Optimization of Alcohol Extraction Process of Antarctic Krill Oil and Study on Thermal Stability of Astaxanthins

In the present study, the alcohol extraction conditions of Antarctic krill oil were optimized using a single factor experiment and response surface methodology. And the effects of extracting solvent, the ratio of liquid to sample and extraction time on yield of Antarctic krill oil, contents of phospholipid and total astaxanthins were investigated. Then, the main bioactive components of Antarctic krill oil, were prepared under the optimal conditions and were determined by HPLC and GC/MS. Furthermore, the effects of various antioxidants on the stability of astaxanthins in Antarctic krill oil were explored during the heat treatment test. The results suggested that the optimum extraction condition of Antarctic krill oil was achieved at a ratio of liquid to sample 10 mL/g with an extraction time of 137.3 min, using 95% ethanol-water solution as extraction solvent. Under the optimized condition, the yield of Antarctic krill oil, contents of phospholipid and total astaxanthins were 13.6%±1.2%, 33.62%±2.48% and 210.46±5.95 mg/kg, respectively. While the polyunsaturated fatty acid accounted for 41.58% of the total fatty acid, in addition, the krill oil was rich in vitamin E and vitamin A. Moreover, the hydrothermal stability of astaxanthins was effectively improved by the addition of antioxidants to the Antarctic krill oil. The effectiveness of the additives that inhibiting the degradation of the astaxanthins were evaluated, with rosemary extract (0.02%, w/v) combined with tocopherol (0.02%, w/v) ranked first, t-butylhydroquinone (0.02%, w/v) ranked second, rosemary extract (0.02%, w/v) ranked third and tocopherol (0.02 %, w/v) was the least effective additive. These results provide important evidence for the industrialization of Antarctic krill oil, as well as improving its stability during long-term storage.