Microcapsules biologically prepared using Perilla frutescens (L.) Britt. essential oil and their use for extension of fruit shelf life

Preparation of Perilla frutescens L. essential oil hydrogel beads and preservation application research in strawberry

Perilla frutescens L. essential oil (PLEO) has antibacterial and antioxidant properties, which can effectively maintain the quality of fruits and extend their shelf life. In this study, sodium alginate and chitosan were used as wall materials, and PLEO microcapsule powder was used as the core materials to prepare PLEO hydrogel beads. The best results were obtained by using 2%w/v sodium alginate and 1.5%w/v chitosan as wall materials, with a core-to-wall ratio of 2:1 and homogenized for 15 min producing PLEO hydrogel beads with encapsulation efficiency of 82.61 %. For strawberries preservation, PLEO hydrogel beads preservation group had a better effect after 5 d of storage, showing a lower decay rate (15.71 %), better maintaining the hardness of 1.75 kg/cm2, and a weight loss of 3.29 %. Furthermore, organic acids and total phenols were retained more in this group, the number of microorganisms was significantly reduced, and sensory qualities were improved, especially taste and color. This study provides important insights into the application of natural preservatives in the food industry and promotes sustainable practices in food preservation.

Preservation of chilled beef using active films based on bacterial cellulose and polyvinyl alcohol with the incorporation of Perilla essential oil Pickering emulsion

In this study, Perilla essential oil (PEO) Pickering emulsions, prepared using soybean protein isolate-chitosan nanoparticles (SPI-CSNPs) as emulsifiers (SCEO), were used to improve the performance of bacterial cellulose/polyvinyl alcohol (BC/PVA) films for application in chilled beef preservation. The SCEO has a smaller particle size (185 nm), higher viscosity, a more uniform dispersion and was more stable at an oil phase volume fraction of 80 %. An increase in the films' surface roughness and in the hydrogen bonding between SCEO and the films' matrix was also observed, resulting in a lower tensile strength (TS, 94.75-62.02 MPa) and higher elongation at break (EAB, 26.78-55.62 %). Moreover, the thermal stability, water vapor permeability, antioxidant and antibacterial properties of the composite films improved as the SCEO content increased. Furthermore, the Pickering emulsion method was effective in preventing the loss of PEO during storage. Overall, one particular composite film, BP/SCEO3, could prolong the shelf life of chilled beef by up to 14 days, and hence was promising for food preservation.

Preparation, characterization and release kinetics of a multilayer encapsulated Perilla frutescens L. essential oil hydrogel bead

Encapsulation has been widely used as the protection of essential oils, which gives the possibility of their implementation as food preservatives. In this study, Perilla frutescens L. essential oil (PLEO) microcapsule powders were prepared firstly by spray drying method using octenyl succinic anhydride starch (OSAs) as wall material, and then they were further encapsulated by sodium alginate and chitosan via polyelectrolyte complex coacervates method. The best results were obtained by using 4 % of OSAs-PLEO microcapsule powders, 2 % of sodium alginate and 1.5 % of chitosan producing PLEO hydrogel beads with encapsulation efficiency of 61.29 % and loading degree of 41.11 %. Morphology observation showed PLEO hydrogel beads was a millimeter scale spherical particle. FTIR assay confirmed the physical embedding of OSAs on PLEO and the formation of complex coacervates between sodium alginate and chitosan. TG and DSC assay showed the chitosan/alginate/OSAs complex coacervates as wall materials substantially improved the thermal stability of PLEO. Besides, PLEO hydrogel beads had a better stability in aqueous and acidic food formulations, which achieved a complete and prolonged release of PLEO. The Peppas-Sahlin model was the best approach for PLEO release profile, and release phenomenon was mainly governed by Fickian diffusion.

Stabilization of Essential Oil: Polysaccharide-Based Drug Delivery System with Plant-like Structure Based on Biomimetic Concept

Essential oils (EOs) have stability problems, including volatility, oxidation, photosensitivity, heat sensitivity, humidity sensitivity, pH sensitivity, and ion sensitivity. A drug delivery system is an effective way to stabilize EOs, especially due to the protective effect of polymeric drug carriers. Polysaccharides are frequently employed as drug carrier materials because they are highly safe, come in a variety of forms, and have plentiful sources. Interestingly, the EO drug delivery system is based on the biomimetic concept since it corresponds to the structure of plant tissue. In this paper, we associate the biomimetic plant-like structures of the EO drug delivery system with the natural forms of EO in plant tissues, and summarize the characteristics of polysaccharide-based drug carriers for EO protection. Thus, we highlight the research progress on polysaccharides and their modified materials, including gum arabic, starch, cellulose, chitosan, sodium alginate, pectin, and pullulan, and their use as biomimetic drug carriers for EO preparations due to their abilities and potential for EO protection.

Toxic Effects of Perilla frutescens (L.) Britt. Essential Oil and Its Main Component on Culex pipiens pallens (Diptera: Culicidae)

Sustainable control of mosquitoes, vectors of many pathogens and parasites, is a critical challenge. Chemical insecticides are gradually losing their effectiveness because of development of resistance, and plant metabolites are increasingly being recognized as potential alternatives to chemical insecticides. This study aimed to analyze the main components of Perilla frutescens essential oil (PE-EO), investigate the specific activity of PE-EO as a botanical insecticide and mosquito repellent, and explore whether its main constituents are potential candidates for further research. The larvicidal activity assay showed that LC50 of PE-EO and 2-hexanoylfuran was 45 and 25 mg/L, respectively. In the ovicidal activity assay, both 120 mg/L PE-EO and 80 mg/L 2-hexanoylfuran could achieve 98% egg mortality. Moreover, PE-EO and 2-hexanoylfuran showed repellency and oviposition deterrence effects. Notably, 10% PE-EO maintained a high rate of protection for 360 min. Although PE-EO and its main component had certain toxic effects on zebrafish, no significant harmful effects were detected in human embryonic kidney cells. Therefore, perilla essential oil is an effective agent for mosquito control at several life stages and that its main component, 2-hexanoylfuran, is a potential candidate for developing novel plant biopesticides.

Effect of sustained-release tea tree essential oil solid preservative on fresh-cut pineapple storage quality in modified atmospheres packaging

The quality and safety of fresh-cut pineapple deteriorate during handling and storage due to physicochemical and microbial changes, so its preservation has attracted extensive attention. This study prepared sustained-release tea tree essential oil (TTO) solid preservative (SP) with an encapsulation efficiency of 71.45% and applied it on fresh-cut pineapple in modified atmospheres packaging (MAP). Results showed that TTO adsorbed on nano silicon dioxide (SiO₂) was embedded in the starch-carboxymethyl cellulose network structure by extrusion. The hydrogen bond and hydrophobic interaction resulted in compact structure and good sustained-release performance of SP. The SP improved sensory quality and reduced nutrient loss and microbial spoilage of fresh-cut pineapple, which extended its shelf-life to four days. In addition, antioxidant capacity was enhanced with increasing antioxidant enzyme activity, antioxidant content, and 2,2-diphenyl-1-picrylhydrazine scavenging capacity and decreasing MDA accumulation. Therefore, sustained-release TTO solid preservative has potential for the preservation of fresh-cut pineapple.

Temperature controlled microcapsule loaded with Perilla essential oil and its application in preservation of peaches

In this study, Perilla frutescens essential oil (PEO) loaded microcapsules (PEOM) were successfully prepared and their thermal stability, temperature-responsive releasing effect, antioxidant activity, antibacterial activity, and preservation of peach were systematically investigated. PEOM showed excellent encapsulation efficiency (91.5%) with a core-shell ratio of 1.4:1 and exhibited high thermal stability, indicating that PEOM could effectively maintain PEO release rate. In vitro assays indicated that the optimal kinetic model for PEO release fitted well with first order with a diffusion mechanism. A high level of antioxidant and antibacterial activity of PEOM was maintained. In addition, owing to its sustained release, PEOM could prolong the shelf life of peaches significantly. Therefore, PEOM has potential application and development prospects in the field of food preservation.

Citral Essential Oil-Loaded Microcapsules by Simple Coacervation and Its Application on Peach Preservation

Citral essential oil (CEO) was encapsulated by the single coalescence method, and its stability, release properties, and ability to maintain freshness were evaluated for the first time. The microshape characteristics of a CEO-loaded microcapsule (CM) were analyzed by inverted microscopy (OM) and scanning electron microscopy (SEM). The encapsulation efficiency, stability, and release behavior of CEO were evaluated using Fourier transform infrared spectroscopy (FTIR), thermogravimetric/differential thermal comprehensive analysis (TG/DSC), and gas chromatography mass spectrometry (GC/MS). Moreover, peaches were used to evaluate the preservation properties of the CEO-loaded microcapsule. The results showed that the microcapsule produced using simple coacervation had better microstructure and the ability to reduce and control the release of citral essential oil. The qualities of peaches, such as appearance changes, hardness, soluble solid content, total acids, and total bacterial counts, were significantly improved in the CM system during storage, in comparison with the control and cold storage groups. Therefore, the CM has potential applications and development prospects in the food, drug, and other industries.

Recent advances in essential oil complex coacervation by efficient physical field technology: A review of enhancing efficient and quality attributes

Although complex coacervation could improve the water solubility, thermal stability, bioavailability, antioxidant activity and antibacterial activity of essential oils (EOs). However, some wall materials (such as proteins and polysaccharides) with water solubility and hydrophobic nature limited their application in complex coacervation. In order to improve the properties of EO complex coacervates, some efficient physical field technology was proposed. This paper summarizes the application and functional properties of EOs in complex coacervates, formation and controlled-release mechanism, as well as functions of EO complex coacervates. In particular, efficient physical field technology as innovative technology, such as high pressure, ultrasound, cold plasma, pulsed electric fields, electrohydrodynamic atomization and microwave technology improved efficient and quality attributes of EO complex coacervates are reviewed. The physical fields could modify the gelling, structural, textural, emulsifying, rheological properties, solubility of wall material (proteins and polysaccharides), which improve the properties of EO complex coacervates. Overall, EOs complex coacervates possess great potential to be used in the food industry, including high bioavailability, excellent antioxidant capacity and gut microbiota in vivo, masking the sensation of off-taste or flavor, favorable antimicrobial capacity.

Preparation, characterization, and antifungal property of the inclusion complex of Litsea cubeba essential oil/hydroxypropyl-β-cyclodextrin and its application in preservation of Shatang mandarin

To explore the potential application of plant essential oil in the postharvest preservation of fruits, the inclusion complex (IC) of Litsea cubeba essential oil (LCEO) with hydroxypropyl-β-cyclodextrin (HPβCD), prepared by the saturated aqueous solution method, was studied. LCEO/HPβCD-IC was characterized by fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), particle size distribution, and thermogravimetric-differential scanning calorimetry (TG-DSC) analysis. The formation of LCEO/HPβCD-IC was confirmed, and the volume average particle diameter was 24.376 µm. Due to the inclusion of HPβCD, the volatility of LCEO was significantly reduced and the thermal stability was significantly improved. In addition, the antifungal activities of the LCEO ICs were compared, and LCEO/HPβCD-IC was more effective against the citrus postharvest pathogens (P. italicum and G. citri-aurantii). The effects of the LCEO ICs on the postharvest quality of Shatang mandarin were studied. Compared with the control group (CK) and LCEO/βCD-IC group, the LCEO/HPβCD-IC group showed a significant delay in the decrease of good fruit rate, hardness, total soluble solids (TSSs), and Vitamin C (Vc) content, with a lower weight loss rate of Shatang mandarin. Therefore, LCEO/HPβCD-IC is expected to be used as a green preservative for the storage and preservation of citrus fruits. PRACTICAL APPLICATION: In this study, LCEO was encapsulated in HPβCD by the saturated aqueous solution method and the prepared inclusion complex was characterized. The effects of LCEO/HPβCD-IC and LCEO/βCD-IC on postharvest preservation of Shatang mandarin were compared. This work offers valuable insights into the postharvest preservation of citrus fruit by essential oil inclusion complexes.

Electrospun Poly (Vinyl Alcohol) Nanofibrous Mat Loaded with Green Propolis Extract, Chitosan and Nystatin as an Innovative Wound Dressing Material

Purposes

The objective of this work was to produce and characterise biodegradable poly (vinyl alcohol) (PVA) nanofibre loaded with green propolis extract (GPE), chitosan (CS) and nystatin (NYS) alone and in mixtures as a potential wound dressing material.

Methods

The GPE, NYS and CS1% were loaded in electrospinning compositions based on PVA 7%, 8% and 12% solubilised in milli-Q water or a mixture of water and glacial acetic acid. The electrospinning compositions without actives (blank) and those loaded with actives were characterised by determining the pH, electrical conductivity and rheological properties. An image analysis procedure applied to photomicrographs obtained by scanning electronic microscopy (SEM) allowed the determination of the nanofibres' diameter distribution and average surface porosity. The disintegration time and swelling ratio of the nanofibre mats were also determined.

Results

The physicochemical parameters of the electrospinning compositions (pH, electrical conductivity and rheology) and the incorporated active ingredients (GPE, CS and NYS) affected the electrospun nanofibre mats properties. The electrospun nanofibres' mean diameters and surface porosity ranged from 151.5 to 684.5 nm and from 0.29 ± 0.04 to 0.50 ± 0.05. The PVA/CS electrospun nanofibres fibres exhibited the smallest diameters, high surface porosity, water absorption capacity and disintegration time. The characteristics of the PVA/CS nanofibres mat associated with the biodegradability of the polymers make them a novel material with the potential to be applied as wound and burn dressings.

Perilla frutescens: A Rich Source of Pharmacological Active Compounds

Perilla frutescens (L.) Britton, an important pharmaceutical and nutraceutical crop, is widely cultivated in East Asian countries. In this review, we present the latest research findings on the phytochemistry and pharmacological activities of P. frutescens. Different databases, including PubMed, Scopus, CNKI, Agricola, Scifinder, Embase, ScienceDirect, DOAJ, and Web of Science, were searched to present the best review. In this review, we clearly represent the active constituents responsible for each and every pharmacological activity, plausible mechanism of action, and maximum inhibitory concentrations, as well as IC₅₀ values. Approximately 400 different bioactive compounds, including alkaloids, terpenoids, quinines, phenylpropanoids, polyphenolic compounds, flavonoids, coumarins, anthocyanins, carotenoids, neolignans, fatty acids, polycosanols, tocopherols, and sitosterols, have been reported in the leaves, seeds, roots, and aerial parts of P. frutescens. The bioactive constituents of P. frutescens exhibited different enzyme-inhibition properties, including antihyaluronidase effects and aldose reductase inhibitory, α-glucosidase inhibitory, xanthine oxidase inhibitory, and tyrosinase inhibitory properties. P. frutescens showed strong anti-inflammatory, antidepressant, anti-spasmodic, anticancer, antioxidant, antimicrobial, insecticidal, neuroprotective, and hepatoprotective effects. Hence, the active constituents of P. frutescens used in the treatment of diabetes and diabetic complications (retinopathy, neuropathy, and nephropathy), prevention of hyperuricemia in gout patients, hyper pigmentation, allergic conditions, skin inflammation, skin allergy, atopic dermatitis, periodontosis, androgenic alopecia, gastric inflammation, oesophagitis, carcinogenesis, cardiovascular, Alzheimer’s, Parkinson’s, and cerebral ischemic disorders. Furthermore, we revealed the most active constituents and possible mechanisms of the pharmacological properties of P. frutescens.

Optimization of Enzymatic Hydrolysis of Perilla Meal Protein for Hydrolysate with High Hydrolysis Degree and Antioxidant Activity

Botanical oils are staple consumer goods globally, but as a by-product of oil crops, meal is of low utilization value and prone to causing environmental problems. The development of proteins in meal into bioactive peptides, such as Perilla peptide, through biotechnology can not only solve environmental problems, but also create more valuable nutritional additives. In the present work, the hydrolysis process of Perilla meal protein suitable for industrial application was optimized with the response surface methodology (RSM) on the basis of single-factor experiments. Alcalase was firstly selected as the best-performing among four proteases. Then, based on Alcalase, the optimal hydrolysis conditions were as follows: enzyme concentration of 7%, hydrolysis temperature of 61.4 °C, liquid-solid ratio of 22.33:1 (mL/g) and hydrolysis time of 4 h. Under these conditions, the degree of hydrolysis (DH) of Perilla meal protein was 26.23 ± 0.83% and the DPPH scavenging capacity of hydrolysate was 94.15 ± 1.12%. The soluble peptide or protein concentration of Perilla meal protein hydrolysate rose up to 5.24 ± 0.05 mg/mL, the ideal yield of which was estimated to be 17.9%. SDS-PAGE indicated that a large proportion of new bands in hydrolysate with small molecular weights appeared, which was different from the original Perilla meal protein. The present data contributed to further, more specific research on the separation, purification and identification of antioxidant peptide from the hydrolysate of Perilla meal protein. The results showed that the hydrolysis of Perilla meal protein could yield peptides with high antioxidant activity and potential applications as natural antioxidants in the food industry.

Pro-Angiogenic Effects of Essential Oil from Perilla frutescens and Its Main Component (Perillaldehyde) on Zebrafish Embryos and Human Umbilical Vein Endothelial Cells

Purpose

Perilla frutescens (L.) Britt., a traditional edible-medicinal herb in China, has been used to treat cardiovascular and cerebrovascular (cardio-cerebrovascular) diseases for thousands of years. However, knowledge of the mechanisms underlying the effects of essential oil from P. frutescens (EOPF) in the treatment of cardio-cerebrovascular diseases is lacking. The promotion of angiogenesis is beneficial in the treatment of ischemic cardio-cerebrovascular diseases. The current study investigated the pro-angiogenic role of EOPF and its main component perillaldehyde in sunitinib-injured transgenic Tg (flk1:EGFP) zebrafish embryos and human umbilical vein endothelial cells (HUVECs) for the first time.

Materials and Methods

The pro-angiogenic effects of EOPF and perillaldehyde were observed in vivo using transgenic Tg (flk1:EGFP) zebrafish embryos and in vitro using HUVECs. Cell viability, proliferation, migration, tube formation, and protein levels were detected by MTT, EdU staining, wound healing, transwell chamber, and Western blot assays, respectively.

Results

EOPF and perillaldehyde exerted a significant stimulatory effect on the formation of zebrafish intersegmental vessels (ISVs). Moreover, EOPF and perillaldehyde promoted proliferation, migration, and tube formation in sunitinib-treated HUVECs. Additionally, our findings uncovered that the pro-angiogenic effects of EOPF and perillaldehyde were mediated by increases in the expression ratios of p-ERK1/2 to ERK1/2 and Bcl-2 to Bax.

Conclusion

The present study is the first report to provide clear evidence that EOPF and perillaldehyde promote angiogenesis by stimulating repair of sunitinib-injured ISVs in zebrafish embryos and promoting proliferation, migration, and tube formation in sunitinib-injured HUVECs. The underlying mechanisms are related to increased p-ERK1/2 to ERK1/2 and Bcl-2 to Bax expression ratios. EOPF and perillaldehyde may be used in the treatment of cardio-cerebrovascular diseases, which is consistent with the traditional application of P. frutescens.

Encapsulation of volatile compounds in liquid media: Fragrances, flavors, and essential oils in commercial formulations

The first marketed example of the application of microcapsules dates back to 1957. Since then, microencapsulation techniques and knowledge have progressed in a plethora of technological fields, and efforts have been directed toward the design of progressively more efficient carriers. The protection of payloads from the exposure to unfavorable environments indeed grants enhanced efficacy, safety, and stability of encapsulated species while allowing for a fine tuning of their release profile and longer lasting beneficial effects. Perfumes or, more generally, active-loaded microcapsules are nowadays present in a very large number of consumer products. Commercial products currently make use of rigid, stable polymer-based microcapsules with excellent release properties. However, this type of microcapsules does not meet certain sustainability requirements such as biocompatibility and biodegradability: the leaking via wastewater contributes to the alarming phenomenon of microplastic pollution with about 4% of total microplastic in the environment. Therefore, there is a need to address new issues which have been emerging in relation to the poor environmental profile of such materials. The progresses in some of the main application fields of microencapsulation, such as household care, toiletries, cosmetics, food, and pesticides are reviewed herein. The main technologies employed in microcapsules production and the mechanisms underlying the release of actives are also discussed. Both the advantages and disadvantages of every technique have been considered to allow a careful choice of the most suitable technique for a specific target application and prepare the ground for novel ideas and approaches for encapsulation strategies that we expect to be proposed within the next years.

Preparation and characterization of polylactic acid nanofiber films loading Perilla essential oil for antibacterial packaging of chilled chicken

Biodegradable and eco-friendly food packaging materials have attracted attention. Novel blending films were prepared with polylactic acid (PLA) and Perilla essential oil (PEsO). The morphological features of the nanofibers were modulated by adjusting process parameters (e.g. PLA solution concentration, applied voltage and ultrasonic power). The optimal spinning concentrations, applied voltages and ultrasonic power of the PLA solutions were set at 15% (m/v), 20 kV and 640 W, respectively. Compared with the PLA films, the addition of PEsO increased the diameter of the nanofibers and solvent resistance and reduced the swelling rate of the PLA/PEsO films. The breakage elongation and the gas barrier properties significantly improved when 2% (w/w) PEsO was used. Fourier infrared spectroscopy, X-ray diffractometer, thermogravimetry and differential scanning were used in analyzing the potential interactions of the film matrices. The PLA/PEsO films had good biocompatibility and antibacterial and antioxidant properties. The PLA/PEsO (1:0.02) film loaded with 2% PEsO extended the shelf life of chilled chicken to 12 days, as indicated by the measured total volatile basic nitrogen (TVB-N), total viable count and pH value. Therefore, PLA/PEsO films have great potential as fresh-keeping packaging.

Development and evaluation of lutein-loaded alginate microspheres with improved stability and antioxidant

BACKGROUND

Lutein has been of great interest to the food processing and pharmaconutrient industries owing to its beneficial effects on human health. However, lutein is very sensitive to heat, light, pH and oxidative conditions, which limits its application in food systems. The present study aimed to prepare lutein-alginate microspheres by a calcium chloride gelation method with the purpose of improving the stability and antioxidant abilities of lutein.

RESULTS

The loading capacity of lutein in the microspheres was approximately 5.3% (w/w) and the entrapment efficiency was about 63%. The loaded microspheres were nearly spherical with an average size of 150 μm. They exhibited a crimped surface by scanning electron microscopy. The lutein was in amorphous state by X-ray powder diffraction. Analysis by Fourier transform infrared spectroscopy and molecular docking revealed an intermolecular hydrogen bond interaction between lutein and sodium alginate. In vitro release experiments showed that the microspheres presented slower release at acidic conditions than at neutral intestinal conditions. The 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity of the microencapsulated lutein was higher than that of free lutein. The stability of lutein in the microspheres was improved significantly when compared with that of free lutein at various temperatures.

CONCLUSION

The present work successfully developed well-protected lutein-alginate microspheres. This indicates that it is feasible to use microspheres loaded with lutein as antioxidant functional ingredients in food products. © 2019 Society of Chemical Industry.

A Review on Nutritional Value, Functional Properties and Pharmacological Application of Perilla (Perilla Frutescens L.)

Perilla frutescens is an annual herb belonging to the mint family (Lamiaceae). It is majorly produced in countries like China, Japan, India, Thailand and Korea. Recently, Perilla plant is gaining more attention because of its medicinal benefits and phytochemical contents. The major phytochemical compounds reported in this species are phenolic compounds (Rosmarinic acid, caffeic acid, ferulic acid), flavonoids (luteolin, apigenin), Phytosterols, Tocopherols, Policosanols and Fatty acid. Perilla seed oil is also a rich source of essential fatty acid such as α-linolenic acid (54-64%) and linoleic acid (14%). Perilla seeds and its oils have been widely used in traditional nutritional and medicinal formulations. Biological analysis of Perilla seeds revealed that it showed anticancer, ant-diabetic, antiasthma, antimicrobial, anti-inflammatory, antioxidant and cardioprotective effect. The aim of this review is to provide an update on the nutritional composition, phytochemical profile and pharmacological research of Perilla seed.

Microencapsulation of Thymol in Poly(lactide-co-glycolide) (PLGA): Physical and Antibacterial Properties

Thymol has been shown to be a safe and effective broad-spectrum antimicrobial agent that can be used as a food preservative. However, its volatile characteristics and strong odor limit its use in food products. The microencapsulation of this essential oil in biopolymers could overcome these disadvantages. In this work, thymol-loaded poly(lactide-co-glycolide) (PLGA) microparticles were successfully prepared and the optimal encapsulation efficiency was obtained at 20% (w/w) thymol. Microparticles containing thymol presented a spherical shape and smooth surface. Microencapsulation significantly improved the thermal and storage stability of thymol. In vitro release profiles demonstrated an initial fast release followed by a slow and sustained release. Thymol-loaded microparticles had strong antibacterial activity against Escherichia coli and Staphylococcus aureus, and the effectiveness of their antibacterial properties was confirmed in a milk test. Therefore, the thymol-loaded microparticles show great potential for use as an antimicrobial and as preservation additives in food.

Preparation of Tea Tree Oil/Poly(styrene-butyl methacrylate) Microspheres with Sustained Release and Anti-Bacterial Properties

Using butyl methacrylate (BMA) and styrene (St) as monomers and divinylbenzene (DVB) as a crosslinking agent, P(St-BMA) microspheres were prepared by suspension polymerization. Tea tree oil (TTO) microspheres were prepared by adsorbing TTO on P(St-BMA) microspheres. The structure and surface morphology of P(St-BMA) microspheres and TTO microspheres were characterized by Fourier transformed infrared spectroscopy (FTIR), optical microscopy, and Thermogravimetric analysis (TGA). In doing so, the structural effect of P(St-BMA) microspheres on oil absorption and sustained release properties could be investigated. The results show that the surface of the P(St-BMA) microspheres in the process of TTO microsphere formation changed from initially concave to convex. The TTO microspheres significantly improved the stability of TTO, which was found to completely decompose as the temperature of the TTO increased from about 110 °C to 150 °C. The oil absorption behavior, which was up to 3.85 g/g, could be controlled by adjusting the monomer ratio and the amount of crosslinking agent. Based on Fickian diffusion, the sustained release behavior of TTO microspheres was consistent with the Korsmeyer-Pappas kinetic model. After 13 h of natural release, the anti-bacterial effect of the TTO microspheres was found to be significantly improved compared to TTO.