Measuring Brix for Wine
Grapes are often tested prior to harvest for sugar level, measured in Brix, pH and Titratable Acidity. This segment will focus on the first of these measurements, Brix. Brix is a measurement of the concentration of sucrose in water, so 20 degrees brix is 20 grams of sucrose in 100 grams of solution. A refractometer is an instrument that measures the refractive index of a solution to obtain the brix. It is calibrated at a temperature of 68 F for most meters, and is primarily used for juice samples that have not started a fermentation. A hydrometer measures the specific gravity of a liquid sample, converted to brix. It is used to test both juice and wine as it progresses through fermentation. The equipment needed to test brix in juice with a refractometer include: Refractometer Eye dropper Juice sample DI water bottle Kimi Wipes The equipment needed to test brix in juice with a hydrometer include: Hydrometer 250 ml graduated cylinder A 150-200 ml juice sample A sample of grapes must be obtained. The sample should represent the variety of growing conditions and not just from a single plant to obtain a representative sample of the vineyard. Once the grapes are obtained, they will need to be crushed. This can be done manually by placing the grape clusters into a clean strainer. With gloved hands, crush the grapes thoroughly capturing the extracted juice into a clean container. Mix the sample thoroughly to provide a homogenous sample and then allow the solids to settle. Extract a sample for testing with the refractometer or a larger 150-200ml sample for testing with a hydrometer. In preparation for testing juice with a refractometer, it is a good practice to verify the calibration of the device using DI water. First, clean the refractive lens prism with DI water. Place a sample of DI water onto the prism. Observe sample measurement in viewfinder Verify sample measurement is 0.0 Wipe prism surface dry with Kim Wipe The refractometer is now ready for sampling. To test a juice sample using the refractometer, make sure the prism surface is clean and dry. Place 1-2 drops of the juice sample onto the prism and close the prism cover. Observe sample measurement in the viewfinder. The scale is visible through the viewfinder and the measurement is taken by observing a blue line on the scale indicating the brix level of the sample. The view finder focus can be adjusted by rotating the eye piece. Record sample measurement as the scale point when the blue line becomes solid. Rinse the prism with DI water between samples. Wipe prism surface dry with Kimi Wipe. Testing a juice or wine sample using a hydrometer requires a larger product sample of 150-200 mls. Place the strained and settled juice sample into a 250 ml graduated cylinder. Select the appropriate clean hydrometer for the anticipated brix level. Place hydrometer into cylinder containing the juice sample, giving the hydrometer a slight spinning action. Allow Hydrometer to stabilize in the sample before taking reading. Record hydrometer reading when the hydrometer scale point is in contact with the sample in the graduated cylinder. Equipment used for testing brix should be cleaned thoroughly between each test and after final use to prevent cross contamination of samples. Clean prism surface and lens cover with DI water immediately after sampling. Dry lens with Kimi Wipe. Clean exterior of refractometer with damp cloth to remove any spilled juice sample. Clean all labware with lab cleaner and rinse with DI water. Dispose of juice samples and grape must to prevent insect infiltration in winery and lab.