- by Clinitest® or OenoCheck® (rapid method using test pills)
- by reaction/titration
- by enzymatic assay
- by high performance liquid chromatography (HPLC)
- References and further reading
This page provides a brief summary of the procedures and equipment requirements for some commonly used techniques for determination of the concentration of residual sugar (predominantly glucose and fructose) in wines. There are several techniques of varying degree of difficulty and analytical accuracy that are used for this purpose.
Clinitest® or OenoCheck® (rapid method using test pills)
Description: This rapid technique is useful to establish the approximate sugar content of wines in the range 0.1-2.0% (i.e. 1-20 g/L). Commercially available test kits (such as Clinitest® or OenoCheck®) use a reagent tablet based on the Benedict’s copper reduction reaction, combining reactive ingredients with an integral heat generating system. The product is used to determine the amount of reducing substances (glucose and fructose) in wine. The kits supply instructions and colour charts to assist in interpretation of results.
Equipment: Rapid test kit
Services: Wash up area
Space required: Minimal bench space
Reaction/titration
Description: There are two procedures commonly used to estimate sugars in wines using this technique. These are the (i) Lane and Eynon and (ii) Rebelein methods, both of which rely on reacting the sugars with alkaline cupric tartrate and then titrating to determine the excess copper ions (Cu2+). In the Lane and Eynon method, standard glucose solution is used as titrant, but in the Rebelein method, the concentration of Cu2+ is determined by reacting with excess iodine and then estimating the remaining iodine by titrating with standard thiosulfate solution. In both cases, red wines must be decolourised (Iland et al. 2000).
It should be noted that both of these techniques measure all of the sugars in the wine (commonly referred to as reducing sugars) including those like the pentose sugars which are not considered fermentable. These tests will therefore give higher results than tests that determine just the concentration of glucose and fructose.
Equipment: Flasks, flame or hotplate for boiling, burette
Calibration: Made-up standard solutions of sugar in water
Services: Flame burner, wash up area
Space required: Bench space
Enzymatic assay
Description: The conversion of glucose and fructose by specific enzymes can be monitored directly by measuring the absorbance (340 nm) resulting from the generation of a by-product of the reaction (NADPH). The test is quite straightforward to conduct and requires only sample dilution. Kits for this assay are commercially available.
Equipment: UV spectrophotometer and cuvettes, autopipettes
Calibration: Made-up and kit-supplied standard solutions of glucose in water
Services: Electricity, wash up area
Space required: Bench space depending on spectrophotometer footprint
High performance liquid chromatography (HPLC)
Description: High performance liquid chromatography (HPLC) is a technique that offers several advantages for the analysis of compounds including sugar in wine, including potential for automation, high precision and it is relatively fast. However, there is a fairly high capital cost and skilled personnel are required to operate and maintain the instrument. Generally, this technique is only used where there are other applications of HPLC being used by the winery on a routine basis (e.g. organic acids).
Equipment: High performance liquid chromatograph
Calibration: Use made-up standard solutions of sugar in water
Reagents: Mobile phase, standard solutions for calibration
Services: Electricity
Space required: Significant bench area, gas bottle storage area
References and further reading
- Amerine, M.A.; Ough, C.S. (1980) Methods for analysis of musts and wines. New York Wiley-Interscience.
- Iland, P.; Ewart, A.; Sitters, J.; Markides, A.; Bruer, N. (2000) Techniques for chemical analysis and quality monitoring during winemaking. Campbelltown, SA Patrick Iland Wine Promotions.
- Rankine, B.C. (1998) Making good wine: a manual of winemaking practice for Australia and New Zealand. South Melbourne, Sun Books (Macmillan Australia).
- Zoecklein, B.W.; Fugelsang, K.C.; Gump, B.H.; Nury, F.S. (1995) Wine analysis and production. New York Chapman & Hall.