Recommendations adopted at the 21st Session of ICUMSA, Havana, Cuba, 16-20 May 1994
General Subject 1: Raw Sugar
Referee: R J McCowage (Australia)
I. Any approaches which offer the potential to determine the sucrose content of raw sugar with similar efficacy and precision to the polarisation test should be studied.
2. Studies of alternative clarification agents to basic lead acetate for cane and beet raw sugar polarisations should be undertaken, focusing on relativities in results, solution clarity, pH and filtration rates, with the objective of specifying a replacement for basic lead acetate.
3. Basic studies to provide data suitable for accurate calibration of polarimeters in the NIR wavelength range, and for temperature corrections in the NIR wavelength range, should be undertaken as a matter of urgency.
4. Work should be undertaken on the effect of different levels of non-sugars in lead-clarified and in unclarified solutions.
5. Work should be undertaken to determine suitable conditions for determining the ash content of raw sugar with one incineration only, with a view to modifying the Official ICUMSA method (ICUMSA Method GSl/3/4/7/8-11) accordingly.
6. Investigations should continue on methods to prepare raw sugars for dry sieving with a view to developing a dry sieving method for fine grain analysis. Also, developments in instrumental methods for determining grain size should be monitored.
7. The modified haze test procedure (ICUMSA Method GSl-15), as described in Appendix I of the Referee’s Report, is adopted as an Official ICUMSA method.
8. Work on the evaluation of standard affination procedures for raw sugar should continue.
9. Work on the selection of a method for the determination of starch in raw sugar should be undertaken, with particular consideration being given to the choice of a suitable standard for the test.
General Subject 2: White Sugar
Referee: C W Hanrvey (UK)
1. The method for the ‘Particle Size Analysis of White Sugar’ (ICUMSA Method GS2-37) is adopted as an Accepted method. The mathematical methods for the evaluation of particle size data, as given by Powers, Rens, Butler and Rosien, Rammler, Sperling. and Bennet (RRSB) are appended to Method GS2-37, but the selection of the method for eyaluations is at the option of the user
2. The Official status of the Knight & Allen method for the determination of reducing sugars in white sugar (ICUMSA Method GS2/3-5) is retained, but the method should be further studied and collaboratively tested on an urgent basis [Editorial note: See also Subject 15, Recommendation 3).
3. The Emmerich method for the determination of reducing sugars in white sugar (Sugar Analysis: ICUMSA Methods, 1979, 61-63) is adopted as an Accepted method.
4. The Berlin Institute method and the Ofner method for the determination of reducing sugars in white sugar (Sugar Analysis: ICUMSA Methods, 1979, 55-59) should be added to the Methods Book.
5. The Official status of the ‘Moisture by Loss on Drying’ method for white sugar (ICUMSA Method GS2/l/3-l 5) is retained, but further studies should be undertaken on an urgent basis, either to improve the reproducibility of the existing method or to find a better alternative.
6. ICUMSA Method GS2/3-19 for the determination of insoluble matter in white sugar should be collaboratively tested to validate the method to IUPAC standards. The collaborative test should inelude the modification of the method for sugars with poor filtration characteristics.
7. The rosaniline method for the determination of sulphite in white sugar (ICUMSA Method GS2-33) retains its Official status.
The enzymatic method for the determination of sulphite in white sugar (ICUMSA Method GS2/3-35) is also Officially adopted.
8. The Miller-Ihli method, given in Appendix 3 of the Referee’s Report, should be drafted into ICUMSA format and adopted as the Official ICUMSA Method for ‘Lead in White Sugar’. This method will then replace the HGA/AAS method for lead given in ICUMSA Method GS2/3-23.
9. ICUMSA should cooperate via the US National Committee in the collaborative studies proposed by the ILSI and the AOAC to develop new HGA/AAS methods for the determination of arsenic and copper in white sugar.
10. The colorimetric methods for iron (ICUMSA Method GS2/3/7/8-31 ), arsenic (ICUMSA Method GS2/3-25), lead (ICUMSA Method GS2/l /3-27) and copper (ICUMSA Method GS2/3-29), contained in the Methods Book, are adopted as Accepted methods.
11. The method for the determination of the reflectance of white sugar (ICUMSA Method GS2-13) is Tentatively adopted.
12. The Tentatively adopted Coca-Cola method for the determination of acid-floc in white sugar (Sugar Analysis: ICUMSA Methods, 1979, 186-187) should be added to the Methods Book.
13. The Tentatively adopted method of Schneider, Emmerich and Ticmanis for the determination of surface and total water in white sugar by Karl Fischer titration (Sugar Analysis: ICUMSA Methods, 1979, 117-119) should be added to the Methods Book.
1-1. The white sugar methods in Table 2 of the Referee’s Report, i.e. for citric acid, betaine, reduced buffer power and the Dubourg method for pH, are withdrawn.
15. The method for the determination of gravimetric ash in white sugar is no longer required and is therefore withdrawn.
16. Further work of this General Subject should be directed at continuing the collaborative test programme listed in Table 1 of the Referee’s Report.
The priority allocated to testing a method should accord with that shown in the Table. Where new methods are required, collaborative studies should be delayed until the new method is in place.
General Subject 3: Speciality Sugars.
Referee: R W Plews (UK)
1. The Boehringer Mannheim method for the determination of sulphite in Specialty Sugars (ICUMSA Method GS2/3-35) is Tentatively adopted for such sugars [Editorial note: Under General Subject 2, ICUMSA Method GS2/3-35 was Officially adopted for the determination of sulphite in White Sugar].
2. The Reichel method for the determination of anti-caking agents in powdered sugar (ICUMSA Method GS3-21) is adopted as an Accepted method and collaborative tests should be undertaken with a view to making it an Official method. Similarly, polarisation methods for the determination of anti-caking agents should be collaboratively tested.
3. A definitive method for the determination of colour in brown sugar should be further studied.
4. ICUMSA Method GS3/5/7/8-3 is Officially adopted for the determination of sucrose in sugar syrups.
5. HPLC, HPIC, NIR and enzymatic studies applied to Specialty Sugars should be ongoing [Editorial note: Later, under Subject 2 “Olioosaccharides and polysaccharides”, it was recommended that the HPAEC method described in Appendix 5 of the Subject 2 Report could qualify for Tentative adoption under General Subject 3, being valid for monosaccharide contents >5% and sucrose contents >10%. The question of Official adoption for monosaccharides should be decided by the Referee for Subject 3. However, this was not made a General Subject 3 Recommendation. It was agreed to make reference to it here.]
6. The determination of the dry substance of very pure syrups by refractometric techniques (see Specification & Standard SPS-3 and ICUMSA Method GS4-13) is Officially adopted.
7. The determination of the dry substance of Specialty Sugars by modern Karl Fischer techniques should be investigated.
General Subject 4: Molasses
Referee: C J Shelton (UK)
1. ICUMSA Method GS4/7-l is adopted as an Accepted method.
2. ICUMSA Method GS4-5 is adopted as an Official method.
3. ICUMSA Methods GS4-13 and GS4-15 are adopted as Accepted methods.
4. A collaborative trial should be conducted between expert sugar analysis laboratories on the following ICUMSA molasses methods:
GS4/7- 1 Polarisation
GS4/3-3 Reducing sugars (Cane); Lane and Eynon
GS4-5 Reducing sugars (Beet); Lane and Eynon
GS4/3-7 Total reducing sugars; Lane and Eynon
GS4/3-9 Total reducing sugars; Luff-Schoorl
GS4- 1 3 RDS %
GS4- I 5 Brix; hvdrometer
5. The performance criteria established by Recommendation 4 should be appended the relevant method descriptions in the Methods Book.
6. ICUMSA Method GS4/3-9 is adopted as an Official method.
7. ICUMSA Method GS4/7-l l “The Determination of Dry Substance and Moisture in Molasses by Vacuum Oven Drying and Sand’ is adopted as an Official method.
8. Studies should be undertaken with the aim of developing an alternative clarification agent to lead in ICUMSA Method GS4/7-1.
9. Work should be undertaken to investigate the feasibility of developing a modern Karl Fischer method for the determination of water, and hence dry substance, in molasses.
General Subject 5: Cane
Referee: M A Brokensha (South Africa) – Report presented by K J Schäffler (South Africa)
1. Clarification reagents for polarisation measurements based upon aluminium salts, e.g. aluminium chlorides combined with calcium hydroxide, with or without flocculating agents, as well as membrane filtration systems, should be studied and compared, as a matter of urgency, with a view to replacing lead-based reagents.
2. Investigation into the application of near infrared spectroscopy to cane analysis should be continued.
3. Development of a suitable cane juice preservation procedure, to facilitate international collaborative studies, should be continued.
General Subject 6: Beet
Referee: W Mauch (Germany)
I. In view of the importance of samples being both representative and homogeneous, proposals should be developed 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. To minimise negative influences on the brei during deep-freezing and deep-freeze storage, standard conditions should be developed.
3. In view of the widespread use of digestion-filtration units, proposals for the standardisation of relevant instrumental and analytical parameters should be developed.
4. Since the results of comparisons of potassium and sodium determinations after clarification with aqueous solutions of lead acetate and aluminium sulphate are available, a collaborative test using aluminium sulphate clarification should be conducted to establish Official status for this method.
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 methods should also be checked for causes of systematic errors.
General Subject 7: Cane Sugar Processing·
Referee: O L Crees (Australia)
1. ICUMSA Methods GS7-25 and GS7-27 derived from the ASTM method for the analysis of available calcium oxide in lime, are Officially adopted.
2. The methods listed in Table 1 of the Referee’s Report, other than those referred to in Recommendation 1 (i.e. ICUMSA Methods GS7-3, GS7-5, GS7-7, GS7-9, GS7-1l , GS7- 13, GS7- 15, GS2-33, GS7- 19 and GS7-21 ) are adopted as Accepted methods for the analysis of cane processing products [Editorial note: ICUMSA Method GS2-33 remains Official for sulphite in white sugar and in the next updating of the Methods Book the Accepted status of this method for cane processing products will be noted].
3. The possibility of modifying the methods for polarimetric sucrose analysis, to include optional use of alternatives to lead salts, should be investigated.
4. It is recommended that methods of measuring the extent of microbiological degradation during processing are to be investigated in collaboration with the Referee for Subject 14.
General Subject 8: Beet Sugar Processing
Referee: J-P Lescure (France)
1. The Schäffler GC method (ICUMSA Method GS3/5/7/8-3) is Officially adopted for sucrose determination in intermediate processing products after juice purification. To extend the applicability of this method, further studies should be undertaken on the preparation of cossettes and raw juice.
2. The method derived from the 2nd Commission Directive of the European Union (formerly EEC), No. 71/393, for the determination of the moisture content of animal feeding-stuffs by heating under a reduced pressure of 13.3 kPa, with the sample prepared manually or mechanically without heating, is Tentatively adopted for the determination of the loss on drying of beet pulp pellets.
3. The Luff Schoorl method derived from the 1st Commission Directive of the European Union (formerly EEC), No. 7l/250, for the determination of the total sugar content of beet pulp after inversion by hydrochloric acid and the ICUMSA method (Proc. 20th Session ICUMSA, 1990, 324-327) applicable to pulp pellets, are adopted as Accepted methods and written up as ICUMSA Method GS8-5.
4. ICUMSA Method GS8-7 for the determination of crude ash in beet pulp at 550 °C, derived from the 1st Commission Directive of the European Union (formerly EEC), No. 71/250 and the ICUMSA method for the determination of sulphated ash at 650 °C (ICUMSA Method GS 1/3/4/7 /8-11 ) are Officially adopted for the analysis of ash in pulp pellets. Because the results obtained by these two methods are not equivalent, ‘Crude Ash’ or ‘Sulphated Ash’ should be indicated with the results.
5. Methods for the determination of ash which is insoluble in hydrochloric acid and for calcium. potassium and sodium, which are in the hydrochloric acid-soluble portion. derived from the 1st Commission Directive of the European Union (formerly EEC), No. 71/250. are adopted as Accepted methods for beet pulp pellets.
Sample ashing may be either by the sulphated ash method at 650 °C or by the crude ash method at the relevant suitable temperature (450 °C for potassium and sodium determinations and 550 °C for other determinations).
6. Further studies should be undertaken on methods of sampling and preparation of homogeneous and representative sub-samples of pellets of dried beet pulp.
7. The enzymatic GPT method (Proc. 18th Session ICUMSA, 1982, 320-323) for L- and D-lactic acids, written up as ICUMSA Method GS8/4/6-13, is adopted with Accepted status for lactic acid determinations in process products.
8. It is recommended that ICUMSA, through the Referee for Subject 3, give consideration to endorsing, or commenting on, the application of the “Harmonised ISO/IUPAC/AOAC Protocol for the Proficiency Testing of (Chemical) Analysis Laboratories” to process control laboratories.
9. Alternative methods for process control should be evaluated against a reference method within the laboratory. AFNOR work should be used as a guide for this purpose.
10. Studies should continue to eliminate lead clarification in laboratory work.
General Subject 9: Starch-derived Sweeteners.
Referee: G Mitchell (Belgium) – Report presented by W Uhlenbrock (Germany)
No Recommendations were adopted. The President is to discuss the future of this Subject with the Referee.
Subject 1: Constitution and By-Laws
Referee: M R Player (Australia)
The revised Constitution and By-laws which formed Appendix 1 of the Referee’ s Report is adopted, with the exception of Article V of the By-Laws which will be changed to read:
“The language to be used shall preferably be English but simultaneous translation will be conducted in French and/or German.”
Subject 2: Oligosaccharides and Polysaccharides
Referee: K Thielecke (Germany)
I. The role of the oligosaccharides and polysaccharides in cane and beet sugar products according to the recommendations of the US-NCSA, given in Appendix 1 of the Referee’ s Report, should be further studied.
The modified C&H method for starch in raw sugar should be further investigated in comparison with other methods.
2. Enzymatic methods, such as the modified FZB method for dextran determination, given in Appendix 4 of the Referee’s Report, should be further studied. The separation step and the colour reagent in this method both seem capable of being improved. Any improved method ultimately devised should also be extended to the determination of levan.
3. Immunological and other practical methods for dextran determination should be further studied. The molecular weight range of the analyte should be defined.
4. Pectic acid methods based upon enzymatic hydrolysis with pectinases or pectate lyase should be further developed. Quantitative evaluation of the reaction products should be made by HPAEC and the results obtained compared with those obtained by photometric techniques.
5. The Tentatively adopted enzymatic method for a-galactosides and raffinose in beet processing samples (ICUMSA Method GS8/1/2/3/4-19) should be collaboratively tested with a view to making it Official.
6. The Schiweck HPLC method for raffinose, galactinol and kestoses, which was Tentatively adopted (Proc. 18th Session ICUMSA, 1982, 262), is now withdrawn.
7. A collaborative test should be carried out for the determination of raffinose in beet molasses, using the HPAEC method with PAD detection. The test method should be drawn up by combining the details from the following methods:
a) The Braunschweig Institute method for fructose, glucose and sucrose in liquid sugars (Appendix 5 of the Referee’s Report).
b) The IRIS method for raffinose in beet molasses (Appendix 3 of the Referee’s Report).
c) The SMRI method for raffinose in beet molasses (Appendix 1 of the Subject 8 Report).
8. The extension of the HPAEC/PAD technique to the determination of other primary oligosaccharides in impure sugar products should be studied. The use of pH reference electrodes for PAD detection should also be studied.
9. The HPAEC method for fructose, glucose and sucrose described in Appendix 5 and tested as described in Appendix 6 of the Referee’s Report, could qualify for Tentative adoption under the auspices of General Subject 3, being valid for monosaccharide contents >5 % and sucrose contents > 10 %. The question of Official adoption for monosaccharides should be decided by the Referee for Subject 3.
10. Work aimed at preparing analytical standards, especially kestoses, nystose and galactinol, should be encouraged.
Subject 3: Method Format, Collaborative Testing and Statistical Treatment of Data
Referee: Mary Ann Godshall (USA) – Report presented by R Wood (UK)
1. The minimum requirement of 8 laboratories for a collaborative test continues, but it is desirable that 9-10 laboratories participate whenever possible.
2. A method should not be precluded from being collaboratively tested if only one instrument meets the specifications for the test.
The method specifications should be written generically. The report of the test should carry a disclaimer that, at the present time, this is the only instrument which meets the criteria but, as other instruments become available, they too will be accepted. The acceptability of the test method does not constitute an endorsement of any manufacturer by ICUMSA.
3. In collaborative testing, great care must be taken with sample selection, distribution and handling. There should be only a single preparer of samples; samples should be sent out together at one time and blind duplicates should be used whenever possible.
4. The method write-up must be clear, concise, and very detailed to prevent, as much as possible, ambiguities and opportunities for misinterpretation. It is better to spell everything out rather than to assume that something is understood because of familiarity with the method.
Circulation of the method write-up to participants prior to the test, for comments, continues to be recommended.
Subject 4: Polarimetry and Quartz Plates
Referee: A Emmerich (Germany)
1. The principles laid down in Appendix 1 of the Referee’s Report (and in ICUMSA Specification & Standard SPS-1) for the calculation of the rotation values of a normal sucrose solution and the 100 °Z point for quartz control plates, as well as the figures given there. rounded to 3 decimal places, are Officially adopted.
2. Efforts to establish basic rotation values for sucrose solutions and quartz in the near infrared region of the spectrum should be pursued urgently. with the aim of presenting the final results during the current Session.
Subject 5: Dry Substance
Referee: G Vaccari (Italy) – Report presented by G Mantovani (Italy)
1. Based upon the results of the collaborative tests carried out on cane and beet raw sugars having different moisture contents, but bearing in mind the desirability of having a single method for raw sugar analysis, ICUMSA Method GS2/l /3-15 is to be used for the determination of moisture by loss on drying for both cane and beet raw sugars.
2. Modern Karl Fischer titration methods should be collaboratively tested for the determination of moisture in molasses as well as raw and refined sugars.
3. NIR spectroscopy for the determination of moisture should be further studied to decide whether collaborative studies are feasible.
4. The infrared radiation method for the determination of moisture of various products should be further investigated to decide whether collaborative studies are feasible.
5. Problems concerning methods for the determination of dry substance in products such as liquid sugars, vinasse and beet pulp should be included in Subject 5, in cooperation with other Subjects.
Subject 6: Spectrophotometry
Referee: G Mantovani (Italy)
1. As recommended by the Referee for General Subject 2, the Miller-Ihli method is Officially adopted for the determination of lead in white sugar and the new HGA/AAS methods proposed by the ILSI and the AOAC for the determination of arsenic and copper in white sugar are to be collaboratively tested.
2. The method for the determination of formaldehyde in white sugar, as described in Appendix l of the Referee’s Report. is Tentatively adopted.
3. Near infrared spectrophotometric methods should be further studied.
4. The Blue Number method and fluorometric analysis for the determination of α-amino nitrogen should be further studied.
Subject 7: Colour, Turbidity and Reflectance Measurements
Referee: R Riffer (USA) – Report presented by S J Clarke (USA)
1. Ceramic or other stable standards should be investigated as reference materials for reflectance measurements on white sugar.
2: The determination of turbidity in sugar solutions by measurement of the 90° scatter should be further studied.
3. Investigation of reflectance measurement for the evaluation of the colour-type of white sugars should be continued, including comparison with tristimulus systems.
4. Efforts should continue, at a low priority, to test reflectance measurements of brown sugars internationally.
5. In the measurement of sugar colour (ICUMSA Methods GS1-7 and GS2/3-9), the data presented in Table 3 of the Referee’s Report should be adopted as guidelines for solution concentration and cell length.
6. The filtration step in the ICUMSA Method GS1-7 for raw sugar colour should be further studied with the aim of specifying conditions under which faster filtration rates can be obtained.
7. Studies should be undertaken on white and raw sugars to compare the results for solution colour using TEA buffer for pH adjustment with the results obtained using HCI/NaOH. The stability of the TEA buffer itself and the pH and/or colour stability of solutions buffered with TEA should also be investigated. If these initial studies are satisfactory, collaborative tests should be undertaken.
Subject 8: Chromatographic Techniques for Sugars
Referee: K J Schäffler (South- -Africa)
1. The HPIC procedure, described in Appendix l of the Referee’s Report, is Officially adopted for the analysis of sucrose, glucose and fructose in cane molasses and for sucrose in beet molasses.
2. The GC procedure described in Appendix 8 of Subject 8 in 1986 (Proc. 19th Session ICUMSA, 1986, 134-141) is Officially adopted for the analysis of sucrose, glucose and fructose in cane molasses.
3. The use of GC and HPLC for the determination of glucose and fructose in specially, raw and white sugars should be further investigated.
Subject 9: Chromatographic Techniques for Non-Sugars
Referee: P Bourlet (France)
1. The ion chromatography method for the determination of chloride, sulphate and oxalate in white sugar, refined sugar products and raw sugar could be evaluated in a collaborative test if the Referee for General Subject 2 so requests it.
2. Investigation of the determination of sulphite by HPIC is required to compare the results obtained with those given by the optimised Monier Williams method published by the AOAC.
3. The determination of the inorganic anions in various factory samples, including molasses, should be evaluated in a collaborative study.
4. The HPLC procedure for the determination of betaine in beet brei and beet molasses should be evaluated in a collaborative study. It must be ensured that there is no interference between the analyte and other compounds, especially glutamine.
5. Developments in new separation techniques involving capillary electrophoresis and isotachophoresis should be monitored.
Subject 10: Enzymatic and Immunological Methods
Referee: S J Clarke (USA)
1. A series of criteria should be established for the standardisation of enzymatic reagents used in both existing and new 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 cooperation with the appropriate Referees, in order to assess the validity of existing enzymatic methods (e.g. for sulphite, glucose, fructose, lactic acid etc.). Specifically, the Referee for Subject 10 should cooperate with the Referee for Subject 15 with the goal of replacing the currently available reducing sugar methods with more direct methods.
4. New enzymatic methods should be developed with the collaboration of interested laboratories (e.g. for pectin, glutamine, ammonia etc.)
5. Methods that use enzyme electrodes and other biosensors should continue to be studied. This work should be done in close collaboration with the instrument manufacturers.
6. An intensive literature search should be conducted on biosensors used in carbohydrate and related analyses.
Subject 11: Density
Referee: F Spieweck (Germany) – Report presented by A Emmerich (Germany)
For technical application in aqueous sucrose solutions, the values of the polynomials (2) and (3) in the Referee’s Report are Officially adopted.
Subject 12: Rheology
Referee: R Broadfoot (Australia) – Report presented by O L Crees (Australia)
1. The viscosity data for pure sucrose solutions having dissolved solids concentrations of greater than 75 % m/m, given in Table 1, Part 1 of ICUMSA Specification & Standard SPS-5, are Officially adopted.
2. The Pidoux formula, given in Part 2 of ICUMSA Specification & Standard SPS-5, is adopted with an Accepted status.
3. The Breitung diagram, given in Part 2 of ICUMSA Specification & Standard SPS-5, is adopted with an Accepted status.
4. The rotating cylinder method for undertaking rheological measurements on molasses, given in Part 3 of ICUMSA Specification & Standard SPS-5 is Officially adopted.
5. Further studies should be conducted into the pipeflow method for both massecuites and molasses.
6. In using the 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 coaxial 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. Further studies into this aspect should be conducted.
7. Studies should continue to investigate those factors which influence the rheological properties of molasses and massecuites. This work should include problems of crystal migration and sedimentation which may occur in the field of shear while measuring the viscosity of massecuites.
8. Investigations of the elastic flow properties, tack, interfacial tension and surface tension of molasses and massecuites should be continued.
Subject 13: Refractive Index
Referee: K-J Rosenbruch (Germany)
1. Table 2 of the Referee’s Report (and Table F of ICUMSA Specification and Standard SPS-3), giving corrections to the refractometric determination of dry substance for very high purity syrups containing sucrose and invert sugar, is Officially adopted.
2. Studies of the accuracy achievable in refractive index measurements on technical sugar solutions using commercially available refractometers should be continued.
Subject 14: Microbiological Tests
Referee: Ruth Strauss (Germany)
1. To facilitate comparative investigations, an ICUMSA procedure for microbiological sampling should be prepared.
2. Comparisons of nutrient media for the determination of slime-forming bacteria should be made on samples examined for such bacteria in practice.
Either the pour plate method or the membrane filter method may be used.
The comparison should be between the Weman and McClesky-Faville media described in ICUMSA Method GS2/3-45, as well as the MRS Agar medium, viz.
| MRS Agar | (1 L) |
| Peptone | 10 g |
| Beef extract | 8 g |
| Yeast extract | 4 g |
| Glucose | 20 g |
| Di-calcium hydrogen phosphate | 2 g |
| Tri-ammonium citrate | 2 g |
| Sodium acetate 3 H2O | 5 g |
| Magnesium sulphate 7 H2O | 0.2 g |
| Manganese sulphate 4 H2O | 0.05 g |
| ‘Tween 80’ | 1 mL |
| Agar | 10 g |
| pH | 6.2 |
3. For detecting yeasts and moulds using ICUMSA Method GS2/3-47. comparative studies should be made using an incubation temperature of 25 °C. as recommended by ISO. with using a temperature of .30 °C, as presently specified in the method.
4. A method based on ICUMSA Method GS2/3-47 should be developed for the detection of osmophilic yeasts in liquid sugars. In this connection Recommendation 3(b) (Proc. 20th Session ICUMSA 1990, 308 should be taken into account. Additionally, double concentrated Wort Agar should be enriched by the addition of 400 g of sucrose and 20 g of glucose per litre, in order to promote the growth of osmophilic yeasts. Where a membrane filter technique is used, the washing steps should be carried out with bacteriological sodium chloride solution.
5. In ICUMSA Method GS2/3-49 for the determination of thermophilic spore-forming bacteria, the bromocresol purple acid-indicator may he left out if there is no need to determine ‘flat sours’. It has been demonstrated in a number of comparative studies that growth-inhibition occurs with this indicator. Further studies are therefore recommended with phenol red as an alternative acid-indicator at concentrations of 0.8 and 0.4 g/L of medium employed.
6. It is recommended that those laboratories with experience of the rapid automated bacterial impedance technique submit their findings to the Referee for inclusion in the 1998 Report.
7. Investigations should be undertaken into methods for the detection of pathogens, with attention being directed to Salmonella in the first instance.
Subject 15: Reducing Sugars
Referee: J Laursen (Denmark) – Report presented by R F Madsen (Denmark)]
1. The Luff-Schoorl method (ICUMSA Method GS4/3-9) is Officially adopted for the determination of total reducing sugars in syrups.
2. The Luff-Schoorl method, (ICUMSA Method GS4/3-9), Officially adopted under General Subject 4 for the determination of reducing sugars in molasses, should be collaboratively tested on molasses.
3. Increasing the range of the Knight and Allen method (ICUMSA Method GS2/3-5) by adding pure, invert sugar-free sucrose is, in practice, impossible. This problem must be solved by those in favour of this method before considering a collaborative study [Editorial note: See also General Subject 2, Recommendation 2].
4. The Berlin Institute method (Sugar Analysis: ICUMSA Methods, 1979, 55-56) for the determination of reducing sugars in white sugar should be collaboratively tested.
5. The Lane and Eynon method (ICUMSA Method GSl/3/7-3) and the Berlin Institute method should be collaboratively tested for the determination of reducing sugars in raw sugar.
6. All details of the protocol of a method should be clarified before starting collaborative studies. This is best done by sending the written-up method to participants for their comments.
7. Instrumental methods for the determination of reducing sugars should be studied.
Subject 16: Ash
Referee: J-P Ducatillon (France)
1. The crude ash method (ICUMSA Method GS8-7) and the sulphated ash method for analysing beet pulp are recommended to the Referee for General Subject 8 for validation.
2. A collaborative study should be carried out on raw sugar samples and in cooperation with the Referee for General Subject I to compare the WAP method and the CSR method with the Official ICUMSA sulphated ash method (ICUMSA Method GS 1/3/4/7/8-11).
3. Regarding temperature corrections in conductivity ash determinations, Recommendation 2 of Subject 16 in the 16th Session, 1974 is withdrawn. The following new Recommendation replaces it:
“For the determination of conductivity ash, the standard temperature is 20.0 °C. Measurements at other temperatures (T in °C) are to be corrected by the following formulae:
For measurements at 28 g/100 g: χ20 = χ/[1 + 0.026 (T – 20)]
For measurements at 5 g/100 ml: χ20 = χ/[l + 0.023 (T – 20)]
The maximum permissible temperature deviation from 20 °C is ± 5 °C.” [Editorial Note: ICUMSA Methods GS2/3- l 7 (28 g/100 g) and GS l /3/4/7/8 -13 (5 g/100 ml) each give these latest temperature correction formulae.]