Light travels in a pure sucrose solution in a straight line. If the sugar solution contains suspended solids, agglomerates of coloidal matter or a very high molecular weight compounds, light will be scattered and sugar solution becomes turbid.
Turbidity of a sugar solution can be measured in two ways: by measuring the quantity of light scattered; or by measuring the solution colour before and after filtrate the solution through a 0.45 micrometer filter.
The first measurement is made in special instruments named nephelometers. The instrument is calibrated previously with standards solutions with different turbidities and the problem solution is placed in a cuvette and light scattered is measured.
The second measurement system applies the ICUMSA color measurement before and after filtration (ICUMSA Method GS2/3-18). Turbidity in IU will be the difference of color (IU) before and after filtration. The value can be expressed in ICUMSA unities or in European turbidity points that are the ICUMSA turbidity divided by 7.5 (Roge et al., 2007).
Turbidity in sugar solutions is an inconvenient both for the process and for sugar users.
In beet syrups turbidity will decrease crystals growth velocity during crystallization and affect crystals morphology (Roge et al., 2007).
In sugar crystals, compounds that provokes turbidity can be placed in the crystal surface or in the crystal interior.
Microcrystals of calcium dihidrated in the crystal surface can provoke turbidity in the respective sugar solutions (Roge et al., 2007). These authors also demonstrate that there is a good correlation between calcium content in sugar ant turbidity of the respective solutions.
Macromolecules with molecular weights higher than 10,000 D and 300,000 D if present in sugar solutions can be responsible for sugar turbidity. In this case turbidity is placed in the interior of sugar crystals (Roge et al., 2007).
In white sugars with MA of 0.5 mm or lower, turbidity of respective solutions increase with decrease of MA (Roge et al., 2007).
Roge B., A. Bebsoussi, M. Mathlouthi, 2007, Effects of calcium on white sugar turbidity, Zuckerindustrie, n.3,