Sustained-release mechanism of ß-Cyclodextrin/cationic cellulose-stabilized Pickering emulsions loaded with citrus essential oil.

Citrus oil (CO) is a commonly used natural flavor with high volatility, which is not conducive to sustained release under food environmental stress. This study constructed novel ß-cyclodextrin/cationic cellulose nanocrystal (ß-CD/C-CNC) complexes via noncovalent interaction, which were used to stabilize CO-loaded Pickering emulsions (PEß-CD/C-CNC). The C-CNC greatly improved the physical stability, droplet dispersion and viscoelasticity of PEß-CD/C-CNC by forming a tight network structure, as verified by rheological behavior. Moreover, C-CNC improved the wettability of ß-CD/C-CNC complexes and enhanced the interaction between adjacent ß-CD/C-CNC complexes. C-CNC also contributed to the interfacial viscoelasticity, hydrated mass, and layer thickness via the interfacial dilational modulus and QCM-D. ß-CD/C-CNC complexes adsorbed on the oil-water interface gave rise to a dense filling layer as a physical barrier, enhancing the sustained-release performance of PEß-CD/C-CNC by limiting diffusion of citrus essential oil into the headspace. This study provides new technical approaches for aroma retention in the food industry.

In Silico Study on Natural Chemical Compounds from Citric Essential Oils as Potential Inhibitors of an Omicron (BA.1) SARS-CoV-2 Mutants' Spike Glycoprotein.

BACKGROUND: SARS-CoV-2's remarkable capacity for genetic mutation enables it to swiftly adapt to environmental changes, influencing critical attributes, such as antigenicity and transmissibility. Thus, multi-target inhibitors capable of effectively combating various viral mutants concurrently are of great interest. OBJECTIVE: This study aimed to investigate natural compounds that could unitedly inhibit spike glycoproteins of various Omicron mutants. Implementation of various in silico approaches allows us to scan a library of compounds against a variety of mutants in order to find the ones that would inhibit the viral entry disregard of occurred mutations. METHODS: An extensive analysis of relevant literature was conducted to compile a library of chemical compounds sourced from citrus essential oils. Ten homology models representing mutants of the Omicron variant were generated, including the latest 23F clade (EG.5.1), and the compound library was screened against them. Subsequently, employing comprehensive molecular docking and molecular dynamics simulations, we successfully identified promising compounds that exhibited sufficient binding efficacy towards the receptor binding domains (RBDs) of the mutant viral strains. The scoring of ligands was based on their average potency against all models generated herein, in addition to a reference Omicron RBD structure. Furthermore, the toxicity profile of the highest-scoring compounds was predicted. RESULTS: Out of ten built homology models, seven were successfully validated and showed to be reliable for In Silico studies. Three models of clades 22C, 22D, and 22E had major deviations in their secondary structure and needed further refinement. Notably, through a 100 nanosecond molecular dynamics simulation, terpinen-4-ol emerged as a potent inhibitor of the Omicron SARS-CoV-2 RBD from the 21K clade (BA.1); however, it did not show high stability in complexes with other mutants. This suggests the need for the utilization of a larger library of chemical compounds as potential inhibitors. CONCLUSION: The outcomes of this investigation hold significant potential for the utilization of a homology modeling approach for the prediction of RBD's secondary structure based on its sequence when the 3D structure of a mutated protein is not available. This opens the opportunities for further advancing the drug discovery process, offering novel avenues for the development of multifunctional, non-toxic natural medications.

Pickering emulsions stabilized by soybean protein isolate/chitosan hydrochloride complex and their applications in essential oil delivery.

In this work, fabrication of soybean protein isolate (SPI)/chitosan hydrochloride (CHC) composite particles stabilized O/W Pickering emulsions using soybean oil as an oil phase was optimized by examining the effects of pH, SPI/CHC mass ratio, SPI/CHC composite particle concentration and oil phase fraction on the stability of the emulsions. The results showed that under the conditions of SPI/CHC mass ratio 1:1, pH 4 and particle concentration 2 %, the SPI/CHC composite particles could stabilize the emulsions with oil phase fraction up to 80 %. At an oil phase fraction of 60 %, the emulsions had a minimum particle size. The microstructure, storage and oxidation stabilities and rheological properties of the emulsions were determined. Using this SPI/CHC composite particle-stabilized Pickering emulsion template, citrus essential oil (CEO) Pickering emulsion (CEOP) was prepared. CEOP was found to markedly inhibit two food-related microorganisms, Staphylococcus aureus and Escherichia coli. In addition, the CEOP emulsion dilution (containing 4500 µL CEO/L) not only improved the water solubility of CEO, but also effectively retarded the browning and bacterial growth of fresh-cut apple. The SPI/CHC-stabilized Pickering emulsion template constructed in this work provides a promising alternative for the delivery of antimicrobial essential oils in the food industry.

The Chemical Composition and Antibacterial and Antioxidant Activities of Five Citrus Essential Oils.

Increasing concerns over the use of antimicrobial growth promoters in animal production has prompted the need to explore the use of natural alternatives such as phytogenic compounds and probiotics. Citrus EOs have the potential to be used as an alternative to antibiotics in animals. The purpose of this research was to study the antibacterial and antioxidant activities of five citrus EOs, grapefruit essential oil (GEO), sweet orange EO (SEO), bergamot EO (BEO), lemon EO (LEO) and their active component d-limonene EO (DLEO). The chemical composition of EOs was analyzed by gas chromatography-mass spectrometry (GC-MS). The antibacterial activities of the EOs on three bacteria (Escherichia coli, Salmonella and Lactobacillus acidophilus) were tested by measuring the minimum inhibitory concentration (MIC), minimal bactericidal concentration (MBC) and inhibition zone diameter (IZD). The antioxidant activities of EOs were evaluated by measuring the free radical scavenging activities of DPPH and ABTS. We found that the active components of the five citrus EOs were mainly terpenes, and the content of d-limonene was the highest. The antibacterial test showed that citrus EOs had selective antibacterial activity, and the LEO had the best selective antibacterial activity. Similarly, the LEO had the best scavenging ability for DPPH radicals, and DLEO had the best scavenging ability for ABTS. Although the main compound of the five citrus EOs was d-limonene, the selective antibacterial and antioxidant activity of them might not be primarily attributed to the d-limonene, but some other compounds' combined action.

Exploring the effect of a microencapsulated citrus essential oil on in vitro fermentation kinetics of pig gut microbiota.

Essential oils (EOs) have emerged as a potential alternative to antibiotics in pig breeding due to their antimicrobial properties. Citrus EOs, a common by-product of the orange juice industry, can be an interesting alternative from a financial perspective due to their huge offer in the global market. Thus, the effect of a citrus EO, and specifically different formulations of Brazilian Orange Terpenes (BOT), on pig gut microbiota was evaluated by means of an in vitro fermentation model simulating different sections of the pig gut (stomach, ileum, and colon). Treatments consisted in: BOT in its unprotected form (BOT, 1.85 and 3.70 mg/mL), microencapsulated BOT (MBOT, 3.50 and 7.00 mg/mL), colistin (2 µg/mL), and a control. BOT and MBOT altered in a similar way the total bacterial 16S rRNA gene copies in the stomach only from 18 h of incubation onwards, and no metabolite production in terms of short-chain fatty acids (SCFAs) was detected. In ileal and colonic fermentations, BOT and MBOT affected ileal and colonic microbiota in terms of total bacterial 16S rRNA gene copies, reduced phylogenetic diversity, and altered composition (p < 0.05) as evidenced by the significant reduction of certain bacterial taxa. However, more pronounced effects were found for MBOT, indicating its higher antimicrobial effects compared to the unprotected BOT, and suggesting that the antibacterial efficiency of the unprotected BOT was probably enhanced by microencapsulation. Furthermore, MBOT stimulated lactate production in ileal fermentations and greatly stimulated overall SCFA production in colonic fermentations. This indicates that besides the shifts in ileal and colonic microbiota by the delivered EO (BOT), the wall material of microcapsules (chitosan/modified starch) might have worked as an additional carbon source with prebiotic functioning, stimulating growth and metabolic activity (SCFAs) of colonic bacteria.

Citrus Essential Oils: a Treasure Trove of Antibiofilm Agent.

Biofilms are groups of adherent cell communities that cohere to the biotic and abiotic surfaces with the help of extracellular polymeric substances (EPS). EPS allow bacteria to form a biofilm that facilitates their binding to biotic and abiotic surfaces and provides resistance to the host immune responses and to antibiotics. There are efforts that have led to the development of natural compounds that can overcome this biofilm-mediated resistance. Essential oils (EOs) are a unique mixture of compounds that plays a key role in preventing the development of biofilm. The present overview focusses on the role of various types of citrus essential oils in acting against the biofilm, and the antibiofilm properties of natural compounds that may show an avenue to treat the multidrug-resistant bacteria.

Mandarin essential oil as an antimicrobial in ethanolic fermentation: Effects on Limosilactobacillus fermentum and Saccharomyces cerevisiae.

The antibacterial activity of citrus essential oils (EOs) in the context of combating Limosilactobacillus fermentum, one of the most important bacterial contaminants in the bioethanol production industry, has never been explored previously. Industrial processes usually utilize sulfuric acid for cell treatment to decrease bacterial contamination. However, due to the hazardous nature of sulfuric acid, an alternative to it is highly desirable. Therefore, in the present study, the efficacy of Fremont IAC 543 mandarin EO against a strain of L. fermentum (ATCC® 9338™) was evaluated under proliferative/nonproliferative conditions, in both pure culture and co-culture with an industrial strain of Saccharomyces cerevisiae. The mandarin EO exhibited higher effectiveness against L. fermentum compared to that against S. cerevisiae under nonproliferative conditions (added to water rather than to culture medium). At the concentration of 0·05%, the EO was as effective as the acid solution with pH 2·0 in reducing the count of L. fermentum almost 5 log CFU ml-1 cycles, while the concentration of 0·1% led to the complete loss of bacterial culturability. When L. fermentum was co-cultured with S. cerevisiae, the efficacy of the EO against the bacterial strain was reduced. However, despite this reduced efficacy in co-culture, mandarin EO may be considered effective in combating L. fermentum and could be applied in processes where this bacterium proves to be unfavourable and does not interact with S. cerevisiae.

Effects of citrus essential oils on the oxidative stability of microencapsulated fish oil by spray-drying.

The effects of citrus essential oils (orange, lemon, mandarin, and grapefruit) on the oxidative stability of microencapsulated fish oil by spray-drying were evaluated. The encapsulation efficiency of microcapsules was in the range of 42.25 and 62.43%. Twelve active substances were determined as major volatile components of citrus essential oils. The highest phenolic content was obtained from grapefruit essential oil (44.32 mg GAE/g). Lower values of thiobarbituric acid reactive substances (TBARs) were obtained for microencapsulated fish oils with essential oils compared to control. At the end of storage, the highest peroxide value (PV) was observed in the control group (25.30 meq O2/kg oil) while the lowest value was in the lemon (13.40 meq O2/kg oil) and orange group (13.91 meq O2/kg oil). The results of this study showed that citrus essential oils can be used to improve the oxidative stability of fish oil microcapsules.

Antibacterial Effects and Mechanism of Mandarin (Citrus reticulata L.) Essential Oil against Staphylococcus aureus.

Staphylococcus aureus (S. aureus) creates an array of challenges for the food industry and causes foodborne diseases in people, largely due to its strong antibiotic resistance. Mandarin (Citrus reticulata L.) essential oil (MEO) is recognized as a natural and safe preservative; however, the antibacterial effects and mechanism of MEO to combat S. aureus are not yet clearly understood. This study will examine the inhibitory effects of MEO against S. aureus and explore the antibacterial mechanism thereof from the perspective of membrane destruction. The antibacterial activity of MEO on planktonic S. aureus was examined to determine the minimal inhibitory concentration (MIC). Scanning electron microscope (SEM) images revealed the direct impacts of MEO treatment on the cell structure of S. aureus. The cell membrane was observed to be depolarized, the determination of extracellular nucleic acids, proteins and intracellular adenosine triphosphate (ATP) confirmed the increased permeability of the cell membrane, its integrity was destroyed and the cellular constituents had leaked. These results, thus, provided conclusive evidence that MEO constrains the growth of planktonic S. aureus by affecting the permeability and integrity of its cell membrane. Our study provides a basis for the further development and utilization of MEO as a natural antibacterial agent in the food industry.

In-Depth Qualitative Analysis of Lime Essential Oils Using the Off-Line Combination of Normal Phase High Performance Liquid Chromatography and Comprehensive Two-Dimensional Gas Chromatography-Quadrupole Mass Spectrometry.

The present research is focused on the in-depth qualitative analysis of three types of lime essential oil (EO), viz., Key (A and B) and Persian, using the off-line combination of normal phase high performance liquid chromatography (NP-HPLC) and comprehensive two-dimensional gas chromatography-quadrupole mass spectrometry (GC × GC-QMS). The first analytical dimension (NP-HPLC) was exploited for the isolation of the hydrocarbon constituents from the oxygenated ones. Each fraction was then reduced in volume and analyzed using (cryogenic modulation) GC × GC-QMS. Peak assignment was carried out through the combined use of mass spectral database and linear retention index matching processes. The powerful four-dimensional technology enabled the separation and identification of a very high number (153) of lime essential oil volatile compounds.

Antioxidant and antibacterial properties of coating with chitosan-citrus essential oil and effect on the quality of Pacific mackerel during chilled storage.

The goal of the study was to investigate whether chitosan-citrus essential oil composite works as an efficient preservative in Pacific mackerel (Pneumatophorus japonicus) during chilling storage. FT-IR analysis showed that chitosan-citrus essential oil coating was successfully prepared. Our results demonstrated that chitosan-citrus essential oil coating possessed significantly higher capability of scavenging reactive oxygen species ( O 2 - and OH-) than chitosan. Furthermore, Pacific mackerel coated with chitosan-citrus essential oil composite could significantly reduce parameters of corruption including physicochemical (drop loss, biogenic amine, and thiobarbituric acid-reactive substances) and microbiological parameters (total viable count), as compared with untreated and chitosan groups after 12 days of storage at -3°C. These results indicated that CS-CEOs could work as efficient preservative for Pacific mackerel storage through ameliorating redox state and inhibiting microbial growth and suggested that chitosan-citrus essential oil composite has great potential in preservation of aquatic products during superchilled storage.

Volatile Compounds in Citrus Essential Oils: A Comprehensive Review.

The essential oil fraction obtained from the rind of Citrus spp. is rich in chemical compounds of interest for the food and perfume industries, and therefore has been extensively studied during the last decades. In this manuscript, we provide a comprehensive review of the volatile composition of this oil fraction and rind extracts for the 10 most studied Citrus species: C. sinensis (sweet orange), C. reticulata (mandarin), C. paradisi (grapefruit), C. grandis (pummelo), C. limon (lemon), C. medica (citron), C. aurantifolia (lime), C. aurantium (bitter orange), C. bergamia (bergamot orange), and C. junos (yuzu). Forty-nine volatile organic compounds have been reported in all 10 species, most of them terpenoid (90%), although about half of the volatile compounds identified in Citrus peel are non-terpenoid. Over 400 volatiles of different chemical nature have been exclusively described in only one of these species and some of them could be useful as species biomarkers. A hierarchical cluster analysis based on volatile composition arranges these Citrus species in three clusters which essentially mirrors those obtained with genetic information. The first cluster is comprised by C. reticulata, C. grandis, C. sinensis, C. paradisi and C. aurantium, and is mainly characterized by the presence of a larger abundance of non-terpenoid ester and aldehyde compounds than in the other species reviewed. The second cluster is comprised by C. junos, C. medica, C. aurantifolia, and C. bergamia, and is characterized by the prevalence of mono- and sesquiterpene hydrocarbons. Finally, C. limon shows a particular volatile profile with some sulfur monoterpenoids and non-terpenoid esters and aldehydes as part of its main differential peculiarities. A systematic description of the rind volatile composition in each of the species is provided together with a general comparison with those in leaves and blossoms. Additionally, the most widely used techniques for the extraction and analysis of volatile Citrus compounds are also described.

The off-line combination of high performance liquid chromatography and comprehensive two-dimensional gas chromatography-mass spectrometry: a powerful approach for highly detailed essential oil analysis.

The present contribution is focused on the off-line combination of high performance liquid chromatography (HPLC) and comprehensive two-dimensional gas chromatography-quadrupole mass spectrometry (GC×GC-quadMS), and its application to the detailed qualitative analysis of essential oils. Specifically, a silica column was exploited for the separation of the essential oil constituents in two groups, namely hydrocarbon and oxygenated compounds. After, each HPLC-fraction was reduced in volume, and then subjected to cryogenically modulated GC×GC-quadMS analysis. The volatiles were separated on a normal-phase GC×GC column set, and identified through database matching and linear retention index information. The concentrated HPLC fractions gave origin to unexpectably crowded chromatograms, due to two fundamental GC×GC characteristics, namely the enhanced separation power and sensitivity. The results attained were particularly stimulating with regards to the oxygenated compounds, namely those constituents which contribute most to the essential oil aroma, and are of more use for the evaluation of quality and genuineness. Two genuine Citrus essential oils, bergamot and sweet orange, were subjected to analysis, and compared to applications carried out with a GC-quadMS instrument.

A direct sensitivity comparison between flow-modulated comprehensive 2D and 1D GC in untargeted and targeted MS-based experiments.

The present contribution is focused on the measurement of the analytical sensitivity attained in untargeted/targeted MS/MS experiments, performed using flow-modulator comprehensive 2D and 1D GC. The comprehensive 2D experiment was performed by diverting part of the high flow (circa 80%) to flush the accumulation loop (about 28 mL/min) to waste, to reduce the gas flow entering the ion source. 1D analyses were performed through: (i) unmodulated and (ii) single column applications. An equivalent temperature program was applied in the modulated and unmodulated analyses, while a faster one was employed in the single column one. In all application types, the (same) triple quadrupole instrument was operated in the full-scan and multiple reaction monitoring modes. A genuine sweet orange oil and the same sample spiked with 20 phytosanitary compounds were employed to reach the research objective. The results highlight the problems related to the flow modulation-MS combination. Specifically, it was found that sensitivity was on average three to four times higher in unmodulated and optimized single-column applications.