Measurement of Cane Preparation Milling Seminar 11 May 2005 Peter Rein Audubon Sugar Institute

Measurement of Cane Preparation Cane Preparation has a very large effect on extraction and moisture content of bagasse It is important to measure preparation Methods of measurement include: –Bulk density –Mean particle size –Extent of breakage of cells

Sampling The measurement is only as good as the sampling It is difficult to get a representative sample, unless a full-width hatch sampler is used Sampling from the top layer gives a biased sample (classification of fines) Cane is non-homogenous and requires that a number of samples across the conveyor at different depths be taken Mixing and sub-sampling is difficult If the sample is not well-prepared, biased sampling sometimes omits large chunks

Mean Particle Size Particle size measurement by screening is possible The sample needs to be dried first The sieving efficiency is low, because of the large length/diameter ratio of the particles The results are technique and equipment dependent Reliable measurements can be obtained from a standardized procedure May be expressed as a mean particle size or a “fineness figure”

Bulk Density Compressing a sample under standard conditions gives the bulk density, which depends on the cane preparation. Fine preparation leads to a high bulk density Crawford (Australia) compressed a 15 lb sample at 15 psi for 5 minutes Pressure chosen so that no juice expression occurs

Correlation between bulk density and fineness (Crawford 1970)

Measurement of Cell Breakage This is the best method, since it characterizes the preparation in terms of its extractability Cane and water tumbled together for a standard length of time, and the sucrose content of the extract measures the extent of cell breakage and the availability of juice If the ratio of water to sample is the same in the tumbler and in the cold digester, PI = 100.(tumbler conc.)/(digester extract conc.) Cane sample is small (~ 500 g) and needs replicates

Equipment Used

Problems Different test conditions lead to different results Test conditions in Australia, Hawaii, South Africa and Louisiana are all different PI is affected by excessive trash in cane Pi is not reliable with coarse preparation; should not be used if PI < ~80

Comparison of Test Conditions AustraliaHawaiiSouth Africa (ICUMSA) Louisiana Test duration (min.) Measure of juice conc. PolPol (Brix)BrixPol

Conclusions It is worthwhile to measure the degree of preparation routinely PI is probably the best routine method It is not a precise measure, but the average over time gives the best indication of preparation In making comparisons, be aware which method is being used PI (SA) is greater than POC (Austr.) by about 5 units PI (La) is greater than PI (SA) by about 5 units