Microencapsulation Methods of Volatile Essential Oils - A Review

Recent advances of antibacterial starch-based materials

Starch has attracted a lot of attention because it is biodegradable, renewable, nontoxic and low cost. By adding antibacterial substances to starch, starch-based materials have antibacterial properties. The composite with other materials can improve the comprehensive performance of starch-based materials, thus broadening the application field of the material. In this paper, we focus on antibacterial starch-based materials and review their preparation and applications. It was found that antibacterial starch-based materials were most widely used in packaging, followed by medicine, and the research on smart starch-based materials was relatively less. This review may provide some reference value for subsequent studies of starch-based materials.

PMMA Microcapsules for the Inactivation of SARS-CoV-2

Surface disinfection currently plays a decisive role in the epidemiological situation caused by the SARS-CoV-2 coronavirus. However, most disinfection products available on the market have a high evaporation rate and only an immediate action and not continuous, creating the need for a high frequency of disinfection. To overcome this limitation, in the present work, poly(methyl methacrylate) (PMMA) microcapsules were developed with an active agent (hydrogen peroxide) encapsulated, which has the ability to inactivate/neutralize the SARS-CoV-2 virus. PMMA-H₂O₂ microcapsules have a spherical shape and a smooth structure with low porosity and were successfully attached to nonwoven fabrics, as observed from scanning electron microscopy. The thermogravimetric analysis shows that PMMA-H₂O₂ microcapsules have high thermal stability and can increase the stability of H₂O₂. Nonfabric substrates functionalized with PMMA-H₂O₂ microcapsules were tested by a highly sensitive and specific reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR)-based method to evaluate antiviral activity through the degradation of SARS-CoV-2 deoxyribonucleic acids. The highest percentage of viral nucleic acid elimination was obtained when exposing the viral sample for 1 h to PMMA-H₂O₂ microcapsules, resulting in an elimination of >97% of the coronavirus. In addition, the microcapsules are stable over a period of three weeks and retain the ability to eliminate SARS-CoV-2. Hence, it is demonstrated that this microcapsule system is efficient for SARS-CoV-2 elimination and inherent surface disinfection.

Impact of microencapsulated Ziziphora tenuior essential oil and orange fiber as natural‐functional additives on chemical and microbial qualities of cooked beef sausage

The aim of the current study was to investigate the suitability of Ziziphora tenuior essential oil (ZEO) as a preservative. For this purpose, the effect of free and microencapsulated ZEO, combined with orange fiber, was determined on the chemical and microbial qualities of cooked beef sausage. In this study, modified starch was used for encapsulation of essential oil, and subsequently, 0.5% ZEO and 1% orange fiber were used for preparing cooked beef sausages during 60 days of storage at 4°C. To assess the microbial quality of samples, total viable count (TVC), psychrophilic count (PSY), and lactic acid bacteria (LAB) were analyzed. Furthermore, peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) were tested to examine lipid oxidation. The most components of ZEO were pulegone (47.12%), isomenthone (14.57%), and 1,8‐cineole (12.84%) according to GC–MS analysis. The reducing power, DPPH radical scavenging activity, MIC, and MBC of ZEO were 16.44 (EC₅₀), 8.36 (IC₅₀), 0.625–2.5, and 1.25–5 mg/ml, respectively. Moreover, sausage containing 0.5% microencapsulated ZEO in combination with 1% orange fiber showed the best results with the following values (p ≤ .05): TVC (3.69 log CFU/g), PSY (3.51 log CFU/g), LAB (3.1 log CFU/g), PV (10.41 meq/kg lipid), and TBARS (3.1 mg MDA/kg). This is due to the antimicrobial and antioxidant properties of microencapsulated essential oil. Therefore, the results of the present study can be applied in the meat industries as a new natural preservation method.

Development of Innovative Chewable Gel Tablets Containing Nutmeg Essential Oil Microcapsules and Their Physical Properties Evaluation

Chewable gel tablets are a dosed pharmaceutical form, which can have an active substance, pharmacological effect, or value of nutrition. The texture of these tablets is soft, springy, flexible, and elastic-this is influenced by the chosen ingredients. The aim of this study was to prepare chewable gel tablets with nutmeg essential oil-loaded microcapsules and determine the volatile compounds released from this pharmaceutical form. Gel tablets were prepared by using gelatin as basis, nutmeg essential oil as active compound, and natural ingredients: thyme-sugar syrup, thyme extract, and citric acid as taste and color additives. Texture properties were measured by a texture analyzer. The release of volatile compounds from nutmeg essential oil and gel tablets were analyzed by headspace-gas chromatography with mass spectroscopy in control and artificial saliva conditions in vitro. Nutmeg essential oil microcapsules had influence on the gel tablet's physical properties (p < 0.05, by comparing tablets without glycerol and relative sample with glycerol); glycerol protects the tablets from the formation of sugar crystals on top and keeps good physical parameters (p < 0.05). A total of 12 volatile compounds were identified in nutmeg essential oil, and the six compounds with the highest amounts were selected as controls. Gel tablets prolong the release time of volatile compounds and reduce the amount of the compounds compared to the microcapsules (p < 0.05).

Improving the storage stability of tomato paste by the addition of encapsulated olive leaf phenolics and experimental growth modeling of A. flavus

It is necessary to apply some preservatives for tomato paste since in the harvest season, a high load of tomatoes need to be processed as they are among highly perishable products. Application of antimicrobial extracts or essential oils, as natural preservatives, in their raw forms might reduce their efficiency when they are exposed to environmental conditions. However, microencapsulation is a well-known method to solve this problem. Our main goal was to restrict fungal growth rate in stored tomato paste and increase its storage stability by incorporating encapsulated olive leaf phenolic-rich extract. Total Soluble Solids (TSS), consistency, pH, color indices and diametrical growth rate of Aspergillus flavus were measured for different samples. The treatments designed in terms of considering two levels of non-encapsulated olive phenolics extract with 500 and 1000 ppm (NE₅₀₀ and NE₁₀₀₀), the same levels with encapsulated extract; i.e., 500 and 1000 ppm (ME₅₀₀ and ME₁₀₀₀), and similar levels of the common preservative of sodium benzoate with 500 and 1000 ppm (B₅₀₀ and B₁₀₀₀). Antifungal properties of NE samples were higher than ME ones during storage although ME samples could maintain diametrical growth rate of the fungus more stable than NE ones. NE samples justified lower maximum growth rate than ME samples while ME samples could extend lag phase of microbial growth compared with NE one and delay their internal deteriorative reactions. Among Baranyi, modified Baranyi, Modified Gompertz, and Logistic models, Modified Gompertz model represented the best model and could fit the growth factors of A. flavus on tomato paste with higher R² index as well as lower RMSE and SSE indices. Based on the results obtained, it could be concluded that usage of encapsulated olive leaf extract in tomato paste is an effective, natural and sustainable approach to improve the shelf life of tomato paste since this natural compound could perform as favourable as preservatives; also it could maintain physicochemical as well as microbial properties of tomato paste for a long term. Thus, it is strongly recommended that application of encapsulated olive leaf extract to be considered seriously by the tomato paste industry as it can effectively reduce the mold and fungal contaminations which are very common and prevalent in the plants. The future work in this regard should focus on sensory evaluations when incorporating encapsulated olive leaf extract into tomato paste.

Development of New Formula Microcapsules from Nutmeg Essential Oil Using Sucrose Esters and Magnesium Aluminometasilicate

Essential oils are volatile liquids which evaporate and lose their pharmacological effect when exposed to the environment. The aim of this study is to protect nutmeg essential oil from environmental factors by encapsulation (shell material, sodium alginate) and determine the influence of crosslinker concentration (2%, 5% calcium chloride), different emulsifiers (polysorbate 80, sucrose esters), and magnesium aluminometasilicate on microcapsule physical parameters, encapsulation efficiency (EE), swelling index (SI), and other parameters. Nutmeg essential oil (NEO)-loaded calcium alginate microcapsules were prepared by extrusion. The swelling test was performed with and without enzymes in simulated gastric, intestinal, and gastrointestinal media. This study shows that the crosslinker concentration has a significant influence on EE, with 2% calcium chloride solution being more effective than 5%, and capsules being softer with 2% crosslinker solution. Using sucrose esters, EE is higher when polysorbate 80 is used. The swelling index is nearly three times higher in an intestinal medium without enzymes than in the medium with pancreatin. Microcapsule physical parameters depend on the excipients: the hardest capsules were obtained with the biggest amount of sodium alginate; the largest with magnesium aluminometasilicate. Sucrose esters and magnesium aluminometasilicate are new materials used in extrusion.