Lynne Wong's PhD thesis

91
BHR
Clerget purity of mixed juice and BHR
89
87
85 Clerget purity of mixed juice
83
1960 1965 1970 1975 1980 1985 1990 1995 2000
Figure 1.7. Changes in Clerget purity of mixed juice and boiling house
recovery (BHR) from 1960-2004.
During the pre-mechanization era of 1960 to 1975, the decrease in boiling house recovery
is in line with the decrease in mixed juice purity as indicated by the same slope of the two
downward curves. From 1975 to 1996, however, the boiling house recovery curve did not
parallel the increase in mixed juice purity and in fact, registered a decrease of 0.7 unit.
Wong Sak Hoi and Autrey (1997) attributed this to the result of extraction of melassigenic
impurities in trash and tops, the concentration of which is not high enough in juice to affect
mixed juice purity, but is sufficiently high in molasses for their effect to be felt. From
1996 to 2004, the boiling house recovery curve seems to have levelled off except during
the drought year of 1999.
1.4.2 Cane quality trends in other sugar-producing countries
Ideally, cane delivered to sugar factories should be cleaned of immature tops, leaves
whether green or dry, and soil. This practice was possible when man-power was abundant;
however, with economic development in other sectors, the shortage of agricultural labour
led to mechanization of cane loading in Louisiana in mid-1940. In Australia, mechanical
loading started in mid-1950 and mechanical harvesting in early 1960 (King, 1969). In
South Africa, cane loading started in the early 1970s, while in Mauritius, in the mid-1970s;
with the consequence that a progressive increase is observed in the quantity of extraneous
matter being introduced at the mills with the cane.
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