Ethanol-assisted Aqueous Enzymatic Extraction Of Peony Seed Oil

Peony seed oil is rich in polyunsaturated fatty acids,of which the content of linolenic acid is as high as 42%.Meanwhile,the contents of the active substances such as tocopherol and polyphenols are high,which contribute to the abundant nutritional value.With the advantages of low planting cost and large seed production,the oil peony has been greatly promoted by the state in the field of planting.Many cultivation areas have been formed.At present,the main production technologies of peony seed oil in the market are squeezing and supercritical fluid extraction.But due to the problems of low oil yield of squeezing and high production cost of supercritical extraction,the productivity of peony seed oil is limited.Therefore,the application of aqueous enzymatic extraction of peony seed oil has become a research hotspot.However,the high cost of enzyme,the long production cycle and the difficult demulsification make it difficult to break through and realize large-scale production.In the dissertation,ethanol-assisted aqueous enzymatic extraction combined with cooking pretreatment was used to extract peony seed oil,and the quality,antioxidant capacity and preservation stability of peony seed oil were also investigated.Firstly,taking the peony seed oil yield as an index,the conditions of dry-heating and cooking pretreatment were optimized respectively.The optimum conditions of dry-heating were:temperature 115°C,time 2 h.Under the conditions,the oil yield was 81.54%.The optimum conditions of cooking were:temperature 115°C,time 1 h.Under the conditions,the oil yield was 85.54%.Secondly,the difference between dry-heating and cooking was compared and analyzed on the microstructure change of peony seeds,oil yield and crude oil quality.The results of confocal laser scanning microscope(CLSM)showed that the effect of cooking was better on destroying the cell structure of peony seeds and conduciving to the rupture of the oil body,which was beneficial to improve the oil yield.The crude oil had a good quality,and the acid value and peroxide value were both low.Therefore,cooking pretreatment was used as a pretreatment method.The ethanol-assisted aqueous enzymatic extraction of peony seed oil was further investigated and optimized.At first,the average particle size of peony seed powder reached about 31.29?m after crushing.Then,cellulase,complex enzyme G,medium temperature?-amylase and glucoamylase were selected and compounded.And the effects of different enzymes on the system viscosity and peony seed oil yield were analyzed.Complex enzyme G was selected for enzymolysis at last.The optimum conditions of complex enzyme G hydrolysis were:solid-to-liquid ration 1:7(w/v),enzyme dosage 0.75%(w/w)(the required enzyme activity was 247.5 U/g raw material),temperature 50°C,pH 4.5,time 1 h.The surface tension of ethanol was less than that of water,which could destabilize the oil-water emulsification system and help to reduce or break the emulsion.The optimum conditions of aqueous ethanol extraction were:ethanol concentration 30%(v/v),temperature 60°C,pH 9.0,time 1 h.Under the above conditions,the peony seed oil yield reached 92.25%,the residual oil content in water and sediment phase decreased to 4.05%and 3.21%,respectively.In addition,the quality and antioxidant capacity of peony seed oil were analyzed.The results showed that the quality and fatty acid content of the refined oil were all in line with the standard of first-grade refined oil.The contents of active substances such as tocopherol,sterol,squalene and polyphenols were high.The oil had good scavenging effect on DPPH radicals and ABTS~+radicals,which showed the stronger antioxidant capacity.Besides,the oil contained little trans fatty acids and 3-chloropropanol esters,while glycidyl esters and benzopyrenes were not detected,indicating that the process contributed to the high safety of oil instead of causing the generation or improvement of harmful substances in peony seed oil.Finally,the preservation stability of peony seed oil was explored.The effects of vitamin E oil,phytosterols,soybean phosphatidylcholine powder and TBHQ on the oxidative stability of oil were compared by determining the changes of peroxide value,conjugated dienes(CD)value,conjugated trienes(CT)value and anisidine value during the 150-day storage period.The results showed that the addition of phospholipid and TBHQ inhibited the growth trend of the indicators and enhanced the oxidative stability of peony seed oil significantly.Phospholipid,as a natural antioxidant and active substance,had a great development prospect in oil preservation.