Lynne Wong's PhD thesis

4.8 SUMMARY AND CONCLUSIONS
An analytical method has been developed to determine the Brix-free water in fibres
obtained from various component parts of sugar cane plant. Prior to analysis, the fibre
sample is dried in an air oven at 65 °C for one hour with occasional stirring, followed by
vacuum oven drying at 65 °C under 875 mbar vacuum for 16 hours. The method involves
contacting the sample with a 10° Brix sucrose solution for one and a half hours, during
which time the sample is shaken every 10 minutes. The Brix-change in the contact
solution gives a measure of the Brix-free water capacity of the sample. The ratio of the
contact solution to sample size is kept at 20. Good separation of fibre and fines in the
sample is essential to obtain reproducible results. The method makes use of a distilled
water blank to compensate for any residual sucrose in the sample, since residual sucrose in
the fibre sample was found to inflate the results. This method showed that:
- An increased concentration of the sucrose contacting solution increased the Brix-free
water values of the fibre samples, contrary to the findings of previous workers, who
found a decrease in the Brix-free water value.
- A ratio (14-26) of the volume of the contact solution to the mass of sample used did
not affect the Brix-free water value of a stalk fibre sample. However, if the ratio
became much higher, the analytical errors became large as the Brix-change after
equilibrium would be less than 0.1 unit, and at low ratio, e.g. 5, pith samples would
not be completely wetted.
- Sample fineness did not affect Brix-free water value of sample analysed. When
some fibre samples were reduced to a finer state (about 3 mm long) by cutting with a
pair of scissors, there was no change in the Brix-free water value obtained, contrary
to the findings of Mangion and Player (1991).
- For 21 Brix-free water values of various cane component parts (Table 4.16), a
standard error of the mean of 0.547 was obtained for a mean of 12.82 on the original
samples, and 0.500 for a mean of 12.72 on finely cut samples.
- A halogen thermogravimetric method was developed to determine residual moisture
in dried fibre samples. The method requires about 0.6 g of sample and takes a few
minutes to execute instead of the three hours required by the standard drying method.
Statistical analyses showed that the halogen method gave results comparable to that