| Antarctic krill is usually a guide to the largest krill.Its body length is generally 4to 6 cm,and its biological reserves are large.Its growth and reproduction are susceptible to the Antarctic water environment.Therefore,the distribution density in the Antarctic is extremely different.Commercial trials of Antarctic krill began internationally in the former Soviet Union,and Japan,South Korea,and Norway have also begun research and development of Antarctic krill resources.However,China officially entered the Antarctic krill fishery in late 2009,and in recent years it has become China’s important strategic resources.Antarctic krill is also rich in various nutrients and active ingredients,which can be widely used in aquaculture,food,medicine and other fields.However,at present,Antarctic krill products are still dominated by primary products.Therefore,it is necessary to research and develop more mature products with high added value,and optimize the comprehensive utilization of Antarctic krill resources so that they can bring greater economic benefits and development space..Astaxanthin is an orange-red xanthophyll carotenoid,which has unique chemical properties based on its molecular structure.Due to the presence of hydroxyl and keto groups on the ring of iononone,astaxanthin has more carotenoid than other carotenoids.The higher antioxidant activity has an important role in anti-oxidation,anti-inflammatory and immunity enhancement,prevention of cardiovascular diseases and anti-tumor.There are three main natural sources of astaxanthin:yeast,microalgae and various aquatic animals.As an active ingredient in Antarctic krill,astaxanthin exists mainly in the form of astaxanthin esters.Because astaxanthin molecules are easily damaged by the effects of light,heat,oxygen,etc.,and poor water-solubility,this has made their application in various fields very limited.Therefore,it is necessary to carry out certain modification studies on them,to improve its physical and chemical properties and expand its application in many other aspects.In this paper,Antarctic krill was used as raw material.The astaxanthin of Antarctic krill was firstly extracted by complex enzymolysis method,after a further separated and purified.Then the astaxanthin obtained was microencapsulated and embedded to prepare astaxanthin microcapsule products by spray drying.and the physicochemical properties and stability of the product are studied..The purpose of this study is to provide theoretical and technical support for the utilization and key preparation techniques of astaxanthin in the Antarctic krill.The main research contents and results are as follows:1.Using Alcalase Alkaline Protease and papain complex enzymolysis method to extract astaxanthin with absolute ethanol as extractant.On the basis of single factor test,the extraction rate of astaxanthin as response value,and the response surface was used to optimize the design to explore the best extraction conditions of astaxanthin.The results showed that,the ratio of enzyme base,enzymolysis time and temperature of enzymatic hydrolysis were selected as the main factors of astaxanthin extraction rate by single factor test.The extraction conditions optimized by response surface methodology were as follows:the enzyme-substrate ratio was 1.6%（the ratio of alkaline protease Alcalase to papain was 3:2）,enzymolysis time was 2.1 h,enzymolysis temperature was 51℃,water-material ratio was 4:1 g·mL-1,material-ethanol ratio was 1:4 g·mL-1,and the oscillation time was 10 min.Under these conditions,the extraction percentage of astaxanthin was 90.42±0.39%,which relative error is about 0.79%from theoretical value.2.The saponification and purification of astaxanthin crude extracts of Antarctic krill were determined by HPLC,and the final saponification conditions were determined as follows:the solution concentration of NaOH-ethanol was 0.010mol·mL-1,saponification time was 18 h;the crude astaxanthin after saponification was further separated and purified by HSCCC,and determined the solvent system was n-heptane-acetone-ethanol-water 5:4:6:5,the retention rate of stationary phase was60.15%.Under this condition,250.0 mg of Antarctic krill astaxanthin crude product can collect 20.1 mg astaxanthin product with a purity of 98.12%.3.With the microencapsulation encapsulation rate of astaxanthin as the index,the best process condition for microencapsulation of astaxanthin was determined by single factor test and Box-Behnken response surface optimization test,the result was that use the mass rate of maltodextrin and HP-β-CD was 1:3 as a wall material,added mass fraction of astaxanthin was 4.76%,added mass fraction of Tween-80 was0.87%,solid concentration was 0.20 g·mL-1,while the theoretical value of microencapsulation efficiency is 99.15%,the measured value is 98.77%,the relative error is about 0.38%.The moisture content of astaxanthin microcapsule product was3.11±0.11%,the solubility was 94.32±0.08%,and the angle of repose was34.16±0.24°,indicating that the product had good fluidity and solubility.The astaxanthin retention rate was used as an indicator of temperature,light,and oxygen for astaxanthin microcapsules supplemented with a mass fraction of 1%α-tocopherol,astaxanthin microcapsules withoutα-tocopherol,and astaxanthin not microencapsulated.Compared to non-microencapsulated astaxanthin crystals,astaxanthin microcapsules with a mass fraction of 1%α-tocopherol and astaxanthin microcapsules withoutα-tocopherol,at high temperatures,the retention rate of astaxanthin increased from 28.72%to 80.94%and 78.32%,respectively;after 30days of storage,the astaxanthin retention rate increased from 45.27%to 88.97%and84.88%,respectively,under light conditions;under aerobic conditions,the retention rate of prime increased from 20.76%to 69.38%and 74.97%,respectively.The result shows that microencapsulation can significantly improve the sensitivity of astaxanthin in light,heat,and oxygen,which aslo indicats that the astaxanthin microcapsule product should be kept at low temperatures,avoid light and oxygen to prevent its hygroscopic swelling,which may lead stability decreases.while in aerobic condition,the addition ofα-tocopherol has disadvantages for the stability of astaxanthin microcapsules. |
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