ICUMSA News n°4 – 1988

Message from the President

In the May issue we commented on the methods which seemed appropriate for the analysis of raw sugar, white sugar and molasses. Following discussion with the respective General Referees we are able to report their thinking with respect to the analysis of cane, beet and their processing, together with refined products other than white sugar.

Subject G5: Cane

Mr Brokensha, General Referee reports that the full width hatch method of sampling will be tested with the intention of seeking tentative status at the 20th Session. The method of cane analysis which will be pursued is the wet disintegrator cum indirect fibre method which gained tentative status at the 19th Session. As regards the fibre assessment, work will also be carried out on an independent direct method and the two fibre methods (direct and indirect) will be compared.

There are competing methods of sampling and analysis which are set down for further investigation. The combination of core sampling and analysis using the hydraulic press method is practised in many countries and work is to continue on these methods.

The GLC method for determining sucrose in cane juice presently enjoys tentative status (19th Session) and effort will be directed towards meeting the format and testing requirements so that it can achieve official status. Because HPLC presents the opportunity to determine sucrose in cane juice without the derivatisation needed for GLC, it also represents an important competing method and will be further investigated.

Efforts will also be directed towards finding a suitable non-toxic reagent to replace the lead salts currently used for clarifying cane juice samples prior to polarimetric analysis.

Subject G6: Beet

The General Referee, Professor Mauch summarizes the position with respect to beet analysis. At present ICUMSA does not have any methods for sampling beet and preparing brei. Given the obvious importance of these preparatory operations, effort will be made in the present session to standardize a method.

In the routine method for determining sucrose content, parts of the method have official status while other parts have either tentative or no status at all. It is clearly desirable to resolve these shortcomings so that a single methodology acceptable to all users can gain official recognition. There also exists two isotope dilution methods with official status for determining sucrose content. These methods, the Hirschmüller and Hörning and that of Sibley et al., are regarded as basic methods because they fundamentally determine sucrose but are very time consuming. Sucrose determination by gas chromatography is another basic method which enjoys tentative status. It would seem desirable to adopt a single official basic method. In this way ICUMSA would be recommending the most appropriate method for accurately measuring sucrose in beet.

Concerning the measurement of a-amino nitrogen content there are two methods – the official ninhydrin method and the tentatively adopted blue number method. Here too it would be desirable to settle on one or the other to be the officially recognized method.

There are a number of determinations important to the analysis of beet but which have no ICUMSA methods. The Referee is keen to entertain discussion on methods for dry substance, ash, potassium and sodium, raffinose, invert sugar, saponin, total non-sucrose, and the macro-molecular and colloidal substances content. He also believes there may be a place for tests to determine mechanical properties of beet like shear strength, cutting quality, elastic properties and so forth.

Subject G7: Cane sugar processing

Dr Charles Tsang, General Referee has considered carefully the recommendations of the 19th Session and drawn up a list of substances for which analytical methods should be selected as suitable for cane sugar processing. In process syrups and liquors, methods for determining sucrose, glucose and fructose, ash, colour and tri-, oligo- and polysaccharides are sought. Standard methods for the determination of sugars in bagasse, filter mud and scums, and process effluents require investigation. The determination of moisture in bagasse is important in sugar milling. The Referee would welcome discussion about the need for physical measurements such as density of products and crystallization rate in process syrups.

Subject G8: Beet sugar processing

The General Referee, Mr J.P. Lescure has consulted with his Associate Referees and produced a comprehensive outline of proposed activities for the 20th Session. The main thrust will be to propose methods for chemical balance purposes. The most important role of the technologist in a factory is to be able to account for the substances entering the process in beet and leaving the process in pulp and molasses. The development of analytical methods for sugar products will be undertaken by other referees. Because the use to which the analyses are put differs from the requirements for the commercial transactions of buying and selling beet and molasses, it is felt that the methods for beet sugar processing should be appropriate to that particular application. Because the,requirements for reproducibility between factories do not have the same importance as in commercial transactions, the referee questions whether the same rigour and expense of collaborative testing is required. He proposes that collaboration might involve fewer laboratories so that only the strict technical requirements are satisfied.

The high priority tasks to be attempted in the current session involve collaborative testing competing methods for sucrose determination in beet cossettes, thick juice and molasses. Two HPLC methods, GLC and polarization will be investigated.

As a result of reallocating recommendations of the 19th Session, collaborative testing of a number of other methods will be discussed and untertaken only if resources permit. The next most important goal after the chemical balance will be the nomination of methods for reducing sugar on process materials, the determination of pectins and polysaccharides extracted during diffusion and eliminated to a greater or lesser extent in juice purification, and the measurement of sulphur dioxide, ammonia and formaldehyde for factory control purposes.

Subject G3: Refined Sugar products other than white sugars

The General Referee, Mr R.W. Plews reports having received a good response to his invitation to appoint Associate Referees. Representatives from eight countries – Australia, Canada, Cuba, France, Germany, South Africa and U.S.A. have expressed interest in participating in the work of this subject. Because the subject is new and since its scope had not been defined previously, discussion is taking place to decide what particular products should be dealt with here. At the same time, methods which are currently in use for the analysis of refined products are being discussed with a view to deciding which ones should be promoted for which products. Methods under consideration include Karl Fischer moisture, fructose and glucose by enzymatic methods, sucrose by GLC, HPLC analysis using reverse phase cation exchange columns, polarization, reducing sugars, ash, non- sugars, betaine, particle size, colour and microbiological methods. Some of these methods already enjoy official status while others hold tentative status. In any event, once methods appropriate to the analysis of particular refined products have been selected, there will be a need for collaborative testing to establish repeatability and reproducibility values in accordance with the new requirements of Subject 3.

Collaborative Testing Programmes

Subject Gl: Raw Sugar

The General Referee for Subject G 1, Mr Robert McCowage indicates that while present methods will be examined to see if any conform to recently announced IUP AC requirements for collaborative testing, he anticipates conducting such tests on the analytical methods for determination of reducing sugars, sulphated ash, conductivity ash, moisture content, colour, pH and fine grain in raw sugar.

All Associate Referees for Subject G 1 will be invited to participate in collaborative testing of these procedures. Others are invited to contact the General Referee directly if they have an interest in participating. It is intended to circulate one set of sugars on which all the above tests would be undertaken. Accordingly, collaborators with an interest in any number of the above procedures can be accommodated.

Subject 15: Reducing Sugars

The Referee for Subject 15, Mr J. Laursen, is planning two collaborative test programmes to pursue Recommendations to investigate the Luff Schoorl method and the sucrose correction factor for the constant volume modification of the Lane and Eynon method.

The planned test for the Luff Schoorl method will involve two samples each of beet and cane molasses and one sample of Quentin process beet molasses. A comparison with the Lane and Eynon method will be conducted with the same samples.

The sucrose correction factor for the Lane and Eynon method will be collaboratively tested using a single sample of sucrose with an invert content of less than 10 mg/kg. Factors will be determined for the addition of zero to 20 g of sucrose in 2 g increments.

For this latter test programme, the Referee is looking for at least eight participating laboratories, this being the number advised by the Subject 3 Working Group on Collaborative Studies. Any laboratory wishing to participate in one or the other or both of these studies, and has not already indicated, is urged to contact the Referee without delay (NS De Danske Sukkerfabrikker, 5, Langebrogade, PO Box 17, DK-1001 Copenhagen K, Denmark, Telephone 1546130, Telex 31430 dansuk dk, Fax 1540044).


Miss Mary O’Sullivan is now retired from Irish Sugar plc and has announced her resignation from the chairmanship of the Irish National Committee and Vice President ICUMSA. Mr Tadg Quill has been nominated as new chairman of the Irish National Committee. The commission deeply appreciates the contribution Mary has made over many years especially her involvement in hosting the 18th Session in Dublin. We all wish her a long and happy retirement.