ABSTRACT
For many years, the industry has been faced with the challenges of improving sugar quality. With all quality factors of concern, the industry has lost millions of dollars due to penalties and failures to maximize our earnings from premiums.
Progress towards correcting this problem by having high factory operating time and processing clean, fresh canes has been very slow.
As concerns get greater, an organic product, Sugarex, was put on trial at JAMAICA during the 1998/99 and 2000/01 crops. The early results were indeed encouraging, not only in terms of improved sugar quality, but also in factory recovery. These results are presented and discussed.



INTRODUCTION
Over the past many years, there has been serious concerns about the quality of our sugar produced. This is particularly so with respect to the shipments to the United States, where this market has very punitive measures, especially for dextran where the standard is set at 250 mau or 560 ppm. As a result, the industry has incurred penalties amounting to millions of United States dollars, eg.:-


Table I
Comparison of the annual cost in penalty for dextran to the U.S. market

While dextran is the main concern, we have incurred further penalties on whole raw colour, affined colour and ash and have failed to maximize our earnings from premiums on polarization due to low values.

Since 1997, the European refiners have been complaining about the these poor qualities including invert levels (which exceed the range of 0.50 - 0.70 percent) and filterability which reduces the refinery capacity. The answer to these problems is to have factories operating at least 85% of the time, processing clean, fresh canes.

The JAMAICA sugar factory is the main contributor to these problems, with dextran levels for the period 1996 to 2001 as follows:-

*The 2000 result was due to the improved cane quality due to improved harvesting conditions.



JAMAICA Trial 1998/99 Crop
With factories failing to improve on the quality of sugar under existing conditions, chemical products have been used in an attempt to improve our quality. One such product is "Sugarex" which was put on trial at JAMAICA over the last twenty-five (25) days of the 1998/99 crop.

The manufacturers of this product have claimed the following advantages:-
a) Stabilization of the purity of the cane juice and prevention of degradation of sucrose in the milling process.
b) Prevention of dextran and reducing sugars formation during the milling process by the total reduction/elimination of the leuconostoc types, bacteria present in the juice.
c) Improves viscosity and allows for easier handling of materials which enhances sugar recovery.
d) Improves sugar quality.



Procedure
With the very high dextran values reported at JAMAICA, it was decided to shock-treat the milling station at 130 ppm for one day, then continue at the recommended dosage of 66 ppm on cane or at .066 kg per metric tonne. Its application was controlled by metering devices and applied at the crusher and at the last mill juice receiver.



Observations
- Sugar Quality From the results of the sugar quality obtained, there was an immediate positive response to the treatment which began on the 17/05/99 (see Table II). Comparisons are made for the periods
- four (4) days prior to treatment. Seven days of treatment and a further seven days without treatment.



TABLE II
SUGAREX STUDY AT JAMAICA

Cane Quality - Dextran Value
Dextran monitoring in press, crusher and mixed juices commenced four days prior to the trial (see results in Table III).


Table III
Comparison of Dextran in Juices

As expected, the dextran levels will increase in the cane yard, resulting in higher levels in the crusher compared to the core press juice.


For both periods, the results showed that the incoming level for press juice was stable, compared to a reduction in crusher and mixed juices of 77 and 48 ppm or 47.82 and 37.21%, respectively.


Mill Extraction - Purity Drop
The period of the trial coincided with the reduction in throughput due mainly to the shortage of cane. This should give rise to a reduction in the milling efficiency due mainly to an increase in the losses due to sanitation. The comparative results are shown in Table IV.

Table IV
Production Report

Using the purity drop crusher to mixed juice as an indicator, the improvement is suggesting the tremendous effect the product had on the mill sanitation.


Boiling House
The recovery of the factory is determined by expressing the pol recovered in sugar as a percentage of that entering in cane. This may be compared to the boiling house efficiency (BHE) which takes into account the available sugar based upon the Winter and Carp formula. Comparisons of these data are set out in Table V.

Table V

*F.R.I. is the Factory Recovery Index i.e. tonnes 96 degrees sugar recovered/tonnes 96 degrees sugar received in cane at the core sampler.



Observations
The data of the May 15, 1999 was used as the basis for this evaluation. Pol % cane was on the decline, which would have a negative impact on processing.

The molasses pol loss was significantly reduced from 11.44 for week-ending May 15, 1999 to 9.18 on the May 22, 1999 and an increase to 11.73 on May 29, 1999. The undetermined losses were at very good levels. As a result, the factory recovery, the boiling house efficiency (BHE) and factory recovery index (FRI) immediately showed significant improvements (see Table V).




The 2000/2001 Results
Using the report submitted by JAMAICA this has been upgraded making same more detailed.
"JAMAICA ended the year 2000 with one of the lowest level of dextran on sugar in recent times, 150 MAU. This was an unusual reduction considering that the previous year, 1999 crop the level stood at 700 MAU".

The 2000/01 crop began in December with dextran on sugar emerging at 650 MAU and ended with an overage of 576. It is stated that this was a year when typical reaping and factory operations prevailed. Comparison of dextran in 1998 (a typical year) versus 2001 are made in figure 1.

The comparative data of the 2000/01 crop, versus 1999/2000 crop are given in Table VI.


Table VI
Comparative dextran data 2000/01 Vs 1999/00

* M.A.U. calculated from the formula-M.A.U=((PPM-118)x.657)

This shows that-
(a) the incoming dextran in crusher was 37.81% higher than that in core juice for 2000/01 compared to 12.3% in 1999/2000.
(b) the levels in crusher was 6.38 times (or 538.38% more than that in 1999/00).
(c) the levels in sugar was 3.84 times or 284.00%.

Using the 1999/00 data the out-turn dextran in sugar of 150 MAU was 81.08% of the 185 entering in crusher juice a reduction of 18.92%. In extrapolating the 2000/01 level of 1181 MAU under similar conditions, the level in sugar would have been 958. MAU. The 576 MAU reported shows an improvement of 382 MAU or 66.32%.

This improvement must be attributed to changes in the chemical and process control during the crop. The penalty (at the extrapolated level of 958. MAU and US$430.00 per tonne sugar) would be US$34.39 per tonne compared to $13.06 at the 576 MAU achieved a saving of ($34.39-13.06) US$21.33 per tonne.


The major change in the process control at JAMAICA for this crop was the use of Sugarex which was applied over two periods from December 30, 2000 to March 10, 2001 and from April 10, 2001 to May 30, 2001 when a total of 447,643 tonnes of cane or 60.04% of the total of the 745,523 tonnes milled. See Table VII. Further comparisons are made in figure 2 of dextran in press juice and sugar.



Method of Application
The chemical was administered after the first cane knives in the mixed juice trough and into the fifth mill juice tank. This was done on both tandems. The method of dosing was by gravity from two 200-litre tanks, one for each tandem. The actual dosage was regulated by the aid of flowmeters at each dosing point.

The dosing was done for 24 hours with two persons having the responsibility. This was done over 12-hour shifts for each day of operation. They were required to maintain the dosing rate, as prescribed by the laboratory and change the dosing according to the directions of the Quality Control Manager. They were also required to refill the tanks and to ensure that all dosing lines were free and clear of obstructions, in addition to other duties.

The dosing of the chemical encountered problems in the form of:-
1) blockages
2) low chemical dosages due to changing of drums, and
3) defective pump

The nature of the chemical also posed problems of dosing, as attendants in and around the dosing points occasionally turned off or lowered the flow because of the fumes emanating from the chemicals mixing with the warm juices. This impacted on the average dosing.



Results
First Phase
The first phase of dosing was from December 30, 2000 to March 8, 2001. There were occasional stoppages during this period for reasons stated above.

Dosing began after the dextran levels in sugar showed signs of increasing steadily. The dextran in sugar reached an alarming 1500 MAU and was lowered to 220 MAU and 215 MAU two days later. With this pattern, it was then decided to begin dosing continuously as the levels were unpredictable. During this period, the average levels were 924 ppm at the core, 1522 ppm or 922 MAU at the crusher and 494.64 in sugar a reduction of 427 MAU or 46.35%.

During the period without Sugarex (March 9 2001 to April 27, 2001) a total of 209,214 tonnes cane was processed without any chemical treatment. The levels of dextran were of 1760 ppm in crusher juice or 1078.79 MAU and 879 MAU in sugar, a reduction of 200 MAU or 18.52%.

Final Phase
This phase started on April 28, 2001 until May 30, 2001 with a dilution of 2:1, i.e. two parts of water to one part Sugarex. This was done as the final shipment was said to be triple strength.

During this final phase of dosing, the rate went as low as 43 ppm as a result of triple strength dosing. This would therefore translate to one hundred and twenty-nine parts per million (129 ppm) This however did not result in a corresponding reduction in dextran in sugar. In straight figures, dextran in core juices were at 2181 ppm crusher juice 2635 ppm or 1654 MAU and dextran in sugar was 830.01 MAU. This showed a reduction of 824 MAU or 49.82%. This was by far the highest loading of dextran for the entire crop. One major contributor was the increased rainfall, resulting in excess mud entering the factory an ideal conditions for the proliferation of the Leuconostoc Mesenteriodes bacteria.

The higher dosing rate required in this phase introduced the thought that the bacteria may be building up resistance against the biocide. However, the buildup of the bacteria during the non-treatment period in the system must be considered as with constant dosage this would have been prevented.

The average dextran after June 6 until June 16, 2001 showed core 2544 ppm; crusher 3435 ppm; MJ 3938 ppm and sugar 1255 MAU. There was a marked increase in dextran at the core and a corresponding increase on the mills-the dextran in sugar showed a slight decrease. The residual Sugarex in the process during the milling of 45,523 tonnes cane is not considered. See TABLE VII

TABLE VII
Comparative for the five periods of operations - 2000/01

*Periods of sugarex treatment



Discussion
The rise in the incoming dextran at the core triggered a corresponding rise in the dextran levels of the subsequent juices.

The fact that there may not be an exponential growth on the mills can be directly attributed to the mill sanitation programme practiced. The factory utilized the hot condensate to clean the mills and the DSM screens whenever the factory stops for more than thirty minutes. While the dextran in mixed juice is not available for comparison with that in crusher juice and sugar, there was an additional positive impact of the sugarex treatment as follows:

(a) Polarisation/W.R. Colour/AFF. Colour/Starch/Filterability/Inverts
As the data shows all these quality factors showed immediate positive movement with the highest values recorded in the periods of treatment as set out below:

N/A = not available
* Periods of treatment

Comparative graphs are attached showing

(b) Factory Recovery Index (F.R.I)
This indicator of factory efficiency is severely influenced by cane quality, factory operating time and process control. Comparison of the data for the five periods of operations shows:

For the second period, the improvements in JRCS from 8.16 to 9.39 FRI brought about an increase of 6.27 units of FRI with the use of sugarex. This resulted in an increase in sugar production of 1,889.92 tonnes.

The third period showed a further increase in JRCS but a significant decline in FRI below the second period. Interestingly, this was the peak period for cane quality and the F.R.I. should have been maintained. This resulted in a loss of production of 1099.37 tonnes of sugar if the 95.76 F.R.I. was maintained compared to the 90.53 reported.

In the fourth period the cane quality declined and the F.R.I. fell by 8.84 units. This was at a time when the incoming dextran was extremely high making the recovery difficult. For the fifth and last period the decline continued. See Figure 9



(c) Boiling House Operations
M. Ju Pty/Pol in M.Ju/B.H.E./Molasses Pol.Loss/Undetermined losses
Like the F.R.I. data the best period of performance was period two- the first phase of sugarex application. Although this coincided with a slight improvement in mixed juice purity over period one, it was lower than period three when the best juice quality was experienced. B.H.E. peaked and molasses Pol loss was at its lowest in period two. The decline in period four (that is the final phase of treatment) coincided the declining juice quality.

The comparative date are presented below:

Comparative Boiling House Data

*Period of sugarex treatment

The comparative data for B.H.E. and undetermined losses are presented in figure 10. Note the immediate and continued improvement upon treatment for the two phases.



Conclusion
The total tonnes of cane treated was 447,643 with 150 drums of chemical or 30,600 kilograms of Sugarex costing US$114,750.00, at average dosing rate of 68 ppm. This is 60% of the total canes crushed and was done for 101 days. The non-dosing periods saw higher dextran levels entering the factory and emerging in the sugar.



Benefits
The benefits of using sugarex may be quantified in terms of savings in dextran penalty and revenue for Pol Premium as follows:

Dextran Penalty @US$430.00/T.sugar

*Periods of treatment = average savings/tonne=$16.89



Pol Premium

*Periods of treatment using period "two" as a standard the improvement due from premium averages $2.84 per tonne compared to period "one" and "three".


For the first phase when the F.R.I. improved to 95.76 an additional 1,889.76 tonnes sugar was produced. Should the treatment be credited with 50% of this increase this amounts to US$406,332.80.

The cost of sugarex at 11.63 tc/ts and 66ppm was US$2.91 per tonne sugar treated.

JAMAICA ended the crop with dextran in sugar being 576 M.A.U (SIRI). This happens to be a year when typical reaping and factory operation patterns prevailed.

The chemical was fully tested during the operations and at times did not seem to be effective at higher dextran levels. The fact that JAMAICA ended crop with a dextran of 576 M.A.U, compared to the average of Easter (12/4/2001) highlights the point of the significant increases of the last part of the crop, which was phenomenal. The high mud levels as a result of rain and the corresponding rise in the dextran emphasizes the importance of ending the crop before Easter to avoid the rains. The increase in the rain also triggers increased dextran and other factors, which are counter-productive to good factory operations and high quality sugar.

The five-year average of JAMAICA's dextran shows that the trend for dextran is going in the right direction, and that is down. This year 2001 will be the second time in eight years that the dextran level fell below 580 M.A.U., as in 1998 the average was over 1000 M.A.U.