| Peony has a history of more than one thousand years of ornamental and medicinal use in China.The oil content of peony seed is more than 30%and the protein content is about 22%.In particular,the content of unsaturated fatty acids in peony seed oil exceeds 90%(more than olive oil and camellia oil).Additionally,it also contains 0.1%vitamin E,0.46%plant sterol and other active substances.Therefore,peony oil has a variety of functions such as lowering blood lipid and anti-oxidation,which is praised by nutritionists as"the best edible oil in the world".In the extraction methods of peony seed oil,there are some problems in producing oil by traditional pressing and solvent extraction,such as the generation of trans fatty acids and solvent residue,although the present aqueous enzymatic process solves the problems existing in the traditional process,it adopts multi-enzyme system,and the oil emulsification phenomenon is serious,with the free oil and the total oil yield less than 60%and 85%respectively.The main reason is that carbon bonds such as peptides,dextrin,pectin and cellulose in the aqueous enzyme system contain hydrophilic groups such as hydroxyl,amino group and carboxyl group,as well as phospholipids and sodium fatty acids,and these substances are amphiphilic,so they have a strong oil-water emulsification ability.At present,it is a key problem that the process of aqueous enzymatic extraction cannot be industrialized to break the powerful emulsification system and improve the oil yield.Based on the above understanding,this paper pretreated peony seed powder with acid and ethanol,following by enzymatic hydrolysis.By applying suitable acid treatment to peony seed powder,it not only curbed the free fatty acid carboxyl ionization process,but also,promoted the dissolution effect of soluble protein and carbohydrate in peony seed cells.In this way,the oil emulsification effect was relieved from the source,and the cell structure was loosed,which contributes to the contact between enzymes and substrate;A certain concentration of ethanol solution was used to dissolve phospholipids,fatty acids and other substances in peony seed powder and reduce the solubility of proteins,thereby reducing the degree of emulsification of oil from the source.The main conclusions of this paper are as follows:1.Study on aqueous enzymatic extraction oil by acid pretreatment with peony seed.In this study,acid pretreatment,enzymatic hydrolysis and demulsification were optimized.The optimal conditions for acid pretreatment were:ratio of material to water 1:6(w/w),pH 3.5,temperature 40℃,reaction 8 h;The optimal conditions for enzymatic hydrolysis were:under the optimal conditions of alkaline protease(pH 8.5,55℃),the amount of 3%(enzyme/seed·dry mass)was added,and enzymolysis time was 5 h.Under this case,the yield of free oil and peony peptides reached 86.21%and90.43%respectively.The best demulsification method is:freezing and thawing demulsification,demulsification rate is 5.78%.In summary,under the optimal process,the total oil yield of peony seed can reach 91.99%,and only a single enzyme protease is used.The physical and chemical indexes of the peony seed oil prepared by this process all accord with the characteristic indexes of the peony seed oil,and the acid value and other indexes generally meet the second-grade quality standard.The content of total unsaturated fatty acids was as high as 92.21%,of which the linolenic acid content was 42.46%higher than that of commercially available peony seed oil by more than 10%.2.Study on aqueous enzymatic extraction oil by ethanol pretreatment with peony seed.On the basis of the optimal conditions for alkali extraction and enzymatic hydrolysis determined by the previous experiments,the optimum conditions of ethanol pretreatment were:the ratio of material to liquid 1:9(g/mL),the concentration of ethanol 80%(v/v),the temperature 35℃,and the reaction 7 h.The results show that the yield of free oil is as high as 92.24%.The physical and chemical indexes of peony seed oil prepared by this process all accord with the characteristic indexes of peony seed oil,and the indexes such as solvent residue all meet the first-grade quality standard.The content of total unsaturated fatty acids was up to 91.16%,of which the linolenic acid content was 41.62%,about 10%higher than that of commercially available peony seed oil.3.Study on recovery of peony peptides by membrane technology.The hydrolytic solution from the optimum process of aqueous enzymatic extraction oil by acid pretreatment with peony seed was studied.The optimal process conditions for recovery of peony peptides by ultrafiltration membrane were:ultrafiltration membrane with molecular weight cut-off is 1kDa,adjusting hydrolysate pH 8(i e.,the original pH),and ultrafiltration at the operating pressure of 0.18MPa and temperature of 35℃.The results showed that the maximum membrane flux was 7.12L/(m~2·h)and the retention rate of peony peptides was 89.05%.4.Economic benefit analysis of aqueous enzyme method.Based on the annual treatment of 5,000 tons of peony seeds,it is estimated that the annual after-tax profit of this study using the chemically modified aqueous enzymatic oil extraction process is about 227.336 million yuan,which is 17.527 million yuan higher than the annual after-tax profit of other scholars’aqueous enzyme extraction process.Thus,this process has both economic and environmental protection significance. |
PDF Full Text Request