Degrees Brix is the
sugarSugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...
content of an aqueous solution.
One degree Brix is 1 gram of
sucroseSucrose is the organic compound commonly known as table sugar and sometimes called saccharose. A white, odorless, crystalline powder with a sweet taste, it is best known for its role in human nutrition. The molecule is a disaccharide composed of glucose and fructose with the molecular formula...
in 100 grams of solution and represents the strength of the solution as percentage by weight (% w/w) (strictly speaking, by mass). If the solution contains dissolved solids other than pure sucrose, then the °Bx is only approximate the dissolved solid content. The °Bx is traditionally used in the wine, sugar, fruit juice, and honey industries.
The °Bx represents the same thing as the degree Plato (°P) widely used by the brewing industry, and degree Balling (the oldest of the three systems and still used in some parts of the world) found in older textbooks.
For example, a sucrose solution with an apparent
specific gravityRelative density, or specific gravity, is the ratio of the density of a substance to the density of a given reference material. Specific gravity usually means relative density with respect to water...
(20°/20°C) of 1.040 would be 9.99325 °Bx or 9.99359 °P while the representative sugar body, the
International Commission for Uniform Methods of Sugar AnalysisThe International Commission for Uniform Methods of Sugar Analysis is an international standards body, founded in 1897, that publishes detailed laboratory procedures for the analysis of sugar....
(ICUMSA), in favor of "mass fraction", would report the solution strength as 9.99249%. Because the differences between the systems are of little practical significance (the differences are less than the precision of the instruments) and wide historical use of the Brix unit, modern instruments calculate mass fraction using ICUMSA official formulas but report the result as °Bx.
Background
First Karl Balling, then
Adolf BrixAdolf Ferdinand Wenceslaus Brix was a German mathematician and engineer...
and finally the
Normal Eichungskommission under Fritz Plato prepared pure sucrose solutions of known strength, measured their specific gravities and prepared tables of percent sucrose by weight vs. measured specific gravity. Balling measured specific gravity to 3 decimal places, Brix to 5 and the Normal Eichungskommission to 6 with the goal of the Kommission being to correct errors in the 5th and 6th decimal place in the Brix table.
Equipped with one of these tables, a brewer wishing to know how much sugar was in his
wortWort may refer to:* Wort, the liquid created by the mashing of malted barley to use in brewing beer* Worting, Hampshire, a large district and suburb of the town of Basingstoke, in Hampshire, England....
could measure its specific gravity and enter that specific gravity into the Plato table to obtain °Plato which is the same as % sucrose w/w. A
vintnerA vintner is a wine merchant. You pronounce it like this In some modern use, in particular in American English, the term is alsoused as a synonym for winemaker....
could measure the specific gravity of his
mustMust is freshly pressed fruit juice that contains the skins, seeds, and stems of the fruit. The solid portion of the must is called pomace; it typically makes up 7%–23% of the total weight of the must. Making must is the first step in winemaking...
and enter the Brix table to find the must °Bx value i.e. its % sucrose w/w. It is important to point out that neither wort nor must is a solution of pure sucrose in pure water. Many other compounds are dissolved as well but these are either sugars, which behave very similarly to sucrose with respect to specific gravity as a function of concentration, or compounds which are present in small amounts (minerals, hop acids in wort, tannins, acids in must). In any case even, if °Bx are not representative of the exact amount of sugar in a must or fruit juice they can be used for comparison of relative sugar content.
Measurement
As specific gravity was the basis for the Balling, Brix and Plato tables dissolved sugar content was originally estimated by measurement of specific gravity using a
hydrometerA hydrometer is an instrument used to measure the specific gravity of liquids; that is, the ratio of the density of the liquid to the density of water....
or pycnometer. In modern times hydrometers are still widely used but where greater accuracy is required an electronic
oscillating U-tubeThe oscillating U-tube is a technique to determine the density of liquids and gases based on an electronic measurement of the frequency of oscillation, from which the density value is calculated. This measuring principle is based on the Mass-Spring Model....
meter will be employed. Whichever means are used, the analyst enters the tables with specific gravity and takes out (using interpolation if necessary) the sugar content in percent by weight. If he uses the Plato tables (maintained by the
American Society of Brewing ChemistsThe ASBC is a professional organization of scientists and technical professionals in the brewing, malting, and allied industries. It publishes a journal, the Journal of the American Society of Brewing Chemists, usually four times a year....
) he reports in °P. If using the Brix table (the current version of which is maintained by NIST and can be found on their website) he reports in °Bx. If using the ICUMSA tables, he would report in mass fraction (m.f.). It is not, typically, actually necessary to consult tables as the tabulated °Bx or °P value can be printed directly on the hydrometer scale next to the tabulated value of specific gravity or stored in the memory of the electronic U-tube meter or calculated from polynomial fits to the tabulated data. Both ICUMSA and ASBC have published suitable polynomials, in fact the ICUMSA tables are calculated from the polynomials. The opposite is true with the ASBC polynomial. Also note that the tables in use today are not those published by Brix or Plato. Those workers measured true specific gravity reference to water at 4 °C using, respectively, 17.5 and 20 °C, as the temperature at which density of the sucrose solutions was measured. Both NBS and ASBC converted to apparent specific gravity at 20°C/20°C. The ICUMSA tables are based on more recent measurements on sucrose, fructose, glucose and invert sugar and tabulate true density and weight in air at 20 °C against mass fraction.
Dissolution of sucrose and other sugars in water changes not only its specific gravity but its optical properties in particular its
refractive indexIn optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....
and the extent to which it rotates the plane of linearly polarized light. The refractive index, nD, for sucrose solutions of various strengths by weight has been measured and tables of nD vs. °Bx published. As with the hydrometer, it is possible to use these tables to calibrate a
refractometerA refractometer is a laboratory or field device for the measurement of an index of refraction . The index of refraction is calculated from Snell's law and can be calculated from the composition of the material using the Gladstone-Dale relation....
so that it reads directly in °Bx. The hand held instrument illustrated in the accompanying photograph is typical of an electronic instrument calibrated in this way. Calibration is usually based on the ICUMSA tables, but the user of an electronic refractometer should verify this.
Sugars also have known
infraredInfrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
absorption spectra and this has made it possible to develop instruments for measuring sugar concentration using NIR (Near Infra Red) and FT-IR (Fourier Transform Infrared Spectrometry) techniques. In the former case, in line instruments are available which allow constant monitoring of sugar content in sugar refineries, beverage plants, wineries, etc. As with any of the other instruments NIR and FT-IR instruments can be calibrated against pure sucrose solutions and thus report in °Bx but there are other possibilities with these technologies as they have the potential to distinguish between sugars and interfering substances.
Tables
Approximate values of °Bx can be computed from 261.3 × (1 − 1/S), where S is the apparent
specific gravitySpecific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...
of the solution 20°C/20°C. More accurate values are available from °Bx = (((182.4601*S -775.6821)*S +1262.7794)*S -669.5622), derived from the NBS table with S as above. This should not be used above S = 1.17874 (40 °Bx). RMS disagreement between the polynomial and the NBS table is 0.0009 °Bx. The Plato scale can be approximated by the Lincoln Equation °P = (463-205*S)*(S-1) or values obtained with high accuracy with respect to the ASBC table from the ASBC polynomial °P = (((135.997*S - 630.272)*S + 1111.14)*S - 616.868).
The difference between the °Bx and °P as calculated from the respective polynomials is: °P - °Bx = (((-2.81615*S +8.79724)*S - 9.1626)*S +3.18213). The difference is generally less than ±0.0005 °Bx or °P with the exception being for weak solutions. As 0 °Bx is approached °P tend towards as much as 0.002 °P higher than the °Bx calculated for the same specific gravity. Disagreements of this order of magnitude can be expected as the NBS and the ASBC used slightly different values for the density of air and pure water in their calculations converting to apparent specific gravity. It should be clear from these comments that Plato and Brix are, for all but the most exacting applications, the same. Note: all polynomials in this article are in a format that can be pasted directly into a spreadsheet.
When a refractometer is used, the Brix value can be obtained from the polynomial fit to the ICUMSA table: Bx = (((((11758.74*nD -88885.21)*nD + 270177.93)*nD - 413145.80)*nD + 318417.95)*nD -99127.4536) where nD is the refractive index, measured at the wavelength of the sodium D line (589.3 nm) at 20 °C. Temperature is very important as refractive index changes dramatically with temperature. Many refractometers have built in "Automatic Temperature Compensation" (ATC) which is based on knowledge of the way the refractive index of sucrose changes. For example, the refractive index of a sucrose solution of strength less than 10 °Bx is such that a 1 °C change in temperature would cause the Brix reading to shift by about 0.06 °Bx. Beer, conversely, exhibits a change with temperature about three times this much. It is important, therefore, that users of refractometers either make sure the sample and prism of the instrument are both at very close to 20 °C or, if that is difficult to insure, readings should be taken at 2 temperatures separated by a few degrees, the change per degree noted and the final recorded value referenced to 20°C using the Bx vs. Temp slope information.
Usage
The three scales are often used interchangeably since the differences are minor.
- Brix is primarily used in fruit juice, wine making, carbonated beverage industry, starch
Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...
and the sugarSugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...
industry.
- Plato is primarily used in brewing
Brewing is the production of beer through steeping a starch source in water and then fermenting with yeast. Brewing has taken place since around the 6th millennium BCE, and archeological evidence suggests that this technique was used in ancient Egypt...
.
- Balling appears on older saccharimeters and is still used in the South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
n wine industry and in some breweries.
Brix is used in the food industry for measuring the approximate amount of sugars in fruits, vegetables, juices,
wineWine is an alcoholic beverage, made of fermented fruit juice, usually from grapes. The natural chemical balance of grapes lets them ferment without the addition of sugars, acids, enzymes, or other nutrients. Grape wine is produced by fermenting crushed grapes using various types of yeast. Yeast...
, soft drinks and in the starch and sugar manufacturing industry. Different countries use the scales in different industries; in the UK brewing is measured with
specific gravityGravity, in the context of fermenting alcoholic beverages, refers to the specific gravity, or relative density compared to water, of the wort or must at various stages in the fermentation. The concept is used in brewing and wine making industry...
X 1000, European brewers use Plato degrees, and US industries use a mix of specific gravity, Brix,
degrees BauméThe Baumé scale is a pair of hydrometer scales developed by French pharmacist Antoine Baumé in 1768 to measure density of various liquids. The unit of the Baumé scale has been notated variously as degrees Baumé, B°, Bé° and simply Baumé . One scale measures the density of liquids heavier than water...
and Plato degrees. For fruit juices, 1.0 degree Brix is denoted as 1.0% sugar by weight. This usually correlates well with perceived sweetness.
Modern optical Brix meters are divided into two categories. In the first are the Abbe based instruments in which a drop of the sample solution is placed on a prism; the result is observed through an eyepiece. The critical angle (the angle beyond which light is totally reflected back into the sample) is a function of the refractive index and the operator detects this critical angle by noting where a dark-bright boundary falls on an engraved scale. The scale can be calibrated in Brix or refractive index. Often the prism mount contains a thermometer which can be used to correct to 20°C in situations where measurement cannot be made at exactly that temperature. These instruments are available in bench and hand held versions.
Digital refractometers also find the critical angle, but the light path is entirely internal to the prism. A drop of sample is placed on its surface (at the center of the circular well in the accompanying photograph) and so the critical light beam never penetrates the sample. This makes it easier to read turbid samples. The light/dark boundary, whose position is proportional to the critical angle, is sensed by a
CCDA charge-coupled device is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by "shifting" the signals between stages within the device one at a time...
array. These meters are also available in bench top (laboratory) and portable (pocket) version. The photograph shows an example of the latter. These are the easiest to use of all the methods for estimating Brix and can be used on location with minimal training. A drop of distilled water is placed on the prism and the calibrate button pressed. The distilled water is now replaced by a drop of juice from the fruit being measured. The read button is pressed and the display indicates °Bx directly. This ability to easily measure Brix in the field makes it possible to determine ideal harvesting times of fruit and vegetables so that products arrive at the consumers in a perfect state or are ideal for subsequent processing steps such as vinification.
Brix and Actual Dissolved Solids Content
When a sugar solution is measured by
refractometerA refractometer is a laboratory or field device for the measurement of an index of refraction . The index of refraction is calculated from Snell's law and can be calculated from the composition of the material using the Gladstone-Dale relation....
or densitometer, the °Bx or °P value obtained by entry into the appropriate table only represents the amount of dry solids dissolved in the sample if the dry solids are exclusively sucrose. This is seldom the case. Grape juice (must), for example, contains little sucrose but does contain glucose, fructose, acids and other substances. In such cases the °Bx value clearly cannot be equated with the sucrose content but it may represent a good approximation to the total sugar content. For example, an 11.0 %w/w D-Glucose ("grape sugar") solution measured 10.9 °Bx using a hand held instrument similar to the one in the photograph. For these reasons, the sugar content of a solution obtained by use of refractometry with the ICUMSA table is often reported as "Refractometric Dry Substance" (RDS) which could be thought of as an equivalent sucrose content. Where it is desirable to know the actual dry solids content empirical correction formulas can be developed based on calibrations with solutions similar to those to be tested. For example in sugar refining dissolved solids can be accurately estimated from refractive index measurement corrected by an optical rotation (polarization) measurement.
Alcohol has a higher refractive index at 1.361 than water at 1.333. As a consequence, a refractometer measurement made on a sugar solution once fermentation has begun will result in a reading substantially higher than the actual solids content. Thus, an operator must be certain that the sample he is testing has not begun to ferment, if the results are to be relied upon. Brix or Plato measurements based on specific gravity are also affected by fermentation, but in the opposite direction. As ethanol is lighter than water, an ethanol/sugar/water solution gives a Brix or Plato reading which is low compared to the actual dissolved sugar content.
See also
- Baumé scale
The Baumé scale is a pair of hydrometer scales developed by French pharmacist Antoine Baumé in 1768 to measure density of various liquids. The unit of the Baumé scale has been notated variously as degrees Baumé, B°, Bé° and simply Baumé . One scale measures the density of liquids heavier than water...
- Oechsle scale
- Sweetness of wine
The subjective sweetness of a wine is determined by the interaction of several factors, including the amount of sugar in the wine to be sure, but also the relative levels of alcohol, acids, and tannins. Briefly: sugars and alcohol enhance a wine's sweetness; acids and bitter tannins counteract it...
- polarimetry
Polarimetry is the measurement and interpretation of the polarization of transverse waves, most notably electromagnetic waves, such as radio or light waves...
- Plato Scale
Further reading
ISBN 0-412-06411-1— Martinez describes the theory and practice of measuring brix on-line in beverages.
External links