Lynne Wong's PhD thesis

and on agricultural products such as potatoes (McMinn and Magee, 2003; McLaughlin and
Magee, 1998), starch (Al-Muhtaseb et al., 2004a) and cowpea (Ayranci and Duman, 2005).
Fibres from eucalyptus (Moreira et al., 2001) and fibres from flax, hemp and reed canary
grass (Nilsson et al., 2005) have also been the subjects of study. The above list is by no
means exhaustive; many more publications exist on other materials.
5.4.1 Sugar cane fibre
One of the few works on the determination of adsorption isotherms involving cane fibre
dates back to the late 1950s, when Kelly (1957) studied the water adsorption of sugar cane
fibre in an atmosphere of constant water vapour pressure provided by sulfuric acid
solutions of appropriate concentrations at two temperatures. Sugar cane fibre samples after
fibration were washed free of sucrose and other water-soluble materials. The dry samples
were then exposed to an atmosphere of constant water vapour pressure in a desiccator
placed in a thermostatically-controlled oven for at least 40 hours. After which period, it
was assumed that the condition of equilibrium had been reached. The tests were carried
out at 27.2 °C and 51.0 °C. Approximately one gram of fibre was spread as a thin layer on
a flat silica dish and allowed to remain in the prepared atmosphere for the required time.
To determine the equilibrium moisture content, the sample was quickly transferred to a
stoppered weighing bottle and weighed after cooling before and after drying to constant
mass at 105 °C. The technique was found to operate satisfactorily even when the samples
were in an atmosphere of 100% humidity, when water was the air-conditioning reagent.
He estimated a value of 35% Brix-free water at 100% relative humidity.
When the log of adsorbed water per 100 g dry fibre was plotted as ordinate against the log
of water vapour pressure as abscissa, for each temperature, there exist two equilibrium
conditions for which straight lines obeying a Freundlich type of equation were shown
above and below a transition point occurring at an EMC value of 14.5% of fibre (Fig 5.2).
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