Kulkarni, V.M.
Proc. Int. Soc. Sugar Cane Technol., Vol. 26, 2007
________________________________________________________________________________________________
IMPROVING SUGAR QUALITY AND REDUCING PROCESS DIFFICULTIES BY
EMPHASISING IMPURITIES RATHER THAN PURITY: MINIMISING SOLUBLE
POLYSACCHARIDES BY USE OF BIOCIDES
By
V.M. KULKARNI
V.M.Biotech, 1004, Siddharth Towers (2), 12 / 3 B Kothrud, Pune 411029, India
[email protected]
Abstract
POLYSACCHARIDES, such as sarkaran, pullulan, dextran, and starch, and
oligosaccharides are impurities that significantly influence sugar quality and recovery.
Most of them are produced due to the activities of yeasts, fungi and bacteria, including
Leuconostoc. These saccharides consume a lot of sucrose during their formation and
lose more sucrose to molasses, besides hindering the process, which adversely affects
sugar quality. Microbes grow at cane stations, cane carrier, and mills, and proper cane
and mill sanitation is essential in order to minimise their growth. Microbes capable of
growing at high temperature can be minimised at mills by use of proper technology,
including biocide use. Many factories using such technology can reduce the rise in
reducing sugars, acidity and dextran contents of final molasses. Data from sixteen
representative sugar factories are presented.
Introduction
Consideration of impurities rather than ‘purity’ or sucrose is better ideology. This
proposition is based on the fact that it is impurities that affect the fate of the sucrose present in
juice/syrup, in the bag, or in molasses. Thus, if we concentrate on the reduction of impurities, then
final sucrose yields will improve.
Soluble impurities that are formed during the process depend on the harvesting practice,
transport conditions, environmental factors and the chemicals/technology used during the process
and can be grouped into two phases: a) cane preparation to first juice heater and b) juice heater
onwards, until molasses formation.
a) The period from entry of the cane onto the unloading table to the first juice heater is much
shorter as compared to the earlier. However, there is significant sugar loss and
concomitant rise in the soluble impurities as the cane is fiberised, which increases the
surface and is in the form of juice at mills. This phase can be subdivided in two different
regions: 1) cane carrier, fiberisor and the first mill which handles solids and 2) remaining
mills until the first juice heater. These two distinct regions have different needs and cane
/juice is handled only for 2 min in the first region, and about 15 min in the second
region.. About 8 kg of sugar can be lost per tonne of cane during this period (Cuddihy et
al., 1997) and there is a phenomenal rise in non-sucrose – sucrose content/ microbial
metabolites of the juice.
b) Once the juice has passed the first juice heater, there are dramatic changes in
microbiology. There is a drastic reduction in the microbes that grow under normal mill
conditions. But microbes that are capable of growing at high temperature can grow after
the first juice heater, which can result in sugar losses and the formation of soluble
impurities such as polysaccharides and organic acids.
These impurities influence the sugar industry in two ways: (1) reducing sucrose in the juice
and (2) losing sucrose to molasses, besides causing several process difficulties that badly affect
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Kulkarni, V.M.
Proc. Int. Soc. Sugar Cane Technol., Vol. 26, 2007
________________________________________________________________________________________________
sugar quality and recovery. Thus, controlling these impurities is of significant economic
importance. At present, biocides are being used by mills to control these losses and polysaccharide
levels in the factory.
However, whatever biocide may be used at mills even if we assume that it works well, it
cannot prevent sugar losses and microbial growth until the cane reaches the first crusher/mill. Thus,
biocides are grossly insufficient to control microbes and their metabolites. Ideally, biocides should
be used depending on the needs of each region and this can be termed as cane sanitation and mill
sanitation for each region, respectively.
Fiberisor sanitation
This is an important phase as far as controlling sugar losses after the cane enters the factory.
The fiberisor / shredder is used to improve sugar extraction at mills by improving the Preparation
Index, but this has given rise to chances of microbial infection.
The better the cane preparation, the more will be chances of microbial growth; and indeed,
the fiberisor hammer itself acts as a source of contamination! It has a very special requirement
especially with respect to the time of action by the biocide.
Cane is held for only a couple of minutes during the period between the cane leveller to the
first mill. Thus, the biocide intended to be used for cane sanitation should have efficient killing
ability within one minute of application; or otherwise total benefit will not accrue from using the
biocide.
Mill sanitation
Many chemicals are used for this purpose and there are many conflicting reports on their
profitable usage. This could be due to many reasons: large variation in juice quality, sampling error,
analytical error, improper selection of biocide, and inability of the biocide to perform in the cane
juice within the available time. Perhaps the last reason is most important.
The time available for the biocide to perform will be <20 min even for slow mills with long
distance. Therefore, biocides need to perform rapidly and this can be achieved by formulating
synergistically acting dithiocarbamates with certain inert activators/penetrating agents (Kulkarni,
1999b). We have formulated two biocides that can achieve the killing of about 90% microbes,
including microbes capable of growing at high temperature, in the cane juice at 10 ppm dose in 10
min and 1 min, respectively. Due to their rapid action, these formulations are ideal for mill
sanitation and cane sanitation.
Materials and methods
Evaluation of sugar losses were carried out in various factories representing all sugar
producing states of India. They have crushing capacities between 3500 to and 10 000 tonnes of cane
per day. This evaluation was undertaken using a single variation procedure where all
factors/parameters remained unchanged except the mill sanitation chemical, which was replaced by
the rapid-acting biocide formulation Polmax ESR used at 10 ppm in the juice collectors of the last
mill and the penultimate mills. Polmax Supreme was sprayed on the prepared cane entering the
fiberisor at 3 – 5 ppm. The factories have used different types of biocides and thus Polmax ESR was
compared with all reputed biocides available in India. Data from one sugar factory with a crushing
capacity of 3500 tonnes are illustrated in Figures 1 to 3.
Primary juice, mixed juice, clear juice, unsulfated syrup and final molasses samples (two
hourly composite) were analysed and evaluated for reducing sugars by the Lane & Eynon method,
acidity by titration with 0.1 N NaOH (pH 8.3 by digital pH meter as end point) and brix using
brixometer/hand refractometer (Kulkarni, 1999a). Samples of sugar and final molasses were also
analysed on HPLC using calcium nitrate column RI detector and water as solvent for
polysaccharides, glucose, fructose and sucrose content.
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Kulkarni, V.M.
Proc. Int. Soc. Sugar Cane Technol., Vol. 26, 2007
________________________________________________________________________________________________
Fig. 1—Rise in acidity per 100 Brix from PJ-MJ ovserved during various biocide treatments.
Fig. 2—Rise in reducing sugar per 100 Brix from PF-MJ observed during varuous biocide treatments.
Fig. 3—Polysaccharide content in molasses and sugar after various treatments.
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Kulkarni, V.M.
Proc. Int. Soc. Sugar Cane Technol., Vol. 26, 2007
________________________________________________________________________________________________
Table 1—The effect of using rapid action biocide from PJ to MJ in selected mills.
Mill No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Rise from primary juice to mixed juice
Reducing sugar1 Acidity by titration2
Other
Polmax
Other
Polmax
biocide
ESR
biocide
ESR
2.28
0.48
5.14
2.86
1.15
0.52
2.79
1.38
0.81
0.26
1.55
0.21
0.68
0.31
1.89
0.66
0.84
0.34
2.12
1.26
3.08
0.57
1.65
1.02
0.88
0.38
2.33
0.77
0.68
0.35
2.38
0.45
1.20
0.42
2.37
0.26
1.42
0.40
2.30
0.19
2.16
0.49
2.38
1.87
0.58
0.29
1.98
1.00
1.19
0.36
2.15
0.90
1.13
0.45
3.21
1.21
0.65
0.45
2.33
0.85
1.02
0.35
2.00
0.92
% reduction due
to polmax–ESR
Acidity
RS
78.90
54.80
67.90
54.40
59.50
81.50
56.80
48.50
65.00
71.80
77.30
50.00
69.70
60.20
30.80
65.70
44.40
50.50
86.50
65.10
40.60
38.20
67.00
83.80
88.50
91.70
21.40
49.50
58.10
62.30
63.50
54.0
Table 2—Effect of rapid action biocide treatment in on final molasses.
Mill No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Rise in RS from
PJ to molasses1
Other Polmax
11.40
10.46
14.46
9.63
15.49
11.78
12.92
7.63
19.92
17.12
16.27
10.77
10.97
9.80
10.01
8.77
14.01
10.06
23.64
19.05
17.30
13.80
19.91
13.12
20.74
16.29
18.51
12.70
15.78
12.26
16.06
11.81
Rise in acidity from
Cl.J to molasses2
Other
Polmax
29.13
21.65
50.90
39.48
24.58
18.26
19.93
16.33
22.27
16.38
14.73
10.86
20.98
15.75
16.98
11.33
14.93
5.08
21.34
17.00
22.37
18.88
24.42
15.38
22.87
19.92
13.15
11.40
17.55
16.10
28.17
22.70
% Reduction due
to Polmax–ESR
Acidity
RS
8.25
25.68
33.40
22.44
23.95
25.71
40.94
18.06
14.06
26.45
33.80
26.27
10.67
24.93
12.39
33.27
28.19
65.97
19.42
20.34
20.23
15.60
34.10
37.02
21.46
12.90
31.39
13.31
22.31
8.26
26.46
19.42
1
difference of invert sugars % brix.
difference in acidity titre (mL of 0.1 N NaOH required to titrate 10 mL
sample to achieve pH 8.3) % brix.
2
Results and conclusions
Results of the benefits obtained by using the rapid action biocide formulations Polmax
Supreme for cane sanitation and Polmax ESR for mill sanitation are illustrated in Figures 1 and 2.
Fig. 3 shows the average polysaccharide contents in sugar and molasses after the use of various
biocides.
Tables 1 and 2 summarise results obtained in various sugar factories from all sugar
producing states of India and indicate benefits of using the rapid action biocide Polmax ESR over
other biocides supplied by various reputed manufacturers in India.
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Kulkarni, V.M.
Proc. Int. Soc. Sugar Cane Technol., Vol. 26, 2007
________________________________________________________________________________________________
Figure 3 represents the average data of 7 sugar / molasses samples collected per shift except
when treated with Polmax ESR and Polmax Supreme where 10 samples are analysed.
From the above mentioned plots and tables it is evident that:
š
Microbes should be killed at early factory stages to achieve significant benefits.
š
Rapid action biocides kill about 90% microbes in cane juice.
š
Thermophilic microbes should also be killed in their dormant stage in mixed juice.
š
Killing of thermophilic microbes results in a significant reduction in the rise in
reducing sugars and especially in the acidity from clear juice to final molasses.
š
Effective killing of microbes in cane juice at early stages reduces the rise in reducing
sugars and acidity from primary juice to mixed juice.
š
Reduction in acidity of mixed juice will require less lime addition. This helps in
reducing non-sugars – sugars due to lower calcium transfer to the juice. This also
will help to minimise scale problems.
š
Effective killing of microbes by using proper biocides results in significant reduction
of the polysaccharide content of sugar and molasses.
š
Biocide treatment improves the keeping quality of sugar and molasses.
š
Use of rapid action biocide formulations gave significant improvements in all
factories irrespective of the geo-climatic location of the factory, cane variety, and /
or the local harvesting practices.
REFERENCES
Cuddihy, J.A., Rauh, J.S. and Porro, M.E. (1997). Improving sugar recovery with process
chemicals. Int. Sugar J., 99: 78–84.
Kulkarni, V.M. (1999a). A novel method to evaluate efficacy of mill sanitation biocides: reducing
sugar and titrable acidity analysis of final molasses. In : Sugar Tech – An Int. J. Sugar Crops
& Related Ind.,1: September 1999.
Kulkarni, V.M. (1999b). A process to make biocide composition for rapid action in sugar cane
juice. Indian Patent No. 190474 Dt. 23.4.1999.
AMELIORATIONS DE LA QUALITE DU SUCRE ET REDUCTIONS DES PROBLEMES
DU PROCESS A TRAVERS LES IMPURETES PLUTOT QUE LA PURETE : LES
BIOCIDES POUR SOLUBILISER LES POLYSACCHARIDES
Par
V.M. KULKARNI
V.M.Biotech, 1004, Siddharth Towers (2), 12 / 3 B Kothrud, Pune 411029, INDIA.
[email protected]
Résume
LES POLYSACCHARIDES, tels que le dextrane, le sarkaran, le pullulan et l’amidon sont des impuretés
qui ont une grande influence sur la qualité du sucre et sur la performance de la sucrerie. Ces
impuretés sont introduites dans la sucrerie grâce à l’activité des organismes tel que les levures, les
bactéries et les moisissures. La formation de ces saccharides consomme beaucoup de saccharose et
leurs présences augmentent les pertes en mêlasse ; ils causent des problèmes au process et affectent
la qualité du sucre négativement. Les organismes sont présents aux moulins, sur les cannes et sur les
transporteurs ; l’hygiène au train de moulins est essentielle. Les organismes qui tolèrent des
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Kulkarni, V.M.
Proc. Int. Soc. Sugar Cane Technol., Vol. 26, 2007
________________________________________________________________________________________________
températures assez fortes doivent aussi être contrôles, préférablement avec des biocides. Les
sucreries se servant de ces approches peuvent réduire la formation de sucres réducteurs, l’acidité et
la concentration du dextrane. On donne des résultats obtenus dans 16 sucreries.
MEJORANDO LA CALIDAD DEL AZÚCAR Y REDUCIENDO DIFICULTADES EN
PROCESOS A TRAVÉS DE UN ENFOQUE EN IMPUREZAS EN VEZ DE PUREZAS:
MINIMIZANDO POLISACÁRIDOS SOLUBLES A TRAVÉS DEL USO DE BIOCIDAS
Por
V.M. KULKARNI
V.M.Biotech, 1004, Siddharth Towers (2), 12 / 3 B Kothrud, Pune 411029, India
[email protected]
Resumen
LOS POLISACÁRIDOS como sarkaran, pullulan, dextrana, y almidón, y los oligosacáridos son
impurezas que afectan significativamente la calidad de azúcar y el recobrado. La mayoría de ellos
son producidos debido a la acción de levaduras, hongos y bacterias, incluyendo Leuconostoc. Estos
sacáridos consumen sacarosa durante su formación y pierden mas sacarosa en las mieles, además de
dificultar el proceso, lo cual afecta adversamente la calidad del azúcar. Los microbios crecen en la
caña, en los conductores y molinos y una adecuada sanitización de caña y molinos se hace necesaria
para minimizar su crecimiento. Los microbios capaces de crecer a alta temperatura pueden ser
minimizados en las fábricas con el uso de tecnologías adecuadas, incluyendo el uso de biocidas. El
uso de estas tecnologías puede reducir el incremento en azúcares reductores, acidez y contenido de
dextrana en mieles finales. Se presentan datos de dieciséis ingenios representativos.
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