ICUMSA News n°31 – 1997

Message from the President

With our call for nominations for President closing on the 30th June 1997 we now have two nominations: the Indian National Committee has nominated Mr Shivajirao G. Patil, presently a Vice-President of ICUMSA and Mr Patil has accepted their nomination, and the Czech National Committee has nominated Professor Giuseppe Vaccari who is considering his position before accepting. We expect to publish candidates’ manifestos in our January 1998 issue.

It is now time to consider future directions for the Commission.

When I became President in 1986, I valued greatly the discussion at Cannes on what members thought needed to be done. Out of that discussion emerged the agenda for the next three Sessions. We have largely achieved what we set out to achieve: the reorganisation of Subjects, a new Methods Book, publicity for what we are doing through ICUMSA News, writing our History and recognition of members outstanding achievements in Meritorious Service Awards.

Before enunciating our vision for the future, it is appropriate to take stock of our present situation. Things have changed over the past twelve years. On the positive side, the demands of ISO 9000, HACCP and such like have made the role of ICUMSA more relevant in that uniform methods have all of us speaking with one tongue. On the other hand, downsizing in our organisations has given us smaller budgets and fewer people with which to achieve our goals. There seems to be enthusiasm for exploring new instrumental methods that are less labour-intensive than the traditional classical wet methods.

Because of the high cost of research and development work there will be an increasing incentive to undertake collaborative projects to share the cost. This means we may have to entertain more cooperative projects like our successful measurement of the 100-degree point and rotatory dispersion of quartz at near infrared wavelengths.

My vision for the next 100 years is that we have more cooperative research that leads to the universal adoption of uniform methods. We acknowledge that we live in a changing world and are determined that we will respond to the challenges that are imposed on us. We seek to enhance the authority of ICUMSA in promoting uniform methods of sugar analysis.

Progress Report on General Subject 2: White Sugar

by Geoff Parkin (UK), Referee

Collaborative studies

Preliminary studies of the following methods published in:

GS2/3-5: The Determination of Reducing Sugars in White Sugar by the Knight & Allen EDTA Method

GS2-13: The Instrumental Determination of the Reflectance of White Sugar

GS2/3-19: The Determination of Insoluble Matter in White Sugar clearly showed that the 1994 method details needed revision. In the case of Method GS2-13 the revisions were quite minor, whilst for Methods GS2/3-5 and GS2/3-19 more extensive revisions were necessary. Therefore, the method details circulated for the full-scale collaborative tests were redated 1997, 1996 and 1996 respectively, as listed below together with the summarised findings.

GS2/3-5(1997): Six pairs of blind duplicate samples were sent to ten participating laboratories. The results show good agreement between seven of the participants. The results from the latter were also in good agreement with both the HPAEC method (Schäffler ) and the GC method (Hoebregs). Statistical evaluation of the results is in hand.

GS2-13 (1996): Five pairs of blind duplicate samples were sent to thirteen participating laboratories. The results show very good agreement between participants with the duplicates being correctly identified in each case. There was no significant bias with either of the two main instruments (Saccharoflex or Sucroflex). Statistical evaluation of the results is in hand.

GS2/3-19 (1996) This collaborative test showed a wide variation of results and generally poor agreement between the participating laboratories (five pairs of blind duplicates sent to fifteen laboratories). The disagreement was particularly marked with those samples containing high levels of insoluble material. Severe problems were also experienced by some laboratories with “difficult to filter” samples. I welcome comments from any members on our findings (Fax +44 1733 422283; e-mail GPARKIN@BRITISHSUGAR.CO.UK) but our view is that the method needs further revision, particularly in the detail relating to “difficult to filter” samples. Following such further revision, if time permits, a limited further study on two samples only will be conducted on Method GS2/3-19(1997).

Other analytical methods

In my report in “ICUMSA News” No.26, September 1996, I referred to other methods which I hoped would be pursued during this Session. Thus, following my predecessor’s Recommendation 9 (see “ICUMSA News” No. 22, September 1994) we had hoped to participate in ILSI/AOAC proposed ring tests utilising GFAAS to determine arsenic and copper in sugars. Recently I was given to understand that there are no such proposed tests in the offing, but I am now planning to discuss this matter with the appropriate AOAC International General Referee. As it seems too late to participate in a full-scale study, my stop-gap proposal is for the British Sugar GFAAS method for arsenic, cadmium, copper and iron to be written up to replace Method GS2/3-23 as a Tentative method in the Methods Book. If any member wishes to suggest an alternative procedure, then I would be pleased to hear their views.

As yet I have no information on the progress of possible methods to replace Method GS2/1/3-15: Moisture by Loss on Drying, but I am seeking information from those who wished to carry out such work.

Recommendation 12 at the 21st Session conference (see ICUMSA News No. 22, September 1994) was aimed at getting the Tentatively adopted Coca-Cola method for acid-floc included in the Supplement to the Methods Book. A worldwide survey which I carried out showed that there were several variants of the original Coca-Cola method in use to test for acid-floc, as well as some other companies’ methods. I am seeking an explanation from the Coca-Cola company about the variants and whether they want to describe to me their “official” method. With such information I hope to be able to come to an informed decision about the merits or otherwise of including their method in the ICUMSA Methods Book. It is possible that no method can be included, even at Tentative status. I would therefore greatly appreciate having members views on my not taking any action on Recommendation No.12(1994) for this Subject in 1998.

Progress Report on Subject 5: Dry Substance

by G. Vaccari (Italy), Referee for Subject 5

Following up my last Progress Report in ICUMSA News No. 25, September 1995 (Zuckerind. 120 (1995) 791) and bearing in mind, that Referee’s final Report must be ready by the end of this year, I would like to present a picture of what we have done under Subject 5 and to seek the opinions both of the Associate Referees and other scientists working in this subject area and about some points as follows.

First of all, I must point out that following our programme it was possible to organise a ring-test of the application of the modern Karl Fischer method to the analysis of cane and beet molasses, as well as of cane raw sugar. In fact, the minimum number of participants in the ring-test was achieved; each of them received from Mr Faviell the relevant samples of cane molasses and raw sugar, whilst samples of beet molasses were sent out from Italy. Unfortunately, not all of the participants were able to complete their analyses in a short time as scheduled, so that the results could have been affected. These results have been submitted to Mary An Godshall, the Referee for Subject 3 “Method Format, Collaborative Testing and Statistical Treatment of Data”. She is now working on the statistical evaluation of these data in cooperation with Mrs M. Nemeth of the Monsanto Company. The results of their evaluation and subsequently the proposal regarding adoption of the method as Official will be discussed in the final Report.

As far as NIR spectroscopy is concerned, I was not inclined to set up specific ring-tests, either due to the limited number of available participants or because of the objective doubts put forward by some of them. We have to realise that the NIR technique is really a continuously evolving technique but it can only predict and not determine data. In other words, although it seems today possible to transfer calibration curves from one instrument to another, even one manufactured by another company, the NIR technique always needs another Official methodology for calibration.

This situation affects the type of status which ICUMSA might ascribe to such an analytical method. The opinions of anyone interested in this particular question would therefore be welcome.

A similar problem applies to the utilisation of other instruments based on either Infrared radiation (Omnimark, Sartorius, Arizona Instruments, Mettler etc) and on other physical principles e.g. a dielectric constant meter (Euromix) for the determination of the moisture content (loss on drying) of sugar. Such instruments, which require previous calibration and comparison with traditional methods of analysis, can be advantageously used for factory control purposes because of their very rapid response time. Consequently, it seems difficult to imagine ICUMSA recommending some uniform procedure for such measurements. Again, on this particular item, the opinions of interested analysts would be welcome. I am available for comments on Fax +39 532 291 168, e-mail Vcg@IFEUNIV.UNIFE.IT.

Comment from the Editor

Prof. Vaccari raises questions regarding ICUMSA recommending methods such as NIR, Infrared Radiation, or those depending on the dielectric properties, because they have to be calibrated using traditional methods.

My personal opinion is that these methods have similar characteristics to RDS and conductivity ash, for example, neither of which gives the exact dry substance or the gravimetric ash, respectively. All such methods can be made Official providing they stand up to collaborative testing.

Progress Report on Subject 15: Reducing Sugars

by L.B. Jørgensen (Denmark), Referee for Subject 15

Collaborative tests are currently in progress to find at least one classical method that can be used for the determination of reducing sugars in raw sugar and in white sugar. In view of the problems experienced in earlier collaborative work in this Subject a dummy run was carried out prior to the actual collaborative tests. The status of this work is as follows:

Reducing Sugars in White Sugar. Two methods are being collaboratively tested. It was initially intended to use the Berlin Institute method for the determination of reducing sugars in white sugar. Preliminary investigations, however, showed the Modified Ofner Titrimetric Method, as written by Dr. Emmerich, to be more suitable than the Berlin Institute method for this purpose. These findings are confirmed by previous ICUMSA work. As such the Modified Ofner method is being collaboratively tested instead of the Berlin Institute method. The collaborative test of the Knight & Allen method (ICUMSA method GS2/3-5) is being conducted by G. Parkin, Referee of General Subject 2 (see accompanying report).

Reducing Sugars in Raw Sugar. Three methods are being collaboratively tested for the determination of reducing sugars in raw sugar.

These are the Lane & Eynon method (ICUMSA method GS1/3/7-3), the Berlin Institute method (provisionally numbered GS1-5) and the Luff-Schoorl method (provisionally numbered GS1-9).

As part of the dummy run, participating laboratories were supplied with four samples, i.e. pairs of both raw beet and raw cane sugar. The reducing sugar content of the raw beet sugar samples fell well within the range of that of white sugar. This proved to be below the limit of reliable measurement for both the Lane & Eynon and the Berlin Institute methods, with the 95% confidence limit falling into negative figures. This meant some participants were unable to detect the presence of any reducing sugar in the raw beet sugar with either method. As a result, the full-scale collaborative tests on raw sugar have been confined to raw cane sugar only.

The dummy run proved very helpful in identifying and resolving some of the practical problems experienced with the individual methods prior to the actual collaborative tests which are now in progress.

As part of the collaborative tests, 10 samples of sugar have been sent out to at least eight different laboratories around the world for testing by each of the methods. The results are currently being received for evaluation and will be reported upon at the next ICUMSA session in 1998.

Editor: Rud Frik Madsen, Strandpromenaden 38, 4900 Nakskov, Denmark – Tel: +45 5392 1675; Fax +45 5495 1675, e-mail