Extraction And Fiber Membrane Encapsulation Of Proanthocyanidins From Lycium Ruthenicum

Lycium ruthenicum is rich in nutrients,especially proanthocyanidins.As a natural antioxidant and free radical scavenger,proanthocyanidins have a variety of pharmacological activities such as anti-aging,anti-inflammation and anti-radiation,and play an important role in protecting human health.However,the stability of proanthocyanidins is poor that is easy to be oxidized and degraded by light and heat.In this thesis,Lycum ruthenicum was used as raw material to extract the proanthocyanidins by an ultrasonic cell crushing method,and the proanthocyanidins were encapsulated by an electrospinning technology.At the same time,the antioxidant activity and stability of the proanthocyanidins before and after encapsulation were studied.The main results were as follows:.(1)After optimization by response surface analysis,the optimal extraction conditions of proanthocyanidins by the ultrasonic cell crushing method were as follows:ethanol volume fraction is 50%,solid-liquid ratio is 1?29 g/m L,ultrasonic time is 26 min,and ultrasonic power is 220 W.Under these conditions,the extraction yield of proanthocyanidins from Lycium ruthenicum was 6.10%,and the relative error is 1.02%as compared with the predicted value of 6.17%.(2)AB-8 macroporous resin was used to purify proanthocyanidins of Lycum ruthenicum.The purity of proanthocyanidins was 86.75%after purification,which was23.52%higher than that before purification.The typical characteristic absorption peak of proanthocyanidins from Lycium ruthenicum was obsered at 280 nm by UV scanning.FT-IR spectra proved that the main structural unit of proanthocyanidins from Lycium ruthenicum was proanthocyanins.(3)The antioxidant activity of proanthocyanidins from Lycium ruthenicum was studied by vitro antioxidant assay.Proanthocyanidins from Lycium ruthenicum had high scavenging rates of DPPH and·OH free radicals at low concentrations,and the total antioxidant capacity of proanthocyanidins was close to Vitamin C.At the same time,the stability of proanthocyanidins from Lycium ruthenicum under different conditions was studied.The results showed that the stability of proanthocyanidins was greatly affected by light,temperature,and acid and alkali environment.Some metal ions such as Al³⁺,Fe²⁺and Fe³⁺would destroy the structure of proanthocyanidins and make their stability decrease sharply.(4)Gelatin/poly ethylene oxide/Lycidum ruthenicum Proanthocyanidins fiber membranes(GEL/PEO/LPC)were prepared by the electrospinning technology.It was found that different polymer ratios had great influence on the properties of the spinning solution.The higher the relative content of PEO,the higher the viscosity of the spinning solution,and the higher the encapsulation efficiency of fiber membranes for proanthocyanidins.Furthermore,the viscosity also had big effect on the morphology of the fiber.When the viscosity was lower,beads appeared on the fiber;when the viscosity was higher,the diameter of the fiber will became larger,even unable to electrospin.(5)The stability of GEL/PEO/LPC fiber membrane under strong light and high temperature was studied.The results showed that fiber membrane encapsulation could effectively improve the photothermal stability of proanthocyanidins from Lycium ruthenicum.The preservation rate of proanthocyanidins in fiber membrane was 35.14%higher than the free proanthocyanidins from Lycium ruthenicum after being treated at high temperatures 12 h.The enhancement percentage was up to 12.08%when the GEL/PEO/LPC fiber membrane was treated under strong light for 5 d.(6)The release characteristics of GEL/PEO/LPC fiber membranes in simulated aqueous and acidic food matrix were studied.It was found that the release equilibrium of the GEL/PEO/LPC fiber membranes was reached in the acidic food matrix for 90 min and in the aqueous food matrix for 150 min,respectively.The release rate of the GEL/PEO/LPC fiber membranes was high in the two simulated food substrates.The released proanthocyanidins from Lycium ruthenicum could effectively scavenge DPPH free radicals,and the fiber membrane with higher the encapsulation efficiency has higher antioxidant activity.