2010_Relationship between the kinetics.pdf

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188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 Statistical analysis and kinetics modelling Carotenoid contents and norisoprenoid contents were determined on a fresh weight basis. Data were processed on SPSS 15.00 software by one or two way-ANOVA (Analysis of variance; p
213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 Results & Discussion Carotenoid degradation kinetics The effect of temperature (10; 20; 30; 40 ºC) on -carotene degradation is described in Table 1A. Coefficients of correlation (R 2 ) suggest that a first-order equation fitted well the carotenoid degradation. An exception nonetheless was at 10 ºC where correlations observed were lower (R 2 ~0.8). Lower correlations at low temperatures where there is minimum carotenoid degradation could be explained by experimental errors (Hidalgo & Brandolini, 2008). Degradation rates of trans--carotene were significantly different at the four tested temperatures (10; 20; 30; 40 ºC). (ANOVA one way p 0.990 and 0.989 respectively). 5,6 epoxy-- carotene, another carotenoid present in fresh sweet potato (Kosambo, Carey, Misra, Wilkes, & Hagenimana 1998), also followed a first order rate reaction that could also be fitted to the same models (R 2 > 0.997 and 0.996 respectively). Using the models, the activation energy (Ea) for -carotene and for 5,6-epoxy--carotene was calculated as 64.2 and 78.8 kJ.mol -1 respectively and the enthalpy was 61.7 and 76.3 kJ.mol -1 respectively (Table 2). The energy of activation and enthalpy were both 23% higher on 5,6 epoxy--carotene compared to trans--carotene. This means that the degradation rate of 5,6 epoxy-β-carotene was more sensitive to the variation of temperature than trans β-carotene. 11/30
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Page 23 and 24: Hidalgo, A.H.& Brandolini, A (2008.
Page 25 and 26: Moisture (M) g water/g dry weight b
Page 27 and 28: B-carotene content (μg.g-1) Ratio
Page 29 and 30: Table 2. Parameters of the Arrheniu

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