Investigating carotenoid loss after drying and storage of

185
8. Study under controlled conditions
demonstrated that peroxidase activity dramatically decreased (Kamiya and Nagamune
2002) and these results have been confirmed in Chapter 7. Dioxygenases known for their
ability to degrade carotenoids into aroma compounds (Auldridge et al. 2006) also lose
activity in non-aqueous environments (Sanakis et al. 2003). For these different reasons,
in this study, the possibility of carotenoid degradation due to enzymatic activity seemed
unlikely.
Oxygen
Degradation of !-carotene was highly related to the oxygen level flushed through the
sample as seen in Figure 8-10B. Under different levels of oxygen and at 40ºC,
carotenoid degradation fitted first order kinetics (Table 8-8).
Table 8-8: First order rate of carotenoid degradation of (k) expressed in day -1 at
various water activities at 40ºC in dried sweet potato chips on a dry weight basis.
Mean of triplicate thermal treatment (standard deviation). Oxygen level 21% (air).
Flushed gaz N2
2.5% O2:
97.5% N2
10% O2:
90% N2
21% O2:
79% N2
Oxygen concentration (%) 0 2.5 10 21
Trans-!-carotene*
k
R
0.0143 (0.0022) 0.0338 (0.0056) 0.0543 (0.0021) 0.0887 (0.0038)
2 0.754 (0.216) 0.949 (0.020) 0.963 (0.007) 0.961 (0.012)
Degradation rate constants significantly differed between samples (One way-ANOVA
p