A new clarifier for the Polarization Analysis of

Sugar Solutions

Dawei Gao, Chung Chi Chou, Marie Kuebel

Sugar Processing Research Institute, Inc.

ABSTRACT

In this paper, research for the development of a new clarifying reagent for polarization analysis of various sugar solutions is described. Researchers at SPRI combined a DEAE reagent, a typical ion exchanger, with other reagents that enhanced its performance. These enhancing reagents were selected by orthogonal tests. In order to verify and compare the efficiency of XYZ to commercial clarifying reagents currently used by sugar industry, a series of experiments were designed to measure the pol, Brix, pH, color and turbidity of various sugar solutions clarified by XYZ and commercial clarifying reagents.

After hundreds of parallel tests, it has been verified that the new clarifying reagent, XYZ, showed some desirable properties, which can be described briefly as followings:

Chemical and physical stability, which enabled it to be used and stored easily in various conditions. For example, a sample of XYZ maintained its high efficiency after being left uncovered for one month.

No initial preparation for activation was required.

When XYZ was compared to commercial clarifiers, the following characteristics were observed: better color and turbidity removal for most samples, the Brix and pol were more independent of the dosage, a higher pH range (usually over 7) and faster filtration rates.

1.0 Introduction

Clarification of sugar containing solutions is an important analytical procedure during the pol analysis in the sugar industry1. In recent years, sugar analysts have concentrated on improving this area and have developed new clarifiers to replace the efficient but toxic lead reagent2-5. Due to the complexity of sugar solutions, many problems still exist with these clarifiers. It is optimal for clarified sugar solutions to have low color and turbidity. SPRI has found that DEAE reagents, such as DEAE Bagasse (U.S. Patent No. 5,504,196), exhibit a superior capacity for removing color and turbidity from sugar solutions while not significantly affecting the pol. SPRI has developed a new DEAE-based clarifier, XYZ, that combined the properties of DEAE with other clarification enhancing compounds.

The functional group believed to be responsible for aiding clarification of the sugar solution is the N-group of the DEAE reagent6. When it is combined with other ingredients, its capability to react with many types of colorants and impurities improves. The components of XYZ are not optically active and the clarification is independent of the sample’s pH; thus the XYZ reagent can be used for clarifying various sugar solutions from cane mills, beet factories and raw sugar refineries.

2.0 Apparatus and Reagents

Refractometer with temperature compensation (TC) system

Automatic polarimeter equipped with 586nm and 880nm wavelengths

pH meter with automatic temperature compensation (ATC)

Spectrophotometer equipped with 420nm wavelength

Magnetic stirring plate, 6 heads with suitable stirring bars

Flasks--100, 200, 500 and 1000 ml volumetric flasks

Beakers--150, 250, 1000 ml

Stemless glass funnels

Watch glasses, 90-mm dia.

Filter paper, Whatman #91

XYZ reagent, prepared at SPRI

Commercial clarifying reagent (I)

Commercial clarifying reagent (II)

Wet Lead reagent

Other commercial reagents for regular ICUMSA pol analysis

 

3.0 Procedures

The experimental procedures are a modified ICUMSA method7 derived from current, common clarifiers used for routine pol analysis in various sugar mills8. The following are described briefly:

3.1 Raw sugar (A or B sugar)

Weigh 26.00g of raw sugar into a 100ml volumetric flask; add 70ml water to dissolve then carefully fill it to the mark and stir. Pour the solution into a 150ml dry beaker and cover with a watch glass (take the Brix if purity is tested).

Add 2-5g of XYZ, or other reagent, and stir for one minute, covered with a watch glass.

Seat a stemless funnel on a 150ml beaker and filter the solution through a Whatman #91 filter paper. Cover the funnel with a watch glass while filtering.

Discard the first 10ml of filtrate; then collect a volume sufficient for pol analysis.

Rinse the monitor tube 3 times with the clarified solution; then fill it without trapping any air bubbles.

Put the tube in the Automatic Polarimeter and read the figure displayed. Repeat the reading at least 3 times for each sample.

 

3.2 Masscuite and molasses (including the C sugar)

Dilute 13.00g of material with water to the mark of a 200ml flask and stir, covered with a watch glass.

Pour 100ml into a 150ml dry beaker and measure the Brix by an Automatic Refractometer.

Add 5-8g of a clarifying reagent (10-15g for final molasses) and stir 1 minute, covered with a watch glass.

Filter as above and measure according to the procedure for raw sugar analysis.

 

3.3 Syrup

Dilute 26.00g of syrup with water to the mark of a 200ml flask and stir, covered with a watch glass.

Pour 100ml into a 150ml dry beaker and measure the Brix.

Add 4-6g of a clarifying reagent and stir 1minute, covered with a watch glass.

Filter and measure according to the above procedure.

 

3.4 Mixed, clarified juice and other juices

Pour 100ml of juice into a 200ml beaker and measure the Brix.

Add 5-7g of a clarifying reagent and stir 1 minute, covered with a watch glass.

Filter and measure according to the above procedure.

For the comparison of tests, the solution should be scaled to the desired volume then divided to several parts. For example, 260.00g of raw sugar are dissolved and diluted to 1000ml then divided into several aliquots of 100ml for clarification by various reagents or various dosages.

4.0 Results and discussion

4.1 Influence of the reagent dosage on the Brix and pH of various clarified solutions.

4.1.1 Influence on the original Brix and pH.

Method: In a 150ml beaker, weigh different dosages of various reagents and bring to a volume of 100ml with water. Stir for 3 min and filter through a Whatman #41 filter paper, check the Brix and pH of the filtrate. The results are shown in Table 1.

Discussion: XYZ (I) and XYZ (II) increased the pH value of water, but XYZ (I) had nearly no influence on its Brix value. Commercial clarifying reagents and lead decreased the pH and increased the Brix of water; these characteristics may affect polarization readings in actual analysis.

4.1.2 Influence on the Brix and pH of clarified sugar solutions.

Method: according to the procedures in 3.0. The results are shown in Table 2.

Discussion: The values of the Brix of filtrates clarified by commercial clarifying reagents are always higher than the original Brix and the values of the pH are always lower than 7. For XYZ (I), Brix values are closer to the original and the pHs are higher than 7.

4.2 The ability of a reagent to minimize the effect of dextran on the pol of a pure sucrose solution.

Method: Dissolve 26.00g pure sucrose in 70ml water in a 100ml volumetric flask; then add 1000ppm of dextran and dilute with water to volume; stir. Add the reagent and check the pol by the usual method. The results are shown in Table 3.

Discussion: It has been established that dextran falsely exaggerates the Pol reading. XYZ elevated the pol less than that of commercial clarifying reagent (I).

4.3 The efficiency of a reagent after being stored uncovered.

Method: Weigh a desired quantity of reagent, put it on a lab shelf uncovered and check its performance after various time periods. Color and turbidity were determined according to the ICUMSA method. The results are shown in Table 4. Reagent dosage: 5 grams.

 

*C.R.---Commercial Clarifying Reagent **XYZ (II)---For dark materials

Discussion: After only 2-4 days of storage, C.R. (II) was lumpy mainly due to absorption of moisture. A similar situation occurred in C.R. (I). XYZ (II) did not become lumpy. The commercial clarifying reagents easily form lumps when stored uncovered and gradually lose their efficiency while XYZ (II) is more stable.

4.4 Effectiveness for dark materials.

Method: According to the procedures listed in 3.0. Original color and turbidity were

determined according to the ICUMSA method. The results are shown in Table 5.

Discussion: XYZ (II) showed a superior ability in both color and turbidity removal and increased filtration rates for an array of dark materials when compared to commercial clarifying reagents.

4.5 Effectiveness for light materials.

Method: According to the procedures listed in 3.0. Original color and turbidity were determined according to the ICUMSA method. The results are shown in Table 6.

4.6 Filtration rates and colors of various materials.

Method: According to the procedures listed in 3.0. The colors were determined according to the ICUMSA method. The results are shown in Table 7.

4.7 The pol and purity of processing samples.

Method: According to the procedures listed in 3.0. The results are shown in Table 8.

4.7.1 The pol and purity of various processing samples-2.

4.7.2 Analysis of polysaccharides in A, B, and C sugars before and after clarification by XYZ and A.R.(I).

Method: According to the procedures listed in 3.0. Polysaccharide content was determined by the SPRI procedure. The results are shown in Table 10.

5.0 Conclusion

The XYZ clarifier for polarization analysis is a new DEAE-based clarifying reagent. The performance of XYZ was enhanced by addition of other reagents. In comparison to other commercial clarifying reagents used by the sugar industry, the XYZ clarifying reagent displayed the following desirable properties:

Chemical and physical stability, which enabled it to be used and stored easily in various conditions. For example, a sample of XYZ maintained its high efficiency after being left uncovered for one month. It required no initial preparation for activation.

The Bx and pol of solution clarified by XYZ vary only slightly with different dosages. Commercial clarifying reagents are more dosage dependent. The Bx of a filtrate treated by a commercial clarifying reagent was always higher than that of the original solution. The increase in Brix may introduce error in polarization measurement.

For some sugar materials, especially the darker materials, XYZ exhibited a better capacity for decolorizing, removing turbidity and increasing filtration rates when compared to commercial clarifying reagents. These characteristics enable one to check the pol of a sugar solution at a higher concentration, i.e. without "double dilution" or even further dilutions.

The pH values of sugar solutions clarified by XYZ ranged from 7 to 9, whereas those of other reagents ranged from 4 to 7. This low pH range may contribute to the inversion of sucrose.

For some solutions with abnormally high turbidity, such as the retentate from a membrane ultrafiltration system or deteriorated mixed juice, XYZ can only give a clear solution when cooperating with some finer filter-aid or coagulation reagent. More research needs to be done in the future to alleviate this problem.

 

6.0 #9; References

Chen, J. C. P. and C. C. Chou, Cane Sugar Handbook, 12th Edition. 1993. John Wiley & Sons, Inc., New York, NY.

Clarke, M. A. et al. 1989. Replacement of Lead Salts In Polarimetric Analysis. Proc. Sugar Ind. Tech., pp 219-239.

Chou, C. C. (1987). Alternate Methods of Polarizing Sugar. Proc. Sugar Ind. Tech., pp.1-26.

Clarke, S. J., and Joy Bourgeois. 1990. A simple and safe replacement for dry lead subacetate. Int. Sugar J., 92: p.35.

U.S. Patent No. 5,110,363

U.S. Patent No. 5,504,196

ICUMSA Method Book, 1994 and 1st Supplement 1998, GS1-7, GS1/2/3-1, GS2/3-1, GS2/3-9, GS4/13, GS5/7-1, GS6-1.

Baddley Chemicals, Inc, (1999) Lab Procedure for Using a Commercial Clarifying Reagent In Cane Factory Processing Streams.