Effects Of Vacuum Desolventizing Process On Antarctic Krill Oil And Stability Of Astaxanthin During Storage

The astaxanthin(AX) of quantitative information on this aspect is still very limited. An effective and accurate method was developed to determine astaxanthin in krill oil(KO). The effect of vacuum desolventizing process on the residual hexane, AX content, and fatty acid composition of KO has been investigated, in which the appropriate level of parameters for vacuum desolventizing was established in terms of safety and stability of KO. Since it is known that storage conditions affect the stability of astaxanthin in Antarctic krill oil, the kinetics of AX degradation was investigated under different storage conditions.The saponification conditions saponification temperature( 5 ℃、 25 ℃) and alkali concentration(0.100,0.105,0.110,0.115M) of AX esters were studied. The highest amount of free AX at 5℃ was obtained with 0.105 mol/L NaOH at 3.5 h. The degradation of AX was found to follow a first-order kinetic reaction. The temperature dependence of reaction constants was found to be well explained by the Arrhenius relationship.A laboratory model vacuum oven capable of creating a absolute vacuum of up to 12±2 Pa was used throughout this study.The analysis of data reveals that temperature showed marked effect on residual hexane level within the temperature range studied. The rate of desolventization was faster initially but slowed down as the time progressed. The results of the investigation further indicates that KO obtained by vacuum desolventizing process at 40℃ for 90 min, 50℃ for 40 min. 60℃ for 20 min, and 70℃ for 10 min, respectively, would have the residual hexane content less than 50 mg/kg, which as per Chinese Standard is within acceptable limits. However, the content of AX diminished during vacuum desolventizing depending on the degree of heating. Higher temperatures and longer heating times caused higher AX degradations. The degradation of the AX followed the first order reaction kinetics over temperature ranges from 40℃ to 70℃. The reaction rate constant of degradation of AX increased with increasing heating temperature. And the total proportion of SFA, MUFA, and PUFA remained stable when KO was processed to vacuum desolventizing. Furthermore, when the FA composition was examined, stability was found for most of the compounds in all samples.Three types of KO, namely, whole-type, triglyceride-type, and phospholipid-type, was extracted using hexane, supercritical CO2, and ethanol, respectively. Three types of KO and various storage parameters, namely, storage atmosphere(air, nitrogen), storage temperature(-20, 5 and 25℃) and storage time(0, 2, 4, 6, 8, and 10-week) on the kinetics of AX degradation was established. Considering the effect of the three types of krill oil on AX degradation, slightly higher degradation rates of AX were observed in the case of phospholipid-type KO(at the same storage condition). Considering the effect of storage temperature on AX degradation, it was found that AX degradation rates seemed to be higher at higher storage temperatures. Under nitrogen, AX degradation rates were lower than those under air atmosphere at all storage temperatures. The first-order kinetic model was the best fit for the AX degradation.