ICUMSA News n°20 – 1994

Message of the President

Future of ICUMSA

This will be the last opportunity before our 21st Session to discuss our future directions, but I would first like to review our past and present. We have been in existence since 1897, a period of 96 years of which thirty odd years were lost due to the World Wars. There have been continuous operations since the Tenth Session held in 1949. The size of our membership, if judged by the attendance at the Session meetings, reached its maximum in the 1970′ s and has remained fairly steady since then.

The level of funding in real terms expended by sugar companies on the Commission’s activities has undoubtedly declined over the last twenty years. Probably this is related to the general profitability of the sugar industry.

The role of the Commission at its inception was to promote dialogue and obtain agreement between countries on methods of analysis to be used especially for trade in sugar products. While this role continues right up to the present, the Commission has become a technical forum for discussion of subjects of universal interest to sugar processors but not necessarily vital to the trade of sugar products.

Indeed, the reforms of the last two Sessions have been directed toward bringing the Commission back to its earlier role of being more concerned with the analytical methods applicable to commercial products.

That this has been an appropriate course is evident by the call for more rigorous documentation by international bodies like Codex Alimentarius and users of ISO 9000.

Our new Methods Book is a significant achievement of our present Session and it will be the centre piece of our future activities. Because it is a living document which can be revised and added to as necessary, it will rival the Proceedings as the reporting medium of the Commission.

With the world becoming a smaller place and trade between countries increasing with respect to the variety of sugar products manufactured, we can expect a continuing demand by authorities for our methods and for an increasing rigour in their presentation and content. I believe we need to examine the best way to undertake large collaborative projects like determining the 100-degree point at higher wavelengths.

Logically, such projects should be funded by all the Commission’s membership and all members should have input into the planning of such an undertaking.

It is also evident that there is inefficiency in the introduction and Official adoption of new analytical methods. We would benefit by streamlining this process, because we are presently achieving too little with the limited resources available to us.

At the 19th Session, we discussed briefly the need for a full-time professional secretariat. Generally, this idea was not pursued because it was believed that National Committees and sugar companies would not fund such a proposal. I still believe this is the situation today.

The present voluntary arrangements are satisfactory as long as it is possible to obtain an administration which is supported by a National Committee and sugar industry willing to provide the services required for the Commission’s day to day operation.

Standardisation in Europe: Mutual recognition of results – will ICUMSA be affected?

by Roger Wood, Food Science Laboratory Ministry of Agriculture, Fisheries and Food, Norwich NR4 7UQ, United Kingdom

There has recently been a significant change with regard to foodstuffs within the EU. This has been mainly as a result of the ,,New Approach” that has taken place. One effect of this is that vertical (commodity) Directives are now being developed within the Community in the foodstuffs area, but emphasis is being placed on horizontal Directives. The development of the vertical Directives dealing with one specific foodstuff (e.g. dealing with coffee, sugar, bread, edible ices) has, with a few exceptions, ceased.

There is, as part of, instead central to, the ,,New Approach” and of the Single Market of the Community, a need for the recognition and acceptance of results and certificates from one Member State in other Member State (i.e. ,,mutual recognition”).

In order to promote the recognition and acceptance of other Member States’ results, approved laboratories will of necessity have to conform to agreed standards of competence.

The Commission introduced an initiative in 1983 on the provision of information in the field of technical standards and regulations, this being Directive 83/189. This has reduced duplication of work by the Commission and its Working Parties by requiring the use of a technical standard if one already exists.

However, for ICUMSA, the philosophy that is being adopted by the EU may be best ascertained by consideration of the Food Control Directive that was adopted by the Community in June 1989 (Directive 89/397 /EEC).

This lays down standards of proficiency for food control laboratories (see also ICUMSA News No. 14 of December 1991) who will, on adoption of the Directive, have to use fully validated methods of analysis, i.e. methods which have been validated by collaborative trial. Industry/trade will have to follow suit to ensure that common standards are being applied.

The importance of the preparation of validated methods of analysis for foodstuffs cannot be over-emphasised. In the case of sugar it means that the work of ICUMSA in preparing a series of validated methods of analysis for the sugar sector is vital to ensure the uniform application of sugar standards.

Sucrose determination in refined sugars using mass relationships

by Francisco Perez Sanfiel, Julian Rodriguez Lopez, Ms Josefa Castro Franco, Zunilda Hernandez Barrera, Cuban National Committee


One of the methods used to determine the purity of refined sugars is by measuring the impurities present (water content, sulphated ash, reducing sugars, organic matter and raffinose for beet sugars) and to subtract this contribution from 100 % [1].

This method is more time consuming and labour intensive than direct polarimetric analysis according to the BSC method [2].

After 1982 the Commission tentatively adopted the Braunschweig method [3] and in 1990 Officially adopted it [4]. This new method, although operationally similar to the raw sugar polarisation method, attains a lower repeatability than the BSC method because the volume correction by weighing eliminates the making of the mark error and the associated flask calibration error. Its main difficulty, especially in tropical countries, is that it requires making to the mark and reading at 20 ± 0.1 °C which implies the use of thermostatted polarimetric tubes and the additional time to reach thermal equilibrium.

In order to avoid these inconveniences, a method has been developed by ICINAZ based exclusively in mass relationships (mass of sugar/mass of solution) covering an interval which straddles the normal value obtained with 26 g of sugar in 100 ml of solution and which is valid for a temperature range of 10 to 30 °C.

This paper describes the method details and results obtained in a test comparing it with the BSC method.

Method development

A mass of 26.000 g of sucrose (weighed in air) dissolved in 100 ml of solution is equivalent to 23.7097 g sucrose in 100 g of solution. Using polynomials relating density and concentration [5] we have constructed a table which permits the determination of the equivalence [6, 7] in g/100 ml of a mass/mass relationship where both the sugar and the solution are weighed in air. Where the actual mass/mass result differs from that corresponding to 26.000 g in 100 ml the following formula is used to correct the polarimetric reading:


Pt         polarimetric reading at temperature t in °C for solution as prepared

M         g/ml equivalent read from table for the m/m solution prepared

        is the corrected polarimeter reading equivalent to 26.000 g in 100 ml at temperature t in °C

If the temperature t differs from 20 °C, then polarimeter reading corrected to 20 °C is calculated:

The coefficient used takes into account changes in the length of the polarimetric tube, specific rotation and density of the solution with temperature [8, 9].

ICINAZ Method for the determination of sucrose in refined sugar

1. Weigh (to the nearest 0.1 mg) a weighing bottle (tall form) of 150 ml, clean, dry, without cap and with a plastic-coated iron mixing bar already inside.

2. Add 23.710 ± 0.001 g approx. of refined sugar and distilled water until the mass/mass relationship is within the range of the table. A very thin dropper helps to obtain this relationship. When adding distilled water do not wet the ground part of the weighing bottle.

3. Cover the weighing bottle and dissolve the sugar with the magnetic stirrer.

4. Homogenize the solution and transfer it to the polarimetric tube after two washings with the solution. Measure the temperature of reading to the nearest 0.1 °C.

5. If the mass relationship differs from 0.237097, find the equivalence in the m/v system in the table (not reproduced here) and correct the reading for the normal weight as has been indicated above.

6. If the polarisation temperature differs from 20 °C, apply the formula and obtain the polarimetric sucrose content corresponding to the normal weight of sugar at the standard temperature.

Note: In addition to the above are also applied the usual instrument corrections stipulated by ICUMSA [2] for the determination of po! in raw sugar.

Comparison of ICINAZ and BSC Methods

A trial was conducted comparing the above method with the BSC method using a common set of solutions but with the appropriate weighings and calculations performed as necessary for the two methods. Temperatures ranged from 20 to 30 °C in the trial so temperature correction formulae were tested at one extreme of their range.

The comparison involved the analysis of several refined sugars with a minimum of two and a maximum of 18 replicates per sugar. Some samples were analysed in parallel by two analysts. From the statistical viewpoint 65 independent analyses were considered whose results by analyst and the difference in repeatability between both methods (BSC-ICINAZ) is presented in the Table.

Table 1: Analytical results obtained comparing both methods

Analystn °zsr95 Δr95
r (weighted)BSC0.0900.033

n number of analysis; s standard deviation, ; r95 repeatability,

Examination of Table 1 shows that all analysts attained better repeatability when using the method based on mass relationships. The difference in repeatability obtained (Δr = 0.033) is similar to the one reported in the collaborative test [10] (Δr = 0,043 °C), where the repeatability of the method with volume correction by weighing (equivalent to the ICINAZ method) and without volume correction are greater (0.071 °Z respectively). The better repeatability figures of the method based on mass relationships are justified because these eliminate the errors of making to the mark and the calibration of the volumetric flasks.

The difference of mean °Z values between methods (BSC – ICINAZ) is positive and increases according to the descending experience of the analysts (0.00, 0.02 and 0.05 °Z). It also maintains the sense reported in the collaborative test (+ 0.030 °Z) already referred to, this difference could be attributed to the volume contraction [11] that is produced when homogenizing the sucrose solution after making to the mark.

Concerning the Braunschweig method, it is operationally similar to the BSC, but in addition, it corrects the volume of the solution by weighing, makes to the mark and reads at 20 ± 0.1 °C.

Advantages of the ICINAZ Method

1. It can be employed within a wide temperature range (10 – 30 °C

2. It presents a reasonable flexibility with respect to the mass of solute and solution (range of mass relationships 0.235984 – 0.238209),

3. It does not require volumetric flasks,

4. There is no significant time reduction due to

– the dissolution with a magnetic stirrer is faster than with the Multer type dissolver,

– the sample is weighed in the same container in which it is dissolved.

– it is not necessary to make to the mark,

– it is not necessary to make the polarimetric readings at the standard temperature,

– weighings due to its flexibility, increase the speed of analysis.

5. The time savings and the elimination of constraints make the method more economical and feasible to be carried out,

6. The method repeatability is equivalent to the Braunschweig method.


I Proc. 12th Session ICUMSA, 1958, 46

2 Proc. 16th Session ICUMSA. 1974, 265-266

3 Proc. 18th Session ICUMSA, 1982, 337-338

4 Proc. 20th Session ICUMSA. 1990, 38

5 Proc. 20th Session ICUMSA. 1990, 265-270

6 Hernandez, Z.: Grade Thesis, IPQ. “Martires de Giron” Havana, 1991

7 Perez Sanfiel, -F.; Rodriguez, J.: Castro, J.; Hernandez, Z.: Diversificacion ’93, International Conference Center, Havana, May 1993

8 Wilson, R.A.M.: Int. Sugar J., 67, 1965, 234-236. 263-268

9 Emmerich, A.: Zucker. 30, 1977, 658-661

10 Proc. 20th Session ICUMSA, 1990, 190-200

11 Browne, C.A.: Zerban. F.W.: Physical and Chemical Methods of Sugar Analysis. Third Edition, John Wiley and Sons, Inc, New York, 1941, 56-58

Comment on the above paper

by A. Emmerich, Germanv Referee of Subject 4 “Polarimetry and Quartz Plates”

The white sugar polarization method of Perez Sanfiel et al., outlined above, is an excellent further development of the Braunschweig method, which has been Officially adopted at the 20th Session, 1990. I can only express my congratulations for the fine results of this investigation. Unfortunately, some of the calculations of our Cuban colleagues contain some minor errors and before final action within ICUMSA these should be corrected.