Rapid analytical methods for colour and ash in raw sugar - results of 1996 season

Raw sugar samples produced during the 1996 season were analysed by the ICUMSA conductivity ash method and the new MOPS buffer/filtration colour method. Colour results by the new MOPS buffer/filtration method were found to be higher than the old method by 1.5% when the Millipore Millex HA filters were used. With Sartorius Minisart filters and Whatman polypropylene filters of the same pore size, the differences increased to 9.0% and 11.5% respectively, due to incomplete removal of turbidity. Buffer adjustment to pH 4 by succinate buffer and pH 9 by AMPSO buffer was tested on 17 sugars. Results showed good correlation with the current methods. The ICUMSA method of conductivity ash measurement compared to the current single sulphation method showed an overall increase of 12.4% compared to 12.5% in 1995. The increase was still greater for VHP (16.9%) than other brands but differences between districts were not statistically significant.