Analysis of natural sweeteners

The assessment of the refractometric solids content, generally referred to as the Brix value, is one of die basic tests that is carried out in today s soft drinks 

As with all methods, this approach has some limitations it uses acetonitrile, which is toxic, and the separation of glucose from fructose can sometimes be problematic after extended use of the column. However, sample preparation is easy since it requires only dilution to the required level (often 1 10) and filtration prior to analysis to remove particulate materials, which protects and extends the useful life of the column. The degradation of the resolution between glucose and fructose is caused by the partial inactivation of the column by materials in the matrix, but this resolution can be recovered by reducing the acetonitrile concentration in the solvent. The same column can also be used to assay the level of ascorbic acid (vitamin C) in a soft drink or fruit juice, although different detection and solvent systems are used. 

CHEMISTRY AND TECHNOLOGY OF SOFT DRINKS AND FRUIT JUICES 

The second method, using refractive index (RI) detection, is carried out using a resin-based polymer column. Sucrose elutes first from this column, followed by glucose, fructose and then sorbitol. This type of column is generally more robust than the amino-bonded column and if handled well will last much longer however, it is around three times more expensive. The method has been collaboratively tested for the analysis of sugars and sorbitol in fruit juices by the IFU. The HPLC conditions are given below. 

HPLC conditions column benzene divinylstyrene sulphonated resin in the calcium form 300 X 7.5 mm solvent = 0.1 mM Ca EDTA in HPLC-grade water at 0.6 ml/min at 80°C using Rl detection. 

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