Effect of light and oxygen transmission characteristics of packaging materials on photo‐oxidative quality changes in semi‐hard Havarti cheeses

Changing transmission characteristics of food packaging materials by colouring the materials may be a suitable way of reducing photo‐oxidative quality changes. This study proved that packaging in black laminates provided the best protection of Havarti cheese, followed by a white laminate. However, transparent packaging materials did not protect the product in the critical wavelength range, i.e. 400–500 nm, and changes in colour and odour were already notable after few hours of exposure to fluorescent light. Additionally, secondary oxidation products, hexanal, 1‐pentanol, and 1‐hexanol, were formed in cheese packaged in transparent or semi‐transparent packaging materials. The expected effects of oxygen transmission were difficult to evaluate, due to high residual oxygen levels in the packages. Copyright © 2002 John Wiley & Sons, Ltd.     

Shelf life prediction of oxygen‐sensitive products: The influence of moisture on prediction accuracy for freeze‐dried coffee

Optimised packaging requires that properties are matched to the protection requirements of food for its shelf life duration. Benefits include reduced packaging costs, use volumes, and potentially improved environmental performance. The ability to predict product shelf life in different materials can assist in selecting optimal packaging. However, the availability of such tools is limited, and risk for over packing exists. The aim with this work is to develop a prediction approach which can be applied to assist users to select more optimal packaging materials. Soluble coffee was used to develop the approach, where oxygen consumption of the product is used as a quality indicator. The effect of moisture content on O₂ consumption was studied to determine its influence on prediction accuracy. Samples were prepared with different levels of moisture content. O₂ consumption rates were measured, and a notable influence of moisture was observed. A model was developed to predict the O₂ consumption of the product when packed in a pouch. The model considers oxygen and moisture permeation properties of the packaging film, O₂ and moisture differential between the interior and exterior of the packaging, and the evolution of the O₂ consumption rate as a function of moisture increase. To test model accuracy, coffee samples were packed in flexible pouches, and O₂ consumption was measured which showed that predicted and measured values shared the same trend characteristics. We show that considering both moisture and O₂ ingress simultaneously leads to more precise shelf life prediction as oxidation rate is influenced by moisture content.     

Development of Palladium‐based Oxygen Scavenger: Optimization of Substrate and Palladium Layer Thickness

Oxygen scavenging films based on vacuum deposited palladium layers were developed to remove residual oxygen remaining in food packages after modified atmosphere packaging. Palladium (Pd) was coated on to a range of packaging films and in different thicknesses using magnetron sputtering technology. To improve the substrate surface, an additional silicon oxide (SiO_x) layer was also applied to the films before Pd deposition. To determine the oxygen scavenging activity, the scavenger films were placed into an airtight cell, which was flushed with a gas mixture containing 2 vol.% oxygen and 5 vol.% hydrogen. The results showed that the oxygen scavenging rate was strongly dependent on the coating substrate as well as on the Pd deposition thickness. Packaging films such as polyethylene terephthalate, aluminium oxide‐coated polyethylene terephthalate, oriented polypropylene and polylactic acid were found to be the most suitable substrates for Pd‐based oxygen scavengers. Moreover, it was demonstrated that the intermediate SiO_x layer between the substrate and the Pd layer led to a substantial increase in the oxygen scavenging activity rate (up to 33‐fold) for all applied packaging films. Additionally, it was shown that the optimal Pd layer thickness for the investigated oxygen scavenging films lies between 0.7 and 3.4 nm. The resulting scavenger films have the potential to scavenge residual headspace oxygen of sensitive foods within a matter of minutes leading to shelf life extension and overall quality improvements. Copyright © 2015 John Wiley & Sons, Ltd.     

A Modular Approach of Different Geometries for Non‐invasive Oxygen Measurement inside Moving Food Packages

The importance of a controlled atmosphere in food packages is paramount to maximize shelf life, limit bacterial activity and avoid mould growth. Residual oxygen is one of the most important gases related with ageing of products meant to have a long shelf life. As oxygen is a main component in the atmosphere, it can be present in foods after manufacturing and usually needs to be removed during the packaging process. An experimental set‐up for non‐invasive gaseous oxygen sensing inside food packages using laser spectroscopy has been studied in order to easily adapt the measurement technique on a wide range of trays with different geometrical and optical properties. Different measurement arrangements have been considered and evaluated in order to provide guidelines to the applicability of this system to samples in a continuously moving production line. Copyright © 2017 John Wiley & Sons, Ltd.     

Effect of chitosan coating and vacuum packaging on the quality of refrigerated grilled pork

The effects of chitosan coating and vacuum packaging on the quality and shelf‐life of retail packaged grilled pork in a PVDC/nylon pouch during refrigerated storage at 2 ± 1°C were investigated. Grilled pork without chitosan coating and packaged in 100% air was used as the control sample. Firmness, pH, colour, peroxide values, microbial population and shelf‐life (as determined by sensory characteristics) of the samples were determined during the storage. The results showed that colour, peroxide values and microbial population coincided with sensory characteristics. The delayed growth of microbes in vacuum packaging can be attributed to inhibition by low levels of O₂. Chitosan coating was shown to minimize oxidation, as reflected by the peroxide values, colour changes and microbial counts of the samples. Vacuum‐packaged chitosan‐coated grilled pork showed negligible microbial growth and was found to be organoleptically acceptable throughout the storage period. Chitosan coating along with vacuum packaging provided a type of active packaging to maintain quality and extend the shelf‐life of grilled pork. Copyright © 2006 John Wiley & Sons, Ltd.     

Evaluation of Antimicrobial Active Packaging to Increase Shelf Life of Gluten‐Free Sliced Bread

This paper presents a complete study and comparison of the efficiency of three types of packaging system: active packaging, modified atmosphere packaging (MAP) and combinations of both. To choose the best option, we must take into account microbiological results as well as sensory quality; therefore, a complete sensory study and an in‐depth statistical study were carried out, in order to evaluate each option and their interactions. The results showed that active packaging considerably increases the shelf life of packaged food, so it could be an attractive option to extend the shelf life. The active packaging provided better sensorial properties than the MAP option. Positive factors like characteristic flavour and spongy texture had higher values in the absence of MAP, and negative properties like cinnamon flavour, crumbly texture and hardness reached higher values when MAP was present in the packaged food. So when microbiological and sensorial properties are taken into account, the active packaging is a better option than MAP to increase shelf life because it inhibits microbial growth while maintaining the high quality of sensorial properties for gluten‐free breads. Copyright © 2011 John Wiley & Sons, Ltd.     

Non‐intrusive Measurements of Headspace Gas Composition in Liquid Food Packages Made of Translucent Materials

The increase in chilled food consumption requires enhanced food safety and quality assurance. Food deteriorating processes are affected by the presence of oxygen, combined with factors such as time and temperature. To slow down deterioration processes and prolong shelf life, traditional packaging methods are being replaced by modified atmosphere packaging, for example. Oxygen, which is naturally present in the headspace of most food packages, is then reduced and controlled. Many sensing techniques for food quality assurance have been developed; however, almost all are intrusive, increasing the complication level and causing sample waste. The purpose of this paper is to introduce a non‐intrusive technique [gas in scattering media absorption spectroscopy (GASMAS)] for measuring gas composition in the headspace of liquid food packages. The GASMAS method uses diode laser absorption spectroscopy combined with diffuse light propagation to analyse gas located inside solids and liquids. By illuminating the package from the outside and analysing the scattered light that emerges, the absorption from the gas inside the headspace can be studied.The GASMAS technique was evaluated on a series of carton packages with a high‐quality orange juice and a nitrogen headspace. A clear variation in oxygen content was measured for samples with different storage times. The results demonstrate the possibility of using the GASMAS method for non‐intrusive quality measurements in food products and packaging. They also indicate the potential for the non‐intrusive quality assurance applications without waste of samples. A further development of the technique could include ‘in‐line’ quality control of packed food items throughout the food packaging supply chain. Copyright © 2011 John Wiley & Sons, Ltd.     

The influence of packaging materials on the dissolved oxygen content of probiotic yoghurt

The health benefits of probiotic functional foods have been widely reported. However, manufacturers face great challenge in guaranteeing delivering beneficial numbers of viable probiotic bacteria through to the end of the product shelf life. The oxygen toxicity of some probiotic species has been shown to contribute to reduced viable counts. The packaging system favoured by manufacturers may play a negative role, promoting oxygen uptake in the product. The research detailed herein evaluates the performance of current packaging materials and an alternative, oxygen‐barrier material. Commercial stirred‐type probiotic yoghurt was evaluated for dissolved oxygen content over a 6 week period from manufacture to expiry date. The results indicate a rising level of dissolved oxygen in the yoghurts over time. The distribution of oxygen throughout the product was also examined by measuring concentrations in two lateral positions, at three different depths. It was found that oxygen was not distributed homogenously, but was in significantly different concentrations (p < 0.05) at most sampling points. At some locations (near packaging weak spots), readings were approaching saturation, hardly an environment suited to the survival of the anaerobic and probiotic Bifidobacterium species. Yoghurt stored in packaging materials with improved gas‐barrier properties was also tested, displaying a decrease in dissolved oxygen levels during storage. It was concluded that using packaging materials with greater gas‐barrier properties would help remove a hurdle to the viability of the probiotic bacteria within the food. Suggestions for further steps, such as the addition of an oxygen‐scavenging technology, are also made. Copyright © 2002 John Wiley & Sons, Ltd.     

Quality Evaluation of Grated Graviera Cheese Stored at 4 and 12°C using Active and Modified Atmosphere Packaging

The effect of active [oxygen absorber (OA) combined with an ethanol emitter (EE)] and modified atmosphere (100% Nitrogen) packaging in combination with a high barrier experimental polyethylene terephthalate‐silicon oxides//low density polyethelene film on shelf‐life extension of grated Graviera cheese stored at 4 and 12°C was investigated. Microbiological (total viable counts, Pseudomonads, lactic acid bacteria, Enterobacteriaceae and Yeasts/Moulds), physico‐chemical (pH, thiobarbituric acid and colour) and sensory (odour and taste) changes occurring in the product were monitored as a function of treatment and storage time (10 weeks). Sensory shelf‐life was approximately 1, 1.5, 4.5, 6, 9 and at least 10 weeks for control samples (12 and 4°C), for N2 packaged samples (12 and 4°C) and samples packaged with the OA + EE (12 and 4°C), respectively. At the point of sensory rejection, yeasts and moulds increased from 2.00 to 3.60 and 5.55 log CFU/g for control samples stored at 4 and 12°C, respectively. Similarly, for samples stored under nitrogen, yeasts and moulds reached 2.00 and 2.32 log CFU/g at 4 and 12°C, respectively. Yeasts and moulds in samples with the OA + EE remained below 2 log CFU/g throughout the entire storage period, irrespective of storage temperature. pH varied between 5.72 and 6.49 depending on specific treatment. Malondialdehyde absorbance ranged between 0.05 for fresh samples and 0.79 mg/kg at the time of sensory rejection of samples. Light parameters L and b decreased while parameter a increased during storage, reflecting a gradual discolouration of all samples and especially those stored at 12°C.     

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.     

The influence of α‐tocopherol concentration on the stability of linoleic acid and the properties of low‐density polyethylene

In food packaging applications where low‐density polyethylene (LDPE) film containing α‐tocopherol is used, the antioxidant may have a dual function, i.e. to protect the polymer from oxidative degradation during processing, and to delay the onset of oxidation of the packaged foodstuff during storage. Incorporation of high levels of α‐tocopherol into LDPE film was found to inhibit oxidation of a linoleic acid emulsion stored in contact with the film at 6°C. However, the presence of 360 ppm caused changes in mechanical properties and an increase in oxygen transmission. Levels as high as 3400 ppm α‐tocopherol also caused yellowing and reduction in crystallinity of the material. Thus, the use of high amounts of α‐tocopherol in LDPE, which might be needed in active packaging applications, requires careful consideration of the protective requirements for each specific food and the maintenance of the desired properties of the packaging material. Copyright © 2000 John Wiley & Sons, Ltd.     

Comparative effects of de‐aeration and package permeability on ascorbic acid loss in refrigerated orange juice

Several factors including pH, cultivar, extraction method, metal ion content and storage conditions affect the rate of ascorbic acid loss in refrigerated fruit juices. While oxygen permeation rate and product de‐aeration also influence ascorbic acid loss, little comparative data on these two variables exist despite the potential usefulness of such data in optimizing the packaging of juice. De‐aerated and non‐de‐aerated single‐strength orange juices were packaged and stored at 7°C in experimental glass containers constructed with oxygen permeability rates of 0·35, 0·39, 0·43, 0·79, 1·18 and 1·60 ml/day/container at 7°C. The rate of ascorbic acid degradation inversely correlated with permeation rate for both de‐aerated and non‐de‐aerated juices regardless of initial dissolved oxygen content. Degradation was best described by zero‐order and first‐order kinetics for de‐aerated and non‐de‐aerated juices, respectively. Headspace volume had no effect on ascorbic acid loss in both de‐aerated and non‐de‐aerated juices when nitrogen flushed. Juice in high oxygen permeability containers showed a faster decrease in ascorbic acid content, independent of initial dissolved oxygen content. These results indicate that both package barrier properties and de‐aeration are major factors in maintaining ascorbic acid in refrigerated orange juice. Copyright © 1999 John Wiley & Sons, Ltd.     

Effect of packaging materials and storage conditions on bacterial growth,off‐odour,pH and colour in chicken breast fillets

A comparison was made of the effect of different packaging materials on bacterial growth, off‐odour, pH and colour of chicken breast fillets stored at 4°C. For one of the packaging materials, the effects of temperature (4°C and 8°C) and initial oxygen present (0%, 2% and 4%) on bacterial growth, off‐odour, pH and colour in chicken breast fillets were also evaluated. Chicken breast fillets stored in the packaging material with the highest oxygen transmission rate (OTR) measured at actual storage conditions had the highest bacterial growth and the highest degree of off‐odour. Chicken breast fillets stored in packaging material mainly consisting of expanded PET had similar bacterial growth and off‐odour as in the barrier display film (BDF) packages, despite a smaller headspace volume and lower initial concentration of CO₂. No differences in discoloration and pH of the chicken breast fillets, due to storage temperature and amount of initial oxygen present, were found when one of the packaging materials was studied. In the early phase of the storage period, Pseudomonas spp. constituted the majority of the total viable counts, while after about 12 days, lactic acid bacteria dominated. At the end of the storage period, both Pseudomonas spp. and Enterobacteriaceae were present in high numbers. Significant differences in counts of Brochothrix thermosphacta were only obtained with initial presence of oxygen. The storage temperature had greater impact on microbial growth and off‐odour than the initial presence of oxygen in the packages. Copyright © 2004 John Wiley & Sons, Ltd.     

Inactivation of Palladium‐based Oxygen Scavenger System by Volatile Sulfur Compounds Present in the Headspace of Packaged Food

An oxygen scavenger based on a catalytic system with palladium (CSP) was recently developed to remove oxygen in food packagings. Although the CSP worked with various types of food, with some foods, an inhibition of the CSP was observed. Because such catalytic systems are susceptible to poisoning by sulfur‐containing compounds, the aim of this study was to understand the inactivation of palladium‐based catalysts in presence of foods containing volatile sulfur compounds (VSCs). To achieve this, the oxygen scavenging activity (OSA) of the CSP was evaluated in presence of selected food products. Afterwards, VSCs mainly present in these foods were exposed to the CSP, and the influence on the OSA was evaluated. Finally, headspace analysis was performed with the diluted VSCs and with the packaged food products using proton transfer reaction time‐of‐flight mass spectrometry. It was found that the catalytic activity of the CSP was inhibited when VSCs were present in the headspace in concentrations ranging between 10.8–36.0 ppbv (dimethyl sulfide, DMS), 1.2–7.2 ppbv (dimethyl disulfide), 0.7–0.9 ppbv (dimethyl trisulfide), 2.1–5.8 ppbv (methional) and 4.6–24.5 ppbv (furfuryl thiol). It was concluded that in packaged roast beef and cheese, DMS may be the compound mainly responsible for the inactivation of the CSP. In packagings containing ham, the key compounds were hydrogen sulfide and methanethiol; in peanuts, it was methanethiol; and in par‐baked buns, an accumulation of methional, DMS, butanethiol and methionol. When potato chips were packaged, it was demonstrated that when VSCs are present in low concentrations, oxygen can still be scavenged at a reduced OSA.     

Effect of packaging oxygen transmission rate on the shelf life of ready-to-heat foods susceptible to postcontamination during refrigerated and illuminated storage

Since more and more pressure is exerted to reduce the use of plastic packaging materials, optimizing the use of food packaging is opportune. The aim of this study was to evaluate the combined effect of packaging materials, spanning a range of oxygen transmission rates (OTR), and retail illumination, on the microbial shelf life and safety of refrigerated ready-to-heat foods. Cooked potato slices were packaged in OPA/PP bags with a high OTR (28.85 ccO₂/m²/d) and OPA-EVOH/PP bags with a low OTR (6.57 ccO₂/m²/d). Cooked composite meals were packaged in tray and foil combinations, also spanning a range of OTR: PP trays (2.09 ccO₂/tray/d) with OPA/PP foils (28.85 ccO₂/m²/d), PP trays with OPA-EVOH/PP (6.57 ccO₂/m²/d) foils, and PET trays (0.07 ccO₂/tray/d) with PET top foil (32.86 ccO₂/m²/d) . The packages were stored in a dark environment, or under fluorescent or LED light. Due to the rapid growth of lactic acid bacteria, the microbial shelf life of both food products was largely unaffected by the type of barrier. Illumination at 1000 lux for 12 hours per day led to temperature differences significantly affecting microbial growth. Based on the results, it could be concluded that re-evaluating packaging material choices for these foods may prove valuable, since the use of high-barrier multilayer packaging materials may be considered as a case of overpackaging.     

Characterization of l‐polylactide and l‐polylactide–polycaprolactone co‐polymer films for use in cheese‐packaging applications

Impact‐modified and unmodified l ‐polylactide and l ‐polylactide–polycaprolactone co‐polymer films were evaluated for their suitability as materials for cheese packaging. The polymers were in some cases compounded with nanoclays as a possible route to enhanced barrier properties and/or with cyclodextrin complexes designed to provide slow release of encapsulated antimicrobials for control of mould growth on packaged cheeses. The materials demonstrated complete biodegradation under controlled composting conditions and the extruded films had acceptable transparency. Moisture uptake by films and a decrease in polymer molecular weight with time of exposure to high humidity were identified as areas of concern, although the polymer stability experiments were undertaken at 25°C and stability at normal cheese storage temperatures (～4°C) is expected to be better. Nanoclay addition enhanced the thermal stability of the polymer but reduction of oxygen and water vapour permeability to target levels through incorporation of 5% w/w nanoclay was not achieved, possibly in part due to inadequate dispersion of the nanoclays in the chosen polymer matrices. On the positive side, a novel impact‐modified polylactide was developed that overcame problems with brittleness in unmodified l ‐polylactide and l ‐polylactide–polycaprolactone co‐polymer films, and tests indicated that a cyclodextrin‐encapsulated antimicrobial (allyl isothiocyanate) incorporated in l ‐polylactide–polycaprolactone co‐polymer films would be effective in controlling fungi on packaged cheeses. Migration of substances from the l ‐polylactide or l ‐polylactide–polycaprolactone films into cheese is not expected to be a problem. Copyright © 2005 John Wiley & Sons, Ltd.     

Compatibilized Ny6‐based blends as ­innovative packaging materials: ­determination of some important properties ­relevant to food contact application

Chemical physical analysis, photo‐oxidative stability and lipid oxidation of innovative polymeric films based on blends of nylon 6 and ethylene‐co‐vinyl alcohol for use in food packaging have been investigated. Thermal mechanical analysis showed that the presence of an interfacial agent in the blend stabilized the films towards the action of permeants. Synergistic effects of the interfacial agent are reported with respect to UV photostability. Peroxide value (PV) was used to follow the oxidation of the olive oil, and for this parameter also the influence of the interfacial agent was clearly detected. Copyright © 2001 John Wiley & Sons, Ltd.     

Comparison of Various Packaging Films for Mango Export

This study compared the effects of the use of various types of packaging films in maintaining quality, preserving bioactive compounds and extending shelf life of the ‘Nam Dok Mai’ mango. The principal techniques for maintaining the quality of mangoes are based on modified atmosphere packaging using highly gas‐permeable films and an ethylene‐removing mechanism. The films studied were non‐perforated highly gas‐permeable film, non‐perforated ethylene‐absorbing highly gas‐permeable film (HNPE), micro‐perforated highly gas‐permeable films (HMP) and common non‐perforated polyethylene film (LNP). These films were compared with non‐packaging treatment, which served as a control (C). Gas composition (O₂, CO₂ and C₂H₄) in the package headspace was monitored during storage at 12°C. The quality of mangoes were assessed by weight loss, colour (L* a* b*), texture, total soluble solids, titratable acidity, total phenolics, total flavonoids, ethanol concentration and sensory quality. Equilibrium‐modified atmospheres of 5 kPaO₂ + 5 kPaCO₂ and 4 kPaO₂ + 5 kPaCO₂ were achieved in the non‐perforated highly gas‐permeable film and HNPE packs, respectively. Carbon dioxide accumulation was observed in the HMP and LNP packs where CO₂ reached 17 and 10 kPa, respectively, after storage for 10 days. The shelf life of mangoes was extended to 40 days with HNPE, 35 days with HNP, and 30 days with HMP, as compared with 20 days with control and 5 days with LNP. HNPE, the film incorporated with fine particles of mordenite framework inverted‐type zeolite with ethylene‐absorbing ability, could further extend the shelf life of mangoes in addition to modified atmosphere packaging alone. Copyright © 2011 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.