Effect of the presence of ethyl lauroyl arginate on the technological properties of edible fish gelatin films

Physical, chemical and antimicrobial properties of fish gelatin films with different concentrations of ethyl lauroyl arginate (LAE) were studied. Optical properties of film-forming solution did not vary with increased LAE content. However, pH and surface tension increased. The incorporation of LAE into the formulation increased moisture and solubility of the films. In addition, the presence of LAE affected mechanical properties, making films stronger and more flexible; it had no effect on water vapour permeability. Finally, films with LAE significantly increased antimicrobial properties against Listeria innocua, Shewanella putrefaciens and Pseudomonas fluorescens, but not against Aeromonas hydrophila. These antimicrobial films could be used as an alternative technology for extending shelf-life of fresh fish products.     

Development of cellulose-based bactericidal nanocomposites containing silver nanoparticles and their use as active food packaging

The use of nanomaterials, including metallic as active fillers in polymeric nanocomposites for food packaging has been extensively investigated. Silver nanoparticles (AgNPs), in particular, have been exploited for technological applications as bactericidal agents. In this paper, AgNPs were incorporated into a hydroxypropyl methylcellulose (HPMC) matrix for applications as food packaging materials. The average sizes of the silver nanoparticles were 41 nm and 100 nm, respectively. Mechanical analyses and water vapor barrier properties of the HPMC/AgNPs nanocomposites were analysed. The best results were observed for films containing smaller (41 nm) AgNPs. The antibacterial properties of HPMC/AgNPs thin films were evaluated based on the diameter of inhibition zone in a disk diffusion test against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The disk diffusion studies revealed a greater bactericidal effectiveness for nanocomposites films containing 41 nm Ag nanoparticles.     

Essential oils and their principal constituents as antimicrobial agents for synthetic packaging films

Spices and herbal plant species have been recognized to possess a broad spectrum of active constituents that exhibit antimicrobial (AM) activity. These active compounds are produced as secondary metabolites associated with the volatile essential oil (EO) fraction of these plants. A wide range of AM agents derived from EOs have the potential to be used in AM packaging systems which is one of the promising forms of active packaging systems aimed at protecting food products from microbial contamination. Many studies have evaluated the AM activity of synthetic AM and/or natural AM agents incorporated into packaging materials and have demonstrated effective AM activity by controlling the growth of microorganisms. This review examines the more common synthetic and natural AM agents incorporated into or coated onto synthetic packaging films for AM packaging applications. The focus is on the widely studied herb varieties including basil, oregano, and thyme and their EOs.     

Diffusion of linalool and methylchavicol from polyethylene-based antimicrobial packaging films

The diffusion of linalool and methylchavicol from thin (45-50 μm) antimicrobial low-density polyethylene-based films was evaluated after immersion in isooctane and the effect of temperature (4, 10, or 25 °C) on the diffusion rate was evaluated. The kinetics of linalool and methylchavicol release showed a non-Fickian behavior at the lowest temperature. An increase in temperature from 4 °C to 25 °C resulted in an increase in the diffusion coefficient from 4.2 × 10⁻¹³ m² s⁻¹ to 2.5 × 10⁻¹² m² s⁻¹ for linalool and from 3.5 × 10⁻¹³ m² s⁻¹ to 1.1 × 10⁻¹² m² s⁻¹ for methylchavicol. The effect of temperature on the diffusion coefficient followed an Arrhenius-type model (r² = 0.972) in relation to a time-response function with a Hill coefficient. Activation energies of 57.8 kJ mol⁻¹ (linalool) and 42.8 kJ mol⁻¹ (methylchavicol) were observed.     

Cellulose-based edible films and their effects on fresh beans and strawberries

 Cellulose-based edible films were applied to fresh beans and strawberries. The moisture loss from these food was measured following the application of films of varying composition under different conditions. The effects of the method of application of film solution, the amounts of polyethylene glycol (PEG), stearic acid (SA), palmitic acid (PA) and lauric acid (LA) in the film, the molecular weights of methyl cellulose (MC) and PEG and, finally, the relative humidity of the environment on moisture loss from fresh beans and strawberries coated with films were investigated. The brushing method for the application of film solution to the foods was found to be better than wrapping and dipping methods in terms of reducing the moisture loss. Recommended amounts of PEG-400 and fatty acids in film solution to reduce moisture loss from foods were found to be 11 ml and 40 g per 100 g MC-20000, respectively. A slight decrease in moisture loss was observed when PEG-400 and MC-20000 in the film solution were replaced by PEG-1000 and MC-41000, respectively. Finally, it was found that moisture loss from fresh beans and strawberries coated with films decreased as the relative humidity of the environment in which they were kept was increased. Received: 19 December 1996 / Revised version: 20 May 1997     

Development and characterization of an antimicrobial packaging film coating containing nisin for inhibition of Listeria monocytogenes

The purpose of this study was to develop and characterize a packaging film coating containing nisin. A spot-on-lawn assay was used to determine the effect of acid type (ascorbic, acetic, hydrochloric, lactic) and nisin level (equal increments from 10,000 IU to 9 IU) to be used in the formulation of the film coating. Zones of inhibition were measured after incubation on tryptic soy agar (37 degrees C, 48 h). Low-density polyethylene films coated with differing levels of nisin were characterized by field emission scanning electron microscopy, tensile strength, elongation, and water vapor transmission rate. The MIC of nisin in solution was 157 mg/ml. All acids were equally inhibitory (P > 0.05), but acetic acid produced the largest zone of inhibition (21 mm). Field emission scanning electron microscopy confirmed that the cloudy appearance of the films was due to sodium chloride found in the commercially prepared nisin. Tensile strength increased as nisin concentration increased, which also corresponded to increasing film thickness. The nisin coatings (10,000 and 2,500 IU/ml) did not have a significant effect (P > 0.05) on the water vapor transmission rate of the low-density polyethylene film.     

Development of PLA films containing oregano essential oil (Origanum vulgare L. virens) intended for use in food packaging

Consumers’ concerns about the environment and health have led to the development of new food packaging materials avoiding petroleum-based matrices and synthetic additives. The present study has developed polylactic acid (PLA) films containing different concentrations of essential oil from Origanum vulgare L. virens (OEO). The effectiveness of this new active packaging was checked for use in ready-to-eat salads. A plasticising effect was observed when OEO was incorporated in PLA films. The rest of the mechanical and physical properties of developed films did not show much change when OEO was included in the film. An antioxidant effect was recorded only for films containing the highest percentages of the active agent (5% and 10%). In addition, films exhibited in vitro antibacterial activity against Staphylococcus aureus, Yersinia enterocolitica, Listeria monocytogenes, Enterococcus faecalis and Staphylococcus carnosus. Moreover, in ready-to-eat salads, antimicrobial activity was only observed against yeast and moulds, where 5% and 10% of OEO was the most effective.     

Physical performance of biodegradable films intended for antimicrobial food packaging

Antimicrobial films were prepared by including enterocins to alginate, polyvinyl alcohol (PVOH), and zein films. The physical performance of the films was assessed by measuring color, microstructure (SEM), water vapor permeability (WVP), and tensile properties. All studied biopolymers showed poor WVP and limited tensile properties. PVOH showed the best performance exhibiting the lowest WVP values, higher tensile properties, and flexibility among studied biopolymers. SEM of antimicrobial films showed increased presence of voids and pores as a consequence of enterocin addition. However, changes in microstructure did not disturb WVP of films. Moreover, enterocin-containing films showed slight improvement compared to control films. Addition of enterocins to PVOH films had a plasticizing effect, by reducing its tensile strength and increasing the strain at break. The presence of enterocins had an important effect on tensile properties of zein films by significantly reducing its brittleness. Addition of enterocins, thus, proved not to disturb the physical performance of studied biopolymers. Development of new antimicrobial biodegradable packaging materials may contribute to improving food safety while reducing environmental impact derived from packaging waste. Practical Application: Development of new antimicrobial biodegradable packaging materials may contribute to improving food safety while reducing environmental impact derived from packaging waste.     

Microstructure and physico-chemical evaluation of nano-emulsion-based antimicrobial peptides embedded in bioactive packaging films

Customized application of antimicrobial peptide (AMP) ‘nisin’ directly into food (neither in active packaging nor encapsulated form) is expensive and associated with loss of activity due to deactivation in complex food systems. The purpose of the present study was to fusion the two concepts for improved bioavailability i.e. AMP nanoencapsulation and biopolymer immobilizing to formulate the next generation biodegradable films embedded with either active agent, nano-encapsulated active agent or both of them. Nanoliposomes were prepared using soy-lecithin by microfluidizer at 2000 bar with 5 cycles to generate an average size of 151 ± 4 nm with 50 ± 3% encapsulation efficiency. For active films, nisin had demonstrated no negative impact on transparency, thickness and water sorption behavior obtained by GAB model (25 °C, 0–0.95 a_w). For nano-active films, the results clearly illustrated that different physico-chemical properties including barrier (oxygen and water vapor permeability), color and transparency (200–900 nm) remained comparable to native hydroxypropyl methylcellulose (HPMC) films and were significantly improved than using lecithin directly without nano-scale restructuring. The microstructure studies (topography and morphology) by scanning and transmission electron microscopes (SEM/TEM) revealed different (pore, lamellar, fusion) modes of nisin release from nanoliposomes embedded in HPMC matrix. As microbiological worth, nisin nano-emulsion (encapsulated and free nisin) films were effective against potential foodborne pathogen Listeria monocytogenes. This innovative concept of biodegradable nano-active films may thus be a preventive system toward improved food safety.     

抗菌蛋白膜的包装性能及抑菌性能的研究

以前期均匀实验设计得出的最优配方（5%乳清分离蛋白（WPI）、2%酪蛋白酸钠（NaCas）和50%甘油）为成膜材料,在此基础上,向成膜溶液中添加不同浓度（0、0.025、0.05、0.075、0.1g/200mL）的乳酸链球菌素（Nisin）制备抗菌蛋白膜,研究Nisin对复合蛋白膜的包装性能及抑菌性能的影响。结果表明,Nisin与WPI-NaCas复合膜有较好的相容性,Nisin的添加提高了复合蛋白膜的抗张强度和断裂伸长率,降低了其水蒸气透过系数,但不影响膜的热封温度（145℃）。随着Nisin浓度的提高,膜的耐热性能随之增大。载Nisin的WPI-NaCas复合膜对大肠杆菌和金黄色葡萄球菌均有较强的抑制作用。      

Effectiveness of antimicrobial coated oriented polypropylene/polyethylene films in sprout packaging

This study focused on the effect of antimicrobial incorporated soy protein isolate (SPI) coated oriented polypropylene/polyethylene (OPP/PE) packaging on extended shelf life of fresh sprouts. To develop antimicrobial SPI-coated packages, the minimum inhibitory and bactericidal concentrations of antimicrobial (allyl isothiocyanate, trans-cinnamaldehyde, garlic oil, and rosemary oil) and film properties of antimicrobial incorporated SPI films were investigated. Different concentrations (0.6–1.2%, v/v) of the SPI incorporated antimicrobial compounds were coated onto the OPP/PE film and heat-sealed. Packages containing sprouts (alfalfa, broccoli, and radish) were stored at 10 °C for 5 days. Significant reduction of the total microbial count of sprouts was observed in treated samples. Allyl isothiocyanate was the most effective antimicrobial compound, followed by garlic oil and trans-cinnamaldehyde.     

Development of active packaging containing natural antioxidants

Two active packagings, consisting of PET trays sprayed with citrus fruit extract and α-tocopherol, were developed and tested. A comparison of the antioxidant activity of the two packagings was carried out on cooked meat stored at 4 °C. Lipid oxidation in citrus fruit extract-coated trays, measured with TBARS analysis, was significantly lower (p<0.01) than in uncoated (control) trays. Trays coated with α-tocopherol did not show any antioxidant activity. Morphology examination showed a more irregular coating for citrus fruit extract. Different orientations of the active phenolic groups on the PET surface could explain the differences in antioxidant efficacy of the two packagings.     

Characterisation and antimicrobial activity of active polypropylene films containing oregano essential oil and Allium extract to be used in packaging for meat products

Cooked ham is more prone to spoilage than other meat products, making preservation a key step in its commercialisation. One of the most promising preservation strategies is the use of active packaging. Oregano essential oil (OEO) and Proallium® (an Allium extract) have previously been shown to be useful in polylactic acid (PLA)-active films for ready-to-eat salads. The present work aims to study the suitability of polypropylene (PP) films containing OEO and Proallium® in the preservation of cooked ham. Concerning the technological features of the studied material, no significant changes in the mechanical or optical properties of PP films containing the active substances were recorded in comparison to the PP film without extracts. However, films containing both active substances were more flexible than the control film and less strong, highlighting the plasticisation effect of the natural extracts. Moreover, physical properties changed when active substances were added to the film. Incorporation of 4% Proallium® affected the transparency of the film to a higher extent compared to 8% OEO, undergoing decreases in transparency of 40% and 45%, respectively. Moreover, only the film containing the highest amount of OEO (8%) significantly decreased the thickness. Both active substances showed antibacterial properties; however, Proallium®-active films seemed to be more effective against Brochothrix thermosphacta than PP films containing OEO, with all percentages of Proallium® killing the bacterial population present in the ham after 60 days. In addition, materials containing the lowest Proallium® content exhibited higher acceptability by consumers in the sensory analyses with 63–100% willing to purchase, better even than the control package (56–89%). In fact, 2% of Proallium® obtained the best results in the odour study performed by the panellists.     

Mass transport analysis in perforation-mediated modified atmosphere packaging of strawberries

A space-and-time dependent mathematical model was developed to predict O₂, CO₂, N₂ and H₂O concentration in perforation-mediated polymeric packages during cold-storage of strawberries. The numerical solution of the corresponding mathematical model was obtained by applying the finite element method (FEM). The problem was solved in a domain corresponding to the headspace of a package augmented by the total void spaces of the contained bulk produce and for realistic boundary conditions. Transport of O₂, CO₂, N₂ and H₂O was modelled based on Maxwell–Stefan equations for gas transport through packaging’s headspace and on Fick’s law for diffusion through the micro-perforated packaging. The model predictions were tested against published experimental data of O₂ and CO₂ concentrations in modified atmosphere packaging storage of strawberries and the agreement is satisfactory. As for reaching the recommended in the literature gases concentrations for strawberry storage, the model predictions revealed that the tested micro-perforated polypropylene packaging combined with the adopted storage conditions are marginally adequate. To this end, the theoretical findings are suggestive of improvements, in terms of material properties, especially with regard to the permeability of the polymeric packaging film.     

Mono- and multilayer active films containing lysozyme as antimicrobial agent

Active packaging materials able to release antimicrobial compounds into foodstuff can be used in order to avoid or slow down the bacterial growth during storage. In this work the use of two techniques to control the release of the chosen active compound (lysozyme) from a polymeric material into the foodstuff is proposed: a monolayer cross-linked PVOH film and a multilayer structure made of cross-linked PVOH layers are developed and studied. Lysozyme release tests into water were performed in order to compare the release kinetics from the investigated films. Results suggest that by means of both structures it is possible to control the rate at which lysozyme is released from the PVOH film. The antimicrobial activity of lysozyme released from the investigated films was tested against a suspension of Micrococcus lysodeikticus. Results show that the incorporation of lysozyme into PVOH does not lead to a loss of activity of the enzyme.

Industrial relevance

The increased use of gently processed foods requires packaging to be an integral part of the preservation concept. Consequently additional antimicrobial activity from the packaging material can aid in shelf life extension.This paper concentrates on the release rate of lysozyme, a naturally occuring antimicrobial agent (eg. salvia, mothers milk, raw milk), from multilayer films. A comperision of mono- and multilayer films containing lysozyme regarding their effectiveness on M. lysodeikticus as target organism was also performed. Both aims were met leading to a controlled release of lysozyme with no loss of activity.