Characterisation of physical properties of prepared cane from soft-cane varieties

Concerns have been raised that many sugarcane varieties in the development pipeline, particularly in the Central and Southern regions of Australia, have fiber quality classified as soft, with some soft enough to cause processing problems in the factory. The main issues have been feeding off the cane through the milling train and high bagasse moisture contents, causing subsequent combustion issues and low steam pressure at the boiler station. These cane varieties are usually designated as ‘soft-canes’, and their presence had been noted for at least 60 years. An attractive trait is their relatively high sugar yield per hectare. Some other general characteristics have been reported as often (but not always) having relatively low fiber content and being easier to prepare by the shredder, resulting in a larger number of smaller sized particles in the prepared cane. During the development of new cane varieties, Sugar Research Australia carries out tests for ‘fiber quality’. Experiments were carried out at Isis Central Mill to understand and improve the processing of existing soft-cane varieties. During the 2019 crushing season, a pilot-scale shredder was used to simulate the effect of shredder settings (speed and grid setting) that are known to affect preparation levels. Four existing soft-cane varieties (SRA1A, SRA4A, SRA11A and QN04-1643) were tested, along with Q208A that provided a reference as a middle-of-the-range variety (perceived to be neither a soft nor hard cane). The prepared cane produced was tested for fiber quality at the SRA fiber quality laboratory in Bundaberg. As measured at the factory, the preparation level and two physical properties (compression and permeability) were identified as important for the milling process. All the cane varieties responded similarly to speed and grid setting, with the soft-canes being part of a continuum, not a separate subset. The overall conclusion was that adjusting shredder speed and grid setting can control preparation and potentially address feeding problems at the milling train through improved control strategies.