Low concentrations of sulphuric acid (10 and 30 g kg1)
did not significantly increase the total sugar yield above that
of the control sample. Treatment time is limited to the
boiling point of the sugar broth and thus the microwave
irradiation cannot be continued indefinitely without loss of
liquid at atmospheric pressure. The power input (through
treatment time) for the different sulphuric acid mixtures
were thus limited to ensure a constant temperature of 82 C
throughout each experiment. The use of a domestic microwave
at atmospheric pressure thus limited the treatment
time to 15 min and thus low concentrations of sulphuric
acid is insufficient to liberate meaningful amounts of sugar
from the bagasse plant structure. The sugar yield increased
significantly with increase in sulphuric acid concentration
to 50 and 70 g kg1. This is in accordance with results found
by other researchers [14,15]. The bagasse contained
approximately 25% residual monomeric sugars (glucose,
sucrose and fructose) that were left in the stalks after the
juice was removed by pressing. It is believed that these
sugars were degraded when it came into contact with the
7 wt% sulphuric acid solution and although significant
amounts of sugars were liberated from the cellulose, the
amounts of sugars lost as a result of degrade resulted in an
overall decline in total sugar yield with increased power
input. The 5 wt% acid solution did not significantly degraded
the residual sugars and liberated most of the hexose, but
few of the pentose sugars from the plant material.