Lynne Wong's PhD thesis

⎛ F + G ⎞
TP = 33.9 − 13.4log10
⎜ ⎟
⎝ Ash ⎠
Target purity of molasses is that level of purity below which no more sucrose can be
recovered from molasses. This target purity depends on a number of factors, most
importantly, the viscosity and the crystal content of the massecuite, the saturation
temperature at crystallization and the nature of the non-sucrose fraction in the final
molasses, namely, the reducing sugars, notably fructose and glucose, as well as the
inorganic ash such as potassium, sodium, calcium and magnesium.
Normally the TP of molasses is predicted from molasses data; however, in this experiment,
mixed juice data were used to calculate mixed juice-based TP by using the above equation,
from which molasses-based TP can be deduced since Lionnet and Koster (1986) have
shown that molasses-based TP is two units higher than the mixed juice-based TP.
In Mauritius, average monthly molasses from 17 sugar factories analysed by the Mauritius
Sugar Industry Research Institute (MSIRI) over the years 1996-1999 (unpublished data)
show that the average target purity difference (TPD), the difference between the molasses
true purity (the percentage of sucrose in the dry solids) and its target purity, is on the rise
(Table 2.1). As 1999 was an abnormal year when severe drought conditions prevailed, the
1998 average of 2.4 units was added to the estimated molasses-based TP to predict the
expected true purity of Mauritian molasses. According to the 1998 data, Clerget purity is
0.1 unit higher than the true purity (not shown), therefore a further 0.1 unit was added.
Hence, a constant totalling 4.5 units (2 + 2.4 + 0.1) was added to the mixed juice-based TP
to predict Clerget purity of molasses.
Table 2.1. Mauritian average of molasses target purity difference (TPD)
compiled from MSIRI unpublished data.
July August September October Mean
1999 3.6 3.4 2.5 1.7 2.8
1998 3.4 1.9 2.2 2.2 2.4
1997 2.6 2.3 1.3 1.9 2.0
1996 - 1.7 1.7 1.8 1.7
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