Alcohol content in spirits needs to be determined for labeling conformity, product quality, and tax purposes. The conventional and officially recognized method for determining alcohol content is the measurement of density, which can be converted to alcohol concentration using conversion tables.
On this page you will gain essential knowledge about alcohol content determination in spirits, including an overview of ways to measure alcohol via density.
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Distilled spirits, such as vodka or gin, are considered pure alcohol and water mixtures. The alcohol content of these types of spirits can be measured directly via density measurement - no further sample preparation is required. On the other hand, liqueur or alcopops contain other substances (e.g. sugar or flavors) which strongly influence the result of the measurement. These types of spirits need to be distilled prior to the analysis in order to achieve a correct alcohol content.
Officially recognized instruments for alcohol content determination include hydrometers, pycnometers and digital density meters. With these instruments, the density of spirits is measured, which is then converted into alcohol content (e.g. %v/v, %w/w, Proof) using conversion tables (e.g. OIML, AOAC or Proof).
Learn how to correctly determine alcohol content in spirits, download our free application note.
Generally, ethanol (alcohol) is produced via a natural process known as fermentation. Yeasts consume sugars such as glucose, fructose and sucrose to produce energy, releasing ethanol and carbon dioxide as by-products. Many products can be fermented to obtain alcohol: fruits, honey, grains, and even vegetables (any plant material containing sugar or starch). However, the alcohol concentration can be increased by using another process, the distillation.
Distillation, in contrary to fermentation, needs human intervention. This process will purify the alcoholic mixture by evaporating and condensing the alcoholic vapor from one flask (containing the entire mixture) to another one. The remaining distillate will contain mainly alcohol and water. This process will purify the alcoholic mixture and increase the alcohol concentration.
Distillation can be repeated to increase the concentration of alcohol in water until reaching the limit of 96% ABV (forming an azeotrope).
Spirits can be classified in two categories: Distillates and Liqueurs.
Distillate – Pure Alcohol Water Mixtures
Distillates include spirits or liquors (vodka, gin, brandy, etc.) which do not contain extracts (sugar or other substances added after the distillation). Substances other than alcohol and water may be present in low concentration – they are considered to participate to the character of the beverage. These spirits are considered as pure mixtures of alcohol and water. Thus, the alcohol content can be determined directly via density measurement. There is no need to execute any further sample preparation.
Liqueur – Mixtures with Extracts
Many liqueur contain a significant concentration of other substances such as sugar or flavors, which were added after the distillation. These substances will impact the density measurement and thus distort the alcohol measurement. To determine the alcohol content of these beverages, a distillation is mandatory before measuring the density.
Discover the method how to measure spirits in the application note.
The conventional and officially recognized method for determining alcohol content is the measurement of density, which can be converted to alcohol concentration using conversion tables. In the table below, three types of density measuring devices are compared:
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Definition/Information
A hollow glass tube is filled and vibrates at a certain frequency. This frequency is measured and converted into density. A built-in Peltier thermostat controls the temperature of the benchtop instrument.
Learn how to measure spirits in the application note.
Discover the digital density meter here.
Advantages
Disadvantages
Hydrometer
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Definition/Information
A hydrometer is a glass instrument,used to determine the specific gravity of liquids based on the buoyancy principle. The lighter the liquid, the higher the alcohol concentration.
Advantages
Disadvantages
Pycnometer
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Definition/Information
A pycnometer is a glass flask, that has a defined volume and mass. The density is established by determining the exact mass of liquids by filling the entire instrument's volume at a set temperature.
Learn how to choose, use and calibrate pycnometers
Advantages
Disadvantages
Discover more about all the instrument here.
There are many units for alcohol. The most common units are %v/v (volume/volume), %w/w (weight/weight) and Proof.
Alcohol Unit - %v/v
The alcohol by volume (ABV) is a standard to measure the quantity of alcohol present in a given volume of water at a certain temperature. This unit is temperature dependent, since the volume increases/decreases with the temperature while the mass stays constant.
Alcohol Unit - %w/w
Alcohol by weight (ABW) is the quantity of alcohol expressed as the percentage of the total mass. This unit is independent of the temperature.
Alcohol Unit - Proof
Proof is not a unique unit. The most well-known ones are the US and UK Proof and their definitions are not the same.
US Proof: Mainly used in the USA, Proof equals ABV multiplied by two. This value is temperature dependent.
UK Proof: As the US Proof, the UK Proof can be derived from the ABV. It is ABV multiplied with 1.75. This value is temperature dependent.
Learn more about measuring spirits with the right units with the application note.
Tables used to convert density into alcohol values are published by different insitutions around the world. The most commonly used tables are OIML and AOAC.
OIML
OIML ( French: Organisation Internationale de Métrologie Légale) is an intergovernmental organization based in Paris, France. OIML is active in many domains for the certification of measuring devices and in products, one of them being the alcohol content in beverages. The European Union follows the recommendation from the International Organization of Legal Metrology (OIML).
AOAC
AOAC (Association of Official Analytical Chemists). The international organization for analytical excellence based in Rockville, Maryland, USA, develops and validates standards, methods and technologies of global relevance. Their role in the alcohol content determination is to define the procedure and tables to determine the alcohol content with high precision.
Color in alcoholic spirits
Distillers in certain cases need to conduct complementary analyses. Certain spirits will have a specific color once prepared with specific processes (e.g. aging, coloring agent, fruits or herb maceration).
Why do spirits producers measure color in spirits?
Color is the most recognizable feature of spirits. It is used in the classification of spirits and liqueurs and also plays a key role in the quality control process, as producers strive for consistency in their products. The determination of color is a good indicator for the purity of a certain product.
What is UV Vis measurement in spirits?
Instrumental color determination allows the standardization of measurements and delivers an objective assessment of the chromatic characteristics of a sample.
By using UV Vis spectrophotometry, it is possible to calculate required color values from spectral information to achieve accurate and repeatable color measurements.
Learn more about UV Vis here.
Alcohol or more precisely ethanol is the alcohol predominantly present in all alcoholic beverages. In chemistry, ethanol is represented as the condensed formula CH3CH2OH or the abbreviation EtOH. It is a volatile, flammable organic compound and mostly used as a solvent. Ethanol in the alcohol family is the only alcohol that humans can consume without enduring immediate health damage. Other alcohols are toxic even in small doses and will cause permanent health damage (e.g. methanol).
Alcohol content is determined via density, however density is not specific to alcohol and water. Other substances present in the mixture of interest will have an impact on the density. Measuring the density is not a method of identification, thereby purifying the alcohol by distillation ensures that the mixture will contain only alcohol and water.
Alcohol is determined via density measurement, which is temperature dependent. If an operator is using a hydrometer or a pycnometer, someone needs to take note of the temperature to apply the correct correction factor. Today, most of the digital instruments are provided with a temperature sensor or temperature control. More information on digital density meters can be found here.
The maturation of spirits is performed by storing the distillated alcohol in a barrel or a earthenware jar during a define period of time. The container made of wood or soil will give a certain "character" to the liquor, its flavor and a characteristic yellow to dark black color. The alcohol before this process is practically tasteless and colorless.
Learn about the effective determination of alcohol content so you can more easily comply with national and international standards.
Alcohol content determination is widely used in various industries. Learn more about determining alcohol concentration in %v/v, %w/w, or Proof.
