Towards uniform methods of sugar analysis

Introduction For a hundred years, sugar as a commodity was traded according to types. These types were mostly based on place of origin. Under this system, a distinction was drawn between dark and light or coated sugars. Refineries evaluated sugar visually according to colour, with dark types commanding lower prices. As the beet sugar industry began to flourish in the second half of the 19th century, continental sugar exports, especially those to Great Britain, attained increasing importance. Although analysis and polarimetry made an objective classification of raw sugar quality possible, the results were variable, due to different methods and equipment in sugar analysis. Within the territory of the German Customs Union (Deutscher Zollverein), the first agreement on the use of uniform methods for sugar analysis was made in 1869. Because international standards were lacking, chemists in different countries did not work with uniformly calibrated instruments or equivalent solutions, units of measurements or temperatures. Differences arose especially in polarimetric sugar determinations. These differences caused difficulties in international sugar trading. The desire for an agreement on the use of uniform analytical methods had been growing stronger since the beginning of the 1880s. Sugar manufacturers and commercial chemists from the exporting and importing countries discussed the problems in international conferences. The requirement was for the graduation and calibration of instruments, as well as a working temperature of 20 °C, together with the establishment of an International Commission on the standardisation of methods. Herzfeld’s suggestion, to standardise polarimeters with internationally-certified standard quartz plates, finally succeeded in 1897.

On the development of sugar analysis and sugar evaluation

It was the Berlin chemist, Andreas Sigismund Marggraf, the discoverer of beet sugar, who, 250 years ago, conducted the first analytical sugar determination in plant saps. Using alcohol extraction, he obtained a syrup in which sugar crystals formed as it dried [1]. Until about 150 years ago, the trade and users judged the quality of cone sugar by sight as well as by hardness and sound. Exceptionally white and shiny cone sugar could be produced by repeated refining of the sugar. Inferior grades were speckled, containing both brown and white sugar. The sugar refineries purchased imported cane sugar at auctions and for this purpose in Amsterdam and Rotterdam a distinction was made between seven grades [2]: dark brown, brown, light brown, blond or yellow, grey, half-white and white. These divisions left a lot of room for personal opinion, so 21 (later only 18) standard samples were collected and these were used as a basis for sugar auctions for the first time in 1839 in Holland. In order to protect the standard samples from damage, they were contained in sealed metal boxes. Later evaluation was carried out on the basis of printed colour-tables. This Dutch sugar standard was used in the trade for about 100 years.