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BACKGROUND
Determination of the sugar content in a food sample is important. In developed countries they have strict food and drug regulations and demand the details of the ingredients labelled on the food product. Here we will discuss the dinitrosalicalic acid (DNSA) method to determine the reducing sugar content of a sample.1
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REQUIREMENTS
Apparatus: Test tube,
Burner/spirit lamp,
UV-Vis spectrophotometer.
Materials: Dinitrosalicalic acid (DNSA),
Potassium sodium tartarate (40%) solution,
Glucose.
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PROCEDURE
Add 3 ml of 1% DNSA solution to 3 ml of glucose solution. Heat the test tube at 95 C for 10-15 min, till brown colour appears, allow the solution to cool down and add 1 ml of 40% NaK tartarate solution and record the OD at 575 nm in a spectrophotometer.
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CONCLUSION
The change of colour of the solution is due to reaction of the free –OH group of the reducing sugar with the DNSA, which is facilitated by heating. The Na-K tartarate solution intensifies and fixes the colour of the solution. Using this method, one can prepare a standard curve using the same procedure for known concentration of a reducing sugar and can estimate the concentration in unknown sample.
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REFERENCES
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Sun Y, Cheng JJ. Dilute acid pretreatment of rye straw and bermudagrass for ethanol production. Bioresource technology, 2005;96(14):1599-606.
