Use of filtration and buffers in raw sugar colour measurements

Colour, an important parameter in quality evaluation of raw sugar solutions, is sensitive to and greatly affected by pH and turbidity of the solutions. Buffers and filtration were used to control the problematic colour fluctuations due to the above factors. The buffers used to maintain pH included glutaric acid, citric acid, 3-(N-morpholino)-2-hydroxy-propane sulphonic acid (MOPSO), triethanolamine (TEA) and tris-hydroxymethy-aminomethane (Tris). The turbidity was minimised by using glass-fibre filters with a 0·7-μm pore size in series. The results showed that by using MOPSO buffer and three glass-fibre filters in series, the effect of pH and turbidity on colour measurement of raw sugar solutions can be minimised. MOPSO buffer combined excellent pH stabilisation at pH 7·00 and limited colour alteration.