ICUMSA News n°12 – 1991

Message from thew President


Mr Emile Burzawa has left Sogelerg-GTS and has resigned as Referee for Subject 10, Enzymatic Methods. Announcements concerning the appointment of Referees for Subjects G3, 10 and 17 will be made shortly. Any member wishing to participate in the work of any of the Refereeships who has not yet advised either the Referee or his National Committee, should do so now without delay.

The President is particularly interested in having as Associate Referees for Subject 1 Constitution and By Laws, anyone who is vitally interested in the reworking of that document to remove ambiguities. It is anticipated that a start will be made on this task early July.

Methods Book

Brief mention was made in the September 1990 issue of ICUMSA News of our intention to produce a new methods book to supersede the one edited by Professor F. Schneider in 1978. The new book is expected to have a loose-leaf format, permitting methods to be added, deleted or altered at any time without the work becoming out of date. It will also be possible to buy single copies of a method much the same as standards can be purchased.

The book will contain those methods approved for use in analysing the various sugar products which are the concerns of the General Refereeships. Reference methods and those for routine factory control and research use will also be included. Methods will be presented in a uniform, internationally accepted format. This will include, where available, the repeatability and reproducibility data obtained from collaborative testing.

The methods will be written up by Referees and their Associates then edited by John Dutton. Manager ICUMSA Publications. The Referee for Subject 3 Method format, collaborative testing and statistical treatment of data, will have oversight of the matters concerning that Refereeship. John Dutton will also be responsible for publication and sale of both the individual methods and the loose-leaf book.

The new book is expected to be available in 1994. Since the loose-leaf concept permits it to be added to or altered, it is never really “finished”. It is envisaged that members purchasing the complete book will then pay an annual contribution fee for new methods and changes whenever they take place. Since final decisions concerning the methods book have not yet been taken, comments or suggestions from readers would be welcome.


It is with great sadness that we advise the death of Dr Charles Tsang on 27 March the age of 39 years, following a period of serious illness. Delegates to the 20th Session at Colorado Springs will recall that Dr Tsang as General Referee for Cane Sugar Processing presented a Report which laid the foundations for this new Refereeship. The Commission is grateful for this pioneer contribution and extends its deepest sympathy to Dr Tsang’s family.

ICUMSA publications

by J. V. Dutton


The Proceedings of the 20th Session which are now available have been produced rather more promptly than has been the case for many years and for this we must thank teamwork and today’s methods of communication via facsimile and diskettes. The teamwork involved Dr Milan Vender, who has done all the typesetting in Australia, with editorial support from our President, General Secretary and others including Dr Albert Emmerich in particular. It is to be hoped that a similar team effort may be possible to expedite writing up the methods, to which our President refers above.

The Proceedings have been printed in Australia, but orders should still be addressed to ‘ICUMSA Publications Department, c/o British Sugar Technical Centre, Colney, Norwich, NR4 7UB, England’. The prices are £40.00 (surface mail) and £48.00 (airmail). Copies are now being despatched from Australia and this will continue until August when it is expected that it will be possible to supply the books directly from the Publications Department in England.

We believe we have a publication which is a worthy successor to earlier Proceedings series. The organisational changes as a consequence of the President’s reform will be evident, as well as the way in which ICUMSA is facing up to the legislative, quality assurance and processing analytical needs of the industry as we approach the turn of this century. The book provides rather more than an analytical ‘state-of-the-art’ statement and especially in the discussion reports the reader has an opp011unity to study differing points of view about methods and future developments. For your own views on the Proceedings, please let us hear them through this medium of ICUMSA News.

ICUMSA’s history

Most people will know that we were asked in Cannes to start preparing a history to be published in ICUMSA’s centenary year 1997. Ron Plews, as a member of the Publications Committee, volunteered to start this off on the assumption that help would be forthcoming. However, apart from some advice on style, he has received no response from Chairmen of National Committees to his request for help. Because of this weak response we wish to re-examine the desirability of proceeding with this project. Whilst it remains our view that the contribution of ICUMSA to sugar analysis remains unchallengeable, there may not be sufficient threads with which to weave a history. We invite your views either by letter to the News or direct to Ron Plews so that this project or some other scheme might proceed in due time, or the whole idea be abandoned if that is everyone’s wish. As with our present publications we probably need a committed team!

General Subject 8: Beet sugar processing

Status after the 20th Session

by J.P. Lescure, Referee

Achievements of the 20th Session

When drawing up a list of priorities, the factory’s sugar balance proved to have the highest priority. Studies comparing alternative methods for measuring sugar content show that direct polarisation is invariably the method with the best precision and for this reason it will remain the preferred choice for process control. However, thanks to having some analytical tools (like the continuous flow analyser used by IRIS for fifteen years), sucrose determinations using the enzymatic method can be ca1Tied out very precisely and corrections to the analysis of juice and molasses can be made to explain the anomalies in the sugar balance.

Plans for current Session

At the 20th Session meeting, a working group discussed the objectives to be pursued in the coming years. Once the work on losses in the sugar balance is complete, the next priority will be given to pulp analysis. Since pulp is an important co-product of the industry and its analysis is not dealt with elsewhere in ICUMSA, it was decided to test methods for measuring sodium, potassium, calcium, nitrogen, dry substance, total ash, total sugar and sand content.

Other priorities concern process control and quality assurance. In the former, accurate methods for checking on-line analytical techniques are required as well as the development of methods for determining lactic acid, nitrogen and amide content. Concerning quality assurance, it is important that results can be compared between laboratories and some standardisation of methods used for this purpose would seem to be called for.


The amount of work involved in the above is quite significant. It will need collaboration with Referees in specialist areas – ash, chromatographic techniques for both sugar and non-sugar substances and eventually for statistical treatment of data. We propose to start right away and your Referee invites all who wish to participate to contact him to indicate the area of their interest.

Changes in solution colour measurement

Colour, Turbidity and Reflectance Measurement

by S. Akoglu, Referee Subject 7


At the 17th Session of I CUMSA (1978) it was decided that the measurement of solution colour in all sugars should involve preparing a solution and adjusting its pH to 7.0, filtering it, and then measuring its absorbance at either 420 or 560 nm. The results determined at 420 nm wavelength were traditionally called Method 4 colours while at 560 nm they were Method 2 colours. Method 2 was recommended for the determination of colour in dark sugars such as raw sugars even though laboratories engaged in raw sugars analysis invariably used 420 nm. With the setting up of General Refereeships involving specific sugar products, ICUMSA has revised and clarified its position on some aspects of solution colour determination.

Method changes

Raw Sugars

The use of 560 nm for measurement of colour in raw sugar is now withdrawn and all determinations will be done at 420 nm. While investigation into the use of buffers for pH adjustment continues, for the present such adjustment will be made with dilute hydrochloric acid or sodium hydroxide. Because filtration of raw sugar solutions through 0.45 μm membranes is slow, kieselguhr filtration will generally still be employed. Research is to continue on finding a more satisfactory filtration system.

White Sugars

A major change has been made with the Official Adoption of a triethanolamine-hydrochloric acid buffer solution (TEA/HCI) as the solvent for white sugar in preparing the solution at pH 7.0 for measurement at 420 nm.

Brown Sugars

While the measurement of solution colour in specialty refined sugars like Demerara, light and dark brown soft sugars is not of great commercial significance, a preliminary collaborative test was reported at the 20th Session using the Official Method 4. Further studies are envisaged so that a specific recommendation can be made.

Further studies

Members with an interest in solution colour in any sugar product should contact the appropriate Referees so that all points of view may be properly debated and assessed, and participation in any collaborative testing will be fully representative. Editor: Dr. R. Pieck, Klein Spanuit 9, B-3300 Tienen. Belgium, May 1991 – Telephone +32/16-812436; Telex 22251; Fax: +32/16-820317