To meet internal production control requirements, this article presents the various methods and equipment for measuring the alcohol content in alcoholic beverages.
It guides you in choosing the most suitable method based on your objectives, whether in terms of the type of beverage to be analyzed, the desired result accuracy, response time, frequency of analysis, operator qualifications, or budget constraints linked to investment and operation.
Reminder of the official definition of alcohol content
The Real Volumetric Alcohol Content (A.S.V.) of a beverage corresponds to the volume of ethyl alcohol contained in 100 ml of the product at 20°C, hence the unit expressed in % vol. at 20°C.
- A wine with 12% vol. contains 120 ml of ethyl alcohol (Ethanol) in 1 liter at 20°C.
- A spirit with 40% vol. contains 400 ml of ethyl alcohol (Ethanol) in 1 liter at 20°C.
The 4 main methods of alcohol content measurement for alcoholic beverages
- Direct measurements by densimetry (alcoholometer, pycnometer, hydrostatic balance, or electronic densimeter),
- Ebulliometry, which is based on the boiling point of the product or the temperature of the boiling vapors to determine the alcohol content.
- Distillation to remove the dry extract, followed by alcohol content measurement in the distillate by densimetry. Depending on certain criteria, distillation can be performed either by steam distillation or direct distillation.
- The use of absorbance analyzers in near-infrared (NIR) or mid-infrared (MIR) light.
As for gas chromatography or enzymatic methods, the linearity limits of these methods require significant sample dilution, resulting in a substantial increase in measurement uncertainty. However, they may be of interest for alcohol mixtures other than spirits.
If you have any questions about these methods and associated equipment, please feel free to contact me.
Scope of each alcohol measurement principle
In all four cases, there are different levels of automation available for the equipment.
These equipment options have well-defined scopes in terms of product type :
Densimetry : Reserved for products containing little or no dry extract, primarily used for spirits.
Ebulliometry : Reserved for dry products with an alcohol content not exceeding 17% vol. For certain sweet products, a correction for measurement impact is possible.
Steam Distillation : Without dilution for any product with an alcohol content below 25% vol. (Vinegars, Ciders, Pears, Beers, Wines, Sweet Wines, Wines for distillation, Cane Wines, Wash, etc.). For alcohol content above 25% vol., the method requires dilution during distillation. Refer to the article : « Measurement of Alcohol content – Part 2 : By Distillation with Dilution ».
Since dilution may result in a loss of accuracy, for products with sugar content below 100g/l, it is advisable to prefer the direct distillation method.
Direct Distillation : Without dilution for any product with an alcohol content below 55% vol. and a sugar content not exceeding 100g/l. The method requires dilution in the following cases : alcohol content above 55% vol. or alcohol content above 25% vol. and sugar content above 100 g/l. Refer to the article : « Measurement of Alcohol content – Part 2 : By Distillation with Dilution ».
For alcohol content < 25% vol. and sugar content > 100g/l, it is advisable to prefer the method without dilution by steam distillation.
Near-Infrared : Reserved for products within the range developed by suppliers. Some devices are dedicated to a single type of product (Wines, Beer, Whiskey, etc.).
Middle-Infrared : Reserved for products within the range developed by suppliers, currently mainly wines, liqueur wines, beer, and cider).
Other criteria for choosing the Alcohol Content Measurement Method and Associated Equipment
In addition to the scope of application, the choice of the most suitable equipment for your needs relies on other criteria.
Key criteria to consider when choosing your measurement method and associated equipment :
- Mobility, size, and connection requirements (water, electricity)
- Frequency of analyses
- Deadline for results
- Equipment for preparing samples for analysis
- Qualification and availability of the person in charge of the equipment
- Qualification of operators
- Investment budget
- Operating budget
- Responsiveness and effectiveness of the supplier’s after-sales service
Guidelines for Method and Equipment Selection
At the end of this article, you will find two guides to help you choose the most suitable method and equipment for internal production control, based on your needs and constraints :
Table No. 1 presents, by method and according to product type, an indicative performance level for some selection criteria.
Regarding the investment and operating budgets mentioned in these tables, the price ranges are provided as indicative, based on data collected from leading equipment suppliers.
Annual operating costs exclude electricity, water, personnel expenses, and maintenance contracts but include the costs of self-controls, maintenance products, and the replacement of normal wear and tear parts.
Table No. 2 summarizes the scope of application in terms of product type for each method. It provides insights into the strengths and limitations of each method by equipment type and offers specific recommendations.
The following chapter provides more detailed explanations of the principles of each method and associated equipment for measuring alcohol content in spirits, their scope of application, and the constraints to ensure proper operation.
Methods and Equipment for Alcohol Measurements in Spirits
1. Densimetry : Direct Alcohol Content Measurement via Density Measurement
This method is based on the correlation principle that exists for certain spirits between density and alcohol content : It is commonly accepted that when products contain little or no dry extract, they can be considered as hydroalcoholic mixtures. In this case, the measurement of density is correlated with the measurement of volumetric alcohol content (expressed as % volume of ethanol). The official table to refer to when converting between density and volumetric alcohol content, or vice versa, corresponds to Table II published in Recommendation R22 by the International Organization of Legal Metrology (O.I.M.L.) (1).
For which products ?
Since the vast majority of alcoholic beverages contain dry extract, the direct measurement of volumetric alcohol content using densimetry applies only to distilled products (spirits or alcohol-based mixtures without added sweeteners), justifying the use of density measuring devices such as alcoholometers and electronic densimeters.
What is the maximum dry extract content allowed in spirits ?
The amount of dry extract to consider depends on the alcohol content.
For an alcohol content measurement with an uncertainty of less than 0.05% vol., the calculations lead to the following results (2) :
– For a spirit at 70% vol., the dry extract must be less than 0.2 g/l.
– At 40% vol., the dry extract must be less than 0.1 g/l.
Densimetric measurements in spirits are primarily performed using alcoholometers or densimeters. The next two paragraphs detail the principle of these methods.
About others methods : Pycnometry measurements and hydrostatic balance measurements are not discussed here as they are not recommended equipment for internal production control of spirits.
1.1 Alcoholometers
Measurement Principle :
The alcoholometer operates on Archimedes’ principle : the lower the density of the liquid, the further the alcoholometer sinks. Alcoholometers are directly calibrated in % vol. of alcohol. Therefore, it is sufficient to read the graduation level in the liquid. Since these devices are calibrated for hydroalcoholic mixtures at 20°C, it is necessary to record the temperature at the time of measurement to bring the alcohol value read to 20°C. Conversion is done using alcoholometry tables or computerized applications, such as the “Conversion Alcoholometer” Boxette.
- Version : Alcoholometers come in different versions depending on the desired measurement ranges. For good precision required in regulated use cases such as alcohol stock control and the buying and selling of spirits, it is essential to use professional Class II alcoholometers. These must comply with the Recommendation R44 by the International Organization of Legal Metrology (3) and, in particular, be graduated in 10% vol. increments, calibrated at 20°C, and delivered with a verification certificate.
- Scope of Application : From 0 to 100% vol.
- Response Time : Analysis in a few minutes.
- Ergonomics : While the usage principle may seem simple, it is necessary to be well-trained in the use and maintenance of alcoholometers (4).
- Precision : Professional alcoholometers are accurate to +/- 0.1% vol. By adhering to good handling and maintenance practices (4), precision can reach +/- 0.05% vol.
1.2 Electronic Density meters
Measurement Principle :
The principle involves measuring the oscillation period of a tube containing the sample, which is subjected to electromagnetic excitation. The oscillation period depends on the density. The sample’s temperature is taken within the tube. A calculator provides the sample’s density result at 20°C directly.
- Versions : Electronic density meters are available in portable or benchtop versions. The portable version allows for measurements to be taken directly in cellars or at the base of a truck upon receiving a batch. Unlike benchtop devices, they do not regulate the sample to 20°C. They have their own formulas to convert density into % vol. of alcohol and display the result directly at 20°C.
Some portable devices can scan a container’s barcode for measurement association and data transfer to Excel files.
Benchtop devices, by regulating the sample’s temperature to 20°C, offer better precision. For some, a sample handler can be added. - Scope of Application : From 0 to 100% vol. of alcohol. The latest versions allow for use in fairly wide temperature conditions, ranging from 0 to 30°C.
- Response Time : Analysis in a few seconds.
- Ergonomics : Fairly easy to use for a conscientious operator. Some devices allow for the addition of a sampling extension of several tens of centimeters.
- Precision : Although the stated precision is generally around +/- 0.3% vol., by adhering to proper calibration, usage, and maintenance practices, precision can reach +/- 0.1% vol.
2. Alcohol Content Measurement by Ebulliometry
Although this method is not suitable for measuring alcohol content in spirits, I have chosen to describe the principle as it is very practical and commonly used for analyzing fermented products intended for distillation (wines, cane wines, etc.).
Principle of the Method :
The boiling temperature depends on the alcohol content and atmospheric pressure. After introducing the sample into a boiler, it is brought to a boil. A thermometer records the temperature of either the liquid or the vapors. To account for atmospheric pressure, water or a reference wine must be brought to a boil for the manual version or the electric version, respectively. A calculation disc or the Labox “Ebulliometer” Boxette allows for determining the sample’s volumetric alcohol content based on the boiling temperature of the reference (water or wine) and the boiling temperature of the sample.
- Version : Devices are available in manual or electric versions. The manual version is easily transportable. In both cases, Labox provides a free Boxette to replace the manual calculation disc: “Alcohol by Ebulliometer.”
Scope of Application : Reserved for unsweetened products with an alcohol content < 17% vol..
Response Time : Analysis in a few minutes.
Ergonomics : Fairly easy to use for a conscientious operator.
Precision : Between +/- 0.1 and +/- 0.2% vol. To achieve this level of precision, the thermometer must have a precision of 0.03°C, and the sample must be free of CO2.
3. Alcohol Content Measurement by Distillation – Reference Method for All Alcoholic Beverages
Method Principle :
The purpose of distillation is to remove compounds other than water and alcohol that can alter the density. The volumetric alcohol content (A.S.V.) is analyzed in the distillate using the densimetry principle detailed in the previous paragraph.
Depending on the product’s A.S.V., it can be distilled either by steam distillation or by direct distillation. A precise volume of the sample is introduced into a volumetric flask. The flask’s level is adjusted after the sample is brought to 20°C +/- 2°C. It is then transferred to the distillation flask and distilled. The flask used for sampling is used for recovering the distillate. Distillation is stopped just before the graduation mark. The volume is adjusted with water to the graduation mark after the distillate is brought to 20°C +/- 2°C, and if necessary, after degassing. The A.S.V. is measured in the distillate using alcoholometers or electronic densimeters.
- Versions : Distillation equipment is available in traditional glassware or semi-automated devices, with either steam distillation or direct distillation. For products with an alcohol content of less than 25% vol., especially if they are sweet, it is preferable to perform steam distillation to avoid pyrogenation in the distillation flask.
Glassware setups consist of a heating flask or gas burner, a distillation flask topped with a rectifying column, and a condenser. - Scope of Application : Any product depending on the supplier’s specified scope. In some cases, dilution can be performed for products whose T.A.V. falls outside the equipment’s scope. Refer to the article: Alcohol Content Measurement – Part 2: by distillation with dilution.
- Response Time : The analysis can take over 20 minutes with traditional glassware setups and a few minutes with semi-automated devices.
- Ergonomics : Requires specific training and a meticulous operator. Semi-automated versions allow for automatic adjustment of the distillation duration.
- Precision : Between +/- 0.1 and +/- 0.2 vol. However, the precision of the results obtained depends on many factors: performance of the setup, temperature of the cooling water, potential degassing of the sample before distillation, handling during sample transfers, level adjustments before and after distillation, trapping of distillate alcohol, degassing of distillates before leveling, and not forgetting the precision of alcohol content measurement in the distillate.
Tests to validate distillation equipment and mastery of manipulations :
- For products with A.S.V. < 16% vol. : The performance of the setup and mastery of manipulations must be tested by distilling a 10% vol. hydroalcoholic mixture five times successively. The difference in measurement before and after the five distillations of this mixture should not exceed 0.1% vol. (5).
- For spirits, distillation of a hydroalcoholic mixture close to 50% vol. should not result in a loss of more than 0.1% vol. (6).
In both cases, it is recommended to analyze the A.S.V. of the hydroalcoholic mixture before and after distillation simultaneously using the same device.
4. Alcohol Content Measurement with Near-Infrared (NIR) Analyzers
Method Principle :
The biochemical components of wines and spirits, especially ethanol, absorb light in the near-infrared range at defined wavelengths. The measurement involves illuminating the sample contained in a cell with near-infrared radiation and measuring the reflected energy at each wavelength. Measuring the T.A.V. requires calculating the values of the reflected energies at specific wavelengths for each instrument.
- Versions : Devices are available in automated versions with semi-automated or fully automated sampling (sample handlers).
- Scope of Application : Any alcoholic product based on the specific scope of each device.
- Response Time : Analysis in a few minutes.
- Ergonomics : Easier to use than a distillation apparatus, it can be made available to any operator who follows the provided instructions. However, it is necessary to train a responsible person in calibration and maintenance.
- Precision : It can reach 0.1% vol.. Since measurements with these devices are generally highly reproducible, measurement precision will depend primarily on the precision of measurements made on the products used to develop calibrations, those used to calibrate the slope and bias, or those used as auto controls.
5. Alcohol Content Measurement in the middle infrared with Fourier-Transform Infrared (FTIR) Analyzers
Method Principle :
The equipment uses an interferometer to scan the infrared spectrum in a spectral range of 2000 to 10000 nm, covering part of the near and mid-infrared regions. Fourier Transform is a mathematical procedure that, based on the interferogram, measures signal intensity as a function of wavelength and then reconstructs the infrared spectrum. Specific calibrations for each product type and parameters are provided. After analyzing a sample, spectrum processing allows for the simultaneous determination of numerous parameters within the scope developed for that product.
- Versions : Devices are available in versions with semi-automated (sampling pump), or fully automated (sample handler with sampling pump).
- Scope of Application : In theory, it can analyze any product depending on the scope developed by the supplier. To date, only calibrations intended for the analysis of fermenting musts, wines, ciders or beers are offered in the catalog. Certain versions of devices allow specific developments for spirits.
- Response Time : Analysis in a 30s or few minutes, depending on model.
- Ergonomics : Easier to use than a distillation apparatus, it can be made available to an unskilled operator who follows provided instructions. However, it is necessary to train a responsible person in calibration and maintenance.
- Precision : It can reach 0.1% vol.. Since measurements with these devices are generally highly reproducible, measurement precision will depend primarily on the precision of measurements made on the products used to develop calibrations, those used to calibrate the slope and bias, or those used as autocontrols.
ANNEX: Guides for choosing the method and associated equipment – Summary of the strengths and limitations of measurement equipment.
Tab N°1 :
Table 1 Legend
Equipment Mobility
* = Not recommended for relocation
** = Can be moved provided essential connections (water-electricity) are available for its operation
*** = Portable
Analysis Frequency
* = < 10 analyses per hour
** = Between 10 and 20 analyses per hour
*** = > 20 analyses per hour
Result Turnaround Time
* = > 20 minutes
** = Between 5 and 20 minutes
*** = < 5 minutes
Operator Qualification
* = Minimum training in operation is sufficient
** = Technician-level qualification
*** = Specific qualification for equipment usage
Qualification of the Equipment’s Responsible Person for Proper Operation (Maintenance and Control with “Standard” Products)
* = Training in maintenance and verification of proper operation is sufficient
** = Technician-level qualification
*** = Specific qualification for usage, verification of proper operation, calibration, and equipment maintenance
(a) Investment and operational budgets are provided for reference purposes
Tab N°2 – part 1 : Densimetry – Alcoholometry – Distillation
Tab N°2 – part 2 : Near and Middle Infrared
I would like to thank the following suppliers of analytical equipment for their contribution to the writing of this article :
- Dujardin-Salleron, providers of equipment for density measurement, distillation, and Near-Infrared (NIR) analysis
- Anton Paar, providers of equipment for density measurement, Near-Infrared (NIR) and Middle Infrared analysis (FTIR)
- FOSS, providers of equipment for Middle-Infrared (FTIR) analysis
Evelyne CHANSON – Wine and Spirits Quality Control Consultant at EC Consulting
- OIML Recommendation R022 -f75 – Official alcohol tables
- Calculations performed using formulas and charts from the International Collection of Methods of Analysis for Spirits (refer to the “Extract and Obscuration” Boxette).
- OIML Recommendation R44.
- Refer to the article on this blog: “Good Practices for the use of Alcoholometers and Maintenance.”
- International Collection of Methods of Analysis – OIV – Volumetric Alcohol Content – Method OIV-MA-AS312-01A.
- OIV/OENO Resolution 379/2009 – Method OIV-MA-BS-02.
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