Preservative effectiveness of essential oils in vapor phase combined with modified atmosphere packaging against spoilage bacteria on fresh cabbage

Intrinsic properties and extrinsic factors of food matrix system affecting the effectiveness of essential oils in foods: a comprehensive review

Essential oils (EOs) have been proved as natural food preservatives because of their effective and wide-spectrum antimicrobial activity. They have been extensively explored for potential applications in food industry, and substantial progresses have been achieved. However well EOs perform in antibacterial tests in vitro, it has generally been found that a higher level of EOs is needed to achieve the same effect in foods. Nevertheless, this unsimilar effect has not been clearly quantified and elaborated, as well as the underlying mechanisms. This review highlights the influence of intrinsic properties (e.g., oils and fats, carbohydrates, proteins, pH, physical structure, water, and salt) and extrinsic factors (e.g., temperature, bacteria characteristics, and packaging in vacuum/gas/air) of food matrix systems on EOs action. Controversy findings and possible mechanism hypotheses are also systematically discussed. Furthermore, the organoleptic aspects of EOs in foods and promising strategies to address this hurdle are reviewed. Finally, some considerations about the EOs safety are presented, as well as the future trends and research prospects of EOs applications in foods. The present review aims to fill the evidenced gap, providing a comprehensive overview about the influence of the intrinsic and extrinsic factors of food matrix systems to efficiently orientate EOs applications.

Current status, technology, regulation and future perspectives of essential oils usage in the food and drink industry

Nowadays, essential oils (EOs) have a wide use in many applications such as in food, cosmetics, pharmaceutical and animal feed products. Consumers' preferences concerning healthier and safer foodstuffs lead to an increased demand for natural products, in replacement of synthetic substances, used as preservatives, flavourings etc. EOs, besides being safe, are promising alternatives as natural food additives, and much research has been carried out on their antioxidant and antimicrobial activity. The initial purpose of this review is to discuss conventional and 'green' extraction techniques along with their basic mechanism for the isolation of EOs from aromatic plants. This review aims to provide a broad overview of the current knowledge about the chemical constitution of EOs while considering the existence of different chemotypes, since bioactivity is attributed to the chemical composition - qualitative and quantitative - of EOs. Although the food industry primarily uses EOs as flavourings, an overview on recent applications of EOs in food systems and active packaging is provided. EOs exhibit poor solubility in water, oxidation susceptibility, negative organoleptic effect and volatility, restricting their use. Encapsulation techniques have been proven to be one of the best approaches to preserve the biological activities of EOs and minimize their effects on food sensory qualities. Herein, different encapsulation techniques and their basic mechanism for loading EOs are discussed. EOs are highly accepted by consumers, who are often under the misconception that 'natural' means safe. This is, however, an oversimplification, and the possible toxicity of EOs should be taken into consideration. Thus, in the final section of the current review, the focus is on current EU legislation, safety assessment and sensory evaluation of EOs. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Fabrication and design of poly(l-lactic acid) membrane for passive MAP packaging of Brassica chinensis L

PLD_x L copolymers were synthesized from physically stable rigid poly(l-lactic acid) (PLLA) and a few different molecular weights of polydimethylsiloxane (PDMS) to increase the O₂ and CO₂ permeabilities of PLLA films and make them acceptable for packaging highly respirable products. The effect of PDMS on the morphology, mechanical properties, and gas permeability of PLD_x L was investigated. Copolymers showed approximately 10 times the fracture strain and 1.7 times the CO₂ and O₂ permeabilities of neat PLLA. Additionally, PLD_x L maintained an increased CO₂ /O₂ perm-selectivity consistent between 5 and 40°C. Passive modified atmosphere packaging of Brassica chinensis L was developed to assess the membrane's impact on headspace gas inside the package. The results showed that poly(amide)/poly(ethylene) packaging with 48 cm² PLD_1.8 L membrane as a breathing window can provide 50 g B. chinensis L. with a healthy atmosphere of 3%-8% O₂ and 5%-8% CO₂ between 6 and 22 days. Vegetables packaged in PLD_1.8 L had the lower respiration rate, lower nitrite contents, and less proliferation of microorganisms. Moreover, a suitable atmosphere kept vegetables with higher ascorbic acid and a good appearance after more than 2 weeks of storage at 5°C. PRACTICAL APPLICATION: The permeability of the PLLA-based membrane can be adjusted for the breathable window membrane of sealed fresh products. In the future, several types of film could be developed to match the respiratory and metabolic characteristics of different kinds of products. Such PLLA-based specialized membranes can refine the fresh-keeping function and be more attractive to the customer.

Essential oils and their active components applied as: free, encapsulated and in hurdle technology to fight microbial contaminations. A review

Microbial contaminations are responsible for many chronic, healthcare, persistent microbial infections and illnesses in the food sector, therefore their control is an important public health challenge. Over the past few years, essential oils (EOs) have emerged as interesting alternatives to synthetic antimicrobials as they are biodegradable, extracted from natural sources and potent antimicrobials. Through their multiple mechanisms of actions and target sites, no microbial resistance has been developed against them till present. Although extensive documentation has been reported on the antimicrobial activity of EOs, comparisons between the use of whole EOs or their active components alone for an antimicrobial treatment are less abundant. It is also essential to have a good knowledge about EOs to be used as alternatives to the conventional antimicrobial products such as chemical disinfectants. Moreover, it is important to focus not only on planktonic vegetative microorganisms, but to study also the effect on more resistant forms like spores and biofilms. The present article reviews the current knowledge on the mechanisms of antimicrobial activities of EOs and their active components on microorganisms in different forms. Additionally, in this review, the ultimate advantages of encapsulating EOs or combining them with other hurdles for enhanced antimicrobial treatments are discussed.

Origanum dubium (Cypriot Oregano) as a Promising Sanitizing Agent against Salmonella enterica and Listeria monocytogenes on Tomato and Cucumber Fruits

In recent years, the use of natural products such as essential oils (EOs) and other plant extracts for the preservation of fresh produce has attracted much interest from the food industry. Many endemic medicinal and aromatic plants, such as Cypriot oregano (Origanum dubium), present a plethora of properties that can be utilized by the fruit and vegetable sectors of the food industry. The purpose of the present study was to assess the effects of O. dubium EO and hydrosol (at different concentrations and durations of dipping application) for the preservation of tomato and cucumber fruit quality, and their effectiveness as sanitizing agents against two foodborne pathogens (Listeria monocytogenes and Salmonella enterica). The results of this study indicated that increased concentrations of EO, combined with a longer duration of application, resulted in less marketable fruit compared to hydrosol application. Interestingly, EO application at lower concentrations and shorter durations of application (i.e., 0.01% for 5 min) increased fruit antioxidant, ascorbic acid and carotenoid levels (for tomato fruit), suggesting an increase in the nutritional value of the treated fruit, compared to the control. EO and hydrosol were able to decrease the bacterial populations (both bacteria) on fruits. Both products were especially effective against L. monocytogenes, even seven days after their application and storage at 11 °C (up to an approx. 3 log reduction with the EO application). Overall, the results of this study suggest that the use of O. dubium EO and hydrosol could be considered as alternative sanitation means for tomatoes and cucumbers.

Uncovering the Industrial Potentials of Lemongrass Essential Oil as a Food Preservative: A Review

The food industry is growing vastly, with an increasing number of food products and the demand of consumers to have safe and pathogen-free food with an extended shelf life for consumption. It is critical to have food safe from pathogenic bacteria, fungi, and unpleasant odors or tastes so that the food may not cause any health risks to consumers. Currently, the direction of food industry has been shifting from synthetically produced preservatives to natural preservatives to lower the unnecessary chemical burden on health. Many new technologies are working on natural prevention tools against food degradation. Lemongrass is one such natural preservative that possesses significant antimicrobial and antioxidant activity. The essential oil of lemongrass contains a series of terpenes that are responsible for these activities. These properties make lemongrass acceptable in the food industry and may fulfill consumer demands. This article provides detailed information about the role of lemongrass and its essential oil in food preservation. The outcomes of the research on lemongrass offer room for its new technological applications in food preservation.

Comparison between the Antimicrobial Activity of Essential Oils and Their Components in the Vapor Phase against Food-related Bacteria

In this study, the antibacterial properties of the volatile components of four essential oils (cinnamon, clove, origanum, and peppermint oil) and five of their components (allyl isothiocyanate (AITC), carvacrol, citral, eugenol, and (+)-limonene) against five food-related bacteria (Escherichia coli, Listeria monocytogenes, Salmonella Typhimurium, Pseudomonas fluorescens, and Enterococcus faecalis) were evaluated. The results of disc volatilization method revealed that AITC exhibited antibacterial activity against the five tested strains at the lowest concentration, as did cinnamon oil and carvacrol. Moreover, the total aerobic bacterial count in coleslaw salad was suppressed in all test groups treated with AITC compared to that in control.

Application of essential oils in packaging films for the preservation of fruits and vegetables: A review

Fruits and vegetables are highly perishable in nature. Several factors could affect the quality and shelf life of fruits and vegetables. Packaging materials (usually made up of polymers, proteins, lipids, polysaccharides, etc.,) are incorporated with essential oil (EO) which is high in antimicrobial and antioxidant compounds that can enhance the shelf life of fruits and vegetables without affecting their quality. However, the use of EO for postharvest preservation can alter the organoleptic properties of fresh produce. Exploiting synergistic interactions between several EOs, encapsulation of EO, or combining EO with non-thermal techniques such as irradiation, UV-C, cold plasma, ultrasound, etc., may help in preventing the spoilage of food products at lower concentrations without altering their organoleptic properties. This review aims to discuss the overview and current scenario of packaging film with EO for the preservation of fruit and vegetables. We have also discussed the spoilage mechanism of fruits and vegetables, mode of action of EOs, and the effect of EO with packaging film on antimicrobial and sensory properties of fruits and vegetables.

Antimicrobial activity of various essential oils and their application in active packaging of frozen vegetable products

Essential oils (EOs) have potential utility as clean-label food preservatives due to their antimicrobial and antioxidant properties. In this study, various EOs were screened for their antimicrobial activities against Listeria grayi in vitro. The susceptibility of L. monocytogenes to select EOs was compared with that of L. grayi. The effectiveness of the selected EOs in inhibiting the growth of L. grayi on vegetable products was also investigated. The results showed that cinnamon and oregano EOs and carvacrol were effective in the vapor phase in inhibiting the growth of L. grayi as well as L. monocytogenes, with the susceptibility of L. monocytogenes to cinnamon EO being slightly higher than that of L. grayi. The packaging of green peppers with cellulose stickers impregnated with cinnamon EO at 556 μL/L_headspace reduced the Listeria count to 1 log CFU/g after 2 days of storage as compared to 7.5 log CFU/g for controls.

Volatile Antimicrobial Agents and In Vitro Methods for Evaluating Their Activity in the Vapour Phase: A Review

This review summarizes data on the in vitro antimicrobial effectiveness of volatile agents of plant origin and in vitro methods for evaluating their activity in the vapour phase. As a result of literature analysis, the antimicrobial efficacy of vapours from 122 different plant species and 19 pure compounds examined in 61 studies using different in vitro tests against a broad spectrum of microorganisms was identified and summarized. In addition, 11 different techniques found in the literature are described in detail. An original classification of methods based on the solid and liquid matrix volatilization principle is proposed because carrier medium/matrix selection is crucial for the volatilization of any agents tested. This review should be useful for medicinal, pharmaceutical, food, and agricultural experts working in areas related to the management of infectious diseases (especially respiratory and skin infections), food preservation (active packaging), and protection of agriculture products (controlled atmosphere). It may also stimulate the interest of pharmaceutical, cosmetic, food, and agriculture industries in the research and development of new antimicrobial agents of natural origin. Since several original apparatuses previously developed for antimicrobial susceptibility testing in the vapour phase are described in this review, labware manufacturers may also be interested in this topic. The review also provides specific guidelines and recommendations for researchers studying the antimicrobial activity of volatile agents. The article will therefore appeal to communities of industrial stakeholders, pharmacists, physicians, food experts, agriculturists, and researchers in related areas such as pharmacology, medicinal chemistry, microbiology, natural product chemistry, food preservation and plant protection.

Angelica Essential Oil Loaded Electrospun Gelatin Nanofibers for Active Food Packaging Application

The development of food packaging possessing bioactivities which could extend the shelf life of food has gained increased interest in recent years. In this study, gelatin nanofibers with encapsulated angelica essential oil (AEO) were fabricated via electrospinning. The morphology of gelatin/AEO nanofibers was examined by scanning electron microscopy (SEM) and the addition of AEO resulted in the increase of fiber diameter. The proton nuclear magnetic resonance (1H-NMR) spectra were measured to confirm the presence of AEO in nanofibers. The hydrophobic property of gelatin nanofibers was also found to be improved with the addition of AEO. The nanofibers incorporated with AEO showed significant antioxidant activity and inhibitory effect against both Gram-negative and Gram-positive bacteria in a concentration dependent manner. Furthermore, the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay demonstrated that the developed gelatin/AEO nanofibers revealed no cytotoxicity effect. Thus, gelatin nanofibers incorporated with AEO can be used as potential food packaging.

Food Safety through Natural Antimicrobials

Microbial pathogens are the cause of many foodborne diseases after the ingestion of contaminated food. Several preservation methods have been developed to assure microbial food safety, as well as nutritional values and sensory characteristics of food. However, the demand for natural antimicrobial agents is increasing due to consumers' concern on health issues. Moreover, the use of antibiotics is leading to multidrug resistant microorganisms reinforcing the focus of researchers and the food industry on natural antimicrobials. Natural antimicrobial compounds from plants, animals, bacteria, viruses, algae and mushrooms are covered. Finally, new perspectives from researchers in the field and the interest of the food industry in innovations are reviewed. These new approaches should be useful for controlling foodborne bacterial pathogens; furthermore, the shelf-life of food would be extended.

Development of antimicrobial nanoemulsion-based delivery systems against selected pathogenic bacteria using a thymol-rich Thymus daenensis essential oil

AIMS

Thymol-rich medicinal plants have been used in traditional medicine to relieve infectious diseases. However, the application of essential oils as medicine is limited by its low water solubility and high vapour pressure. The objective of this study was to produce stable nanoemulsions of Thymus daenensis oil in water by preventing Ostwald ripening and phase separation.

METHODS AND RESULTS

The antibacterial activity of bulk and emulsified essential oil against selected pathogenic bacteria including Gram-negative (Haemophilus influenzae, Pseudomonas aeruginosa) and Gram-positive (Streptococcus pneumoniae) were investigated in the liquid and vapour phase. The optimum formulation (L2) contained 2% Tween 80 (surfactant) and 0·1% lecithin (cosurfactant) had a mean droplet diameter of 131 nm. In the liquid phase, the optimized nanoemulsion exhibited good antibacterial activity against S. pneumonia with MIC value of 0·0039 mg mL^-1 . In the vapour phase, the MIC values against S. pneumonia were similar (<7·35 μL L^-1 ) for both bulk and emulsified essential oil. However, there was no antibacterial activity in the vapour phase against H. influenzae and P. aeruginosa. Analysis of thymol concentration in the head space indicated that the nanoemulsion retarded the release of thymol into the vapour phase.

CONCLUSIONS

These findings highlight the potential applications of nanoemulsions containing essential oils as antibacterial products.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results of the current study highlight the advantages of nanoemulsification for improvement of the physicochemical properties and the antibacterial activity of T. daenensis EOs in the liquid and vapour phase for therapeutic purposes.

Effects of Combined Heat and Preservative Treatment on Storability of Ponkan Fruit (Citrus reticulataBlanco cv. Ponkan) during Postharvest Storage

Heat treatment and preservative application have been widely used during postharvest storage of many fresh products, but the effect of their combination on citrus storage has rarely been investigated. In this study, the optimal heat treatment (HT) conditions and HT combined with preservative treatment were investigated for Ponkan fruit (Citrus reticulataBlanco cv. Ponkan) storage. Results indicated that HT at 55°C for 20 s can significantly reduce the decay rate of Ponkan fruit, and a combination of HT and 25% of the preservative dosage used in production of iminoctadine tris (albesilate), 2,4-dichlorophenoxyacetic acid, and imazalil significantly reduced the decay rate without affecting fruit quality. In addition, the increased fiber contents in fruit receiving the HT combined with preservative treatments may be a response preventing fungus infection and enhancing fruit storability and resistance. The above results suggested that the combination of HT and 25% of the preservative production dosage was optimal for controlling Ponkan fruit decay during storage.

Development of Multifunctional Active Film and Its Application in Modified Atmosphere Packaging of Shiitake Mushrooms

Agar-based films with multiple functions (CO₂ absorption, water vapor absorption, and antimicrobial activity) were developed, tested for their properties, and then applied to the packaging of fresh shiitake mushrooms as an insert label. The films were cast from an agar-based aqueous solution containing a dissolving plasticizer (glycerol), a CO₂ absorbent (sodium carbonate [SC] alone or a combination of SC and sodium glycinate [SC-SG]), and a volatile antimicrobial agent (carvacrol [CRV]). The agar of the film matrix is designed to serve as a water vapor absorbent. The multifunctional films tended to have poor mechanical properties, with a hard texture and an opaque and yellowish color. The CO₂ absorbent, either SC alone or SC-SG, affected CRV retention and release along with the CO₂ and water vapor absorption behavior. Both films (SC-CRV and SC-SG-CRV films) showed good inhibitory effects against Pseudomonas fluorescens and Saccharomyces cerevisiae . SC-CRV film had a higher and faster CO₂ absorption property, higher retention and extended release of CRV, and lower and slower water vapor absorption and was assessed to be better suited for use in shiitake mushroom packaging. The packaging in which the SC-CRV film with an appropriate amount of CRV was used as an insert label was able to generate the desired atmosphere and less moisture condensation inside the package, producing the best preservation of quality in terms of mushroom color, firmness, flavor score, and microbial counts after 6 days of storage at 10°C. A tailored modified atmosphere packaging system using multifunctional film would be useful in the preservation of CO₂-sensitive fresh commodities.