NEW! Residual Sugar Assay Kit
Vinmetrica’s new Residual Reducing Sugar (RRS) Assay Kit allows you to accurately measure residual sugar (glucose + fructose) in your sample. The RRS kit is based on the Rebelein, or “Gold Coast” method in which “reducing” sugars are oxidized by alkaline copper sulfate; the amount of copper remaining is then determined by titration to get an accurate value for residual sugar.
Residual sugar (RS) refers to any significant concentration of sugar that is contained in wine, beer or cider at the end of fermentation. Winemakers and brewers are typically most interested in knowing the concentration of the fermentable hexoses glucose and fructose, the main reducing sugars. These determine the level of sweetness of the finished product. At residual sugar levels around 2 g/L (0.2%) or higher, an alcoholic beverage can spontaneously restart fermentation unless it has been properly stabilized.
Note: this kit does not detect sucrose directly. We provide a method for hydrolyzing any sucrose prior to analysis if you want to include sucrose in your results with the RRS kit.
The Kit can be tailored to suit your needs. We recommend purchasing the RRS Kit with the added labware when you first purchase the kit. When you need reagent refills you can simply order the Reagent Kit only. If you do not have a glass burette, lab support stand or burette clamp, you will need to purchase them for this assay. (Bonus: Those three pieces of extra labware can be used with your Free SO2 and TA titrations plus your ABV testing too!)
Provided reagents will allow you to perform ~30 Residual Reducing Sugar tests.
The RRS assay is based on the well-known Rebelein method, which we have adapted to a convenient procedure for winery use.
Simple To Use
- Pretreat sample: filter or decant white wines; red wines need to be decolorized (simple procedure provided).
- Place 2 mL of pretreated wine into reaction flask with 10.0 mL copper sulfate and 5 mL binding solution
- Heat in hot water bath 2.5 minutes. Let cool to near room temperature.
- Add 10 mL acid, and 2 mL each of developer and starch.
- Titrate with the RRS Titrant until black-green color changes to a cream white.
- Calculate g/L reducing sugar from the volume of Titrant used vs. a blank titration.
Complete Reagent Kit Includes Everything You Need to Run 30 Tests.
- Clarifying Powder (PVPP) for decolorizing red wines
- Copper Sulfate Solution
- RRS Binding Solution (Rochelle Salt)
- RRS Titrant (0.20 M sodium thiosulfate)
- RRS Developer Solution (KI)
- RRS (1+5) Sulfuric Acid Solution
- A User Manual
- Reaction Bottles (2)
- 10.00 mL volumetric pipette
- pipetting safety bulb
- 3 transfer pipettes
- 10 mL sampling pipette
- 5 mL sampling pipette
- 15 mL conical tubes (5)
These Labware items can also be purchased indivdually. We offer 10 mL glass burettes, burette holders, and lab support stands separately.
Things you will need:
- Baking soda (sodium bicarbonate), found in stores, to neutralize solutions for safe disposal.
- Additional Reaction bottles (for running more than two tests at one time). Available in sets of two (SC-60-8) or in sets of five (SC-60-8-5). You may use 125-250 mL Erlenmeyer Pyrex flasks in addition to Reaction bottles.
- (Optional) Additional 15 ml conical tube(s) (need 1 per test but they are re-usable)
How It Works
The Residual Reducing Sugar (RRS) test, also known as the Rebelein or Gold Coast Method, determines the amount of residual sugar through the use of excess copper (Cu+2). Reducing sugars are oxidized, reducing the copper. Remaining Cu+2 copper then is converted to iodine, which is titrated with sodium thiosulfate to determine the quantity of residual reducing sugars.
Because of this chemistry, non-reducing sugars are not detected. In general, non-reducing sugars are present in minor amounts in most fermented products and can be neglected. In some cases sucrose may be present in some wines and other beverages; measuring sucrose requires a hydrolysis step; this is described in the manual.
- Sensitivity and range: detects down to 0.5 g/L reducing sugar in a 2 mL sample; upper limit is determined by dilution (samples with more than about 25 g/L can be diluted as needed)
- Accuracy: 0.2 g/L reducing sugar
- Time to complete: less than 1 hour for up to 10 samples
Simple as that!
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