Controlled Release of Volatile Antimicrobial Compounds from Mesoporous Silica Nanocarriers for Active Food Packaging Applications.

Essential oils and their active components have been extensively reported in the literature for their efficient antimicrobial, antioxidant and antifungal properties. However, the sensitivity of these volatile compounds towards heat, oxygen and light limits their usage in real food packaging applications. The encapsulation of these compounds into inorganic nanocarriers, such as nanoclays, has been shown to prolong the release and protect the compounds from harsh processing conditions. Nevertheless, these systems have limited shelf stability, and the release is of limited control. Thus, this study presents a mesoporous silica nanocarrier with a high surface area and well-ordered protective pore structure for loading large amounts of natural active compounds (up to 500 mg/g). The presented loaded nanocarriers are shelf-stable with a very slow initial release which levels out at 50% retention of the encapsulated compounds after 2 months. By the addition of simulated drip-loss from chicken, the release of the compounds is activated and gives an antimicrobial effect, which is demonstrated on the foodborne spoilage bacteria Brochothrixthermosphacta and the potentially pathogenic bacteria Escherichia coli. When the release of the active compounds is activated, a ≥4-log reduction in the growth of B. thermosphacta and a 2-log reduction of E. coli is obtained, after only one hour of incubation. During the same one-hour incubation period the dry nanocarriers gave a negligible inhibitory effect. By using the proposed nanocarrier system, which is activated by the food product itself, increased availability of the natural antimicrobial compounds is expected, with a subsequent controlled antimicrobial effect.

Litsea cubeba fruit essential oil and its major constituent citral as volatile agents in an antimicrobial packaging material.

Food packaging films were coated with polyvinyl acetate (PVA) containing different concentrations of citral or Litsea (L.) cubeba essential oil (EO). Antimicrobial contact trials in style of ISO22916 were performed. Citral coatings achieved bactericidal effects against Escherichia coli (2.1 log) and Staphylococcus aureus (4.3 log) at concentrations of 20%DM. L. cubeba inactivated more than 4 log cycles of both bacteria at a concentration of 20%DM. To determine the antimicrobial activity across the gas phase, a unique method for volatile agents was developed, adapting ISO22196. GC/MS measurements were performed to supplement microbiological tests in a model packaging system with a defined 220 ml headspace (HS). HS-equilibrium concentrations of 1.8 µg/mlAir were found for 20%DM 'citral-coatings, resulting in antimicrobial effects of 3.8 log against of E. coli. Saccharomyces cerevisiae (4.74 log) and Aspergillus niger (4.29 log) were more effectively inactivated by 3%DM and 5%DM coatings. In an application trial with strawberries, simulating a headspace packaging, growth inhibitory effects on the yeast and mold microbiota were found for the 20%DM coatings.

Antimicrobial Food Packaging with Biodegradable Polymers and Bacteriocins.

Innovations in food and drink packaging result mainly from the needs and requirements of consumers, which are influenced by changing global trends. Antimicrobial and active packaging are at the forefront of current research and development for food packaging. One of the few natural polymers on the market with antimicrobial properties is biodegradable and biocompatible chitosan. It is formed as a result of chitin deacetylation. Due to these properties, the production of chitosan alone or a composite film based on chitosan is of great interest to scientists and industrialists from various fields. Chitosan films have the potential to be used as a packaging material to maintain the quality and microbiological safety of food. In addition, chitosan is widely used in antimicrobial films against a wide range of pathogenic and food spoilage microbes. Polylactic acid (PLA) is considered one of the most promising and environmentally friendly polymers due to its physical and chemical properties, including renewable, biodegradability, biocompatibility, and is considered safe (GRAS). There is great interest among scientists in the study of PLA as an alternative food packaging film with improved properties to increase its usability for food packaging applications. The aim of this review article is to draw attention to the existing possibilities of using various components in combination with chitosan, PLA, or bacteriocins to improve the properties of packaging in new food packaging technologies. Consequently, they can be a promising solution to improve the quality, delay the spoilage of packaged food, as well as increase the safety and shelf life of food.

Active Packaging of Immobilized Zinc Oxide Nanoparticles Controls Campylobacter jejuni in Raw Chicken Meat.

Zinc oxide nanoparticles (ZnO NPs) are regarded as a safe and stable antimicrobial that can inactivate bacteria by several potential working mechanisms. We aimed to incorporate ZnO NPs into packaging material to control Campylobacter in raw chicken meat. ZnO NPs were first incorporated into three-dimensional (3D) paper tubes to identify the lethal concentration against Campylobacter jejuni, which was selected as the working concentration to develop 2D functionalized absorbing pads by an ultrasound-assisted dipping technique. The functionalized pad was placed underneath raw chicken meat to inactivate C. jejuni and the predominant chicken microbiota at 4°C within 8 days of storage. Immobilized ZnO NPs at 0.856 mg/cm2 reduced C. jejuni from ∼4 log CFU/25 g raw chicken meat to an undetectable level after 3 days of storage. Analysis by inductively coupled plasma-optical emission spectroscopy showed that the Zn level increased from 0.02 to 0.17 mg/cm2 in treated raw chicken meat. Scanning electron microscopy validated the absence of nanoparticle migration onto raw chicken meat after treatment. Inactivation of C. jejuni was associated with the increase of lactic acid produced by Lactobacillus in raw chicken meat in a pH-dependent manner. Less than 5% of Zn2+ was released from ZnO NPs at neutral pH, while up to 88% was released when the pH was <3.5 within 2 days. Whole-transcriptome sequencing (RNA-Seq) analysis demonstrated a broad effect of ZnO NPs on genes involved in various cellular developmental processes as annotated by gene ontology. Taken together, the results indicate that functionalized absorbing pads inactivated C. jejuni in raw chicken meat by immobilized ZnO NPs along with the controllable released Zn2+IMPORTANCE Prevalence of Campylobacter in raw poultry remains a major food microbiological safety challenge. Novel mitigation strategies are required to ensure the safety and quality of poultry products. Active food packaging can control pathogens without directly adding antimicrobials into the food matrix and extend the food's shelf life. The functionalized absorbing pad with ZnO NPs developed in this study was able to inactivate C. jejuni in raw chicken meat and keep the meat free from C. jejuni contamination during shelf life without any observed migration of nanoparticles. The controllable conversion of immobilized ZnO NPs to free Zn2+ makes this approach safe and eco-friendly and paves the way for developing a novel intervention strategy for other high-risk foods. Our study applied nanotechnology to exploit an effective approach for Campylobacter control in raw chicken meat products.

Invited review: Advances in nisin use for preservation of dairy products.

Dairy product safety is a global public health issue that demands new approaches and technologies to control foodborne pathogenic microorganisms. Natural antimicrobial agents such as nisin can be added to control the growth of pathogens of concern in dairy foods, namely Listeria monocytogenes and Staphylococcus aureus. However, several factors affect the antimicrobial efficacy of nisin when directly added into the food matrix such as lack of stability at neutral pH, interaction with fat globules, casein, and divalent cations. To overcome these limitations, new and advanced strategies are discussed including nisin encapsulation technology, addition to active packaging, bioengineering, and combination with other antimicrobials. This review highlights advanced technologies with potential to expand and improve the use of nisin as a dairy preservative.

Preparation and characterization of poly-lactic acid based films containing propolis ethanolic extract to be used in dry meat sausage packaging.

In this study, active poly lactic acid (PLA) films containing 0, 10, 20 and 40% w/w propolis extract (PE), as active agent, were developed. A high amount of phenolic content (PC) was measured in PE. The antioxidant effect of active PLA films was determined by measuring the PC of sausage slices after 0, 2 and 4 days storage at refrigerator. Results showed that phenolic compounds of PE were released from PLA films in quantities proportional to PE concentration. Disc diffusion test indicated that PE showed an inhibitory effect against Staphylococcus aureus and Pseudomonas aeruginosa bacterial species but was more effective against gram-positive species. PE containing PLA films had antimicrobial effect on S. aureus while in the case of P. aeruginosa, PLA/PE films needed polyethylene glycol (PEG)/CaCO3 content to show inhibitory effect. Addition of PE changed the tensile strength, elongation at break and elastic modulus of PLA films negatively. However, addition of PEG/CaCO3 improved the film mechanical properties and antimicrobial effect of films.

Critical review of controlled release packaging to improve food safety and quality.

Controlled release packaging (CRP) is an innovative technology that uses the package to release active compounds in a controlled manner to improve safety and quality for a wide range of food products during storage. This paper provides a critical review of the uniqueness, design considerations, and research gaps of CRP, with a focus on the kinetics and mechanism of active compounds releasing from the package. Literature data and practical examples are presented to illustrate how CRP controls what active compounds to release, when and how to release, how much and how fast to release, in order to improve food safety and quality.

Influence of factors on release of antimicrobials from antimicrobial packaging materials.

Antimicrobial packaging materials (films or coatings) (APMs) have aroused great interest among the scientists or the experts specialized in material science, food science, packaging engineering, biology and chemistry. APMs have been used to package the food, such as dairy products, poultry, meat (e.g., beef), salmon muscle, pastry dough, fresh pasta, bakery products, fruits, vegetables and beverages. Some materials have been already commercialized. The ability of APMs to extend the shelf-life of the food depends on the release rate of the antimicrobials (AMs) from the materials to the food. The optimum rate is defined as target release rate (TRR). To achieve TRR, the influencing factors of the release rate should be considered. Herein we reviewed for the first time these factors and their influence on the release. These factors mainly include the AMs, food (or food simulant), packaging materials, the interactions among them, the temperature and environmental relative humidity (RH).

Active Packaging Applications for Food.

The traditional role of food packaging is continuing to evolve in response to changing market needs. Current drivers such as consumer's demand for safer, "healthier," and higher-quality foods, ideally with a long shelf-life; the demand for convenient and transparent packaging, and the preference for more sustainable packaging materials, have led to the development of new packaging technologies, such as active packaging (AP). As defined in the European regulation (EC) No 450/2009, AP systems are designed to "deliberately incorporate components that would release or absorb substances into or from the packaged food or the environment surrounding the food." Active packaging materials are thereby "intended to extend the shelf-life or to maintain or improve the condition of packaged food." Although extensive research on AP technologies is being undertaken, many of these technologies have not yet been implemented successfully in commercial food packaging systems. Broad communication of their benefits in food product applications will facilitate the successful development and market introduction. In this review, an overview of AP technologies, such as antimicrobial, antioxidant or carbon dioxide-releasing systems, and systems absorbing oxygen, moisture or ethylene, is provided, and, in particular, scientific publications illustrating the benefits of such technologies for specific food products are reviewed. Furthermore, the challenges in applying such AP technologies to food systems and the anticipated direction of future developments are discussed. This review will provide food and packaging scientists with a thorough understanding of the benefits of AP technologies when applied to specific foods and hence can assist in accelerating commercial adoption.

Oregano essential oil-based natural antimicrobial packaging film to inactivate Salmonella enterica and yeasts/molds in the atmosphere surrounding cherry tomatoes.

This study investigated the effectiveness of a polyvinyl alcohol (PVA) film containing the natural antimicrobial oregano essential oil (OEO) as an active packaging application for decreasing the microbial growth. The film exerted an antimicrobial effect via the atmosphere surrounding the food rather than direct contact, thereby preserving the quality of cherry tomatoes. A packaging film containing microencapsulated OEO was developed. The loading content increased gradually (104.29-234.29 µg OEO/mg film) with the amount of OEO incorporated (1%, 2%, and 3%), where the PVA films containing 2% OEO had the highest loading efficiency (91.64%), followed by 1% OEO (90.96%) and 3% OEO (88.38%). The antimicrobial activities of the films were evaluated by applying it to fresh cherry tomatoes at 4 °C and 22 °C for 7 days. The large 2% OEO film as well as both the small and large 3% OEO films had strong antimicrobial effects against Salmonella enterica, molds and yeasts, and mesophilic aerobic bacteria. The changes in the hardness, weight, and color of the cherry tomatoes during storage did not differ significantly. The films could be utilized as a packaging material for fresh produce with antimicrobial effects because of the controlled atmosphere surrounding the food rather than by direct contact.

Trends in utilization of agro-industrial byproducts for production of bacteriocins and their biopreservative applications.

Bacteriocins are proteinaceous, ribosomally synthesized bio-molecules having major roles in food preservation due to their antimicrobial action against food spoilage microorganisms. These have gained importance in the last decades because of increasing interest in natural products and their applications in the field of biopreservation, pharmaceutical, aquaculture, livestock, etc. Their production is quite expensive which includes the cost of synthetic media and downstream processing of which 30% of the total production cost relies on synthetic media and nutritional supplements used for growth of microorganisms. The low cost agro-industrial by-products, rich in nutritional supplements, can act as a good substitute for high valued synthetic media. This review provides comprehensive information on the use of cost effective, renewable agro-industrial by-products as substrates for the production of bacteriocins and their application in food as biopreservatives.

Nisin as a Food Preservative: Part 2: Antimicrobial Polymer Materials Containing Nisin.

Nisin is the only bacteriocin approved as a food preservative because of its antibacterial effectiveness and its negligible toxicity for humans. Typical problems encountered when nisin is directly added to foods are mainly fat adsorption leading to activity loss, heterogeneous distribution in the food matrix, inactivation by proteolytic enzymes, and emergence of resistance in normally sensitive bacteria strains. To overcome these problems, nisin can be immobilized in solid matrices that must act as diffusional barriers and allow controlling its release rate. This strategy allows maintaining a just sufficient nisin concentration at the food surface. The design of such antimicrobial materials must consider both bacterial growth kinetics but also nisin release kinetics. In this review, nisin incorporation in polymer-based materials will be discussed and special emphasis will be on the applications and properties of antimicrobial food packaging containing this bacteriocin.

Antimicrobial Packaging for Extending the Shelf Life of Bread-A Review.

Antimicrobial packaging is an important form of active packaging that can release antimicrobial substances for enhancing the quality and safety of food during extended storage. It is in response to consumers demand for preservative-free food as well as more natural, disposable, biodegradable, and recyclable food-packaging materials. The potential of a combination of allyl isothiocyanate and potassium sorbate incorporated into polymers in providing the needed natural antimicrobial protection for bread products is discussed. The role of double extrusion process as a means for obtaining a homogeneous mix of the sorbate into the polymer (polyethylene or ethylenevinyalcohol), is highlighted.

Potential of the polymer poly-[2-(tert-butylamino) methylstyrene] as antimicrobial packaging material for meat products.

AIMS: The objective of the study was to investigate the antimicrobial potential of a new SAM(®) polymer poly(TBAMS) as packaging material for meat products. METHODS AND RESULTS: The influence of temperature, time and product factors on the antimicrobial activity of poly(TBAMS) against different bacteria was determined using a modified test method based on the Japanese Industrial Standard 2801:2000. Results showed a significant reduction in bacterial counts on poly(TBAMS) compared with the reference material of several meat-specific micro-organisms after 24 h at 7°C. Bacterial counts of Staphylococcus aureus, Listeria monocytogenes, Lactobacillus spp., Brochothrix thermosphacta and Escherichia coli were reduced by >4·0 log10  units. Pseudomonas fluorescens was less sensitive to poly(TBAMS) within 24 h between 2 and 7°C. Prolonging the storage time to 48 h, however, resulted in an increased reduction rate. Furthermore, antimicrobial activity was also observed if meat components in the form of meat extract, meat juice or bovine serum albumin protein were present. Antimicrobial activity was also achieved if inoculated with mixed cultures. CONCLUSIONS: Poly(TBAMS) showed antimicrobial properties under conditions typical for meat supply chains. SIGNIFICANCE AND IMPACT OF THE STUDY: Poly(TBAMS) bears a high potential to increase safety and shelf life of meat products.

Antimicrobial films containing microparticles for the enhancement of long-term sustained release.

Coated packagings with thin films containing antimicrobial agents are an alternative technology to ensure the protection of products against microbial contaminations. Indeed, they allow lowering the antimicrobial concentration in the bulk of the product while meeting the safety requirements and the growing consumer demand for low preservative concentrations. Microencapsulation is a suitable way for controlling active agent release and providing a long-term activity. This work aims at combining both technical solutions with coatings containing antimicrobial microparticles for the achievement of long-term sustained release. Polyethylene surfaces were functionalized with microparticles of poly(methyl methacrylate) (PMMA) loaded with phenylethyl alcohol (PEA) as antimicrobial agent by the dip coating process using a polyurethane binder. The release of PEA into water from coated polyethylene surfaces and from PMMA microparticles was investigated to assess the sustained release and its mechanisms. Films with various thicknesses of 400-1000 µm containing antimicrobial microparticles demonstrated unusual long-term release longer than 3 months. The diffusion of the antimicrobial agent through PMMA was the rate limiting step of the sustained release. PEA release increased as the contact area of the protruding microparticles with the external medium increased and the thickness of the film decreased. Such antimicrobial agents encapsulated inside thin coatings are promising with regards to antimicrobial preservation of products along their full shelf-life.

Preparation and Application of LDPE/ZnO Nanocomposites for Extending Shelf Life of Fresh Strawberries.

Strawberries have a very short post-harvest life mostly due to their relatively high water content, intense metabolic activity and susceptibility to microbial rot. Antimicrobial low-density polyethylene nanocomposite films containing ZnO nanoparticles at different mass fractions were prepared by melt mixing and followed by compression moulding using a hot press machine. Fresh strawberries were packed in nanocomposite films and stored at 4 °C. Their microbial stability, ascorbic acid content and titratable acidity were evaluated after 0, 4, 8, 12 and 16 days of storage. Microbial growth rate was significantly reduced up to 16 days as a result of the use of nanocomposite packaging material containing ZnO nanoparticles. By increasing the ZnO nanoparticle mass fraction to 5%, the antimicrobial activity of the film increased. All packages containing the ZnO nanoparticles kept the microbial load of fresh strawberries below the level that affects shelf life (5 log CFU/g) up to 16 days. The lowest degradation of ascorbic acid content (6.55 mg per 100 g), and loss of acidity (0.68%) were observed in packages containing 3% of ZnO nanoparticles with 10% polyethylene-grafted maleic anhydride.

Preservation effects of photodynamic inactivation-mediated antibacterial film on storage quality of salmon fillets: Insights into protein quality.

The preservation effects of a photodynamic inactivation (PDI)-mediated polylactic acid/5-aminolevulinic acid (PLA/ALA) film on the storage quality of salmon fillets were investigated. Results showed that the PDI-mediated PLA/ALA film could continuously generate reactive oxygen species by consuming oxygen to inactivate native pathogens and spoilage bacteria on salmon fillets. Meanwhile, the film maintained the content of muscle proteins and their secondary and tertiary structures, as well as the integrity of myosin by keeping the activity of Ca2+-ATPase, all of which protected the muscle proteins from degradation. Furthermore, the film retained the activity of total superoxide dismutase (T-SOD), suppressed the accumulation of lipid peroxides (e.g., MDA), which greatly inhibited four main types of protein oxidations. As a result, the content of flavor amino acids and essential amino acids in salmon fillets was preserved. Therefore, the PDI-mediated antimicrobial packaging film greatly preserves the storage quality of aquatic products by preserving the protein quality.

Enhanced antifungal properties of poly(butylene succinate) film with lignin nanoparticles and trans-cinnamaldehyde for mango packaging.

Sustainable poly(butylene succinate) (PBS) films incorporating lignin nanoparticles (LN) and trans-cinnamaldehyde (CN) have been developed to preserve mango freshness and provide food safety. PBS/LN, PBS/CN, and PBS/LN/CN composite films were produced by blown film melt extrusion. This study investigated the effect of CN-LN on the CN remaining content, thermal, mechanical, and barrier properties, diffusion coefficient, and antifungal activity of PBS films both in vitro and in vivo. Results showed that LN in the PBS/LN/CN composite film contained more CN than in the PBS/CN film. The compatibility of CN-LN with PBS produced homogeneous surfaces with enhanced barrier properties. PBS/LN/CN composite films demonstrated superior antifungal efficacy, inhibiting the growth of Colletotrichum gloeosporioides and preserving mango quality during storage. Results suggested that incorporating LN into PBS composite films prolonged the sustained release of antifungal agents, thereby inhibiting microbial growth and extending the shelf life of mangoes. Development of PBS/LN/CN composite films is a beneficial step toward reducing food waste and enhancing food safety.

Preparation of sodium alginate modified silver-metal organic framework and application in citric acid/PVA antimicrobial packaging.

Silver-metal organic framework (Ag@MOF) has exhibited outstanding antimicrobial activity in antimicrobial applications, and reducing the biotoxicity associated with silver has become a research priority. In this study, Ag@MOF was initially modified with sodium alginate (SA) to form SA-Ag@MOF. The results showed that SA could control the release of Ag+, reducing the release by about 8% at 24 h, and the biotoxicity was significantly reduced. Finally, SA-Ag@MOF was applied as an antimicrobial agent in citric acid-modified PVA film to develop a novel composite antimicrobial film. When added at 2 MIC, the CA3-M2 film can effectively inhibit the growth of E. coli and S. aureus, and the inhibition rate has reached 98%. For white radish packaging applications, CA3-M2 film inhibited the growth of surface microorganisms, while ensuring moisture and tissue hardness to extend shelf-life up to 7 days. Overall, the strategy conceived here can be a theoretical basis for novel antimicrobial packaging.

Microbial load reduction in stored raw beef meat using chitosan/starch-based active packaging films incorporated with cellulose nanofibers and cinnamon essential oil.

Food safety is a global concern due to the risk posed by microbial pathogens, toxins and food deterioration. Hence, materials with antibacterial and antioxidant properties have been widely studied for their packaging application to ensure food safety. The current study has been designed to fabricate the chitosan/starch-based film with cinnamon essential oil (CEO) and cellulose nanofibers for active packaging. The nanocomposite films developed in this study were characterized by using UV-Vis Spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric analysis (TGA), Scanning Electron Microscopy (SEM), and Gas Chromatography-Mass Spectroscopy (GC-MS). The biodegradability, hydrodynamic, mechanical, antioxidant and antibacterial properties of the films were also evaluated. From the results, the addition of CEO and cellulose nanofibers was found to enhance the antimicrobial and material properties of the film. FE-SEM analysis has also revealed a rough and porous surface morphology for the developed nanocomposite film. FT-IR analysis further demonstrated the molecular interactions among the various components used for the preparation of the film. The film has also been shown to have antibacterial activity against Staphylococcus aureus and Escherichia coli. Furthermore, the film was found to reduce the bacterial load of the stored beef meat when used as a packaging material. The study hence provides valuable insights into the development of chitosan/starch-based films incorporated with CEO and cellulose nanofibers for active food packaging applications. This is due to its excellent antimicrobial and physicochemical properties. Hence, the nanocomposite film developed in the study can be considered to have promising applications in the food packaging industry.