Lynne Wong's PhD thesis

campaign was launched to encourage growers to send cane with less than 10% extraneous
matter, and the effects were seen in the drop in fibre % cane in 2000 and 2001.
1.4.1.2 Sucrose % cane
Sucrose % cane is also subject to changes in cane varieties and climatic conditions. In the
pre-mechanization era, sucrose % cane averaged 12.9, whereas from 1975 to 1996 there
was a gradual decline of about 0.3 unit.
Fig 1.6 shows that when fibre % cane is high, sucrose % cane is low, mainly because trash
is weighed as cane and does not contain any sucrose.
1.4.1.3 Sucrose/fibre ratio in cane
Lionnet (1992a) introduced the concept of sucrose/fibre ratio in cane to indicate the
amount of extraneous matter in cane. From Fig 1.6, this ratio was steady at almost 1.0
from 1960 to 1975, with a gradual downward trend from 1975 to 1996 probably due to
increased trash in the cane as a result of increased mechanization in cane loading and
harvesting. From 1996 to 2004, sucrose/fibre ratio in cane appears to be stable.
1.4.1.4 Mixed juice purity
Mixed juice purity is the ratio of sucrose to total solids in solution. It is a good indicator of
the freshness of the cane. It is adversely affected by cane tops but not by trash and soil.
Changes in mixed juice purity and boiling house recovery from 1960 to 2004 are shown in
Fig 1.7. Since mixed juice purity is closely related to boiling house recovery, the direct
relationship between the two parameters, as indicated by the same pattern of the curves, is
as expected.
Without taking into account the cyclonic years in the early 1960s, mixed juice purity can
be seen to decrease from 1965 to 1975. There was then an upward surge to 2004 except
during the drought year of 1999, which may be attributed to more fresh cane being sent to
the mills as a result of mechanization.
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