Beekeepers and takers always check honey for moisture to determine its quality. They do this using a refractometer - a special device that finds the mass fraction of moisture of any sugar-containing food product, regardless of environmental conditions. Read more about this device and the principles of its operation below.
What kind of device is this?
A refractometer is an optical device with or without a power source that measures the concentration of particles dissolved in a liquid medium using a light beam. In beekeeping, it is used to determine the mass fraction of moisture in honey.
According to the requirements of GOST, this indicator should be kept in the range of 18.5-21%, which is also considered a honey quality range. These numbers were not determined by chance, but in connection with such features of beekeeping products:
- With a moisture content of less than 18%, honey becomes excessively viscous.
- At a moisture content of more than 21%, the yeast microorganisms present in honey are activated, which process sugar and affect the sugar content of the product. Moreover, they start the fermentation processes, so the product becomes unsuitable for consumption.
So that the mass fraction of honey water does not exceed 21%, when it is pumped out from the nests of bee colonies, it is necessary to wipe the honeycombs, which are sealed with wax caps at 2/3 of their height. Additionally, you need to control the water content using a refractor.
Different varieties of honey with an organoleptic evaluation have different viscosities, so visually assessing their water content is not always possible.
The main elements of a refractometer are:
- Prism This is a key optical element in the form of a "stage" where the test substance is applied. Made of high refractive index material.
- Hinged safety glass . The smooth surface of the glass falls on a prism and compresses the test layer.
- Calibration screw . Located on an inclined slice. It is involved in the calibration of the device. The kit includes a special miniature screwdriver for rotating the screw until the dividing line is installed at the desired mark.
- Optical lens system . It is located inside the housing, namely in the area of the inclined cut. The lenses are blue and have an optically uniform structure. They perform the function of refraction of light - artificial (from the lamp) or natural (from the sun).
- Bimetal plate . This is a “corrector” that is built into the body and changes the optical characteristics of the refractometer depending on the temperature.
- Scale . Through a system of optical lenses, a ray of light hits a scale - a graduated circle. The illuminated part of the scale will be light, and the rest will be dark (a ray of light does not fall on it). In many models of a refractometer designed for the analysis of honey, there are several scales at once:
- WATER . Water scale with indicators in the range of 12–27%. Helps determine the moisture content of the test product.
- Brix (Brix) . A scale with values of 58-90%, according to which the sugar content in honey is recognized. For example, if the Brix is 80%, this means that 100 g of honey contains 80 g of sugar.
- Baume (Baume) . A scale with arbitrary degrees Baume (Be °), which measures the density of a liquid. For example, the density of pure distilled water at + 15 ° C corresponds to 0Be °, and the indicator 15Be ° corresponds to the density of a 15% sodium chloride solution.
- Monocular . A special hole on the handle of the device, in which you can see the result of the study.
The device of a manual refractometer is depicted in the following diagram:
Principle of operation
The functioning of the refractometer is based on the method of refractometry, which involves the analysis of the test substance by the refractive index of the sun's ray falling on this substance. This principle is implemented as follows:
- Honey is applied to the surface of the prism and covered with protective glass on top to create an even layer of a strictly defined thickness.
- Getting on honey, the ray of incident light passes from one medium to another, and at their border deviates from a straight line by a certain angle, that is, it is refracted. The denser the medium, the more the speed of the beam slows down.
The angle of refraction of light depends on the composition of the solution and its density (concentration).
- Further, inside the body, a ray of light passes through a system of optical lenses, enters the scale of the device and moves up or down depending on the angle of its refraction. The scale itself resembles a mercury thermometer or thermometer for measuring body temperature, where a column of liquid moves up or down.
- One part of the scale is illuminated, while the other remains in the dark. From the dividing line between light and shadow, you can determine the optical density or refractive index of the investigated composition.
Types of instrument
The refractometer can be of several types:
- laboratory - bench-top device of large size and weight;
- industrial (in-line) - an automatic refractometer that is built into technological installations and operates in real time;
- portable is an optical device used by most beekeepers and sellers of honey, because it has a compact size and with maximum accuracy carries out all measurements.
If it is planned to carry out analyzes of the solution in large volumes and quantities at industrial enterprises, industrial refractometers should be selected. For private traders and small business representatives, portable devices are the best choice.
Portable models can also be of two types:
- digital - they have a liquid crystal screen on which measurement indicators are displayed, they usually work on batteries and at the same time can determine various characteristics of honey;
- manual - devoid of electronic circuits and batteries, so for their work requires natural or artificial light.
Hand-held refractometers are attractive in terms of reasonable price, compact size and high speed of analysis, however, digital models that can be used even at night are more practical.
Features of a refractometer with automatic telephone exchange function
In order for the refractometer to accurately show the moisture level in honey, measurements must be carried out at an ambient temperature of + 20 ° C. Of course, in most cases, the beekeeper is difficult to comply with this condition.
This was taught by manufacturers of refractometers, which equipped the produced models with the function of automatic temperature compensation (ATS). It eliminates the influence of fluctuations in ambient temperature on the accuracy of measurements. This is due to the bimetallic plate, which, when the temperature drops, stretches or contracts, maintaining the correct operation of the optical system of the device.
The magnitude of the plate shifts is calculated in such a way as to completely compensate for the effect of temperature on the refractive index.
How to choose a refractometer for honey?
Portable refractometers are designed to study different products, but in appearance they are practically no different. To find out whether a particular device is suitable for honey, one should proceed from two parameters:
- The chemical composition of the test solution . For honey and other sugar-containing solutions, you need a refractometer, which determines the amount of sugar and the humidity of the solution. Instruments that measure the level of protein and solids in a milk sample are suitable for analyzing milk and dairy products. They are not suitable for honey research.
- Brix scale values . Honey belongs to highly saturated solutions, therefore refractometers with the following values of the Brix scale are suitable for it - 45-82%, 58-92% or 0–87%.
Browse Popular Models
Beekeepers often choose the following refractometer models:
- PAL-22S Digital handheld device with a liquid crystal screen, which displays the moisture content of honey. Their range is 12-30%. The refractometer has an ATC function (+ 10 ... + 40 ° C) and runs on two AAA batteries.
- PEN-HONEY . The device also runs on batteries and measures the humidity of honey in the range of 13-30%. Unlike the previous model, the test product does not need to be applied to the prism, but rather touch the sample with the tip of the device. Indications can also be taken with a light source. The body of this refractometer is reliably protected from ingress of water and dust. The prism also has protection against dust and temporary immersion in water. The device is equipped with an ATC function that allows you to accurately analyze the sample at an ambient temperature of + 10 ... + 100 ° C. Calibration is carried out with distilled water.
- HHR-2N . A hand-held device that measures the moisture content of a product from 12 to 30%. He does not need a power source, since there is no electronic "filling" in it. Calibration is carried out using a special fluid that is supplied.
- Master-HONEY . Pocket version of the device, which allows you to analyze honey anywhere. It is equipped with ATC function and determines the moisture content in the range of 13-30%. The difference between this refractometer and others is that the test sample can be both in liquid and in solid (crystallized) form. The case, except for the eyepiece, is protected from water jet and dust. The device operates at an ambient temperature of + 10 ... + 40 ° C.
- Master HONEY / BX . Dual Optical Handheld Optical Refractometer. The first of them determines the humidity of honey (12-30%), and the second (Brix) - sugar content (58-90%). To calibrate the device using distilled water or a special liquid "sucrose". It is equipped with an ATC function and operates at an ambient temperature of + 10 ... + 40 ° C.
- Portable RHB refractometers . All devices of this line allow testing the sample for moisture on the Water scale (12-27%), sugar content on the Brix scale (58-90% on the RHB-90 and RHB-90 ATC models, 58-92% on the RHB-92 ATC ) and density according to the Baume scale (38-43Be °). The RHB-90 model does not have a PBX function, so it is better to choose the RHB-90 ATC and RHB-92 ATC devices. All RHB devices are compact, do not need a power source and are already on sale in calibrated form.
- Refractopolarimeter RePo-4 . The device combines a refractometer and a polarimeter, so it allows you to do a deeper analysis of honey. In addition to moisture (13-30%) and sugar content according to Brix (0-85%), using it you can find out the fructose content (from 0 to 99%). The last indicator allows you to identify fake and determine the type of honey. The device is equipped with ATC function, has protection against dust and water. For its operation, a power source in the form of 4 AAA batteries is required. The required sample volume for research is at least 3 ml.
A review on the RHB 90 ATC refractometer is provided in the video below:
In order for the device to show the result with the least error, it must be calibrated. To do this, you need distilled water or a refractometric liquid, which usually comes with kits.
Calibration of the device is carried out in the following sequence:
- Raise the cover for daylight and use a pipette to apply 2-3 drops of distilled water to the main prism.
- Close the protective glass so that the water is evenly distributed over the entire surface of the prism. There should be no air bubbles or empty spaces.
- Wait about 15-30 seconds for the sample to adapt to the ambient temperature.
- Point the refractometer toward a natural light source and look into the monocular. In the center of the circle you can see the scale with the division. If the calibration is poorly visible, you need to adjust the focus of the monocular.
- Wait until the upper part of the device turns dark, and the lower - light.
- Tighten the calibration screw so that the border between the dark and bright areas is set exactly at zero or at 78.4%, depending on the model of the device.
- Wipe the surface of the prism with a soft, dry cloth and use the refractometer as intended.
An example of how the instrument scale looks before and after calibration is presented below:
All actions are carried out in the same sequence as during calibration, but instead of distilled water, a few drops of honey are applied to the prism. The step-by-step instruction is as follows:
- Take a honey sample from a honeycomb with a glass or plastic stick. If you need to measure the humidity of already collected honey, take a sample from a jar. Pre-heat the crystallized product with a non-uniform consistency and with the presence of solid particles in a water bath (up to 40 ° C), cool to room temperature, mix thoroughly and use as directed.
- Open the protective plate, use a pipette to apply 2-3 drops of prepared honey on the surface of the prism and distribute it evenly, eliminating all bubbles and dry fragments. Cover the prism cover. If excess solution has leaked outside the measurement area, wipe it off with a soft cloth.
The thinner the layer of evenly distributed honey, the more accurate the measurement results will be.
- Wait 30 seconds for the temperature of the sample and the instrument to equalize. In this case, do not touch the calibration screw - it must remain in the original position set during calibration of the device.
- Point the refractometer towards the light source - natural daylight or from an incandescent lamp.
- View through the monocular to see the measurement results. The moisture indicator will be visible at the border of the white-blue scale. To increase the clarity of the calibration, the focus of the monocular can be adjusted.
The accuracy of the measurements depends on the calibration of the device, as well as on the same temperature of the prism and the test sample.
How to check the humidity of honey with a refractometer is clearly shown in the following video:
How to keep a refractometer?
To ensure that the device lasts as long as possible, during its operation it is worth remembering such recommendations:
- Do not immerse the refractometer in water or use it in a humid or damp atmosphere. If water gets inside the case, the image will begin to blur. To fix the problem, you will need the help of a qualified professional.
- After each use, wipe the refractometer with a soft and damp cloth. If this is not done, subsequent measurements will be erroneous, and the surface of the prism will be damaged.
- Do not use abrasive or chemical agents when cleaning the device - they can damage the surface of the main prism.
- In no case do not disassemble the refractometer, so as not to knock down the settings, as well as to prevent it from falling or hitting.
- The optical device must be carefully stored, avoiding any mechanical damage, as any scratch on the surface of the prism will lead to distortion of measurements.
To start pumping out honey in a timely manner, beekeepers can regularly examine its moisture indicators using a hand-held refractometer. Buyers will need this device to determine the quality of honey before buying it. To analyze the beekeeping product, a minimum of raw materials will be required, which is an additional plus of the device.