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{{Short description|Sugar content of an aqueous solution}}
{{other uses}}
[[File:Brix acide sudachi 23-08-2016.jpg|thumb|Measuring brix and percent acidity of a [[sudachi]]]]
'''Degrees Brix''' (symbol °Bx) is a measure of the dissolved solids in a liquid, and is commonly used to measure dissolved [[sugar]] content of an aqueous solution.<ref>{{cite web |title=Definition of brix |url=https://www.foodscience-avenue.com/2013/09/definition-of-brix.html |access-date=2022-10-14 |archive-date=2022-10-14 |archive-url=https://web.archive.org/web/20221014053138/https://www.foodscience-avenue.com/2013/09/definition-of-brix.html |url-status=live }}</ref> One degree Brix is 1 gram of [[sucrose]] in 100 grams of solution and represents the strength of the solution as [[percentage by mass]]. If the solution contains dissolved solids other than pure sucrose, then the °Bx only approximates the dissolved solid content. For example, when one adds equal amounts of salt and sugar to equal amounts of water, the degrees of refraction (BRIX) of the salt solution rises faster than the sugar solution. The °Bx is traditionally used in the [[wine]], [[sugar]], [[carbonated beverage]], [[fruit juice]], [[fresh produce]], [[maple syrup]], and [[honey]] industries. The °Bx is also used for measuring the concentration of a [[cutting fluid]] mixed in water for metalworking processes.
Comparable scales for indicating sucrose content are: the [[Plato scale]] (°P), which is widely used by the [[brewing industry]]; the [[Oechsle scale]] used in German and Swiss wine making industries, amongst others; and the Balling scale, which is the oldest of the three systems and therefore mostly found in older textbooks, but is still in use in some parts of the world.<ref>Hough, J.S., D. E. Briggs, R. Stevens and T. W. Young, ''Malting and Brewing Science, Vol 2 Hopped Wort and Beer'', Chapman & Hall, London,1971</ref>
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In the early 1800s, Karl Balling, followed by [[Adolf Ferdinand Wenceslaus Brix|Adolf Brix]], and finally the ''Normal-Commissions'' under [[Fritz Plato]], prepared pure sucrose solutions of known strength, measured their specific gravities and prepared tables of percent sucrose by mass vs. measured specific gravity. Balling measured specific gravity to 3 decimal places, Brix to 5, and the Normal-Eichungs Kommission to 6 with the goal of the Commission 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 [[wort]] could measure its specific gravity and enter that specific gravity into the Plato table to obtain °Plato, which is the concentration of sucrose by percentage mass. Similarly, a [[vintner]] could enter the specific gravity of his [[must]] into the Brix table to obtain the °Bx, which is the concentration of sucrose by percent mass. 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
==Measurement==
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===Infrared absorption===
Sugars also have known [[infrared]] absorption spectra and this has made it possible to develop instruments for measuring sugar concentration using mid-infrared (MIR), [[Nondispersive infrared sensor|non-dispersive infrared]] (NDIR), and [[Fourier-transform infrared spectroscopy|Fourier transform infrared]] (FT-IR) techniques. In-line instruments are available
== Tables ==
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Approximate values of °Bx can be computed from 231.61 × (SG − 0.9977), where SG is the [[apparent specific gravity]] of the solution at 20 °C/20 °C. More accurate values are available from:
:<math>^{\circ}Bx = 182.
derived from the NBS table with SG as above. This should not be used above SG = 1.17874 (40 °Bx). RMS disagreement between the polynomial and the NBS table is 0.0009 °Bx.
The [[Plato scale]] can be approximated with a mean average error of less than 0.02°P with the following equation:<ref name="jbuhl">{{cite web |last1=Buhl |first1=Josh |title=Physical Equations Relating Extract and Relative Density |url=https://osf.io/9wfym/ |website=OSF Preprints |publisher=Center for Open Science |access-date=13 October 2023 |ref=jbuhl |archive-date=19 October 2023 |archive-url=https://web.archive.org/web/20231019134432/https://osf.io/9wfym/ |url-status=live }}</ref>
:<math>^\circ P = 260.4 - \frac{260.4}{SG}</math>
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or with even higher accuracy (average error less than 0.00053°P with respect to the ASBC tables) from the best-fit polynomial:<ref name="jbuhl" />
:<math>^{\circ}P = 133.5892\
The difference between the °Bx and °P as calculated from the respective polynomials is:
:<math>^{\circ}P-^{\circ}Bx=
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
The ICUMSA polynomials are generally only published in the form where mass fraction is used to derive the density. As a result, they are omitted from this section.
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:<math>^{\circ}Bx= 11758.74n_D^5 -88885.21n_D^4 + 270177.93n_D^3 - 413145.80n_D^2 + 318417.95n_D -99127.4536</math>,
where <math>n_D</math> is the refractive index measured at the wavelength of the sodium D line (589.3 nm) at 20 °C. Temperature is
As solutes other than sucrose may affect the refractive index and the specific gravity differently, this refractive "Brix" value is not interchangeable with the traditional hydrometer Brix unless corrections are applied. The formal term for such a refractive value is "Refractometric Dry Substance" (RDS). See {{section link||Brix and actual dissolved solids content}} below.
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Brix is used in the food industry for measuring the approximate amount of sugars in [[fruits]], [[vegetables]], juices, [[wine]], soft drinks and in the starch and sugar manufacturing industry. Different countries use the scales in different industries: In brewing, the UK uses [[Gravity (beer)|specific gravity]] X 1000; Europe uses [[Plato scale|Plato degrees]]; and the US use a mix of specific gravity, degrees Brix, [[Baumé scale|degrees Baumé]], and degrees Plato. For fruit juices, 1.0 degree Brix is denoted as 1.0% sugar by mass. This usually correlates well with perceived sweetness.
Brix measurements are also used in the dairy industry to measure the quality of [[colostrum]] given to newborn calves, goats, and sheep. <ref>{{Cite journal |last1=Kessler |first1=E.C. |last2=Bruckmaier |first2=R.M. |last3=Gross |first3=J.J. |date=February 2021 |title=Short communication: Comparative estimation of colostrum quality by Brix refractometry in bovine, caprine, and ovine colostrum |journal=Journal of Dairy Science |volume=104 |issue=2 |pages=2438–2444 |doi=10.3168/jds.2020-19020 |issn=0022-0302|doi-access=free }}</ref>
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 handheld versions.▼
▲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
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, 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 [[Charge-coupled device|CCD]] array. These meters are also available in bench top (laboratory) and portable (pocket) versions. 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.
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==Brix and actual dissolved solids content==
When a sugar solution is measured by [[refractometer]] or density meter, 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% by mass D-Glucose ("grape sugar") solution measured 10.9 °Bx using a hand held instrument.{{citation needed|date=September 2014}} 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),<ref>"ICUMSA Methods Book, op. cit. Method GS4/3/8-13 (2009) "The Determination of Refractometric Dry Substance (RDS %) of Molasses – Accepted and Very Pure Syrups (Liquid Sugars), Thick Juice and Run-off Syrups – Official"</ref> 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 being tested. For example, in sugar refining, dissolved solids can be accurately estimated from refractive index measurement corrected by an optical rotation (polarization) measurement.<ref>{{cite journal |last1=Sgualdino |first1=G. |last2=Vaccari |first2=G. |last3=Mantovani |first3=G. |title=Conversion of refractometric dry substance into real dry substance for quentin molasses [Sugar syrups] |journal=Journal of the American Society of Sugar Beet Technologists (USA) |date=1982 |url=https://bsdf-assbt.org/jsbr/volume-21-1981/jsbrvol21no4p395to401conversionofrefractometricdrysubstanceintorealdrysubstanceforquentinmolasses/ |language=English |issn=0003-1216 |access-date=2022-07-20 |archive-date=2022-07-20 |archive-url=https://web.archive.org/web/20220720054741/https://bsdf-assbt.org/jsbr/volume-21-1981/jsbrvol21no4p395to401conversionofrefractometricdrysubstanceintorealdrysubstanceforquentinmolasses/ |url-status=live }}</ref>
Alcohol has a higher refractive index (1.361) than water (1.333). As a consequence, a refractometer measurement made on a sugar solution once fermentation has begun
==References==
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