DEVELOPMENT OF AN ALTERNATIVE METHOD FOR DETERMINING DEXTRAN IN PROCESS MATERIAL FOR ACP SUGAR PRODUCING COUNTRIES Earle V. Roberts Sugar Industry Research Institute of the Sugar Industry Authority of Jamaica Background The sugar cane industries of ACP countries face several challenges to maintain access to existing international markets, especially in Europe and the USA. as a result of the decision by the EU to implement changes to the Sugar Protocol which governs trading arrangements between the two groups of countries. Although the most serious of these was the reduction in the price of raw sugar paid to ACP countries by the EU, the need to meet increasingly rigorous specifications in quality demanded by sugar refiners in the EU (defined as “fair average quality”) poses similar difficulties. There are several parameters which are embodied in the designation of fair average quality: Polarisation (a measure of the Amount of sucrose present) Safety Factor (Moisture) % Ash Grain size Colour (Whole Raw) Colour (Affined Raw) Dextran 98.0˚ (minimum) 0.30% (maximum) 0.35% (maximum) 8% (maximum) on 355micron screen 4500 I.U. (maximum) 1200 I.U. (maximum) 200 m.a.u. (maximum) Acceptable sugar quality is largely dependent on the quality of the raw material (the sugar cane) received for processing. One of the impurities present in raw sugar is dextran, a polysaccharide produced by the action of bacteria, in particular Leuconostoc mesenteroides, which is present in soils. The higher temperatures associated with the growth of sugar cane under tropical conditions favour bacterial growth. Consequently, dextran formation poses a more serious problem for sugar cane producers than for beet growers. Dextran repeating unit The presence of Dextran in raw sugar is a major concern to the sugar cane industry for several reasons, e.g: - cane growers are paid by the miller for their canes based on the amount of sugar (sucrose) present and dextran inflates the estimation of the amount of sucrosepresent. If there are high levels of dextran present in the juice extracted from the cane, then the grower is paid for sugar that is not present with consequent loss in revenue to the miller. - dextran slows the rate of crystallization of raw sugar, leads to the formation of irregularly shaped crystals and decreases the exhaustion of molasses, i.e. it reduces the recovery of sucrose by “dragging” sucrose (possibly equal to its weight) into the molasses mother liquor. Its presence thus results invariably in increased production costs. - because it is a polymer, dextran increases the viscosity of sugar solutions, frequently slowing the passage of sugar solutions through the refining process to a halt; this results in significant losses of production time with corresponding increases in production costs. - raw sugar suppliers receive lower premiums or, as is the case in U.S. markets, suffer penalties for supplying raw sugar containing dextran at levels greater than an acceptable minimum. A method of determining the level of dextran present in cane juice, process materials (syrups, molasses, raw sugar, etc.) is therefore required. This would allow processors to monitor dextran levels and, where possible, take corrective action to minimize its impact on the quality of sugar delivered to our international markets. Such a method must satisfy the following criteria: (i) (ii) (iii) (iv) It must be rapid and quantifiable. It must be accurate, reliable and reproducible. It must be able to process and analyse within a reasonable time frame the large number of samples required for representative acceptance. The equipment required should be robust and manageable by low level technical staff. Several methods of dextran analysis have been published in the technical and scientific literature but they do not show all of the above characteristics. Those currently employed in the sugar industry are listed below: 1. 2. 3. 4. 5. Haze test for sugars Not specific to dextrans; repeatable but not accurate for juice samples SCGC (Belle Glade Rapid Test) Modified for juices but not specific to dextrans. Roberts Copper Test Specific to dextrans but technically difficult and time consuming (2.5 hr). Rapid Test (SPRI) Not specificto dextrans, not reproducible. Midland MCA Sucrotest Specific to dextrans; not reliable, prohibitively expensive for routine analysis. A method developed by a U.K. based firm, Optical Activity Ltd., in collaboration with the University of Westminster, London, Dextran and Sucrose Analysis (DASA), underwent preliminary field trials by the Sugar Industry Research Institute, Jamaica. Results indicated that the method had the potential to satisfy the criteria stated above but it required further refinement and evaluation. The method, based on Near Infra Red (NIR) polarimetry, evolved from experimental studies which explored the possibility of monitoring enzyme-mediated reactions (e.g. the hydrolysis of polysaccharides such as dextran by substrate-specific enzymes such as dextranase) using polarimetric techniques. Dextran is an optically active dextro-rotatory compound. Hydrolysis of dextran by acids or enzymes converts it to simpler compounds (oligo- and monosaccharides) having polarimetric properties different to those of dextran. Thus, changes in dextran concentration can be monitored by following the changes in the polarimetric properties of solutions containing it when these solutions are treated with dextran-specific enzymes and these changes can be measured and quantified by NIR polarimetry. The method, if successfully developed, - would be useful for identifying and monitoring the occurrence and/or development of dextran in sugar processing operations and could result in considerable reduction in production costs. - would permit the implementation of corrections to current payment systems for cane where the presence of dextran causes inflated polarimetric readings resulting in overpayment for contaminated cane. More importantly, it will allow processors to institute quality control measures to minimise the levels of dextran in raw sugar exported to refiners thus eliminating or at least reducing the possibility of shipments being rejected or being subjected to penalties for containing high levels of dextran. The elimination and/or reduction of dextran in raw sugar exports would also increase the fair average quality demanded by refiners, paving the way for payment of increased premiums for improved quality. In addition, NIR polarimetry has the advantage that, unlike polarimetric methods currently used in sugar laboratories, it does not require the use of clarification reagents, some of which are toxic (basic lead acetate) or expensive (Octapol). The successful development and implementation of the DASA method would have clear operational cost benefits (reduction of laboratory expenses) as well as environmental benefits (reduction of health hazards and of disposal problems associated with toxic chemicals). The successful development and implementation of the DASA method would have clear operational cost benefits (reduction of laboratory expenses) as well as environmental benefits (reduction of health hazards and of disposal problems associated with toxic chemicals). It will be necessary to validate both the DASA method and the analytical results determined for dextran in cane juice and raw sugar against an accepted reference analytical method. It is proposed to use as a reference method the method developed by P. G. Morel du Boil, Proc. S. Afr. Sug. Technol. Ass., 74, 317-327, (2000), which is based on the use of enzyme hydrolysis with dextranase followed by High Performance Anion Exchange Chromatography with Pulsed Amperometric Detection (HPAEC-PAD). The method gives accurate, reliable and reproducible results but is too expensive and time consuming for routine use. Finally, given the general nature of the problem of dextran control in sugar cane production, it was recommended that the project be given some regional character by including other participating ACP institutions as collaborating Project Executing Agencies in the project. The laboratories of the Belize Sugar Industries Ltd. (BSIL), Belize and GUYSUCO Sugar Research Institute, Guyana were invited to participate in the project. An overall budget of €1,186,258 has been approved for the project. Project Personnel: Technical: 1 Senior Investigator (Senior Scientific Officer), SIRI, Jamaica 1 Investigator (Scientific Officer), SIRI, Jamaica 1 Investigator (Scientific Officer), Belize 1 Investigator (Scientific Officer), Guyana Administrative Support Staff, SIRI, Jamaica 1 Biometrician for Statistical Analysis, Part Time (5 Months). It is proposed to implement the project in January 2012 and it will have a life time of 3 years. Activities will undertaken in the first year, 2012 - 2013 at SIRI, Jamaica only. If the results obtained indicate feasibility of the DASA method for routine dextran determination and initial validation of the method is achieved, activities will then be extended to the other Executing Agencies in Belize and Guyana (2013 - 2015). Activity 2012 2013 2014 Year Period I II III IV V VI VII VIII Phase 1, Jamaica only 1.1 Appointment of Technical Staff, 1.2 .Preparation of Laboratory Area --------------- 2.1 Training of Technicians ---------- 3.1 Collection and Analysis of Samples ---------- ----------- 3.2 Technical Services for Raw Sugar Analysis ----------- ------------ 3.3 Laboratory Services for testing and validating analyses 3.4 Evaluation and assessment of results ----------- ---------- ------------ ----------- ------------ 3.5 Additional Analyses ------------ Phase 2, Jamaica, Belize, Guyana 2.1 Training of Technicians in Belize, Guyana ------------- 3.1 Collection and Analysis of Samples ------------ ----------------- 3.2 Technical Services for Raw Sugar Analysis ------------- --------------- 3.3 Laboratory Services for testing and validating analyses 3.4 Final Report 3.5 Capacity Building -------------- --------------------------------- IX Current Status: 1. Human Resources: 1.1.1. Senior Technical Investigator appointed, 01/02/12 Technical Investigator appointed, 01/02/12. 3. Equipment and Supplies: 3.3.3. Dextran Analysis System, Jamaica: Pro forma Invoice invited from Optical Activity, UK. 12/03/12 3.3.7. High Pressure Anion Exchange Chromatography (HPAEC) System European Manufacturers of Equipment not yet identified 3.5.3.Laboratory Area to house Equipment: Construction Plans prepared and approved by Manchester Parish Council. Tender document prepared and applications for construction invited. Final date for submission – April 13, 2012. Preliminary Studies: Good Correlation obtained between Pol values for sucrose solutions with varying dextran levels and dextran values measured on a DASA system (borrowed).