the handbook of food engineering practice crc press chapter 10 ...
the handbook of food engineering practice crc press chapter 10 ... the handbook of food engineering practice crc press chapter 10 ...
Table 9. Aspartame degradation in a pH 6.67 aseptic dairy system Time Aspartame concentration (ppm) for temperatures (hr) 30 °C 20 °C 10 °C 4 °C 0 C 10 181 10 175 10 182 23 168 186 23 166 172 23 171 181 38 130 38 127 38 141 48 120 152 48 101 160 48 108 162 78 172 78 154 78 153 95 175 95 173 95 175 121 168 189 198 121 168 180 195 121 167 186 194 143 146 143 129 143 150 262 63 140 165 262 73 134 165 262 94 160 167 455 114 132 159 455 96 117 152 455 118 121 155 599 93 110 136 599 87 104 136 599 91 88 134 694 80 130 694 95 119 694 86 113 767 115 767 109 767 103 60
In Fig. 12a aspartame concentration (APM or A) is plotted vs. time at the 5 temperatures. The best linear fit of the form Q(A)=kt was achieved for Q(A)=ln(A/A o ), i.e. first order kinetics (Fig.12b). All measurements were included in the statistical analysis (no averaging of the 3 samples per time) to increase the degrees of freedom and include the measurement spread in the model. Calculated rate constants and 95% C.I. are given in Table 10. Table 10. Aspartame degradation reaction rate constants with confidence intervals at 5 temperatures. Rate constant 30 o C 20 o C 10 o C 4 o C 0 o C -k (hr -1 ) 0.0125 0.00356 0.00138 0.00121 0.000790 ± 95% C.I. ± 0.0013 ± 0.00046 ± 0.00010 ± 0.00009 ± 0.000062 Figure 12. Aspartame degradation kinetics at five temperatures plot as function of time and as semi-log plot To determine the Arrhenius parameters, -k is plotted in a semilogarithmic scale vs.the inverse of absolute temperature (or ln(-k) vs. 1/T). To increase the degrees of freedom and get a narrower confidence interval for the calculated parameters, the 95% C.I. for k are included (Fig. 13). The Arrhenius plot gives by linear regression the values of k o =3.163 108 hr -1 and activation energy E A = 14560 cal/mol. The coefficient of determination, R 2 , is 0.952 and the 95% confidence interval 1830 cal/mol. 61
- Page 9 and 10: Data can be fitted to these equatio
- Page 11 and 12: criterion. The value of the R 2 , f
- Page 13 and 14: of reaction systems involved in foo
- Page 15 and 16: Lund, 1985). The standarized residu
- Page 17 and 18: When a Michaelis-Menten rate equati
- Page 19 and 20: ∂ ln K eq ∂ (1/T) = - ∆Eo R (
- Page 21 and 22: are available, the confidence range
- Page 23 and 24: kinetic data is compared. Its main
- Page 25 and 26: plot will give a relatively straigh
- Page 27 and 28: temperatures (Fennema et al., 1973)
- Page 29 and 30: Glass transition phenomena are also
- Page 31 and 32: i.e. if T ∞ is chosen correctly,
- Page 33 and 34: A number of recent publications deb
- Page 35 and 36: The study of the temperature depend
- Page 37 and 38: and bakery goods, upon losing moist
- Page 39 and 40: ambient temperatures (e.g loss of c
- Page 41 and 42: temperature and is an area of curre
- Page 43 and 44: and variable temperature conditions
- Page 45 and 46: Figure 8. Characteristic fluctuatin
- Page 47 and 48: 10.3 APPLICATION OF FOOD KINETICS I
- Page 49 and 50: time at each selected temperature.
- Page 51 and 52: TTI can be used to monitor the temp
- Page 53 and 54: 10.4 EXAMPLES OF APPLICATION OF KIN
- Page 55 and 56: Figure 10. Thiamin retention of a m
- Page 57 and 58: S = SS {1+ N p n-Np F[N p, n-N p ,
- Page 59: 10.4.2. Examples of shelf life mode
- Page 63 and 64: the approach to follow to increase
- Page 65 and 66: REFERENCES Arabshashi, A. (1982). E
- Page 67 and 68: Fennema, O., Powrie, W. D., Marth,
- Page 69 and 70: Labuza, T. P. (1975) Oxidative chan
- Page 71 and 72: Mohr, P. W., Krawiec, S. (1980) Tem
- Page 73 and 74: Sapru, V., and T.P. Labuza (1992) G
- Page 75: Yoshioka, S., Aso, Y., Uchiyama, M.
Table 9. Aspartame degradation in a pH 6.67 aseptic dairy system<br />
Time<br />
Aspartame concentration (ppm) for temperatures<br />
(hr) 30 °C 20 °C <strong>10</strong> °C 4 °C 0 C<br />
<strong>10</strong> 181<br />
<strong>10</strong> 175<br />
<strong>10</strong> 182<br />
23 168 186<br />
23 166 172<br />
23 171 181<br />
38 130<br />
38 127<br />
38 141<br />
48 120 152<br />
48 <strong>10</strong>1 160<br />
48 <strong>10</strong>8 162<br />
78 172<br />
78 154<br />
78 153<br />
95 175<br />
95 173<br />
95 175<br />
121 168 189 198<br />
121 168 180 195<br />
121 167 186 194<br />
143 146<br />
143 129<br />
143 150<br />
262 63 140 165<br />
262 73 134 165<br />
262 94 160 167<br />
455 114 132 159<br />
455 96 117 152<br />
455 118 121 155<br />
599 93 1<strong>10</strong> 136<br />
599 87 <strong>10</strong>4 136<br />
599 91 88 134<br />
694 80 130<br />
694 95 119<br />
694 86 113<br />
767 115<br />
767 <strong>10</strong>9<br />
767 <strong>10</strong>3<br />
60
Change language