Lynne Wong's PhD thesis

known as ‘linear spectral unmixing’, the differences among cane, leaves and top could be
detected by visible and very near infrared (VIS-VNIR) spectra, showing promise for online
monitoring of trash levels in cane fed to milling train.
In Mauritius at the end of the millennium, the guess was that dry trash was as high as 7%,
and that green leaves and tops each amounted to less than 5%. Examination of the
experimental and predicted factory performance data obtained in the trial tests due to 5%
each of dry trash, green leaves and cane tops shows that they agree well with the Mauritian
industrial average, for example in 1998 (Anon., 1999) and more recently in 2006 (Anon.,
2007) (Table 2.8). Experimental data indicate that the clean cane used is very rich in
sucrose, hence the relatively high figures of experimental mixed juice purity and the
predicted sucrose recovery % cane. Although press extraction is probably not as efficient
as mill extraction, the predicted boiling house recovery and overall recovery are
comparable with the industrial data.
This shows the validity of the assumption made in the experiment that molasses-based TP
is two units higher than mixed juice-based TP. The experiment enables the precise
measure of each type of EM in cane, as well as the relative effect of dry trash, green leaves
and cane tops on factory performance, contrary to trials carried out by various research
workers in factories, where the level and type of EM are difficult to maintain constant.
Whether the effect of each type of EM on milling performance is additive, however, could
be the subject of further study, and mill modelling with the juice quality obtained could
also be undertaken.
The results obtained will be further discussed in the following section in terms of the
impact of extraneous matter on factory performance.
Table 2.8. Comparison of experimental and predicted data with Mauritian industrial average.
Experimental and predicted data
Mauritian industrial average
clean cane EM in cane 1998 2006
5% dry trash 5% green leaves 5% cane tops
Sucrose % cane 16.0 15.2 15.2 15.3 11.2 12.0
Fibre % cane 13.3 16.2 14.2 13.4 16.0 15.9
Mixed juice purity 90.0 88.8 88.2 88.7 85.2 86.4
Pol % bagasse 2.2 2.3 2.1 2.1 1.2 1.2
Clerget purity of molasses 40.7 40.8 40.3 39.2 39.0 39.5
Mass of molasses at 85 o Brix % cane 2.5 2.6 2.8 2.6 3.3 3.0
Sucrose recovery % cane 14.1 13.0 13.1 13.4 9.5 10.5
Press extraction 96.5 95.3 96.2 96.4 - -
Mill extraction - - - - 96.4 96.9
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