ICUMSA News n°16 – 1992

Message from the President

Methods Book Update

A Table of Contents and Index has been worked up for the new Methods Book. This has been sent as a circular to Chairmen of National Committees and Referees for comment. We have volunteers to write up sixtytwo out of a total of ninetyone analytical methods, specifications and standards. Anyone else wishing to participate in this work should contact one of the Referees or Mr Dutton.

It is expected that the new book will contain 240 pages in A4-size loose leaf format in a ring binder. After the initial publication, it is envisaged that supplements will be provided from time to time to add new methods to the book and revise old methods. Also, copies of individual methods will be available. We are aiming to produce the book by the end of 1993.

Those methods which still require collaborative testing to achieve Official Status in the new publication should be given high priority in the work programmes of Subject Referees. Mrs Godshall is available to advise on the design of collaborative tests to meet the standards called for at the IUPAC Harmonization Workshop.

General Subject 7:

Analytical Methods for Cane Sugar Processing

by Owen Crees, Referee

The list of analytical methods for cane sugar processing proposed for the new Methods Book is reproduced below (p. 730). This article discusses how the list was drawn up and the justification for the methods included. We seek the views of all technologists on any aspect of the methods included in the list.

There are three principal factors which have been used in preparing the list of methods for General Subject 7. Firstly, considerable importance has been placed on establishing a set of common and agreed methods so that published data will have the same significance for everyone. There are numerous analytical methods which are important to Cane Sugar Processing. For many parameters there are also several different procedures or variations thereof used around the world. Many of the variations have been developed and are used to meet the specific needs of individual factories, due to differences in factors such as cane variety. cane quality, factory operations, sugar products and by-products.

The second factor has been a desire to take a more progressive attitude towards technical advancement by adopting new, chemically specific methods as quickly as possible. For example, HPLC and GLC can now readily provide accurate data on the concentrations of sucrose, individual reducing sugars and other impurities. However, the technical advances must be tempered by the third factor which is the recognition that significant numbers of factories do not have access to the equipment and skills required by the emerging methods. Again, HPLC is widely used for sucrose and reducing sugar analyses in Australian factories, but the equipment and skilled operators are simply not available in some parts of the world.

It is therefore not an easy task to determine just which methods should be included in the book. The methods recommended for inclusion comprise a blend of traditional, robust procedures and new analytical technologies.

In selecting the methods to be included for General Subject 7, it was considered by the Referee that the easiest approach was to start with the methods used in one or two countries, to modify the list and to seek the most appropriate methods for general use. To expedite the procedure, the methods used by the Australian and South African industries formed the initial list. The opinions, ideas and suggestions of all Associate Referees were sought, and the list progressively modified.

In the final list, it might appear that we have chosen a disproportionate number of methods drawn from the Australian and South African Laboratory Manuals. We have cited those methods because they are equivalent to similar methods used in many cane sugar industries throughout the world. They are also already well documented and will require very little effort to prepare them for the new book.

Proposed analytical methods for cane sugar processing

1. Polarimetric sucrose content and refractometric dry substance in sugar caneGeneral Subject 5
Milling train analysis
1. Polarimetric sucrose content and refractometric dry substance in cane by wet disintegrationProc. 19th Session ICUMSA. p. 173-5
3. Moisture in cane and bagasse by dryingSASTA Method 8.1.3
4. Polarimetric sucrose content of open cellsSASTA Method 8.1.7
Juice and filter products
5. Phosphate (total and soluble) in juiceBSES Laboratory Manual Method 8
6. Starch in juice and syrupGeneral Subject I
7. Dextran in juice and syrupGeneral Subject I
8. Turbidity in clarified juiceBSES Laboratory Manual Method 10
9. Sulphite in juice
10. Calcium and magnesium in juiceCane Sugar Handbook, 11th Ed. p. 917
11. Fibre in juice, mud and filter cakeBSES Laboratory Manual Method 13
12. Mud solids in juice, mud and filter cakeBSES Laboratory Manual Method 14
13. Polarimetric sucrose content of filter cakeBSES Laboratory Manual Method 11
14. Moisture in filter cakeBSES Laboratory Manual Method 12
Sugar house products
15. Sucrose in sugar house products by double polarisationGeneral Subject 4
16. Soluble solids in sugar house products by refractometerSpecifications and Standards
17. Dry substance in sugar house products by dryingGeneral Subject 4
18. Reducing sugars in juice, syrup and sugar house products (Lane & Eynon constant volume method)General Subject 1
19. Ash in juice and pan products by double sulphationGeneral Subject 4
20. Sucrose and reducing sugars by HPLCSubject 8
21. Polarimetric sucrose content and dry substanceGeneral Subject 4
SugarGeneral Subject l (Raw Sugar)
General Subject 2 (White Sugar)
22. Available calcium oxide in limeASTM C15, 1974, 284
23. Sucrose soluble alkali in limeSASTA Method 9.4.1
24. Analysis of water from cane washing plants

Subject 9:

Chromatographic techniques for non-sugars

by P. Bourlet (IRIS, France)

The work reported at the 20th Session indicated that ion chromatography (IC) techniques were potentially useful tools for the determination of ionic substances in sugar products. Many data for such non-sugars at various stages of factory processing could then be easily obtained, but it is not very easy to handle all these results as a whole.

In a recent paper, Feinberg [1] described what chemometric methods could bring to analytical chemistry. Part of his paper deals with the statistical analysis of results of IC determinations of inorganic anions and organic acids, as well as measurements of inorganic cations by flame spectrophotometry [2]. The aim of his work was to develop a scheme for quality control in order to improve the sugar manufacturing process; the idea being to use the impurities instead of purities, as is the case today, for factory control. So, he investigated the potential determining 15 chemical parameters on samples taken at 35 sampling points right through a sugar factory. In two years, he amassed more than 10,000 individual data on 718 samples. The statistical concept [3] of “‘principle component analysis” (ACP in French) applied to the results gave him three principal components, one of which was related to the sample purities. This included parameters for potassium, sodium, lactate, formiate, acetate, fumarate and pyrrolidone carboxylic acid. The second principal component was related to substances that are eliminated in purification and included phosphate, calcium. citrate, oxalate and malate. The study also showed that there was a redundancy in the analyses needed for control of the sugar process. Thus, the number of products to be analysed could be reduced to about 10, whilst the number of parameters determined could also be reduced. As examples, sulphates, phosphate, chloride and nitrate did not need to be determined by analysis because their levels could be deduced from the other analytical parameters.

Whilst this work is still in its infancy, it does signal the potential of chemometrics to get more valuable information from such analytical data in the future. Thielecke [4] has also recently signalled the importance of IC for the analysis of anions in sugar beet extracts in order to better assess their technical value.

For the present Session we have, of course, to keep up with all new developments of IC in process control. Identifying which improvements have already been achieved using IC for non-sugars in either the beet or cane areas seems to be the first priority for practising factory technologists. This would lead us to develop the writing-up of standardised and adopted technical methods.

Amongst the Recommendations adopted at the 20th Session was one related to the determination of sulphite in white sugar. Such a determination by IC does not seem appropriate in view of the recent decision by the CEN Working Group 275 to adopt an enzymatic method for such low levels, not only in sugars but in foods in general. That Working Group proposed a modification of the Monier-Williams method for high levels of sulphite; it consists of the analysis by IC of sulphate ions formed by the oxidation of sulphite. We think it might be interesting to test this method for syrups and molasses and to compare the results with those obtained by direct IC determination of the sulphite.

To conclude we must recall that ion chromatography offers many possibilities for end-product analyses; however, any development of a commercial method must be subject to a Recommendation of the General Referee within whose Subject area it falls.

Editor: Dr. R. Pieck. Donystraat 85, B-3300 Tienen, Belgium – Telephone: +32 16 823 096 – Fax: +32 1 6 820 826 – Telex: 27 1 05