Message from the President
Those who attended the 20th Session at Colorado Springs, USA in June 1990 would surely agree with me that the United States National Committee hosted a very successful conference. The business sessions were productive, and the decisions taken provide the Commission with guidance for the next Session and beyond. These decisions are embodied in the recommendations to referees’ reports which are published below. Other decisions came from three Executive Committee meetings. Some of these which will be of interest to members who did not attend are discussed below.
Mr John Dutton has been appointed Editor/Manager of the Publications Department and will be paid by the Commission to carry out much of the work whose cost was previously borne by British Sugar. John’s first major task will be the production of the Proceedings which are expected to be available early in 1991. After that he will undertake the editing and publication of analytical methods in the newly approved ISO format. It is expected that a complete set of methods will be available towards the end of the current Session. Additionally, John will strengthen contacts with fraternal organisations like ISO, Codex Alimentarius, AOAC and OIML.
The Executive Committee urged the President to maintain a Steering Committee to assist in the achievements of the 21st Session goals. This committee will comprise Dr Albert Emmerich and the President as members of the previous committee, and Drs Roger Wood and Brian Purchase as new members. We are grateful for the contributions of the two retiring members of the previous committee, Dr Margaret Clarke and Mr John Dutton. The four tasks requiring the immediate attention of the committee are:
– Rearrangement of some subjects prior to the appointment of referees,
– Consideration of priorities between subject recommendations,
– Management of the new methods book,
– Continue implementation of the sugar scale.
Probably the most important measure adopted was the acceptance of IUPAC guidelines for the conduct of collaborative tests on analytical methods. With the goal of having a new methods book completed this Session, we must attempt to test all those methods not yet meeting full international standards. This will be a significant undertaking requiring the dedication of referees and their associates who will carry out the work and the support of companies and research organisations who pay for the time and facilities needed for the work.
During the 20th Session we admitted Portugal and Indonesia as new members. Mr Luis Bento and Dr H. M. Mochtar, the chairmen of their respective National Committees, are well known throughout the sugar world. We look forward to the participation of associates in those countries in the current work programme.
The Executive Committee expressed concern at the number of countries who today are both inactive and in arrears with their dues. It was decided that such countries would have one year to communicate with the Commission and show that a functioning National Committee existed and that a plan for meeting financial obligations would be implemented. The president will shortly be writing to the countries concerned but if those involved read this, it would be appreciated if dialogue was initiated by those committees.
A survey was conducted at Colorado Springs to determine if the format of ICUMSA News was satisfactory to members. The results will be used to give readers more of what they want. Any readers wishing to contribute articles, letters or comments should do so by contacting either the Editor, Dr Robert Pieck, or the President.
Remark of the editor. In the No 8 issue of lCUMSA News (January 1990) we published an article on ”Rapid microbiological tests”. We inadvertently omitted the author’s name which was Dr Ruth Strauss (Südzucker AG Mannheim/Ochsenfurt, Germany). We apologize to Dr Strauss for this omission.
The following recommendations were adopted during the 20th Session of ICUMSA held in Colorado Springs from 4th to 8th June 1990. They will be reproduced, together with the Referees’ Reports, Discussions, etc., in the bound volume of the 20th Session Proceedings, which will be available early in 1991 from ICUMSA Publications Department, c/o British Sugar plc, Technical Centre, Colney, Norwich, England, NR.4 7UB.
General Subject 1: Raw Sugar
Referee: R.J. McCowage (Australia)
1. Any approaches which offer the potential to determine the sucrose content of raw sugar with similar efficacy and precision to the polarisation should be studied.
2. Studies on the effect of different clarification agents on raw sugar polarisation should continue, with the ultimate objective of specifying an alternative clarifying agent to basic lead acetate. Alternatively, a method for determining raw sugar polarisation without clarification should be sought.
3. The Official status of the ICUMSA gravimetric method for determining the sulphated ash of raw sugar, with incinerations at 550 °C and 650 °C, is confirmed.
4. Work should be initiated to determine suitable conditions for the performance of the ICUMSA gravimetric ash method on raw sugar using one incineration only.
5. The Official status of the ICUMSA conductivity ash method, without addition of sucrose, is confirmed for raw sugar.
6. Further work should be carried out to select one classical method for the determination of the reducing sugars content of raw sugar, or at least one method for raw cane sugar and one for raw beet sugar.
7. Instrumental methods for the determination of reducing sugars in raw sugar should be further investigated, with the aim of recommending suitable methods for consideration as Official methods.
8. ICUMSA Method 2 for raw sugar colour is withdrawn.
9. The Official status of ICUMSA method 4 for raw sugar colour is confirmed. It should be re-named ”The ICUMSA method for raw sugar Colour”.
10. Work should continue in an attempt to find a suitable buffer for pH adjustment in the ICUMSA method for raw sugar colour.
11. The filtration step in the ICUMSA method for raw sugar colour should be further studied, with the aim of specifying conditions under which faster filtration rates can be obtained.
12. The Official status of the ICUMSA method of determining the pH of raw sugar is confirmed.
13. Further work should be undertaken to specify a procedure to prepare raw sugar for grist analysis.
14. Work should continue in an attempt to find a specific test for dextran in raw sugar. Approaches based on enzymatic or immunoassay techniques should be pursued. The test should reflect the refinery performance of raw sugar.
15. Work should be initiated in an attempt to define a standardised affination procedure for raw sugar. The procedure should reflect refinery performance and should be capable to widespread application in factory laboratories.
16. Specifications should be developed for temperature measurement of raw sugar.
17. Work should be reinstated in an attempt to specify a test for the determination of starch in raw sugar.
General Subject 2: White sugar
Referee: C.W. Harvey (UK)
1. The assessment of visual appearance of white sugar using Braunschweig colour· type series is confirmed as the Official ICUMSA method, with sufficient experimental data to validate the procedure to IUPAC standards. Work should continue within Subject 7 to develop an instrumental technique to measure visual appearance of white sugar.
2. The method described in Appendix 1 to the Referee’s Report for the measurement of white sugar solution colour using TEA buffer for pH adjustment is Officially adopted and replaces the existing procedure adopted in the 17th Session (Subject 22, Appendix 1).
3. The Braunschweig method for polarisation of white sugar without clarification and with correction of the volume by weighing is Officially adopted. This method is validated to IUPAC standards by collaborative tests (see Referee’s Report Subject 4).
4. For white sugar needing clarification, the “Raw Sugar Polarisation” method description given in Subject 11 up to the 19th Session is recommended as Official. Procedures for determining polarisation of white sugar using clarifying agents other than lead should be sought.
5. The conductivity ash method at 28g/100g is confirmed as the Official method for determining the ash content of white sugar (See Referee’s Report for Subject 16).
6. The method for the determination of particle size should contain all the instructions necessary to produce basic screening data, based on sieves conforming to National Standards, including a specification of the type of sieve shaking-equipment to be used. The evaluation of the data by the methods of Powers, Rens and RRS should be included with their limitations clearly stated. The selection of the method for evaluation does not require a Recommendation from ICUMSA but should remain at the option of the user.
7. The methods of Knight & Allen for low levels of reducing sugars in white sugar and the Berlin Institute or the Ofner method, or a method based on a combination of these methods, for higher levels should be collaboratively tested to IUPAC standards. The choice of the latter method is to be made on the recommendation of the Referee for Subject 15, Reducing Sugars.
8. Methods for the determination of arsenic, copper and lead should be collaboratively tested, following proposals for up-dating the methods from the Referee for Subject 6.
9. Original data from collaborative tests on methods for loss on drying and insoluble matter should be assessed by the Referee for Subject 3. Those methods with sufficient data to meet IUPAC standards should be confirmed as Official ICUMSA methods. Methods that do not reach IUPAC standards are to be included in the collaborative programme.
10. Work should continue on the validation of the Rosaniline method for the determination of sulphite in white sugar.
11. Work should continue on the validation of the loss on drying method for white sugar.
General Subject 3: Refined sugars other than white sugar
Referee: R.W. Plews (UK)
1. The various products which fall within the scope of this Subject, should be classified as follows :
a) Powdered sugars.
b) Partly refined sugars.
c) Brown sugars.
d) Very Pure Syrups.
e) Coloured Syrups.
2. The status of procedures previously adopted (as listed in the Referee’s Report) should be confirmed as applying to products within the scope of this Subject. With respect to the determination of sulphite, this shall apply to powdered sugars only.
3. Methods for the determination of sulphite in products other than white sugars should be studied.
4. The established method for polarisation of raw sugar should be extended to apply to products within the scope of this Subject.
5. Methods for the determination of colour of brown sugars should be studied.
6. Methods for the determination of anti-caking agents in powdered sugars should be studied.
7. HPLC, HPIC and enzymatic methods for the quantitative determination of specific sugars, including sucrose, glucose and fructose, should continue to be studied.
8. Methods for the determination of dry substance in the products within the scope of this Subject should be studied.
9. All proposed studies will be pursued with the co-operation of the appropriate Scientific Referees.
General Subject 4: Molasses
Referee: D.S. Martin (UK)
1. Further studies of the correlation between the Luff-Schoorl and Lane & Eynon constant volume methods should be pursued through the Referee for Subject 15.
2. The Karl Fischer method for water content and its correlation with vacuum oven drying should be pursued through the Referee for Subject 17.
3. A method for total fermentable compounds should be established and fermentation properties in general should be investigated.
4. Co-operation with the Referees for Subjects 8 and 9 on the applications of GLC/HPLC to the analysis of molasses should continue.
General Subject 5: Cane
Referee: M.A. Brokensha (South Africa)
1. Core sampling is adopted as an ICUMSA Accepted method.
2. Full width hatch sampling is adopted as an ICUMSA Accepted method.
3. The hydraulic press method should be further studied, with a view to attaining Tentative or Accepted Status at the 21st Session.
4. The wet disintegrator method (as submitted at the 19th Session) is Officially adopted.
5. The Referee for Subject 9 is requested to recommend the most suitable HPLC method for cane juice analysis and collaborative studies should then be undertaken, subject to the development of a suitable cane juice preservation procedure.
6. Collaborative studies of the GLC method of Schäffler, with the goal of moving to Official status, should be undertaken as soon as a suitable cane juice preservation procedure has been developed.
7. The investigation of freeze-drying of cane juice samples as a means of preservation and thus facilitation of collaborative studies, should be pursued.
8. Investigations into the use of clarification agents or procedures which will eliminate the use of lead salts in cane juice analysis should be pursued with urgency.
9. Investigations into the application of near infra-red spectroscopy for cane analysis should be pursued.
General Subject 6: Beet:
Referee: W. Mauch (Germany)
1. In view of the importance of samples being both representative and homogeneous, proposals should be evolved for standardising apparatus for the preparation of brei and of brei characteristics; consideration should also be given to the comminution and handling of beet cossettes.
2. In order. to create the necessary requirements for inter-laboratory testing, methods for sample preservation of brei and cossettes should be selected and tested.
3. In view of the widespread use of digestion-filtration units, proposals for the standardisation of relevant instrumental and analytical parameters should be evolved.
4. The Recommendation of the 19th Session (Proc. 19th Session of ICUMSA, 1986, 163, Rec. 3) that clarification with aluminium sulphate solution be Tentatively adopted, should continue to be valid and the procedure should be collaboratively tested in order to obtain Official status.
5. The development and examination of alternative routine and standard methods for the determination of sucrose (e.g. HPLC, enzymatic and NIR spectrometric) should be encouraged in collaboration with the Referee for General Subject 8; in doing so, the individual steps of the method should also be checked for causes of systematic errors.
General Subject 7: Cane sugar processing
Referee: W.S.C. Tsang (USA)
1. Due to poor reproducibility, the cation-exchange HPLC method for sucrose in molasses, adopted Tentatively at the 19th Session, should be further studied, under the guidance of the Referee for Subject 9.
2. HPLC methods for the determination of fructose, glucose and sucrose in process syrups and liquors should be studied, under the guidance of the Referee for Subject 9.
3. Methods for the determination of sugars in bagasse and filter muds, as well as in process effluents, should be further studied.
General subject 8: Beet sugar processing
Referee: J.P. Lescure (France)
1. The method described by Ivin*, modified by Schäffler, is Tentatively adopted to correct direct polarisation for the purpose of conducting a sugar balance.
2. The method described by Schäffler**, modified by Oikawa, is Tentatively adopted for the GLC analysis of sucrose in brei or raw juice.
3. The analysis of pulp should be studied, with special attention to sodium, potassium, calcium, nitrogen, dry substance, total ash, total sugar and sand contents.
4. Process control methods should be studied with special attention to lactic acid, nitrogen and amide contents.
5. A standard approach to collaborative tests to assess the performance of process laboratories should be developed.
6. Special attention should be paid to developing procedures for checking on-line analytical techniques.
7. Methods to be used in determining sugar losses during extraction should be studied.
General subject 9: Starch hydrolysis products
Referee: D. B. Whitehouse (Belgium)
1. This Subject should be maintained by ICUMSA, so that contact may be continued with the International Federation of Glucose Manufacturers. In this way, methods of analysis developed by the Starch Industry with application to this Subject may be notified to ICUMSA from time to time; equally, ICUMSA methods of interest to the Starch Industry may be communicated.
* Ivin, P.C.: Proc. 19th Session ICUMSA, 1986, 127-135, and K. J. Schäffler,
Referee’s Report for Subject 9, Appendix I.
** Schäffler, K.J.: Proc. 19th Session ICUMSA,1986, 114-121 and S. Oikawa, Referee’s report.
Subject 1: Constitution and by-laws
Referee: M.R. Player (Australia)
1. The text of the Constitution and By-Laws will be studied with a view to proposing revisions to eliminate ambiguities.
Subject 2: Laboratory apparatus and reagents
Referee: S.A. Brooks (West Indies)
1. Referees for other Subjects are requested to identify and specify specialised sugar apparatus which would be suitable for international standardisation and to co-operate in this respect with the Referee.
2. Referees for other Subjects are requested to identify and specify reagents specially formulated to meet the requirements of the sugar industry, and which could meet with internationally-agreed standards.
This information should be passed to the Referee.
Subject 3: Method format, collaborative testing and statistical treatment of data
Referee: M.A. Godshall (USA)
1. The IUPAC protocol for the design, conduct and interpretation of collaborative studies is officially adopted and this will be incorporated into ICUMSA By-Laws.
2. A Methods Review Committee will be established within the province of the Referee for Subject 3 and it is highly desirable that his Committee review the format and procedures of collaborative
studies proposed by ICUMSA Referees. This is to ensure that these are in accordance with IUPAC requirements and therefore eligible for acceptance by ISO and AOAC.
3. Note will be taken of the Horwitz guidelines for acceptable variability in a method, which are listed below:
“The RSDR (%) of any given test will not usually exceed twice the value given below for chemical analyses:”
|Analyte concentration||RSDR (%)|
|10 ppm (0.001 %)||11|
|100 ppm (0.01 %)||8|
|1000 ppm (0.l %)||5.6|
4. The ISO method format and numbering system is adopted, and the method description will include matrix/analyte/concentration and present performance characteristics, individually for each sample.
5. Fundamental values and reference tables, which cannot be collaboratively tested, are to be recognised as Official if they have met the following criteria:
a) The data are obtained with an accuracy significantly greater than that used in practical applications.
b) The data are published in detail in a refereed journal.
c) There are no substantial objections to the data in 4 years.
d) The data are obtained by a recognised standardising laboratory.
It should also be noted that it is considered highly desirable that referees intending to carry out work in this area should advise others, to give them the opportunity to provide input into the work at an early stage.
6. Recommendations “for further study ” should indicate a plan of action.
7. Ways to shorten the interval required to take action on methods should be explored.
8. The following Recommendations are to serve as guidelines for Referees in their Reports of Collaborative Studies:
a) Report each collaborative study separately.
b) Give a summary of the study at the beginning of the report. This should include:
i) The method tested (with references).
ii) The type and number of samples tested.
iii) The number of participating laboratories.
iv) A summary of the performance characteristics.
v) The recommendations.
c) Include all raw data in a table. This allows others to also perform their own statistics on the data.
d) Include test results, sample by sample, in a table, following the Recommended IUPAC format (Appendices 1 & 3 of the Referee’s Report).
e) Include any other information gained about the method, such as interferences, ruggedness, variations tried, comments from collaborators etc., in the report at the end.
9. Accepted, Tentative and Official status, as described in the Addendum to the Referee’s Report, are Officially adopted. Further work will be undertaken to define a means of developing microbiological tests to Official status.
Subject 4: Polarimetry
Referee: A. Emmerich (Germany)
1. Recommendations 1 to 4 of Subject 5 at the 19th Session, regarding the Official adoption of the new polarimetric scale (Proc. 19th Session of ICUMSA, 1986, 66-68) are confirmed.
2. Emmerich’s formula for temperature corrections to polarimetric measurements, Officially adopted at the 18th Session (Proc. 18th Session of ICUMSA, 1982, 63) is confirmed.
3. The use of near infra-red wavelengths for saccharimetry should be further studied.
Subject 5: Quartz plates
Referee: K. Zander (Germany)
1. Conversion of rotation values at the basic wavelength of λvac = 546.2271 nm to other wavelengths in the range of λvac = 650 nm to λvac = 1000 nm should provisionally be made using the equation given by Bünnagel (Proc. 14th Session of ICUMSA, 1966, 32).
2. For using the 100 °Z point at wavelengths other than 546.2271 nm, the equation agreed at the 14th Session (Proc. 14th Session of ICUMSA, 1966, 17) should also be provisionally used for the wavelength of 650 nm to 1000 nm.
3. Further measurements of the rotary dispersions of quartz and sucrose should be carried out in the spectral region of approximately 850 nm.
Subject 6: Spectrophotometry
Referee: G. Mantovani (Italy)
1. A method for the standard preparation of white and other sugar samples for trace metal determination by atomic absorption and emission spectrophotometry should be chosen and submitted to a collaborative study.
2. Work should be carried out to select a method for determining formaldehyde in white sugar. A collaborative study should then be carried out in co-operation with the Referees for General Subjects 2 (White Sugar) and 8 (Beet Sugar Processing).
3. Near infra-red·spectrophotometric methods should be further studied.
4. The Blue Number method and fluorimetric analysis for aminonitrogen should be further studied.
Subject 7: Colour, turbidity and reflectance measurements
Referee: S. Akoglu (Turkey)
1. Studies on the use of TEA buffer for pH adjustment in the measurement of colour in sugars other than white sugar should be continued, particularly to obtain data on a wide range of sugars.
2. The determination of turbidity in sugar solutions should be further studied. The effect of instrument design should be taken into account in these studies.
3. Studies on the use of probe-type colorimeters for sugar colour measurement should be continued and the results compared with those obtained from standard spectrophotometers.
4. Investigation of reflectance measurement for the evaluation of the colour of white sugars should be continued, giving special consideration to the CIE L* a* b* system.
5. Studies on the application of reflection measurements, visual evaluations and solution colour measurements to the evaluation of brown sugars should be continued.
6. The Imperial Sugar method for reflectance measurement of brown sugars should be studied internationally.
7. Studies on the influence of crystal size, gloss and surface structure on visual grading and on reflectance measurements should be continued at a lower level of priority.
8. In the measurement of solution colour of sugars other than white sugars by the ICUMSA method, the data presented in Table 2 of the Referee’s Report should be adopted as guidelines for solution concentration and cell length.
Subject 8: GLC methods
Referee: N. Kubadinow (Austria)
1. In co-operation with the Referees for the general Subjects, a method should be sought which allows for the simultaneous determination of sucrose, glucose, fructose and trisaccharides in cane and/or beet products.
Subject 9: HPLC methods
Referee: K J. Schäffler (South Africa)
1. Further testing of the cation-exchange HPLC method for sucrose, glucose and fructose in cane molasses is required. The reason that over-estimation is occuring on occasions should be established. Cations other than sodium and calcium should be tested. A new method with tighter control of the major variables should be drawn up.
2. If Recommendation 1 is successful, then the cation-exchange HPLC method should be re-evaluated in a collaborative study.
3. An alternative HPLC method using anion-exchange and pulsed amperometric detection should be drawn up for collaborative studies.
4. An HPLC procedure for betaine in beet molasses should be developed and tested.
Subject 10: Enzymatic & immunological methods
Referee: D.F. Day (USA)
1. A series of criteria should be established for the standardisation of enzymatic reagents used in Recommended methods.
2. A series of criteria should be established for the standardisation of immunological reagents used in new methods.
3. Collaborative tests should be carried out in co-operation with the appropriate Referees, in order to assess the validity of existing enzymatic methods (e.g. SO2, glucose, fructose, sucrose, D- and L-lactic acid).
4. New enzymatic methods should be developed with the collaboration of interested laboratories (e.g. pectin, glutamine: ammonia, etc.)
Subject 11: Density
Referee: F. Spieweck (Germany)
1. Polynomial (1) in the Referee’s Report is Officially adopted in place of Plato’s density table for the determination of the density of aqueous sucrose solutions as a function of mass concentration and temperature.
2. For technical applications, polynomial (2) is Officially adopted for the determination of the density of aqueous sucrose solutions as a function of mass fraction and temperature.
3. Confirmation of the results obtained with polynomials (1) and (2) should be sought by approaching other standardising laboratories to carry out independent checks.
Subject 12: Rheology
Referee: R. Broadfoot (Australia)
1. The Power Law model is adopted for the presentation of rheological data for massecuites and molasses. The range of shear rates used for the measurements should be nominated in addition to the values of consistency and flow index. It is also recommended that the geometry of the measuring systems should be clearly defined.
2. Studies should continue to investigate those factors which influence the rheological properties of molasses and massecuites. This work should include problems of crystal migration which may occur in the field of shear, while measuring the viscosity of massecuites.
3. In using the Official ICUMSA rotating cylinder method for determining the rheological properties of molasses, the geometry of the measuring system, particularly the ratio of the diameter of the spindle to the diameter of the co-axial cylinder reservoir, should continue to be defined, until an assessment is made to determine whether the geometry of the measuring system influences the values of the Power Law parameters.
4. The falling-ball viscometer should be deleted as a suitable alternative to the rotating cylinder method for measuring the viscosity of molasses.
5. Further studies should be conducted into the use of the pipeflow method for both massecuites and molasses. Emphasis should be given to specifying the appropriate tube dimensions or defining a procedure to correct for pressure losses at the tube ends and for wall effects.
6. The pipeflow method should not be offered as an alternative to the rotating cylinder method, for determining the rheological properties of molasses, until the procedures to correct the pipeflow data for tube and effects are defined and further comparisons of data from the two methods are made with molasses showing non-Newtonian behaviour.
7. Investigations of the elastic flow properties, tack, interfacial tension and surface tension of molasses and massecuites should be continued.
8. The work towards establishing standard measurement procedures for the rheological properties of massecuites should be confined to the rotating cylinder and pipeflow techniques. The interest in other viscometric methods should be of a general nature and not directed to developing them as standard techniques.
Subject 13: Refractive index
Referee: K.J. Rosenbruch (Germany)
1. Equation (1) and the associated coefficients described in Table 1 of the Referee’s Report for the refractive index in standard air of aqueous solutions of D-glucose, D-fructose and invert sugar at concentrations of 0 to 85 %, temperatures of 15 °C to 30 °C and wavelengths from 546,1 nm to 589,3 nm are officially adopted.
2. Equation (2) and the associated coefficients described in the Referee’s Report for correcting refractometric dry substance to true dry substance for mixtures of aqueous solutions of sucrose and invert sugar at concentrations from 0 to 85 %, a wavelength of 589,3 nm and a temperature of 20 °C, are Officially adopted.
3. Studies of the accuracy achievable for refractive index measurements of technical sugar solutions, with commercially available refractometers, should be continued.
4. The equation given in subject 12 of the 17th Session (Proc. 17th Session of ICUMSA, 1978, 166) for the refractive index in standard air of aqueous solutions of sucrose at concentrations from 0 to 85 %, temperatures from 15 to 30 °C and wavelengths from 546,l nm to 589,3 nm is Officially adopted.
Subject 14: Microbiological tests
Referee: R. Strauss (Germany)
1. As a result of many collaborative tests by internationally recognised institutes, the method for the enumeration of mesophilic bacteria in sugar by concentrating the sample on membrane filters (pore size between 0.2 and 0.45 μm) and using plate count medium or nutrient medium at 30 °C incubation temperature should be confirmed.
2. With regard to slime-forming bacteria:
a) It is recommended that the development of a test for slime-forming bacteria which indicates the quality of a sugar, should be confirmed.
b) Both Weman (Bl) and McCleskey (B2) (Proc. 19th Session of ICUMSA, 1986, 372) media should be further investigated and compared with other media for the detection of lactic acid-forming bacteria.
3. For yeast and moulds:
a) The nutrient media C1, C2 and C3 (Proc. 19th Session of ICUMSA, 1986, 373) should be investigated in further tests for yeasts and moulds.
b) The following modified medium of De Whalley should be further investigated in testing for osmotolerant yeasts:
|Yeast extract||5g||Fractionated Sterilization:|
|Peptone||2g||3 x 20 min, at l00 °C|
|Ammonium Chloride||1g||30 °C or 25 °’C|
|Agar||16g||72h to 6 days|
c) The incubation temperature for yeasts and moulds should be subjected to further collaborative studies, as the temperature specified in the new ISO standard differs from that recommended by ICUMSA.
4. In the case of thermophilic spore-forming bacteria:
a) Because of improvements in eliminating vegetative organisms in tests for thermophilic spore-forming bacteria, a modification of the AOAC method for the detection of spore-forming bacteria in sugar should be developed.
b) Moreover, the comparative tests should include the method using phenol red as acid indicator.
5. Developments in the area of rapid microbiological testing should be monitored.
Subject 15: Reducing sugars
Referee: J. Laursen (Denmark)
1. The Luff-Schoorl method, as described in Appendix 2 of the Referee’s Report, with the modifications described under point 2.1.5, is tentatively adopted for the determination of total sugars in molasses.
2. The reasons for the difference in total sugars in samples of beet molasses by the Luff-Schoorl method in comparison with the Lane & Eynon method should be further studied.
3. The determination of total sugars in syrups and feedstuffs, other than molasses, by the Luff-Schoorl method, as described in Appendix 2 of the Referee’s Report, with modifications described under point 2.1.5, should be further studied.
The sucrose correction factors for the Constant Volume modification of the Lane & Eynon method, as shown in Table 6 of the Referee’s Report, are Officially adopted. The correction factors adopted at the 17th Session (Proc. 17th Session of ICUMSA, 1978, 194) are withdrawn.
Subject 16: Ash
Referee: J.P. Ducatillon (France)
No Recommendations were adopted under this Subject.
Subject 17: Dry substance
Referee: G. Vaccari (Italy)
1. The method for the determination of moisture in raw sugar, as specified in Appendix 2 of Subject 13 of the 19th Session (Proc. 19th Session of ICUMSA, 1986, 225) is officially adopted when the moisture content of the raw sugar is greater than 0.15 %. In place of aluminium dishes, glass dishes may be used. It is recognised that this method is most reliable above 0.5 % moisture.
2. For raw sugar having a moisture content of less than 0.5 %, the Official method for determining “Loss on Drying” of white sugar (”Sugar Analysis – ICUMSA methods” by F. Schneider, 1979, 113, as modified in Proceedings 18th Session, 1982, 330, and Proceedings 19th Session, 1986, 348) should be taken into consideration. A collaborative test should be carried out, comparing this procedure with the procedure Recommended in 1 above.
3. The formula developed by Morton & Muller for correcting refractometric solids contents of recovery products, which is used by Tate & Lyle, should be taken into consideration. The Associate Referees should evaluate its applicability on their local sugar products, with the aim of its possible adoption as an Official correction.
4. Equation 2 of Subject 13 “Refractive Index ” for correction of the refractometric dry substance of white sugar syrups which contain defined amounts of invert sugar, is Officially adopted.
5. New measurement techniques, such as NlR-spectroscopy, should be further studied if the results which they give are comparable with those obtained by traditional ICUMSA methods.
6. The Karl Fischer and vacuum oven drying methods should be collaboratively tested before being considered for Official adoption.
Subject 18: Sucrose
Referee: S.E. Bichsel (USA)
1. It is Recommended that Subject 18 be discontinued, and the work accommodated in other Subjects.
Subject 19: Oligosaccharides & Polysaccharides
Referee: K. Thielecke (Germany)
1. Specific enzymatic methods for dextran, such as that of Sayama & Kamada (Sugar Industry Abstracts 88-1632) should be further developed. The type of enzyme used, and its purity should be defined.
2. Immunological methods for dextran determination involving the standardisation of antiserum and the development of test kits should be further studied.
3. Following the recommendations of the Review of Methods in Subject 3, the CSR method for estimation of dextran in raw sugar should be renamed the “haze method ” (see Subject 3, Appendix 2). Since the variability is known, the method could qualify for Official status under the auspices of General Subject 1. The method is no longer a matter for Subject 19. (Editor’s Note: The method was not adopted under General Subject 1).
4. Following the adoption of the method by the AOAC, the Roberts method for dextran in raw cane sugar could qualify for adoption under the auspices of General Subject 1. The method is no longer a matter for Subject 19. (Editor’s Note: The Method was not adopted under General Subject 1).
5. Pectic acid methods based upon enzymatic hydrolysis followed by HPLC or enzymatic quantification, should be developed further and compared to photometric methods, such as that of Reinefeld & Schneider (Sugar Industry Abstracts 83-1235).
6. The Referee for Subject 3 should further evaluate the Schiweck & Büsching method for raffinose in molasses and other juices.
The procedure using Carrez clarification, if necessary, as outlined in the Braunschweig modification (Sugar Industry Abstracts 88-1618) should be Tentatively adopted for total α-galactosides.
7. For technical purposes, a 20 % reduction of the enzymatic total α-galactoside resuh may be used to account for the galactinol in impure beet syrups, until suitably accurate enzymatic or other methods for raffinose become available.
8. The official Schiweck & Büsching enzymatic method for raffinose in white sugar should be re-evaluated under General Subject 2 ”White Sugar”. The method is no longer a matter for Subject 19.
9. The use of the I.R.I.S. GLC method (Appendix 2 of the Referee’s Report), as a reference method for raffinose in beet molasses, should be further studied.
10. HPLC and HPIC (HPAEC) methods for technically important oligosaccharides and galactinol should be further studied.
11. Work aimed at preparing analytical standards, especially for galactinol and the kestoses, should be encouraged.
12. Following the recommendations made in the Report on the Review of Methods (Subject 3 Report, Appendix 2), the methods below should be retained, until more advanced methods presently being assessed are considered for adoption:
a) Reinefeld, Thielecke & Lücker TLC method for dextran, levan and araban in technical juices (Tentative adoption, 1982).
b) Carruthers & Oldfield photometric method for pectic acid in beet raw juice (Tentative adoption, 1978).
c) Reinefeld, Thielecke & Lücker photometric method for pectic acid in beet raw juice (Tentative adoption, 1982).
d) British Sugar TLC method for raffinose (Tentative adoption 1974).
e) Schiweck HPLC method for oligosaccharides and galactinol (Tentative adoption, 1982).
These methods are considered to be Accepted methods.
13. Analytical methods for oligo- and polysaccharides and preparation procedures for standards under consideration should be extracted from the literature and tested.
14. Following the recommendations made in the Report on the Review of Methods (Subject 3 Report, Appendix 2), the following obsolete, or seldom-used methods, should be retired:
a) Albon & Gross paper chromatography method for raffinose and kestoses.
b) Braunschweig paper chromatography method for raffinose.
c) Paine & Balch enzymatic-polarimetric method for raffinose.
d) McCready enzymatic-photometric method for raffinose.
e) Böttger & Steinmetzer enzymatic method for raffinose.
f) Serro & Brown paper chromatography method for galactinol.
g) Atterson et al. TLC method for dextran.
h) Atterson·et al. TLC method for levan.
i) British Sugar TLC method for araban.
Subject 20: Ion selective electrodes & ion chromatography
Referee: P. Bourlet (France)
1. Studies of the analyses of the inorganic anions, chloride, sulphate and sulphite in white sugar, refined sugar products and raw sugar should be carried out.
2. Analysis of the inorganic anions, chloride, sulphate, nitrate and nitrite in molasses should be further studied.
3. A list of organic acids for which characterisation would be interesting should be drawn up, in order to define the proper mode of analysis.
4. Monovalent and divalent cation analysis should be further studied, in order to determine the limits of this application of ion chromatography.
Editor: Dr. R. Pieck, Klein Spanuit 9, B-3300 Tienen, Belgium, September 1990 – Tel. +32 16 / 81 24 36 – Telex 222 51 – Telefax + 3 1 16 / 82 03 17.