2. Purity
The percentage ratio of sucrose (or Pol) to the total
soluble solid (Brix) in the sugar product known as
Purity
Purity = Pol % x 100
Brix %
Loss of sucrose purity in one stage to another
stage is known as purity drop
3. Purity drop between juices at
different stages
During milling and clarification of juice the purity drop
from one stage to other stage given as-
1-Primary juice to mixed juice- 1.30 to 1.60 unit
2-Primary juice to last mill juice 10.00 to 13.00 unit
3- Mixed juice to clear juice +0.45 to +0.60 unit
4-Clear juice to Filtrate juice 2.50 to 3.50 unit
5-Clear juice to U. Syrup 0.25 to 1.50 unit
4. Purity drop between massecuite
to molasses
0.25 to 1.50 unit
During sugar production process the purity drop between
different type of massecuite to molasses given as-
1-R1 Mass.to R1 Hy. Molasses 1.00 to 1.50 unit
2-Raw Mass. to Raw Hy Molasses 10.00 to 12.00 unit
3-B Mass.to B Hy. Molasses 20 .00 to 24.00 unit
4-C mass. to Final molasses 20.00 to 22.00unit
5-R3 Mass.to R3 Molasses 10.00 to 12.00 unit
6-C1 Mass.to C1 Hy Molasses 15.00 to 17.00 unit
7-A1 Mass. to A1 Hy Molasses 18 .00 to 20.00 unit
5. Reason of purity drop
The drop in purity of juices and massecuite to
molasses is due to the fallowing factors
Loss of sucrose molecule due bacterial growth
Loss of sucrose molecule due decomposition
of sucrose molecule by over heating
Loss of sucrose molecule due inversion of
sucrose molecule
Deposition of sucrose molecule from mother
liquor to the sugar crystal in case of massecuite
to molasses
Extraction of non sugars
6. Purity drop during cane Harvesting
Sugar cane is raw material for sugar industry.
It is perishable material for microbial deterioration hence
the harvested material is available to the factory at
minimum possible delay.
The microbial deterioration of cane lead the reduction of
recoverable sugar i.e. drop in purity.
The purity drop depend on time lag between harvesting
to crushing, atmospheric temperature and humidity.
About 0.5-1% loss of sugar after one day at the
temperature in range max. 31°C. and min. 5°C
And it increases 4-5 % after one week
7. Purity drop during milling
During extraction of juice the mixed juice purity is near about
1.30-1.60 unit less than primary juice purity and last mill juice
purity is near about 10.00- 13.00 unit less than primary juice
purity
The drop in purity from primary juice to mixed juice or primary
juice to last mill is due to more extraction of non sugars from
mill.
Due to more extraction of non sugar result reduces the purity
of mixed juice or last mill juice
The range of purity drop from primary to mixed juice is limited
if it increases more indicate loss of sucrose in mill due to
bacterial growth indicate poor sanitation in other hand if it
decreases inducate the mill extraction is poor
8. Purity drop during Clarification
of juice
During clarification of juice it is observed that the
purity rise from mixed juice to clear juice 0.45 to 0.65
unit this is due to removal of non sugars during
clarification of mixed juice to clear juice
The purity drop between clear juice to filterate juice in
range 3.0 to 5.0 unit this is due to dissolution of some
non sugars during cake washing at vacuum filters
The range of purity drop between clear to filterate
juice if exceeded from 3.0 to 5.0 indicate bacterial
growth at vacuum filters station
9. Purity drop during setteling of
juice
Low pH with high temperature lead inversion of sucrose the
drop in pH at 70°C is near about 0.1 unit from room temp in
case of mixed juice this is increases about 0.45 to .65 unit
when temperature increases from 70°C to 102°Cthe reason
of drop in pH from defecated juice to clear juice is
Formation of hydroxy apatite
2Ca3(Po4)2.Ca(OH)2
The proteins on longer contact with heat produce amino
acids
Gums and pectins also forms organic acids known as
uronic acids
Reducing sugar on high temperature and alkaline medium
decomposes to organic acids
This drop in pH and retention of juice lead inversion of
sucrose
10. Purity drop during evaporation
of juice
• During evaporation, the juice undergo to high
temperature (115°C-117°C) due to high temperature and
alkaline medium reducing sugars decomposes to acids
such as gluconic , oxalic, sacharanic acids as well as
some volatile amides of amino acids decomposes to form
ammonia.
• Low pH and high temperature of clear juice. (<7.0) leads
inversion of sucrose molecule.
•
Generally the purity drop from clear juice to syrup is near
about 0.25 unit to 1.50 unit.
•
This drop in purity increases with decrease in clear juice
pH and increase in retention time during formation of
clear juice to syrup.
11. Purity Drop between massecuite
to molasses
• The purity drop between massecuite to molasses is less
in case of high grade massecuite and more in low grade
massecuite.
• This drop in purity is due to deposition of sucrose
molecule from mother liquor to sugar crystal during pan
boiling as well as cooling of massecuite in crystallizers.
• The range of purity drop between different type of
massecuite (R1, Raw, B and C ) is 2 to 24 unit.
•
This purity drop between massecuite to molasses is
beneficial due to more purity drop means more sugar
deposition on the sugar crystal.
12. Purity drop between massecuite to
molasses depend many factors such
as:-
1) size of sugar crystal
2) Crystal content of massecuite
3) Boiling time of massecuite
4) Purity of mother liquor
5) circulation of massecuite during
pan boiling
6) viscosity of massecuite
7) cooling of massecuite
8) curing of massecuite
13. Purity Drop during molasses
storage
• During storage of molasses tank the purity drop
0.10 unit to 0.25 unit in 2 to 3 month
•
• This drop in purity is due to chemical reaction in the
molasses. The purity drop is increases with increase
in temperature and composition of molasses
(mainly water content )
•
it observed that annual loss 2-3 % of fermentable
sugar at 30-35 °C which is four times more on
increase of 10 °C temperature
14. How to minimize purity drop
1-Cane Harvesting
The time loss between cane harvesting and milling has to be minimum.it is done
by efficient communication between cane department and factory site (minimum
preferably 12-24 hrs.)
2-Washing and Steaming
(A) Hot water washing of raw juice tank,inter rack carriers at
mills on regular basis sift wise
. we have done every 4 hrs. in each shift
(B) Filterate juice tank mud tanks vacuum filters washing done
regular basis
.
we have change and clean filterate receiving tank
in every shift
(C) Washing and changing of vacuum filters in every shift
15. 3-Exhaust temperature
The exhaust temperature at calandria of 1st effect
evaporator maintain near about 2-3 degree plus to
saturated temp
4-Control of PH in clarification
Control monitoring of pH of clear juice. it should be
maintain between 6.95-7.05.
lower pH of clear juice causes inversion of sucrose and
higher pH causes destruction of reducing sugars
5-Retention
More retention causes more purity drop at low pH and
high temperature
16. This is mainly in clarifier and evaporator bodies by decreasing the
retention time in clarifier and evaporator bodies we have minimize the
purity drop clarifier
6-Use of Chemical
(A)use of Biocides (QAC and DTC )based at mills
(B) use of Biocide at mud run off tank
(C) use of biocide in clarifier during long stoppage
7- Periodic Lab Analysis
(A) Analysis of RS % in primary and mixed juice
(B) Analysis of filtrate juice
(C) Analysis of TRS of final molasses tank
(D) Regular monitoring of temperature of final molasses
8-Final molasses storage tank
(A) Recirculation of final molasses in final molasses tank
(B) Water spraying outside the tank to control the temperature
rise of molasses
17. Loss of sugar due to purity
drop
Example
1-purity of mixed juice -80
2-purity of mixed juice -79
mixed juice % cane-122 %
mixed juice Bx-12.50
Available sugar at purity 80
=80 X 12.50 X 122/(100X100)
= 12.20
Available sugar at purity 79
=79 X 12.50 X 122/(100X100)
=12.04
Loss of sugar = 12.20-12.04
=0.16 unit
1 Unit purity drop of MJ gives 0.16 Unit loss of sugar
18. Gain of sugar due to purity drop from
massecuite to molasses
Example
Purity of Massecuite -86
Purity of Molasses -72
Available sugar at Pty 72 =
𝟏𝟎𝟎(𝟖𝟔−𝟕𝟐)
𝟖𝟔(𝟏𝟎𝟎−𝟕𝟐)
= 0.58
Available sugar at Pty 71 =
𝟏𝟎𝟎(𝟖𝟔−𝟕𝟏)
𝟖𝟔(𝟏𝟎𝟎−𝟕𝟏)
= 0.60
Gain of sugar = 0.60-0.58
Gain in available sugar per unit drop in molasses purity = 0.02
