Composite chitosan films prepared using nisin and Perilla frutescense essential oil and their use to extend strawberry shelf life

Chitosan-based sustainable packaging and coating technologies for strawberry preservation: A review

Strawberry fruits are popular all over the world due to their rich organoleptic properties and enormous health benefits. However, it is highly susceptible to postharvest spoilage due to various factors, including moisture loss, nutrient oxidation, and microbial spoilage. Recently, various researchers have studied the effect of chitosan-based flexible films and surface coatings on the shelf life of strawberries. Despite various reviews providing general information on the effects of chitosan-based films and coatings on various food products, no review has focused solely on their effects on postharvest preservation and the shelf life of strawberries. The purpose of this review is to summarize the current research on chitosan-based formulations for extending the shelf life of strawberries. Chitosan, a cationic carbohydrate polymer, possesses excellent properties such as film formation, mechanical strength, non-toxicity, biodegradability, edibility, UV-blocking ability, antioxidant activity, and antibacterial functionality, justifying its potential as packaging/coating material for fresh agricultural products, including strawberries. This review covers the various factors responsible for strawberry spoilage and the properties of chitosan that help counteract these factors. Additionally, the advantages of chitosan-based preservation technology compared to existing strawberry preservation methods were explained, efficiency was evaluated, and future research directions were suggested.

Fabrication and characterization of an alginate-based film incorporated with cinnamaldehyde for fruit preservation

Sodium alginate (SA) is widely used in the food, biomedical, and chemical industries due to its biocompatibility, biodegradability, and excellent film-forming properties. This article introduces a simple method for preparing uniform alginate-based packaging materials with exceptional properties for fruit preservation. The alginate was uniformly crosslinked by gradually releasing calcium ions triggered by the sustained hydrolysis of gluconolactone (GDL). A cinnamaldehyde (CA) emulsion, stabilized by xanthan without the use of traditional surfactants, was tightly incorporated into the alginate film to enhance its antimicrobial, antioxidant, and UV shielding properties. The alginate-based film effectively blocked ultraviolet rays in the range of 400-200 nm, while allowing for a visible light transmittance of up to 70 %. Additionally, it showed an increased water contact angle and decreased water vapor permeability. The alginate-based film was also employed in the preparation of coated paper through the commonly used coating process in the papermaking industry. The alginate-based material displayed excellent antioxidant properties and antimicrobial activity against Escherichia coli, Staphylococcus aureus and Botrytis cinerea, successfully extending the shelf life of strawberries to 7 days at room temperature. This low-cost and facile method has the potential to drive advancements in the food and biomedical fields by tightly incorporating active oil onto a wide range of biomacromolecule substrates.

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.

Multiplicative Effects of Essential Oils and Other Active Components on Skin Tissue and Skin Cancers

Naturally derived essential oils and their active components are known to possess various properties, ranging from anti-oxidant, anti-inflammatory, anti-bacterial, anti-fungal, and anti-cancer activities. Numerous types of essential oils and active components have been discovered, and their permissive roles have been addressed in various fields. In this comprehensive review, we focused on the roles of essential oils and active components in skin diseases and cancers as discovered over the past three decades. In particular, we opted to highlight the effectiveness of essential oils and their active components in developing strategies against various skin diseases and skin cancers and to describe the effects of the identified essential-oil-derived major components from physiological and pathological perspectives. Overall, this review provides a basis for the development of novel therapies for skin diseases and cancers, especially melanoma.

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.

Potential Impact of Combined Inhibition by Bacteriocins and Chemical Substances of Foodborne Pathogenic and Spoilage Bacteria: A Review

In recent years, food safety caused by foodborne pathogens and spoilage bacteria has become a major public health problem worldwide. Bacteriocins are a kind of antibacterial peptide synthesized by microbial ribosomes, and are widely used as food preservatives. However, when used individually bacteriocins may have limitations such as high cost of isolation and purification, narrow inhibitory spectrum, easy degradation by enzymes, and vulnerability to complex food environments. Numerous studies have demonstrated that co-treatment with bacteriocins and a variety of chemical substances can have synergistic antibacterial effects on spoilage microorganisms and foodborne pathogens, effectively prolonging the shelf life of food and ensuring food safety. Therefore, this paper systematically summarizes the synergistic bacteriostatic strategies of bacteriocins in combination with chemical substances such as essential oils, plant extracts, and organic acids. The impacts of bacteriocins when used individually and in combination with other chemical substances on different food substrates are clarified, and bacteriocin-chemical substance compositions that enhance antibacterial effectiveness and reduce the potential negative effects of chemical preservatives are highlighted and discussed. Combined treatments involving bacteriocins and different kinds of chemical substances are expected to be a promising new antibacterial method and to become widely used in both the food industry and biological medicine.

Effect of Essential Oils from Lemongrass and Tahiti Lime Residues on the Physicochemical Properties of Chitosan-Based Biodegradable Films

This work aimed to evaluate the impact of adding two essential oils (EO) from lemongrass (LEO) and Tahiti lime (TLEO) on the physical, mechanical, and thermal properties of chitosan-based biodegradable films. Six film formulations were prepared: two controls with chitosan concentrations of 1% and 1.5% v/w, two formulations combining the two chitosan concentrations with 1% LEO v/v, and two formulations combining the two chitosan concentrations with 1% TLEO v/v. The films' morphological, water affinity, barrier, mechanical, and thermal properties were evaluated. The films' surface showed a heterogeneous morphology without cracks, whereas the cross-section showed a porous-like structure. Adding EO to the films promoted a 35-50% decrease in crystallinity, which was associated with an increase in the elasticity (16-35%) and a decrease in the tensile strength (9.3-29.2 MPa) and Young's modulus (190-1555 MPa) on the films. Regarding the optical properties, the opacity of the films with TLEO increased up to 500% and 439% for chitosan concentrations of 1% and 1.5%, respectively. While the increase in opacity for the films prepared with LEO was 357% and 187%, the reduction in crystallinity also reduced the resistance of the films to thermal processes, which could be explained by the reduction in the enthalpy of fusion. The thermal degradation of the films using TLEO was higher than those where LEO was used. These results were indicative of the great potential of using TLEO and LEO in biodegradable films. Likewise, this work showed an alternative for adding value to the cultivation of Tahiti lime due to the use of its residues, which is in accordance with the circular economy model. However, it was necessary to deepen the study and the use of these essential oils in the preparation of biodegradable films.

Synergistic antimicrobial effect of nisin-octanoic acid nanoemulsions against E. coli and S. aureus

Food safety is a major public health concern all over the world. Therefore, the prevention of food contamination is becoming extremely crucial. In this study, an antimicrobial nanoemulsion composed of water-soluble nisin and fat-soluble octanoic acid was successfully prepared. The results showed that the average particle size and the polymer dispersity index of the nisin-octanoic acid (NOA) nanoemulsion were around 52.21 nm and 0.253, respectively. The NOA nanoemulsion required less amounts of nisin and octanoic acid to achieve the effective antimicrobial effect against Escherichia coli and Staphylococcus aureus. In addition, the growth curves of E. coli and S. aureus were determined. The OD₆₀₀ of NOA nanoemulsion was significantly lower than free nisin after being incubated for 24 h (p < 0.001), indicating that the antimicrobial effect of NOA nanoemulsion was outstanding. Meanwhile, the synergistic antimicrobial property of NOA nanoemulsion against E. coli and S. aureus was significantly better than free nisin under nonacid conditions (p < 0.05). Overall, the results of this study may provide guidance for the further application of nisin in more forms.

Preparation of robust, water-resistant, antibacterial, and antioxidant chitosan-based films by incorporation of cinnamaldehyde-tannin acid-zinc acetate nanoparticles

Chitosan (CS) films have poor mechanical property, low water-resistance and limited antimicrobial activity, which hinder their application in food preservation industry. Cinnamaldehyde-tannic acid-zinc acetate nanoparticles (CTZA NPs) assembled from edible medicinal plant extracts were successfully incorporated into CS films to solve these issues. The tensile strength and water contact angle of the composite films increased about 5.25-fold and 17.55°. The addition of CTZA NPs reduced the water sensitivity of CS films, which could undergo appreciable stretching in water without breaking. Furthermore, CTZA NPs significantly enhanced the UV adsorption, antibacterial, and antioxidant properties of the films, while reduced their water vapor permeability. Moreover, it was possible to print inks onto the films because the presence of the hydrophobic CTZA NPs facilitated the deposition of carbon powder onto their surfaces. The films with great antibacterial and antioxidant activities can be applied for food packaging application.

Antimicrobial Active Packaging Containing Nisin for Preservation of Products of Animal Origin: An Overview

The preservation of food represents one of the greatest challenges in the food industry. Active packaging materials are obtained through the incorporation of antimicrobial and/or antioxidant compounds in order to improve their functionality. Further, these materials are used for food packaging applications for shelf-life extension and fulfilling consumer demands for minimal processed foods with great quality and safety. The incorporation of antimicrobial peptides, such as nisin, has been studied lately, with a great interest applied to the food industry. Antimicrobials can be incorporated in various matrices such as nanofibers, nanoemulsions, nanoliposomes, or nanoparticles, which are further used for packaging. Despite the widespread application of nisin as an antimicrobial by directly incorporating it into various foods, the use of nisin by incorporating it into food packaging materials is researched at a much smaller scale. The researchers in this field are still in full development, being specific to the type of product studied. The purpose of this study was to present recent results obtained as a result of using nisin as an antimicrobial agent in food packaging materials, with a focus on applications on products of animal origin. The findings showed that nisin incorporated in packaging materials led to a significant reduction in the bacterial load (the total viable count or inoculated strains), maintained product attributes (physical, chemical, and sensorial), and prolonged their shelf-life.

Coacervation as a Novel Method of Microencapsulation of Essential Oils-A Review

These days, consumers are increasingly "nutritionally aware". The trend of "clean label" is gaining momentum. Synthetic additives and preservatives, as well as natural ones, bearing the E symbol are more often perceived negatively. For this reason, substances of natural origin are sought tfor replacing them. Essential oils can be such substances. However, the wider use of essential oils in the food industry is severely limited. This is because these substances are highly sensitive to light, oxygen, and temperature. This creates problems with their processing and storage. In addition, they have a strong smell and taste, which makes them unacceptable when added to the product. The solution to this situation seems to be microencapsulation through complex coacervation. To reduce the loss of essential oils and the undesirable chemical changes that may occur during their spray drying-the most commonly used method-complex coacervation seems to be an interesting alternative. This article collects information on the limitations of the use of essential oils in food and proposes a solution through complex coacervation with plant proteins and chia mucilage.

Preparation and characterization of chitosan/pullulan film loading carvacrol for targeted antibacterial packaging of chilled meat

In this research, the common microorganisms in chilled meat were used as the targeted antibacterial objects. Chitosan, pullulan, and carvacrol were chosen to prepare the edible antibacterial film. The effects of different concentrations of carvacrol on the microstructure, physical properties and antibacterial properties of the films were investigated. The results showed that the antibacterial activity of chitosan/pullulan film (CS/PU) was unsatisfactory, when carvacrol was added, the antibacterial activity of the chitosan/pullulan/carvacrol film (CS/PU/CAR) improved significantly (p < 0.05), and the water vapor permeability (WVP) of the CS/PU/CAR decreased significantly (p < 0.05). When the carvacrol concentration was higher than 1.25% (w/v), the tensile strength and percentage elongation at break of the CS/PU/CAR increased significantly (p < 0.05), and the CS/PU/CAR exhibited satisfying antibacterial activity against the common bacteria in chilled meat such as Pseudomonas fluorescens, Listeria monocytogenes, Escherichia coli, Pseudomonas putida, Enterobacter cloacae, and Staphylococcus aureus. Finally, the CS/PU/CAR film was applied to the preservation of chilled goat meat and extended the shelf life of goat meat to more than 15 days. These results suggested that the targeted CS/PU/CAR film can be used as biodegradable films for the active packaging of chilled meat.

Improving the Shelf Life of Avocado Fruit against Clonostachys rosea with Chitosan Hybrid Films Containing Thyme Essential Oil

Hass avocadoes are one of the most popular fruits consumed worldwide because of their nutritional and nutraceutical content. Nevertheless, these fruits are susceptible to phytopathogen attacks that decrease fruit quality during the postharvest period. Herein we present the results of the in situ fungistatic activity of four hybrid films (FT1−FT4) manufactured with chitosan and different concentrations of the essential oil of thyme (TvEO). The films were evaluated as biodegradable materials to prevent fruit decay triggered by Clonostachys rosea which is considered an emergent phytopathogen of this crop. The in situ fungistatic strength, spectroscopic properties (FT-IR), optical features (transmittance/opacity), and consistency obtained by microscopic analysis (SEM), indicated that the films FT3 and FT4 possessed the best physicochemical properties to protect Hass avocadoes against the soft rot produced by C. rosea. Avocadoes treated with the films FT3 and FT4 significantly (p < 0.01) conserved fruit firmness and nutritional composition (protein, fat, fiber, and reducing sugars) as well as the nutraceutical content (oleic, palmitoleic, linoleic, and palmitic acids) of infected avocados for 21 days. Our results validate the potential use of the films FT3 and FT4 to prevent the soft rot caused by C. rosea and to improve the shelf life of Hass avocadoes.

The Essential Oil Derived from Perilla frutescens (L.) Britt. Attenuates Imiquimod–Induced Psoriasis-like Skin Lesions in BALB/c Mice

Psoriasis is reported to be a common chronic immune-mediated skin disease characterized by abnormal keratinocytes and cell proliferation. Perilla leaves are rich in essential oils, fatty acids, and flavonoids, which are recognized for their antioxidant and anti-inflammatory effects. In this study, the alleviating effect of essential oil (PO) extracted from Perilla frutescens stems and leaves on imiquimod (IMQ) -induced psoriasis-like lesions in BALB/c mice were investigated. Results showed that PO ameliorated psoriasis-like lesions in vivo, reduced the expression of lymphocyte antigen 6 complex locus G6D (Ly-6G), which is a marker of neutrophil activation, and inhibited the expression of inflammatory factors interleukin 1 (IL-1), interleukin 6 (IL-6), inducible nitric oxide synthase (iNOS), and cyclooxygenase 2 (COX2). In addition, PO significantly decreased the expression of cytokines such as IL-6, IL-1, interleukin 23 (IL-23), interleukin 17 (IL-17), and nuclear factor kappa-B (NF-κB). Furthermore, the down-regulation of mRNA levels of psoriasis-related pro-inflammatory cytokines, such as IL-17, interleukin 22 (IL-22), IL-23, interferon-α (IFN-α), and Interferon-γ (IFN-γ) was observed with the treatment of PO. All results show a concentration dependence of PO, with low concentrations showing the best results. These results suggest that PO effectively alleviated psoriasis-like skin lesions and down-regulated inflammatory responses, which indicates that PO could potentially be used for further studies on inflammation-related skin diseases such as psoriasis and for the treatment of psoriasis such as psoriasis natural plant essential oil resources.

Bacteriocins from lactic acid bacteria: purification strategies and applications in food and medical industries: a review

Background

Bacteriocins are generally defined as ribosomally synthesized peptides, which are produced by lactic acid bacteria (LAB) that affect the growth of related or unrelated microorganisms. Conventionally, the extracted bacteriocins are purified by precipitation, where ammonium sulphate is added to precipitate out the protein from the solution.

Main text

To achieve the high purity of bacteriocins, a combination with chromatography is used where the hydrophobicity and cationic properties of bacteriocins are employed. The complexity column inside the chromatography can afford to resolve the loss of bacteriocins during the ammonium sulphate precipitation. Recently, an aqueous two-phase system (ATPS) has been widely used in bacteriocins purification due to the several advantages of its operational simplicity, mild process conditions and versatility. It reduces the operation steps and processing time yet provides high recovery products which provide alternative ways to conventional methods in downstream processing. Bacteriocins are widely approached in the food and medical industry. In food application, nisin, which is produced by Lactococcus lactis subsp. has been introduced as food preservative due to its natural, toxicology safe and effective against the gram-positive bacteria. Besides, bacteriocins provide a board range in medical industries where they are used as antibiotics and probiotics.

Short conclusion

In summary, this review focuses on the downstream separation of bacteriocins from various sources using both conventional and recent ATPS techniques. Finally, recommendations for future interesting areas of research that need to be pursued are highlighted.

Novel application of ion exchange membranes for preparing effective silver and copper based antibacterial membranes

Ion exchange membranes (IEMs) are widely used in water treatment applications such as electrodialysis. However, the exploration of IEMs as effective antibacterial food contact materials (e.g., food packaging membranes) against pathogenic bacteria to ensure food safety has not been reported. Here, we report a simple but effective method to prepare high performance antibacterial membranes via ion exchange coupled with in-situ reduction. The general membrane properties are characterized using SEM, EDS, FTIR, XPS, XRD, DSC, TGA, water uptake, etc. The distribution of silver and copper in the membranes are generally in line with the distribution of sulfur, indicating that the antibacterial ions are introduced into the membranes via ion exchange and are bonded with the sulfonate groups in the membranes. The antibacterial performance is investigated using zone of inhibition tests and continuous bacteria growth inhibition tests. All of the prepared membranes show obvious antibacterial activities compared to the bare cation exchange membranes. The diameters of inhibition zone against Staphylococcus aureus (S. aureus) are all larger than those of Escherichia coli (E. coli), indicating that the prepared membranes are more efficient in inhibiting S. aureus compared to E. coli. Furthermore, the silver-based membrane shows more sustainable antibacterial activities compared to the copper-based membrane. Especially, the results clearly reveal that the silver-based membrane is capable of killing bacteria instead of just inhibiting the growth of bacteria. We have shown for the first time that membranes derived from IEMs have the potential as food contact materials to inhibit the growth of pathogenic bacteria so as to eliminate the risk of bacterial infections and meanwhile delay food spoilage due to bacteria growth.

Bromelain and Nisin: The Natural Antimicrobials with High Potential in Biomedicine

Infectious diseases along with various cancer types are among the most significant public health problems and the leading cause of death worldwide. The situation has become even more complex with the rapid development of multidrug-resistant microorganisms. New drugs are urgently needed to curb the increasing spread of diseases in humans and livestock. Promising candidates are natural antimicrobial peptides produced by bacteria, and therapeutic enzymes, extracted from medicinal plants. This review highlights the structure and properties of plant origin bromelain and antimicrobial peptide nisin, along with their mechanism of action, the immobilization strategies, and recent applications in the field of biomedicine. Future perspectives towards the commercialization of new biomedical products, including these important bioactive compounds, have been highlighted.

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.

Bioactive Peptides: A Promising Alternative to Chemical Preservatives for Food Preservation

Bioactive peptides used for food preservation can prolong the shelf life through bacteriostasis and antioxidation. On the one hand, bioactive peptides can inhibit lipid oxidation by scavenging free radicals, interacting with metal ions, and inhibiting lipid peroxidation. On the other hand, bioactive peptides can fundamentally inhibit the growth and reproduction of microorganisms by destroying their cell membranes or targeting intracellular components. Besides, bioactive peptides are biocompatible and biodegradable in vivo. Therefore, they are regarded as a promising alternative to chemical preservatives. However, bioactive peptides are easily affected by the external environment in practical application, which hinders their commercialization. Currently, the studies to overcome the weakness focus on encapsulation and chemical synthesis. Bioactive peptides have been applied to the preservation of various foods in experimental research, with good results. In the future, with the deepening understanding of their safety and structure-activity relationship, there may be more bioactive peptides as food preservatives.