Stability And Antioxidant Activity Of Chitin Nanofiber-Blueberry Anthocyanin Nanocomplexes

Anthocyanin(ACNs)is an important natural water-soluble pigment in blueberries and other berries,which has a variety of biological activities and health effects.However,the stability of ACNs is poor,and its structure is easily changed by environmental factors,which seriously limits its application in food.Therefore,in this study,firstly,blueberry anthocyanin extract was prepared from blueberry frozen fruit.PH differential method,HPLC and HPLC-MS method were used to qualitatively and quantitatively analyze ACNs in blueberry anthocyanin extract,and combined with different degradation experiments to analyze the factors affecting the stability of ACNs.Then chitin nanofiber(CNF)was used as material to prepare CNF-ACNs nanocomposite,and its structure and properties were characterized by UV-vis photometer,nano-particle size and Zeta potential analyzer and rheometer,and its effects on the stability and antioxidant activity of blueberry anthocyanin were studied by p H difference method and PSC antioxidant method.Simulated digestion experiments in vitro were carried out to investigate its digestibility,in order to provide a new idea for blueberry storage and processing to improve the stability of anthocyanins.The main contents and results are as follows:(1)Study on the Qualitative,Quantitative and Stability of Blueberry AnthocyaninsThe qualitative and quantitative results showed that a total of 15 anthocyanins were identified in the extract,and the total anthocyanin content was 270.5 mg/g;.The stability test showed that the color of anthocyanins changed significantly with the increase of p H,and was stable when p H?3.0.Anthocyanins are sensitive to light,heat and oxidants,which promote the significant degradation of anthocyanins.The degradation kinetics simulation showed that the first-order kinetic equation could well describe the photodegradation of anthocyanins,and the determination coefficients R²were all greater than 0.9.(2)Preparation and Characterization of CNF-ACNs NanocomplexesThe results showed that the entrapment efficiency of the nanocomposites to blueberry anthocyanins was 43.25%.After the introduction of CNF,the turbidity of the nanocomposites decreased sharply,and the characteristic absorption peak of ACNs produced a redshift effect.DLS analysis showed that the particle size of the nanocomposites was 272.5 nm,the Zeta potential was 10.43 m V,PDI was 0.485.Rheological analysis showed that the elastic modulus and shear stress of the nanocomposites were significantly higher than those of Free-ACNs,and the shear difficulty and stability of the nanocomposites increased.(3)Effect of CNF-ACNs Nanocomplexes on the Stability and Antioxidant Activity of Blueberry AnthocyaninsThe stability results showed that the nanocomposites had a significant protective effect on the stability of blueberry anthocyanins under light,different temperature and p H treatment,but not under H₂O₂treatment,and the antioxidant effect of nanocomposites on blueberry anthocyanins was similar to that of stability.(4)In Vitro Digestibility of CNF-ACNs NanocomplexesSimulated digestion in vitro showed that the anthocyanin retention rate and PSC antioxidant value of the nanocomposites after oral,gastric and small intestinal digestion were higher than those of Free-ACNs,indicating that the nanocomposites had a certain protective effect on the digestion of blueberry anthocyanins in vitro.