Lynne Wong's PhD thesis
Lynne Wong's PhD thesis Lynne Wong's PhD thesis
3 0 Stalk fibre 5 0 S talk pith 3 0 Rind fibre 4 0 EMC/% db 2 0 10 EMC/% db 3 0 2 0 EMC/% db 2 0 10 10 0 0 0 . 5 1 1. 5 a w 0 0 0 .5 1 1.5 a w 0 0 0 .5 1 1.5 a w 3 0 Rind fines 5 0 Top fibre 7 0 Dry leaf fibre EMC/% db 2 0 10 EMC/% db 4 0 3 0 2 0 10 EMC/% db 6 0 5 0 4 0 3 0 2 0 10 0 0 0 .5 1 1.5 a w 0 0 0 . 5 1 1. 5 a w 0 0 0 . 5 1 1. 5 a w 4 0 Dry leaf fines 7 0 Green leaf fibre 5 0 Green leaf fines 3 0 6 0 5 0 4 0 EMC/% db 2 0 10 EMC/% db 4 0 3 0 2 0 10 EMC/% db 3 0 2 0 10 0 0 0 . 5 1 1. 5 a w 0 0 0 . 5 1 1. 5 a w 0 0 0 . 5 1 1. 5 a w 30°C 45°C 55°C 60°C Figure 5.9. Experimental sorption isotherms of the nine sugar cane components of R 570 aged 36 weeks. Note the similar behaviour of the nine cane components except those of dry leaf fibre and green leaf fibre. 209
5.6.4.4 Fitting of sorption models to the experimental EMC data In order to determine which isotherm model best described the experimental EMC data obtained, fifteen of the isotherm models listed in Table 5.1 (all except the last two) and the modified Chung-Pfost and modified GAB models in Table 5.2 were fitted to the data. The parameters of the first seven models in Table 5.1 (namely, the Bradley, Caurie I, Caurie II, Halsey, Henderson, Kuhn and Smith models) were estimated by linear regression with Microsoft Excel software whereas those of the GAB model were estimated with the aid of the WATER ANALYSER PROGRAM (Webbtech@bigpond.com). Those of the remaining nine models (namely, BET, modified BET, Day-Nelson, Hailwood-Horrobin, Iglesias-Chirife, Mizrahi, Oswin, modified Chung-Pfost and modified GAB) were estimated by making use of the non-linear regression procedure of SigmaPlot (SPSS Inc.). The values of these parameters together with the calculated regression criteria, i.e. the coefficient of determination R 2 , the mean deviation modulus P and the standard error of the estimate E s , for each model and for each of the nine sugar cane components aged 52 and 36 weeks are shown in Tables 5.19 – 5.27. The BET, Day-Nelson and modified Chung-Pfost models yielded spurious results; they would undoubtedly give poor fit of the experimental results and were not included in the Tables. From Tables 5.19 – 5.27, it can be seen that for the first ten isotherm models, namely the GAB, Hailwood-Horrobin, Henderson, Bradley, Caurie I, Smith, Oswin, Halsey, Caurie II and modified GAB models, the coefficient of determination R 2 approaches one for most temperatures studied (30, 45, 55 and 60 °C) and for all the nine cane component parts of both ages. However, for the last four isotherm models, namely the Kuhn, Iglesias-Chirife, Mizrahi and modified BET models, this was not the case, R 2 was low and mostly below 0.90, and the mean relative deviation modulus P was much greater than 10. They therefore gave a poor fit of the experimental results. As mentioned earlier in Section 5.3.4, for a good fit, R 2 must approach one, the P value must be between 5 and 10, and the standard error of the estimate, E s , must be as small as possible. The poor fit of the last four isotherm models was confirmed from inspection of the isotherm plots for the EMC of stalk fibre of variety R 570 aged 52 weeks shown in Fig 5.10. The complete set of isotherm plots for all the nine components is included on the CD (file: Isotherm plots.xls). The isotherm plots show that in general, apart from the bad fit of the four models mentioned above, the Bradley and Smith models are only applicable within the activity 210
- Page 211 and 212: The crop of R 570 sampled in 2001 w
- Page 213 and 214: 4.7.4. Estimated Brix-free water co
- Page 215 and 216: The main difference in the two sets
- Page 217 and 218: Table 4.27. Predicted Brix-free wat
- Page 219 and 220: 4.8 SUMMARY AND CONCLUSIONS An anal
- Page 221 and 222: component parts, and verify the Bri
- Page 223 and 224: 3) Thermodynamic, water in equilibr
- Page 225 and 226: Langmuir (1916, 1917, 1918) propose
- Page 227 and 228: to determine the moisture sorption
- Page 229 and 230: Table 5.1. Some commonly used isoth
- Page 231 and 232: Lomauro et al. (1985) found that wi
- Page 233 and 234: and on agricultural products such a
- Page 235 and 236: Bruijn (1963) studied the mass incr
- Page 237 and 238: After measuring the EMC of dry corn
- Page 239 and 240: approached, that is, either by adso
- Page 241 and 242: Table 5.4. Water activity (a w ) of
- Page 243 and 244: 5.6.3 Procedure to determine equili
- Page 245 and 246: 5.6.4 Results and discussion An exa
- Page 247 and 248: Table 5.8. Equilibrium moisture con
- Page 249 and 250: Table 5.10. Equilibrium moisture co
- Page 251 and 252: Table 5.12. Equilibrium moisture co
- Page 253 and 254: 30 o C 45 o C 55 o C 60 o C Water w
- Page 255 and 256: m/m of 96% activity, a w (g/100g dr
- Page 257 and 258: vaporisation generally decreases fr
- Page 259 and 260: 30 o C isotherm 45 o C isotherm 55
- Page 261: 4 0 Stalk fibre 5 0 Stalk pith 5 0
- Page 265 and 266: Table 5.19. Parameters of the sorpt
- Page 267 and 268: Table 5.21. Parameters of the sorpt
- Page 269 and 270: Table 5.23. Parameters of the sorpt
- Page 271 and 272: Table 5.25. Parameters of the sorpt
- Page 273 and 274: Table 5.27. Parameters of the sorpt
- Page 275 and 276: Modified GAB Kuhn Iglesias - Chirif
- Page 277 and 278: Table 5.28. Classification of resid
- Page 279 and 280: 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 295 and 296: Stalk fibre Stalk pith Rind fibre 4
- 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 305 and 306: Stalk fibre Stalk pith Rind fibre 1
- 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
3 0<br />
Stalk fibre<br />
5 0<br />
S talk pith<br />
3 0<br />
Rind fibre<br />
4 0<br />
EMC/% db<br />
2 0<br />
10<br />
EMC/% db<br />
3 0<br />
2 0<br />
EMC/% db<br />
2 0<br />
10<br />
10<br />
0<br />
0 0 . 5 1 1. 5<br />
a w<br />
0<br />
0 0 .5 1 1.5<br />
a w<br />
0<br />
0 0 .5 1 1.5<br />
a w<br />
3 0<br />
Rind fines<br />
5 0<br />
Top fibre<br />
7 0<br />
Dry leaf fibre<br />
EMC/% db<br />
2 0<br />
10<br />
EMC/% db<br />
4 0<br />
3 0<br />
2 0<br />
10<br />
EMC/% db<br />
6 0<br />
5 0<br />
4 0<br />
3 0<br />
2 0<br />
10<br />
0<br />
0 0 .5 1 1.5<br />
a w<br />
0<br />
0 0 . 5 1 1. 5<br />
a w<br />
0<br />
0 0 . 5 1 1. 5<br />
a w<br />
4 0<br />
Dry leaf fines<br />
7 0<br />
Green leaf fibre<br />
5 0<br />
Green leaf fines<br />
3 0<br />
6 0<br />
5 0<br />
4 0<br />
EMC/% db<br />
2 0<br />
10<br />
EMC/% db<br />
4 0<br />
3 0<br />
2 0<br />
10<br />
EMC/% db<br />
3 0<br />
2 0<br />
10<br />
0<br />
0 0 . 5 1 1. 5<br />
a w<br />
0<br />
0 0 . 5 1 1. 5<br />
a w<br />
0<br />
0 0 . 5 1 1. 5<br />
a w<br />
30°C<br />
45°C<br />
55°C<br />
60°C<br />
Figure 5.9. Experimental sorption isotherms of the nine sugar cane components of R 570<br />
aged 36 weeks.<br />
Note the similar behaviour of the nine cane components except those of dry leaf fibre and<br />
green leaf fibre.<br />
209