| Tan sheep tail fat not only has a unique flavor,low cholesterol content,but also is rich in conjugated linoleic acid(CLA).In recent years,with the increasing slaughter and processing volume of Tan sheep year by year,Tan sheep tail fat,as an important by-product of the Tan sheep industry,has been massively stockpiled and wasted.In this study,the low temperature crystallization method combined with urea inclusion method was used to extract CLA from Tanyang sheep tail fat based on a single factor orthogonal experiment.Then,using concentrated whey protein,whey isolated protein,whey isolated protein+maltodextrin as the wall material,and Tan sheep tail fat CLA as the core material,the microcapsules of Tan sheep tail fat CLA were prepared.Scanning electron microscopy,laser confocal microscopy,thermogravimetric analysis,and X-ray diffraction analysis were used to investigate the physical and chemical properties,microstructure,thermal stability,and in vitro simulated release behavior of the microcapsules,to clarify the physical and chemical properties of Tanyang Tail Fat CLA microcapsules.At the same time,taking Tan sheep tail fat CLA and its microcapsules as the research objects,the oxidative stability,antioxidant activity,and cholesterol lowering activity of Tan sheep tail fat CLA under different digestion times were measured,and the effect of microencapsulation of Tan sheep tail fat CLA on its antioxidant and cholesterol lowering activity was clarified.1.Study on the extraction and biological activity of CLA from Tanyang sheep tail fat.The results of orthogonal experiments showed that the optimal parameters for the extraction of CLA from Tanyang sheep tail fat by low-temperature crystallization method were as follows:the organic solvent was anhydrous ethanol,the crystallization temperature was-20℃,the crystallization time was 12 hours,and the ratio of mixed fatty acids to anhydrous ethanol was 1:12(g:mL).Under these conditions,the purity of CLA from Tanyang sheep tail fat was(18.62 ± 0.51)mg/g.On the basis of low-temperature crystallization,urea inclusion method was used to further purify the CLA from Tanyang sheep tail fat.The optimal experimental results showed that the optimal conditions for urea inclusion method were:inclusion temperature 25℃,inclusion time 14 hours,mass ratio of fatty acid to urea 1:2,and feed liquid ratio of urea to ethanol 1:5(g:mL).At this time,the CLA purity of Tanyang sheep tail fat reached(28.23±2.36)mg/g.At the same time,the activity validation experiment showed that the CLA extracted by low-temperature crystallization combined with urea embedding method had good antioxidant activity and cholesterol lowering ability.When the concentration of CLA was 6 mg/mL,its scavenging rates for DPPH free radicals and ABTS cationic free radicals were(35.94±4.07)%,(51.76± 5.57)%,and its inhibition rate for cholesterol micelles was(60.33 ± 5.88)%,and for sodium taurocholate The binding rates of sodium glycine cholate and sodium cholate were(16.11±4.01)%,(37.56 ± 3.17)%,and(25.11 ± 4.82)%,respectively.2.Preparation and properties of CLA microcapsules from Tanyang sheep tail fat.The resul ts of single factor experiment and orthogonal experiment showed that the optimal parameters fo r preparing Tan sheep tail fat microcapsule were:the mass ratio of wall material(whey protein isolate:maltodextrin)was 1:2,the mass ratio of core material to wall material was 1:5,the so lid content was 25%,and the air inlet temperature of spray drying was 185℃.Under this con dition,the embedding rate of Tan sheep tail fat CLA microcapsule prepared was(96.18±1.88)%.According to the determination of physicochemical properties,the water content of Tanyan g Tail Fat CLA microcapsules is(2.83± 0.07)%,the solubility is(92.77±0.26)%,the angle of repose is(35.56±0.14)°,and the bulk density is(0.38± 0.06)g/cm3,indicating that Tan yang Tail Fat CLA microcapsules have a moderate water content,good fluidity,and solubility.The results of scanning electron microscopy,laser confocal microscopy,thermogravimetric analy sis,and X-ray diffraction analysis showed that the particles of Tan sheep tail fat CLA microca psules were complete,with a relatively smooth surface,and had good thermal stability.3.Study on the stability and release behavior of Tanyang tail fat CLA microcapsules.It has been verified that after 18 days of storage at 60 ℃,the POV and TBA values of CLA crude oil and CLA microcapsules show a trend of first increasing and then decreasing,and by the third day of storage,both of them reach their maximum values,but CLA microcapsules are significantly lower than CLA crude oil(P<0.05).The results of in vitro simulated digestion experiments showed that after 2 hours of gastric digestion,CLA microcapsules only released 18.09%±0.85%,while after half an hour of intestinal digestion,the microcapsules were rapidly hydrolyzed,and their release increased with the increase of intestinal digestion time.After 2 hours of intestinal digestion,their release reached(68.52±2.87)%.After simulated digestion in vitro,the antioxidant activity and cholesterol lowering activity of Tan sheep tail fat CLA microcapsules were significantly higher than those of CLA crude oil(P<0.05).At the end of in vitro simulated digestion,the scavenging rates of CLA microcapsules on DPPH,ABTS,and superoxide anion free radicals were(70.84± 3.97)%,(78.53 ± 4.28)%,and(59.88±2.58)%,respectively,while the scavenging rates of CLA crude oil from Tanyang Tailfat were only(13.79±1.64)%,(19.88±1.84)%,and(8.27±0.82)%;At this digestion time,the cholesterol micelle inhibition rate of Tan sheep tail fat CLA microcapsule was(73.48±2.53)%,and the binding rates of sodium taurocholate,sodium glycine cholate,and sodium cholate were(40.62±3.14)%,(66.79 ± 3.01)%,and(55.43± 2.39)%,respectively.However,the cholesterol micelle inhibition rate of Tan sheep tail fat CLA crude oil was only(18.11 ±1.36)%,and the cholesterol micelle inhibition rate of sodium taurocholate The binding rates of sodium glycine cholate and sodium cholate were only(2.44 ± 0.12)%,(7.48 ± 1.62)%,and(7.23±0.72)%.The above experimental results indicate that microencapsulation helps to improve the oxidative stability and release behavior of Tanyang sheep tail fat CLA,and the microencapsulated Tanyang sheep tail fat CLA has better antioxidant and cholesterol lowering activities after release. |
