Effect of active films incorporated with montmorillonite clay and α‐tocopherol: Potential of nanoparticle migration and reduction of lipid oxidation in salmon

Fat‐rich fish such as salmon are highly susceptible to lipid oxidation, which affects the quality of the product. The compound α‐tocopherol is widely used as an antioxidant added directly to food or through the incorporation in active packaging besides having activity of vitamin E, which is an essential nutrient to the human body absorbed from food. The objective of this paper was to evaluate the montmorillonite (MMT15A) and α‐tocopherol migration potential and antioxidant effect of chitosan/MMT15A/α‐tocopherol active films on reduction of lipid oxidation in fresh salmon. Chitosan films incorporated with MMT15A (0 and 1 g/100 g) and α‐tocopherol (0, 10, and 15 g/100 g) were applied on the fresh salmon for 8 days. Samples of salmon wrapped in films 3 and 6 (10% tocopherol and 1% MMT15A + 15%tocopherol, respectively) showed the lower values of thiobarbituric acid reactive substances (TBARS) at eighth storage day at 4°C. Film 6 (1% MMT15A and 15% tocopherol) showed better result on reduction in water vapour transmission rate (WVTR) and controlled release of tocopherol. All the films containing MMT15A presented migration of minerals (Mg and Si) for the salmon during the 8 days. Thus, the use of this film for release of active substances is a promising alternative for application as food packaging in order to obtain nutritionally fortified foods and inhibit oxidation reactions.     

Effect of high‐pressure processing on the mechanical and barrier properties of selected packagings

This investigation focuses on the effect of high‐pressure processing (HPP) on possible changes of the mechanical properties and of the water vapour permeability of seven selected packaging materials. NOD 259 (PA‐PE), BB4L (Cryovac‐Grace packaging), PET/BOA/PE, PET/PVDC/PE, PA/SY, LDPE and EVA/PE were investigated (PET, polyester; PE, polyethylene; SY, surlyn; LDPE, low‐density polyethylene; EVA, polyethylene–vinyl acetate co‐polymer; BOA, biaxially oriented polyamide). These packaging materials were selected because of their interest to the food industry. All had an internal film of PE for food use. High‐pressure tests were realized at 10°C for 10 min at pressures of 200, 400 and 600 MPa, with water as a food‐simulating fluid. The depressurization rate was either rapid (pressure drop in <10s) or slow (20 MPa/min). Permeability to water vapour was realized using the NFF H 00 030–ASTM E96‐90 standard. Mechanical tests were carried out with a tensile testing machine (Lloyd LR5K), according to the NF 54‐102 standard. Maximal stress, rupture stress and strain at rupture were evaluated with non‐treated and treated samples. Obtained results showed that HPP minimally affects the mechanical strength of packaging material. The depressurization rate did not have any significant influence in our conditions. The barrier properties to water vapour were not significantly affected and were even slightly enhanced for LDPE, which is a packaging material commonly used for HPP applications and at least as a food contact material. Copyright © 2006 John Wiley & Sons, Ltd.     

Functional Barrier Performance of a Polyamide‐6 Membrane Towards n‐Alkanes and 1‐Alcohols

Polymeric barrier membranes are widely used in the food packaging area. So‐called functional barriers prevent the packed food from contamination of permeants from the environment or from other packaging components. Aim of the study was to determine barrier properties of non‐polar n‐alkanes (n‐pentane up to n‐tetradecane) and polar 1‐alcohols (1‐propanol to 1‐octanol) of a 12 µm biaxially oriented PA6 film at temperatures between 70°C and 100°C. From the experimentally determined lag times, the diffusion coefficients D_P as well as the partition coefficients K of the investigated permeants were calculated. From the correlation between the molecular volume V and the diffusion coefficients D_P, the lag times for lower temperatures can be predicted for temperatures between 20°C and 70°C. In conclusion, the investigated 12 µm PA6 film is a sufficient barrier towards organic compounds. The permeation of substances with molecular volumes above 200 ų is negligible for a shelf life of three years and temperatures below of 60°C. These storage conditions are sufficient for nearly all kinds of food packaging applications. Copyright © 2016 John Wiley & Sons, Ltd.     

Fabrication and Properties of Antioxidant Polyethylene‐based Films Containing Marigold (Tagetes erecta) Extract and Application on Soybean Oil Stability

Four films were extruded in a pilot‐plant scale blown extrusion machine: a monolayer low‐density polyethylene (LDPE) film added with 2.90% of marigold (Tagetes erecta) extract, a two‐layer high‐density polyethylene/LDPE film added with 3.59% of the extract in the LDPE layer and the corresponding two control films without addition of the extract. More than 64% of astaxanthin contained in the extract was lost during the extrusion process. Spectroscopic, optical and mechanical properties of the films were affected by the addition of the marigold extract. The films showed to be light sensitive when exposed to commercial light at 25 °C; however, bags made of the films showed a positive effect on soybean oil stability when used as packaging. Copyright © 2012 John Wiley & Sons, Ltd.     

Effects of PP‐based Nanopackaging on the Overall Quality and Shelf Life of Ready‐to‐eat Salami

A total of 1% nanoclay containing polypropylene (PP)‐nanocomposite and 1% nanoclay plus 5% poly‐beta‐pinene (PβP) containing PP‐active‐nanocomposite materials were produced and tested for packaging of sliced salami. The sliced salami was packaged using both nanofilms and multilayer film of PP/PA/EVOH/PE under vacuum, modified atmosphere packaging under 50% CO₂ and 50% N₂ and air and stored at 4 °C for 90 days. During storage, headspace gas composition; microbial, physical and chemical analyses; and sensory evaluation were performed. The antimicrobial effect of PβP containing nanomaterial was pronounced under vacuum, and no bacterial growth was observed for 75 days. An a* value decreased notably in all applications during storage and preserved best by the multilayered material under vacuum and high CO₂. Thiobarbituric acid reactive substances (TBARS) were 0.63 mg MDA/kg after the processing and gradually increased at all applications during increased storage. TBARS values of all vacuum applications were lower than that of modified atmosphere packaging applications. Rancid taste development was determined by sensory panelists when TBARS values were higher than 0.80 mg MDA/kg on the 90th day. There was no significant moisture loss, and no increase in hardness was determined during the whole storage time. The longest shelf life was 75 days for the sliced salami under vacuum and high CO₂ using the multilayer material. PβP containing nanomaterial provided 50 days of shelf life under vacuum, which is commercially considerable. Copyright © 2017 John Wiley & Sons, Ltd.     

Development and characterization of PET/Fish Gelatin–nanoclay composite/LDPE laminate

A three‐layer laminate film was developed with the following structure: polyethylene terephthalate (PET)/fish gelatin (FG)–nanoclay composite/low‐density polyethylene (LDPE). The FG–nanoclay composite material functioned as the oxygen barrier layer and demonstrated comparable oxygen barrier properties when compared with a similar laminate utilizing ethylene vinyl alcohol as the barrier layer at a relative humidity (RH) of up to 50%. The introduction of nanometer‐sized filler clay into the FG matrix lowered the oxygen permeability (OP) because of the tortuosity effect of the clay particles. In addition, the FG–nanoclay composite film exhibited bond strengths similar to both LDPE and PET. The hydrophilic nature of FG significantly increases OP under high (>50%) RH conditions. However, this new FG laminate film could be a possible alternative for packaging designers desiring a more sustainable packaging material for low‐RH (<50%) applications. Copyright © 2009 John Wiley & Sons, Ltd.     

The effectiveness of hexamethylenetetramine‐incorporated plastic for the active packaging of foods

The feasibility of LDPE films containing 0.2 or 0.5% (w/w) hexamethylenetetramine (HMT) as antimicrobial packaging material to inhibit microbial growth on the surface of foods was investigated. As HMT is allowed in Europe to be used as a preservative under certain conditions, and as it is mentioned on the list of additives notified to the European Commission as substances which may be used in plastics intended in contact with food products, this compound offers good opportunities for the manufacturing of an antimicrobial packaging material. In a first experiment, fresh orange juice was vacuum packaged in LDPE films containing 0, 0.2 and 0.5% (w/w) HMT and stored at 6°C for 39 days. Every day and later every 3 days, packages of orange juice were analysed for yeasts and lactic acid bacteria. The shelf‐life of orange juice, could not be prolonged significantly by packaging into a 0.2% or 0.5% (w/w) HMT‐containing film. In a second experiment, however, packaging of cooked ham in a 0.5% (w/w) containing LDPE film, significantly affected shelf‐life. After 20 days a significant reduction of total aerobic count and lactic acid bacteria was observed. In an additional migration test, it became clear that the level of HMT released into orange juice was close to the specific migration limit of 15 mg CH₂O/kg imposed by the EC. Copyright © 2000 John Wiley & Sons, Ltd.     

Migration of di‐(2‐ethylhexyl)adipate (DEHA) and acetyl tributyl citrate (ATBC) plasticizers from PVC film into the food stimulant of isooctane

Chemical migration from food packing is influenced by several factors such as nature of chemicals, complexity of food, temperature, packing material used and properties of the migrating substances. Chemical compounds that are incorporated within polymeric packaging materials may interact with food components during processing or storage and migrate into the food by jeopardizing the food safety. This migration is higher if food remains in contact with packing material for extended time. Polyvinyl chloride (PVC) film such as di‐(2‐ethylhexyl) adipate (DEHA) and acetyl tributyl citrate (ATBC) are still widely used as a food packing material due to its flexibility, transparency and low water permeability. The present study covers the main migration phenomena of both plasticizers (di‐(2‐ethylhexyl) adipate (DEHA) and acetyl tributyl citrate (ATBC)) from PVC‐film into isooctane food stimulant using a direct gas chromatographic method. An exposure period of 48 h at 30 °C and 4 °C was used. The obtained results showed DEHA levels ranging of 7.2 mg/dm² while, no ATBC migration from PVC‐film was observed. Results are discussed in relation to EU legislation proposed upper limit for DEHA specific migration (18 mg/L or 3 mg/dm²) and overall migration limit (OM) of 10 mg/dm².     

Probing the Domain Architecture in 2D α‐Mo2C via Polarized Raman Spectroscopy

MXenes are emerging 2D materials with intriguing properties such as excellent stability and high conductivity. Here, a systematic study on the Raman spectra of 2D α‐Mo₂C (molybdenum carbide), a promising member in MXene family, is conducted. Six experimentally observed Raman modes from ultrathin α‐Mo₂C crystal are first assigned with the assistance of phonon dispersion calculated from density functional theory. Angle‐resolved polarized Raman spectroscopy indicates the anisotropy of α‐Mo₂C in the b–c plane. Raman spectroscopy is further used to study the unique domain structures of 2D α‐Mo₂C crystals grown by chemical vapor deposition. A Raman mapping investigation suggests that most of the α‐Mo₂C flakes contain multiple domains and the c‐axes of neighboring domains tend to form a 60° or 120° angle, due to the weak Mo? C bonds in this interstitial carbide and the low formation energy of the carbon chains along three equivalent directions. This study demonstrates that polarized Raman spectroscopy is a powerful and effective way to characterize the domain structures in α‐Mo₂C, which will facilitate the further exploration of the domain‐structure‐related properties and potential applications of α‐Mo₂C.     

Effect of hinokitiol impregnated sheets on shelf life and quality of “KEK‐1” tomatoes during storage

Hinokitiol (β‐thujaplicin, volatile oil extracted from the wood of Hiba arborvitae [Thujopsis dolabrata var. hondae], cypress family) is a natural preservative, antimicrobial, and chelating agent, used to prevent decay and extend the shelf life of fruits and vegetables. In the present study, we used nonwoven rayon sheets impregnated with hinokitiol to conduct packaging studies. Mature green tomatoes var. “KEK‐1” were packaged under three packaging conditions, ie, modified atmosphere packaging (MAP), MAP + hinokitiol (MH), and perforated film package (as control), and their quality attributes were compared during storage. The packaging materials used were low‐density polyethylene (LDPE) film (40 μm) and fresh sheets of nonwoven rayon impregnated with hinokitiol. O₂ in the MAP packaged tomatoes were retained throughout the storage period (3% to 5% O₂). Results showed that MH had slightly improved quality attributes throughout the storage period when compared with MAP alone. Expression levels of LeACS, LeADH, and LeTBG4 genes were higher in 5 and 9 days of control when compared with MAP and MH. “KEK‐1” tomatoes had longer shelf life under MAP and MH packaging and maintained the quality at 15°C. Hence, the effect of the MAP with bioactive packaging treatments could be effective in the future application for the extension of shelf life and quality of fruits and vegetables.     

The effects of γ‐irradiation on compositional changes in plastic packaging films

Sterilization of packaging materials for pharmaceutical or food products with ionizing irradiation can cause chemical and physical changes in polymer materials. The effects of γ‐irradiation on the formation of solvent extractable radiolysis products of six flexible packaging materials for foodstuffs and/or pharmaceutical applications were studied after treatment in a ⁶⁰Co‐irradiation plant. The polymer materials polyethylene, polypropylene, poly(ethylene terephthalate), polyamide, polystyrene and poly(vinyl chloride) were investigated after treating with an irradiation dose of 44 kGy. The compositional changes in solvent extractable radiolysis products of each packaging material were quantified. In most cases the radiolysis products formed could be identified using GC/MS. The polyolefine materials (PE and PP) showed an increase of low volatile compounds after irradiation due to an oxidative decomposition of the polymer and typical polymer substances like oligomers and additives. Other packaging materials such as PET, PA and PS did not significantly change their amount of solvent extractable compounds after irradiation with 44 kGy. The PVC packaging material used in this study was not resistant to irradiation treatment at all. Because of the release of HCl during irradiation a large amount of volatile substances could be extracted from the PVC sheet. For consumer protection and also to meet general food packaging legislative requirements for irradiated packaging materials, it is necessary to evaluate the compositional changes in the polymers during irradiation, especially for irradiated polyolefines and PVC. Most attention should be paid to low volatile radiolysis products which are the most likely to migrate into a foodstuff or a pharmaceutical product. Copyright © 1999 John Wiley & Sons, Ltd.     

EVOH Films Containing Antimicrobials Geraniol and α‐Terpilenol Extend the Shelf Life of Snakehead Slices

Various studies have provided information on active packaging to prevent food putrefaction effectively . In this work, ethylene–vinyl alcohol copolymer (EVOH) films with geraniol (Ger) and α‐terpilenol (Ter) were successfully prepared by extrusion. The mechanical, thermal, oxygen barrier and antimicrobial properties of the packaging films were characterized, and the application of the films in snakehead preservation was examined. Thermogravimetric analysis showed that the addition of Ger and Ter did not decrease the films properties but improved their oxygen barrier property and thermostability. Moreover, the incorporation of Ger and Ter inhibited the growth of Escherichia coli, Salmonella enterica and Listeria monocytogenes. Both of the films, EVOH/Ger (EVOH/Ger) and EVOH/Ter (EVOH/Ter), reduced Salmonella enterica by 2.36 ± 0.17 and 1.91 ± 0.06 log units, respectively. Meanwhile, the effects of EVOH/Ger and EVOH/Ter on quality assessment of snakehead slices were examined through sensory tests and analyses of biochemical indices during refrigerated storage (4°C ± 1°C) for 10 days. Sensory properties, total viable counts, total volatile basic nitrogen, thiobarbituric acid and pH values were evaluated. On eight day, compared with the control fish samples, the total viable counts and total volatile basic nitrogen values cut down 1.98 ± 0.02 log units and 11.3 ± 0.11 mgN/100 g, respectively, for fish samples packaged by EVOH/Ger. The active films containing 6% (wt) Ger and 6% (wt) Ter inhibited the growth of E. coli, S. enterica and L. monocytogenes and effectively extended shelf life by 4–5 days under cold‐storage conditions compared with the control group. Copyright © 2017 John Wiley & Sons, Ltd.     

Evaluation of a bio‐coating as a solution to improve barrier,friction and optical properties of plastic films

The present research dealt with evaluating barrier, friction and optical properties of three different plastic films after deposition of a gelatin‐based bio‐coating. The composite films showed improved barrier properties against oxygen and UV radiation. The oxygen transmission rate decreased in the order of 73% for oriented polypropylene (OPP), 56% for low‐density polyethylene (LDPE) and 40% for polyethylene terephthalate (PET). The increased UV barrier characteristics ranged from 20% for OPP to 12% for both LDPE and PET. Static and kinetic coefficients of friction significantly decreased both in the film‐to‐film and in the film‐to‐metal tests, leading to a desirable value for many applications. However, bio‐coated films showed lower optical performances in terms of transparency and haze. Transparency decreased mainly for LDPE (36%), whereas the haze index increased especially for OPP (85%). Non‐significant differences were observed as far as the water vapour permeability was concerned, except for a slight reduction for PET (from 15.78 to 13.53 cm³/m²/day at 23°C and 90% of relative humidity), suggesting that non‐meaningful effects arose from the addition of a hydrophobic component in the original formulation. Finally, the solubility of the coating in water was around 25% for all the three plastic substrates. The obtained data suggest that the lipid protein coating tested in this study, in spite of its great potential for enhancing some characteristics of plastic packaging films, still exhibits negative aspects which necessitate further improvement. Copyright © 2008 John Wiley & Sons, Ltd.     

Effect of high‐pressure food processing on the mass transfer properties of selected packaging materials

The effect of high‐pressure processing (HPP) on the total migration into distilled water and olive oil and on the barrier properties of four complex packaging materials were evaluated. The films were polyethylene/ethylene‐vinyl‐alcohol/polyethylene (PE/EVOH/PE), metallized polyester/polyethylene, polyester/polyethylene (PET/PE), and polypropylene‐SiOx (PPSiOx). Pouches made from these films were filled with food simulants, sealed and then processed at a pressure of 400 MPa for 30 min, at 20 or 60°C. Pouches kept at atmospheric pressure were used as controls. Prior to and after treatment, all films were evaluated for their barrier properties (oxygen transmission rate and water vapour transmission rate) and ‘Total’ migration into the two food simulants. In the case of water as the food stimulant, a low ‘Total’ migration was observed and even a lower one after the HPP treatment. In the case of oil as the food simulant, a higher ‘Total’ migration was found compared to the control as a result of damage to the structures during the HPP treatment. The gas permeability of the films increased after the HPP, compared to the control, due to damages in the structure caused during the treatment. The PET/PE film presented minimum changes in properties after HPP. Copyright © 2010 John Wiley & Sons, Ltd.     

Silicon Migration from High‐barrier Coated Multilayer Polymeric Films to Selected Food Simulants after Microwave Processing Treatments

The use of microwave (MW) technology for in‐package food sterilization and pasteurization has the potential for widespread use in the food industry. Because the use of MW technology requires that food be processed inside its packaging, the interaction between food and its packaging during processing must be studied to ensure package integrity as well as consumer safety. In this study, two commercially available multilayer films developed for retort sterilization were evaluated for their suitability to MW processing. Film A was composed of oriented nylon//coated polyethylene terephthalate//cast polypropylene (CPP); film B consisted of oriented nylon//coated nylon//CPP with overall oxygen transmission rates <0.2 cc/m². day. Silicon (Si) was a major component in the coated polyethylene terephthalate layer and food‐contact CPP layer. This study evaluated the influence of MW processing on Si migration from films into selected food‐simulating liquids (FSLs; water and 3% acetic acid) using inductively coupled plasma‐mass spectroscopy, as compared with conventional thermal processing. This study also assessed migration of Si into FSL in terms of process temperature (70–123 °C) and time (18–34 min). A Fourier transform infrared spectrometer was used to evaluate the stability of the silicon–oxygen (Si–O) bonds in the metal‐oxide coated and food‐contact layer of the packaging film. Overall, there were no significant differences (p > 0.05) between the level of Si migration from films to FSL and the stability of Si–O–Si bonds during MW processing as compared with the conventional thermal processing. However, we found that the final processing temperature and time had a significant (p < 0.05) impact on Si migration into the FSL. Copyright © 2013 John Wiley & Sons, Ltd.     

Mineral Oil Barrier Testing of Cellulose‐Based and Polypropylene‐Based Films

Recycled cardboard has been identified as a major source of mineral oil hydrocarbon (MOH) contamination of foods. Identifying and using appropriate functional barriers is a mechanism through which this problem can be addressed. A number of cellulose‐based and biaxially oriented polypropylene (BOPP) films were evaluated as potential functional MOH barriers. The films were tested using a donor material, a paper containing MOH placed on one side of the film barrier and a paper which acted as the receptor on the other. Testing was performed at accelerated conditions of 60°C, the receptor analysed periodically for MOH. The results demonstrated that the cellulose‐based film types provided an MOH barrier of >3.5 years. This contrasted with the BOPP selected films, for which only the proprietary acrylic‐coated BOPP film provided an effective barrier to MOH migration. Further investigation of the MOH barrier properties of the proprietary acrylic‐coated BOPP film was undertaken. Various coating strategies were employed including increasing the coating application weight, increasing the number of coating lay downs and coating one or both surfaces of the film. It was found that an MOH barrier of 1.5 years when tested at 40°C could be achieved for the proprietary acrylic‐coated BOPP film; however, barrier effectiveness was dependent on the coating integrity of the film. Further work with a vertical form filler packaging machine and the use of a staining technique with transmission microscopy proved effective at highlighting and assessing the coating integrity of packets during a typical packaging operation. Copyright © 2014 John Wiley & Sons, Ltd.     

Thin Laminate Films for Barrier Packaging Application – Influence of Down Gauging and Substrate Surface Properties on the Permeation Properties

A reduction in thickness of barrier laminated film systems generally leads to a quality decrease of the resulting packaging materials' functional properties. Especially for food packaging applications, adequate oxygen and water barrier properties are indispensable. The focus of this study was therefore the development of thin film systems using metallized aluminium or ethyl vinyl alcohol barrier laminates with low oxygen and water vapour transmission properties. Biaxially oriented polyethylene terephthalate and biaxially oriented polypropylene aluminium‐coated thin film laminates as well as corresponding ethyl vinyl alcohol film systems could be successfully produced with oxygen transmission rates of <0.5 cm³(STP)/(m² d bar) and water barrier values of <0.1 g/(m² d). It could be confirmed that the film thickness of these materials within the range of the investigated dimensions does not have an influence on the barrier properties. In fact, the parameters of the production process influence the functional properties of the film systems and must therefore be adapted. Machinability of these excellent thin film systems requires further investigation on packaging lines before they can be transferred to packaging application. Copyright © 2011 John Wiley & Sons, Ltd.     

Compensation of Pinhole Defects in Food Packages by Application of Iron‐based Oxygen Scavenging Multilayer Films

To protect sensitive food products from oxidative deterioration, multilayer barrier film systems and also modified atmosphere packaging are widely applied. However, the preservation of food quality in such packaging systems may be compromised by the presence of defects in the sealing layer of the films, especially when these are below a critical size, typically the detection limit of standard leak testers of 10 µm. The addition of an oxygen scavenger (OS) layer in barrier film structures could therefore provide extended protection against O₂ penetration through such defects. In this study, O₂ absorption of different multilayer film structures including an iron‐based OS were investigated under defined gas atmospheres. Measurement cells were thereby covered with plastic films of defined O₂ permeability to simulate conditions in a food package during storage with pinhole defect sizes of 10 and 17 µm. The results indicated that the OS film structures applied could only compensate for a defect size of 10 µm in the sealing layer. Analysis of the O₂ absorption of different multilayer film structures at 85% and 100% relative humidity showed that higher humidity accelerates the activation of the scavenger. After full activation, the scavenger kinetics are the same for 85% and 100% relative humidity. Long‐term storage experiments using the most effective film structure from the preliminary experiments were carried out to compare O₂ absorption of a snack food product in packages with and without an OS. The analyzed linear gradient of the reaction of the OS film and food product, respectively, indicated first‐order reaction kinetics with corresponding reaction constants calculated to be K (food product) 0.021 mg (O₂) mbar (O₂)^?1 day^?1 and K (OS film) 0.066 mg (O₂) mbar (O₂)^?1 day^?1. The reaction velocity of the OS was thus three times faster than that of the food. The applicability of OS multilayer film systems to compensate a critical pinhole defect size of 10 µm for sensitive food products could therefore be confirmed. The measurement of quality parameters for the status of lipid oxidation processes would help to verify this result. Copyright © 2012 John Wiley & Sons, Ltd.     

Effect of Polyethylene Packaging Modified with Silver Particles on the Microbial,Sensory and Appearance of Dried Barberry

Low‐density polyethylene (LDPE) packages containing submicrometre‐sized silver particles (Ag‐LDPE) were produced by extrusion method and used as packaging material for barberry packaging. The effects of Ag‐LDPE packages on the microbial factors, apparent color and sensory factors of dried barberry were investigated in comparison with the pure polystyrene packages. Ag‐LDPE packages showed antimicrobial effects on barberry compared with pure polystyrene packages. In comparison with pure polystyrene packages, Ag‐LDPE film with 2 weight percent (wt%) of silver particles revealed antimicrobial activity against mold and total bacteria count of approximately 2.3 and 2.84 log₁₀ reductions in colony‐forming units, respectively. Ag‐LDPE packages in concentration of more than 1 wt% of silver particles preserved the appearance quality of the barberry better than pure polystyrene packages. The barberries packaged in Ag‐LDPE film with 1 wt% of silver particles retained their red color and brightness for approximately 2 to 3 weeks more than barberries packaged in pure polystyrene films. Ag‐LDPE packages assisted in the improvement of aroma, taste and total acceptance of barberry in comparison with pure polystyrene packages except in the low concentration of silver particles of approximately 0.02 wt%. The taste, aroma, appearance and also total acceptance of barberries packaged in Ag‐LDPE film with 1 wt% silver particles were preserved for approximately 2 to 3, 1 to 4, 2 to 5 and 2 to 4 weeks, respectively, more than barberries packaged in pure polystyrene films. Copyright © 2012 John Wiley & Sons, Ltd.     

Development of electronic nose method for evaluation of residual solvents in low‐density polyethylene films

Flexible packaging films containing high levels of residual volatile organic compounds (VOCs) can alter the flavour and odour of packaged foods. Currently, a range of gas chromatographic techniques and sensory evaluations are used for assessing the residual VOCs in packaging films. An objective method for assessing the residual solvents from low‐density polyethylene (LDPE) was developed using an Alpha MOS Fox 3000 electronic nose (e‐nose) equipped with 12 metal oxide semiconductor sensors. Three VOCs, ethyl acetate, ethyl alcohol and toluene, were chosen as models for solvents of interest in flexible food packaging analysis. LDPE film samples were spiked with single and binary mixtures of solvents and analysed using the e‐nose and by GC–FID (HP 6890; Hewlett‐Packard Co., Wilmington, DE). The responses obtained from the e‐nose were processed using principal component analysis (PCA) and discriminate factorial analysis (DFA) in order to identify the residual solvents. Partial least squares analysis (PLS) was also used to quantify the amount of residual solvent and to correlate the e‐nose results with gas chromatography, which is currently the standard method for determining residual VOCs in packaging films. There was good agreement between the e‐nose responses and gas chromatography results for single solvents (r = 0.90–0.98). The technique also worked for binary solvent mixtures (r = 0.84–0.99). The electronic nose can be a viable alternative to traditional techniques while providing simplicity and objectivity, which would be extremely advantageous in routine quality control of residual solvents. Copyright © 2006 John Wiley & Sons, Ltd.