Lynne Wong's PhD thesis

Steuerwald (1912) applied sucrose solutions instead of salt solutions, and used two
methods to measure Brix-free water: a contact method and a press method. In the former,
a known mass of sucrose solution was allowed to remain in contact with a known mass of
fibre, the increase in concentration of the sucrose solution was a measure of the amount of
water adsorbed into the fibre. He obtained an average value of 22% for Brix-free water in
fibre, with a range from 15 to 28%. The latter method consisted of adding pure sugar
solution to cane fibre; after pressing, a residue was obtained; by analysing its sugar content
and the total water present, the adsorbed water could be measured. From the mass of sugar
in the residue and the composition of the expressed juice, the respective masses of sugar
solution and adsorbed water could be calculated. With the press method, the value
decreased with increasing pressure until he obtained 16.5% at 300 atmospheres.
Spoelstra (1935) repeated these experiments slightly differently, in that he added
completely dry fibre to salt solutions and determined the increase in concentration of
sodium chloride after equilibrium was obtained. He found Brix-free water values between
26 and 30%.
Van der Pol et al. (1957) pointed out that in the original Prinsen Geerligs method, the use
of solutions of an electrolyte presented conditions far remote from conditions existing in a
cane stalk, and also that the use of high temperatures in either extracting the sucrose from
the fibre or drying the fibre, introduced an uncertainty due to possible irreversible chemical
reactions which could affect the affinity of the fibre for water. They dried fibre in vacuum
over phosphorus pentoxide, P 2 O 5 , at a temperature lower than 60 °C, and then used sucrose
solutions to contact the fibre. After equilibration, the sucrose concentration was
determined with a saccharimeter. They found that at high Brix (60°), the amount of water
absorbed by the dry fibre was less than at lower Brix. The same phenomenon had been
observed by Prinsen Geerligs who attributed it to the absorption of sucrose by the fibre.
Since fibre which had been dried in vacuum over P 2 O 5 at 60 °C still contained 5% moisture
whereas if it had been dried in oven at 105 °C-110 °C, the residual moisture would be
about 0.5%. Van der Pol et al. (1957) corrected their experiments for a residual moisture
content of 5%. They found that by using a 20% sucrose solution, the average Brix-free
water content was 29%.
Kelly and Rutherford (1957) also repeated the experiments of Prinsen Geerligs. After
drying fibre at 120 °C for 5 hours, they put the fibre into various solutions, containing
known concentrations of sucrose, glycerol, sodium chloride and potassium chloride. They
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