Lynne Wong's PhD thesis

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What was actually determined was not hygroscopic water but the fibre saturation point at 20 o C (see Section 6.9). Table 6.9 compiles the values of fibre saturation point bound water of various cane components at 30, 45, 55 and 60 o C. Data at 20 o C were not available, but results calculated for 30 o C were comparable with the 25% value obtained by Foster (1956) at 20 o C, erroneously taken as Brix-free water value. Table 6.9 also shows the Brix-free water values determined in this work. These are in general lower than the fibre saturation point values. Hence, the generally accepted value of 25% is much too high for Brix-free water of cane. 6.10 SUMMARY AND CONCLUSIONS The various parameters calculated have allowed for a better understanding of the nature of the water sorbed onto the sugar cane component parts. As described in literature the bound water occurs in three regions. From the monolayer moisture content and the amount of “hydrated water” as calculated from the Hailwood-Horrobin model it is clear that at EMC values between 0 and 5% the water is tightly bound to the surface of the fibre. The corresponding water activities are 0-0.3. This constitutes what has been termed non-freezable water. The second region starts at EMC values from about 5% and ends at 10-15% depending on the cane components. The corresponding a w values are 0.3 to 0.6-0.8. In this region the bound water has a heat of adsorption, H m , which is 2 to 5 kJ mol -1 greater than the heat of vaporisation H L of bulk pure water. This is termed the freezable water. The third type of water is essentially free water, it exists after the second region and ends at EMC of approximately 25% (where the relative humidity is nearly 100%). This type of water has the same heat of adsorption as the latent heat of vaporisation of pure water. From this study it is apparent that Brix-free water as measured in this work measures the amount of water bound in the first two regions. Treatment of the experimental sorption data according to the GAB, Caurie I and BET equations allowed the evaluation of monolayer moisture content in nine cane components aged 52 and 36 weeks, and in reconstituted cane stalk, dry leaf and green leaf of R 570 aged 52 and 36 weeks. 23
The number of adsorbed monolayers, density of bound water, the percentage of bound water and the surface area available for hydrophilic binding in adsorption in nine cane components, and reconstituted cane stalk, dry leaf and green leaf of R 570 aged 52 and 36 weeks have been successfully calculated at four temperatures. The heats or sorption of monolayer and multilayer have been calculated for nine cane components and reconstituted cane stalk, dry leaf and green leaf of R 570 aged 52 and 36 weeks. The heat of sorption of multilayer for each particular fibre is systematically higher at 52 weeks (48-49 kJ mol -1 ) than at 36 weeks (46-47 kJ mol -1 ), whereas the heat of sorption of monolayer is very variable. The net isosteric heat of sorption and the entropy of sorption have been successfully calculated. The plots of the net isosteric heat of sorption versus the entropy of sorption for water adsorption in fibres of nine cane components of R 570 ages 52 and 36 weeks, within the water activity range 0.17 – 0.98, satisfy the enthalpy-entropy compensation theory. The adsorption process in the fibres of sugar cane plant is essentially enthalpy-controlled (isokinetic temperature > harmonic mean temperature) and non-spontaneous (+∆G). The heat of sorption of monolayer and the plot of binding energy against moisture content lead to the primary, secondary and tertiary bound water, it was found that the secondary bound water corresponds to the Brix-free water values of sugar cane component parts, except in the case of stalk pith, which shows similarity to the tertiary bound water. The dissolved and hydrated waters adsorbed in fibres of sugar cane plant of R 570 aged 52 and 36 weeks during the adsorption process have been quantified. The same applied to reconstituted cane stalk, dry leaf and green leaf of R 570 of two ages. The values of fibre saturation point bound water have also been calculated for the nine cane components of R 570 aged 52 weeks and found to increase with increase of temperature. They vary from about 20% to 37%. The value of 25% traditionally accepted as Brix-free water value of cane was in fact found to be the fibre saturation point bound water determined at 20 °C. 24
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THE BRIX-FREE WATER CAPACITY AND SO
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dissolved and hydrated waters, and
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ACKNOWLEDGEMENTS I am particularly
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Page 1.5 THE DELETERIOUS EFFECTS OF
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Page 2.2 THE PHENOMENON OF BRIX-FRE
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Page 3.4.3.3 Cane tops 83 3.4.4 Cha
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4.3.3 Temperature at which Brix-fre
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4.6.1 Materials 143 4.6.1.1 Samples
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CHAPTER 6. PROPERTIES OF THE SORBED
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APPENDIX 3. CALCULATIONS LEADING TO
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LIST OF FIGURES Page Figure 1.1. Fi
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Figure 3.1. Glucose and fructose an
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Figure 5.11. Residual plots for the
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total adsorbed water (m) and the pr
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Table 2.18. Moisture content in sug
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Page Table 4.4. Results of the dete
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Page Table 4.24. Analysis of varian
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Page Table 5.13. Table 5.14. Equili
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Table 6.3. Heat of sorption of the
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GLOSSARY OF TERMS Absorption is the
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Filterability of a raw sugar is mea
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Sorption is the generic term used w
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LIST OF MAIN SYMBOLS Symbol Descrip
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s c s Slope of Caurie I isotherm pl
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number of 255, and cane land covere
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Nouvelle Mon In Trésor ustrie and
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Figure 1.3. Cane sampling by core s
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In Mauritius, most of the sugar fac
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are: cane tops, dry and green leave
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1.4 TRENDS IN CANE QUALITY RECEIVED
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campaign was launched to encourage
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The level of extraneous matter in c
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In Australia (Cargill, 1976), cane
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The effect of soil on factory perfo
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leaves increased the level of impur
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• From 1976 to 1980, when the pro
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Clerget purity of molasses 40 Clerg
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CHAPTER 2. IMPACT OF EXTRANEOUS MAT
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Since the extrapolated purity of mo
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Figure 2.1. Jeffco cutter grinder.
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2.1.4 Results The analytical result
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Table 2.3. Analytical results of re
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Table 2.5. Composition of dry trash
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Table 2.7. Predicted factory perfor
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Boiling house recovery 91.0 89.8 89
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0 5 10 15 20 % EM in cane y = 0.572
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% EM in cane 0 5 10 15 20 0 -2 -4 -
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1 y = 0.020 (% D) R 2 = 1.00 = 0.03
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% EM in cane 0 5 10 15 20 0 -2 y =
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esulting in 0.015 unit sucrose loss
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2.2.1 Experimental procedure Cane m
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filter paper, rejecting the first f
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Table 2.9. Effect of increased addi
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Table 2.11. Effect of increased add
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Table 2.13. Effect of increased add
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various components such as stalk fi
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in the presence of dry leaves, if c
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Table 2.17. Moisture content in sug
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CHAPTER 3. SEPARATION OF THE SUGAR
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Table 3.1. It can be seen that the
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Table 3.2. Fibrous physical composi
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R 579 R 570 M 1557/70 M 1400/86 74
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loosen the fibre. The woody core is
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agitate the mixture in the pot, and
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Figure 3.7. Custom-built fibre-pith
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The extraction of fibres starting f
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pre-treatment in a Jeffco cutter-gr
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Figure 3.19. Stalk cake washed free
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not have many dry leaves attached t
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Table 3.5. Masses of cane samples a
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Table 3.7. Masses of cane samples a
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Table 3.9. Masses of cane component
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3 57.6 126.3 23.7 97.2 31.1 53.8 11
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Table 3.12. Material loss (%) from
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3.5.3 Fibre/pith ratios in cane com
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Table 3.15. Effect of extraneous ma
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Snow (1974) investigated the season
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from Figure 2.9 that the change in
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Table 3.18. Fibre % cane results by
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110
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(a). Dry leaf (b). Green leaf (c).
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dry fibre, or a factor, is used in
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Steuerwald (1912) applied sucrose s
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solution/fibre ratio was lowered fr
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leave some residual moisture on the
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instead of 150 g of 10° Brix sucro
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Table 4.2. Determination of Brix-fr
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Table 4.3. Comparison of Brix-free
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Table 4.4. Results of the determina
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In order to test for homogeneity of
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Table 4.7. Results of the repeat de
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The experiment was repeated with th
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e any residual moisture in the samp
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By means of the same technique, Won
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was still hot. Since the filter was
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value determined could be corrected
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Qin and White’s finding was confi
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A sample size of 3.5 g with 75 g co
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Figure 4.4. Fibre samples drying in
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- One large fibre sample (rind) of
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Table 4.18. Brix-free water values/
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Table 4.20. Brix-free water values/
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4.7.3 Statistical analysis It is es
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Table 4.23. Analysis of variance (B
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pointing out that at 52 weeks old,
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The crop of R 570 sampled in 2001 w
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4.7.4. Estimated Brix-free water co
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The main difference in the two sets
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Table 4.27. Predicted Brix-free wat
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4.8 SUMMARY AND CONCLUSIONS An anal
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component parts, and verify the Bri
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3) Thermodynamic, water in equilibr
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Langmuir (1916, 1917, 1918) propose
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to determine the moisture sorption
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Table 5.1. Some commonly used isoth
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Lomauro et al. (1985) found that wi
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and on agricultural products such a
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Bruijn (1963) studied the mass incr
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After measuring the EMC of dry corn
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approached, that is, either by adso
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Table 5.4. Water activity (a w ) of
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5.6.3 Procedure to determine equili
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5.6.4 Results and discussion An exa
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Table 5.8. Equilibrium moisture con
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Table 5.10. Equilibrium moisture co
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Table 5.12. Equilibrium moisture co
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30 o C 45 o C 55 o C 60 o C Water w
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m/m of 96% activity, a w (g/100g dr
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vaporisation generally decreases fr
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30 o C isotherm 45 o C isotherm 55
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4 0 Stalk fibre 5 0 Stalk pith 5 0
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5.6.4.4 Fitting of sorption models
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Table 5.19. Parameters of the sorpt
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Modified GAB Kuhn Iglesias - Chirif
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Table 5.28. Classification of resid
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Stalk fibre Stalk pith Rind fibre 4
Page 281 and 282: 5.6.4.5 Calculated EMC values of re
Page 283 and 284: Table 5.30. Calculated equilibrium
Page 285 and 286: m/m of 96% Table 5.32. Calculated e
Page 287 and 288: Table 5.33. Parameters of the Hailw
Page 289 and 290: CHAPTER 6. PROPERTIES OF THE SORBED
Page 291 and 292: where m is the equilibrium moisture
Page 293 and 294: Stalk fibre Stalk pith Rind fibre 8
Page 297 and 298: 6.2 THE NUMBER OF ADSORBED MONOLAYE
Page 299 and 300: 6.3 TOTAL SOLID SURFACE AREA AVAILA
Page 301 and 302: Thus, for each cane component of ea
Page 303 and 304: abscissa. For each moisture level (
Page 307 and 308: A similar procedure was followed to
Page 309 and 310: 10 0 Stalk fibre Stalk pith Rind fi
Page 311 and 312: Moreover, if T β > T hm the proces
Page 313 and 314: Table 6.5. Characteristic parameter
Page 315 and 316: Binding energy/kJ (kg mol) -1 2 0 0
Page 317 and 318: 6.8 CALCULATION OF BOUND WATER AND
Page 319 and 320: The values of K 1 , K 2 and W were
Page 321 and 322: Table 6.7. Separation of the total
Page 323 and 324: Table 6.7. (Contd.) Sample 30 o C 4
Page 325 and 326: 3 0 S talk fibre 4 0 Stalk pith 3 0
Page 327 and 328: 3 0 Reconstituted cane at 30 o C 3
Page 329 and 330: when water is added to dry wood, wh
Page 331: It is evident that in some cases ma
Page 335 and 336: Data in Tables 2.9 and 2.11 show th
Page 337 and 338: particular fibre is systematically
Page 339 and 340: Anon. (1985b). Laboratory manual fo
Page 341 and 342: Blanchi R.H. and A.G. Keller (1952)
Page 343 and 344: Day D.L. and G.L. Nelson (1965). De
Page 345 and 346: Heyrovsky J. (1970). Determination
Page 347 and 348: Kuhn I.J. (1964). A new theoretical
Page 349 and 350: Madamba P.S., R.H. Driscoll and K.A
Page 351 and 352: Prinsen Geerligs, H.C. (1897). Stud
Page 353 and 354: Sing K.S.W., D.H. Everett, R.A.W. H
Page 355 and 356: Van der Pol C., C.M. Young and K. D
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Lynne Wong's PhD thesis

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