Beekeepers and inspectors always test the honey for moisture levels to determine its quality. This is done using a refractometer - a special device that finds the mass fraction of moisture in any sugar-containing food product, regardless of environmental conditions. Read more about this device and the principles of its operation below.
What is this device?
A refractometer is an optical device, with or without a power supply, 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 GOST requirements, this indicator should be kept in the range of 18.5-21%, which is also considered the range of honey quality. These numbers were not determined by chance, but in connection with the following features of beekeeping products:
- At a moisture content of less than 18%, honey becomes too viscous.
- At a moisture content of more than 21%, yeast microorganisms present in honey are activated, which process sugar and affect the sugar content of the product. Moreover, they trigger the fermentation processes, so the product becomes unusable.
So that the mass fraction of honey water does not exceed 21%, when pumping it out of the nests of bee colonies, it is necessary to wipe off the honeycombs, which are sealed by 2/3 of their height with wax caps. Additionally, you need to control the water content using a refractor.
Organoleptic evaluation of different varieties of honey has different viscosity, therefore it is not always possible to visually assess their water content.
Device device
The main elements of a refractometer are:
- Prism. This is a key optical element in the form of a "subject table" where the substance under study is applied. Made from high refractive index material.
- Hinged protective glass. With a smooth surface, the glass is lowered onto the prism and compresses the investigated layer.
- Calibration screw. Located on an inclined cut. Used when calibrating the device. The scope of delivery includes a special miniature screwdriver for turning the screw until the dividing line is 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 refracting 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 (no light beam falls on it). In many models of a refractometer designed for the analysis of honey, there are several scales at once:
- WATER. Water scale with readings in the range of 12–27%. Helps to determine the moisture content of the test product.
- Brix (Brix). A scale with values of 58-90%, by which the sugar content of honey is recognized. For example, if the Brix is 80%, this means that 100 g of honey contains 80 g of sugar.
- 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, where you can see the test result.
The device of a hand held refractometer is shown 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 it deviates from a straight line by a certain angle, that is, it is refracted. The denser the medium, the more the ray velocity slows down.
The angle of refraction of light depends on the composition of the solution and its density (concentration).
- Then, inside the housing, the light beam passes through the optical lens system, hits the instrument scale and moves up or down depending on its angle of refraction. The scale itself resembles a mercury thermometer or thermometer for measuring body temperature, where the column of liquid moves up or down.
- One part of the scale is illuminated, the other - remains in the dark. The optical density or refractive index of the composition under study can be determined from the dividing line between light and shadow.
Varieties of the device
There are several types of refractometer:
- laboratory - a desktop device of large size and weight;
- industrial (in-line) - automatic refractometer, which is built into technological installations and works in real time;
- portable - an optical device that is used by most beekeepers and honey sellers, since it has a compact size and takes all measurements with maximum accuracy.
If the analyzes of the solution are planned to be carried out in large volumes and quantities at industrial enterprises, it is necessary to choose industrial refractometers. For private traders and small businesses, portable devices are the best choice.
Portable models can also be of two types:
- digital - have a liquid crystal screen, which displays measurement values, usually operate on batteries and can simultaneously determine various characteristics of honey;
- by hand - are devoid of electronic circuits and batteries, therefore, natural or artificial light is required for their operation.
Handheld refractometers are attractive in terms of affordable price, compact size and high analysis speed, but digital models that can be used even at night are more practical.
Features of the ATC refractometer
In order for the refractometer to accurately show the moisture level in honey, measurements must be taken at an ambient temperature of + 20 ° C. Of course, in most cases it is difficult for a beekeeper to comply with this condition.
This was taught by the refractometer manufacturers, who equipped their models with an automatic temperature compensation (ATC) function. It eliminates the influence of fluctuations in ambient temperature on measurement accuracy. 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 amount of shift of the plate is calculated in such a way as to fully 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 appliance 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 protein and solids content in a milk sample are suitable for the analysis of 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 Brix scale values are suitable for it - 45-82%, 58-92% or 0-87%.
Browse Popular Models
Beekeepers often choose the following refractometer models:
- PAL-22S. A digital pocket device with a liquid crystal screen, which displays the moisture readings of honey. Their range is 12-30%. The refractometer has an ATC function (+ 10… + 40 ° C) and operates on two AAA batteries.
- PEN-HONEY. The device also runs on batteries and measures the moisture content of honey in the range of 13-30%. Unlike the previous model, the test product does not need to be applied to the prism; it is enough to 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 water and dust ingress. The prism is also protected against dust and temporary immersion in water. The device is equipped with the ATC function, which allows accurate analysis of the sample at an ambient temperature of + 10 ... + 100 ° C. Calibration is carried out with distilled water.
- HHR-2N. Hand-held device that measures the moisture content of the 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 liquid that is supplied in the kit.
- Master-HONEY. Pocket version of the device that allows you to analyze honey anywhere. It is equipped with ATC function and detects 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 body, except for the eyepiece, is protected from water jets 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 moisture content 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.
- Handheld RHB Refractometers. All devices of this line allow to examine the sample for moisture on the Water scale (12-27%), sugar content on the Brix scale (58-90% - for models RHB-90 and RHB-90 АТС, 58-92% - for RHB-92 ATC ) and density on the Baume scale (38-43Be °). The RHB-90 model does not have an ATC 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.
- Refractometer RePo-4. The device combines a refractometer and a polarimeter, so it allows you to make a deeper analysis of honey. In addition to moisture (13-30%) and sugar content according to Brix (0-85%), it can be used to find out the fructose content (from 0 to 99%). The latter indicator allows you to identify a fake and determine the type of honey. The device is equipped with ATC function, has protection against dust and water. It requires a power source in the form of 4 AAA batteries. 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:
Calibrating the Refractometer
In order for the device to show the result with the least error, it must be calibrated. This will require distilled water or refractometric liquid, which is usually supplied with kits.
The device is calibrated in the following sequence:
- Lift up the daylight cover and pipette 2-3 drops of distilled water onto 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 towards a natural light source and look through the monocular. In the center of the circle you can see a scale with a division. If the graduation is poorly visible, you need to adjust the focus of the monocular.
- Wait until the top of the appliance is dark and the bottom is light.
- Tighten the calibration screw so that the border between the dark and bright areas is exactly at zero point or at 78.4%, depending on the model of the device.
- Wipe the prism surface with a soft dry cloth and use the refractometer as directed.
An example of how the instrument scale looks before and after calibration is presented below:
User's manual
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 instructions are as follows:
- Take a sample of honey from the 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, using a pipette, apply 2-3 drops of prepared honey to the surface of the prism and distribute it evenly, eliminating all bubbles and dry fragments. Cover the prism cover. If excess solution has flowed out of the measuring area, remove it with a soft cloth.
The thinner the layer of evenly distributed honey, the more accurate the measurement 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 the calibration of the device.
- Point the refractometer towards the light source - natural daylight or from an incandescent lamp.
- Look 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 keep a refractometer?
In order for the device to last 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 blur. You will need the help of a qualified technician to fix the problem.
- Wipe the refractometer with a soft, damp cloth after each use. 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 may damage the surface of the main prism.
- Under no circumstances should the refractometer be disassembled so as not to knock off the settings, as well as prevent it from falling or hitting.
- The optical device should 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. For the analysis of a beekeeping product, a minimum of raw materials is required, which is an additional plus of the device.