and store: Rinse the electrode with distilled water; do not let it dry out, but keep it in the storage solution recommended by the manufacturer.

What should you look for when choosing a meter?

• Honey refractometer: Scaled for honey moisture, with automatic temperature compensation and an easy-to-read scale, or digital.
• pH meter: Replaceable electrode, two- or three-point calibration, temperature compensation.
• Hygrometer: A model that records minimum and maximum values makes it easier to track storage conditions.
• Moisture analyser: For pollen producers; precise weighing and adjustable drying temperature.

Common mistakes

• Measuring without calibration: An instrument that has drifted can show damp honey as dry.
• Sampling a single cell: It does not represent the whole batch.
• Measuring crystallised honey: The reading will be wrong.
• Judging purity by pH: pH does not prove adulteration; laboratory analysis is needed.
• Keeping no records: A moisture reading that is not recorded with the batch number is useless later.