Preparation And Characterization Of Plant Extracts Loaded Nanofibers By Air-assisted Electrospinning

Objective Plant extracts are obtained from plants by various physicochemical and biological means,and their biological activities,such as antioxidant,anti-inflammatory,antibacterial,or anticancer,improve human health in many ways,including food,clothing,housing,and transportation,but are limited by the stability and biocompatibility in various extreme environments.Their incorporation into different encapsulation matrices holds promise to protect these active ingredients,improve solubility,achieve controlled release,reduce side effects,and improve their biocompatibility,bio-accessibility,and bioavailability.Electrospinning technology is a simple operation,low cost,highly flexible,high load capacity,high encapsulation rate of room temperature,and atmospheric pressure encapsulation technology.This paper used airflow-assisted electrospinning technology to load thymol,cinnamaldehyde,eugenol,and dihydromyricetin to prepare nanofiber systems with high yields and suitable morphological structures and to realize the extended utilization of dihydromyricetin,a characteristic extract of vine tea resources.Methods In this paper,gelatin and zein were used as the electrospinning matrix to construct nanofibers with airflow assistance while loading different additions(0 wt%,0.1 wt%,0.5 wt%,1.0 wt%)of thymol,cinnamaldehyde,eugenol,and dihydromyricetin.The microscopic morphology and diameter distribution of nanofibers were characterized by scanning electron microscopy(SEM).The interaction between protein and thymol was studied by Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),and thermal analysis techniques,so as to interpret the changes in macroscopic performance such as the mechanical property and water vapor permeability(WVP),antioxidant activity and antimicrobial property.Finally,dihydromyricetin nanofiber as mats was applied to pork preservation.Results(1)The gelatin/zein composite nanofibers were successfully prepared by airflow-assisted electrospinning technology,with stable morphological structure,no sticky beads,a diameter of around 500 nm,which increasedthe yield of nanofibers by a factor of 10 times compared to that of traditional electrospinning,and feed rate increased from the traditional 1 m L/h to 10 m L/h.(2)The morphology of nanofibers in all groups was smooth and uniform.The diameters of thymol,cinnamaldehyde,and eugenol nanofibers showed an increasing trend with the increase of addition,in which the diameters of thymol fibers increased from 477 nm to 574 nm.Eugenol nanofibers increased from 472 nm to 632 nm,while adding cinnamaldehyde and dihydromyricetin had no significant significance on the changes in fiber diameters.The FTIR spectra analysis indicated that the above plant extracts were successfully loaded and interacted with gelatin/zein through hydrogen bonding.XRD profiles of the nanofibers indicated that the above plant extracts were uniformly distributed within the nanofibers,and no new crystalline peaks were observed.Thermal analysis techniques showed that nanofibers significantly improved the thermal stability of plant extracts,whereas thymol and dihydromyricetin also improved the thermal stability of nanofibers.The WVP showed that the loading of hydrophobic or low watersoluble plant extracts significantly improved the water vapor barrier of nanofibers and showed a quantitative effect relationship with the amount added.Tensile tests showed that the addition of thymol significantly enhanced the elastic moduli of nanofibers,the addition of 1.0 wt% of cinnamaldehyde nanofibers significantly increased the elongation at break of nanofibers,the addition of 0.5 wt% of eugenol and 1.0 wt% of dihydromyricetin nanofibers had higher elastic modulus and lower elongation at break.A quantitative relationship existed between the addition of eugenol and the tensile strength.(3)The antioxidant capacity of the nanofibers was positively correlated with the number of plant extracts added,in which eugenol and dihydromyricetin nanofibers showed excellent free radical scavenging and ion-reducing abilities in all four systems.In contrast,cinnamaldehyde showed a strong reducing ability against Fe3+ only at 1.0 wt% of the added amount.The nanofibers loaded with four plant extracts showed potent inhibitory effects on E.coli and S.aureus,respectively,and the differences between the other additions were insignificant.(4)Nanofiber loaded with(10 wt%,20 wt%)dihydromyricetin as mats and fresh pork were placed in transparent boxes,encapsulated,and refrigerated at 4℃.The physicochemical parameters of fresh pork during storagewere measured periodically for evaluation.The results showed that the rate of color change,p H,total volatile basic nitrogen(TVB-N)and total viable count(TVC)were significantly lower in the gelatin/zein composite nanofibers loaded with dihydromyricetin compared with the control treated fresh pork during the same storage period.At 6-9 days of storage,the fresh pork in the control treatment had deteriorated,while the deterioration of pork in the(10 wt%,20 wt%)dihydromyricetin nanofiber treatment group was delayed.Conclusion Airflow-assisted electrospinning technology has shown promise in yield and nanofiber structure compared to conventional electrospinning technology.Dihydromyricetin/gelatin/zein nanofibers have comparable or superior physical and functional properties to common thymol,cinnamaldehyde,and eugenol nanofibers,suggesting the potential application of dihydromyricetin nanofibers in food active packaging and dihydromyricetin in functional food delivery systems.