The degree Brix (°Bx) is the most common scale for measuring dissolved or soluble solids. It is used to express the concentration (% weight) or density of sugar in aqueous solutions in a wide variety of quality control operations including food and other industries.1
Each degree brix (°1) is equivalent to 1% sugar concentration when measured at 20°C. The Brix value of a given product can be directly obtained by using a device called refractometer or hydrometer. For example, when using a refractometer, 10°Bx are equal to 10g of sugar in 100g of solution/sample. In most industries, the sugar content is usually expressed as sucrose.
The term Brix owes its name to its inventor Adolf Ferdinand Wenceslaus Brix, a 19th century German mathematician. He is credited with developing and expanding existing density tables using percent sucrose to correspond to solution density, recalculating the Balling tables and inventing the hydrometer, a device for measuring sugar content in solutions.2
How does Brix works?
The Brix value is related to the content of dissolved or soluble solids in a solution, therefore its correlation with density of liquids. The higher the soluble solids or sugar content in a aqueous solution, the higher its specific gravity or density.
The Brix value can be assessed using the refractometer—a device used for the rapid and direct determination of °Bx in carbohydrate-based food products. A refractometer works by measuring the refractive index of a liquid/solution which takes place as a result of changes in the speed of light as it travels through two media of different densities.
Refractive index is calculated by using the equation:
Refractive index = speed of light in vacuum/speed of light through the substance, where the refractive index of vacuum is 1.
Refractometers are available as hand-held (for laboratory or field use) devices or can be installed in-line. Handheld refractometers have graduated Brix scales. To obtain the value, simply place a drop of the sample on a refractometer’s prism and read the percentage of sugars as degrees Brix.
The°Bx value corresponds directly to the refractive index scale, and is used in food and beverage industries such as:
Honey and fruit juice processing
Malt syrup processing
Tomato processing (ketchup)
Icings and glazes production
°Bx can be used for:
Assessing key chemical composition parameters such as soluble solids in food products with standards of identity, e.g., fruits and fruit juices.
Calculating the maturity index (°Brix/acidity ratio), a very important postharvest quality indicator of citric and climacteric fruits.
Assessing sweetness. In fruit processing, the higher the Brix value, the more sweet the fruit or fruit juice is.
Assessing fermentation yield. In winemaking, the alcohol concentration of the final wine is estimated to equal roughly 0.55 times the Brix value of the initial grape juice or must.
Measuring the sugars concentration in malt worts. In brewing, the Brix value is used as a quality and recipe parameter in worts ready to be fermented and turned into beer. It can also be used as a fermentation indicator along with alcohol testing. As the fermentation progresses, the yeast consumes the sugars and the Brix value decreases.
The Brix value can also be used as an evaporation end-point indicator. As evaporation removes water from liquids, i.e., concentrates solids, the final Brix value of the product is expected to increase.
Special considerations when using a handheld or benchtop refractometer:
A refractometer requires a very small sample, but there are certain precautions that users need to take into account to maintain the reliability of refractometric measurements. Care must be exercised in the maintenance of the prism surface as the presence of dust, soil and debris might lead to scratches and inaccuracy in the result. It is important that the prism be rinsed well with distilled water and dried with a proper cloth after each reading.3
When assessing °Bx, it is important that samples be equilibrated or tempered to room temperature before taking these measurements.
Brix measurements are best applied to the analysis of solutions consisting of only one solute in a liquid medium or solvent, such as water.4 Other dissolved solutes solids such as amino acids, organic acids, minerals, dextrins and pectins, and suspended solids, may contribute to the reading and hence interfere with accurate results. This is why the Brix value is an excellent approximation to the sugars concentration of liquid food materials, in cases where sugars are the major chemical component after water.
Refractometry is useful only when the analyzed material is known. A sugar and a salt solution may have the same refractive index but different solute concentrations.
Boulton, C. “D.” Encyclopedia of Brewing, John Wiley & Sons, Ltd, 2013, p. 171.
Kimball, D., Parish, M.E., and Braddock, R. “Oranges and Tangerines.” Processing Fruits: Science and Technology, 2nd edition, CRC Press LLC, 2005, pp. 633–634.
Pojić, M., Kravić, S., and Stojanović, Z. “Analytical Methods for Determination of Moisture and Ash in Foodstuffs.” Handbook of Food Analysis, 3rd edition, Volume I, CRC Press, Taylor & Francis Group, LLC, 2015, p. 285.
Mauer, L.J., and Bradley Jr, R.L “Moisture and Total Solids Analysis.” Food Analysis, 5th edition, Springer International Publishing, 2017, p. 270.
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