Assessment of oxygen levels in convenience‐style muscle‐based sous vide products through optical means and impact on shelf‐life stability

An optical oxygen analyser was used in two small‐scale industrial trials to non‐destructively assess the quality of packaged convenience foods and packaging process. Beef lasagne packed under 70% vacuum and cooked under standard sous vide conditions was monitored for residual oxygen, using disposable sensors incorporated in each pack and a benchtop optical oxygen analyser. High levels of residual oxygen close to ambient were determined in the majority of packs after packaging, as opposed to anticipated levels of 4–5%. Residual oxygen was monitored over product shelf‐life (4 weeks at +4–10°C) along with measurement of microbial growth and lipid oxidation in food by conventional destructive methods. Oxygen levels in packs went down to almost zero between weeks 2 and 3 indicating deterioration of packaged product. Correlation between oxygen profiles and the rate of microbial growth and lipid oxidation was established. The optical oxygen sensor system was shown to provide valuable information about performance of the packaging process, product storage conditions and food quality in a convenient and cost‐efficient fashion and non‐destructively. Copyright © 2004 John Wiley & Sons, Ltd.     

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.     

同时测定包装中 O2 与 CO2 比例含量的顶空分析技术的研究

通过抽样时间以及样气分析时间的选择条件试验,测试了多种形式包装的不同样品中 O2 与 CO2 的比例含量,验证了同时测定包装中 O2 与 CO2 比例含量的顶空分析技术,在食品、药品包装中的应用范围及测试数据的稳定性。 为需要调整包装内部气体成分比例的食品、药品生产行业以及研究机构提供参考。     

Effects of Transportation Hazards on Barrier Properties of Gas Flushed Retort Pouches

Clear high‐barrier retort pouches were filled with water and gas flushed with nitrogen. Headspace volumes utilized for this study were 200 and 400 cm³. Retort pouches were fitted with an OxyDot® as a non‐invasive measurement technique to monitor percent package headspace oxygen. The retort pouches were packaged inside regular slotted containers and subjected to laboratory simulated transportation performance tests for small parcel and unit load delivery systems. To evaluate the effects of the simulated transport tests, control retort pouches of each variable were used for comparison. Headspace oxygen levels were measured for all retort pouches (test and control) for 63 days. Results indicated that there were significant differences in all variables when comparing the simulated transport samples to the control samples. Comparing headspace volumes, the 400 cm³ pouches yielded less oxygen ingress into the pouch as compared with the 200 cm³ pouches in the small parcel simulation (p < 0.05). There were not significant differences for the two headspace volumes in the unit load simulation. Results from this study indicate packaged products being distributed through small parcel supply chains, which are handled more vigorously than those being shipped palletized, the increased headspace volume protected against oxygen ingress for certain distribution channels.     

Role of package headspace on multilayer films subjected to high hydrostatic pressure

The objective of this study was to systematically examine the effect of high‐pressure processing and package headspace on package integrity and properties. Working pressures were 400 and 600 MPa, and starting vessel temperatures were 30°C, 60°C, and 90°C. Coextruded and laminated multilayers packaging films were studied: film A: (PA/EVOH/PP) and film B: (PET‐AlO_x‐OC/PA6/PP), respectively. The films were made into pouches (0.05 m × 0.10 m) and filled with 30‐mL water as a model food. Various headspace volumes (0, 0.05, 0.10, 0.15, 0.20, 0.25, and 0.30‐cc air/mL H₂O) were introduced into the packaging before processing. Imaging was used to quantify defects such as the formation of white spots on the package surface and delamination of film layers. The results showed that the headspace level and processing initial temperature had a greater effect than the operating pressure on visual defects. The package with 0% headspace did not show any physical damage to the tested films. Furthermore, thermal and mechanical analyses showed that the coextruded film A had better resistance to testing conditions than the laminated structure of film B. The X‐ray diffraction results showed that film B had more defects than film A that altered the crystalline structure. Visual observation revealed white spots and delamination in the inside layer (PP) in both films. The same processing conditions affected the oxygen and water vapour transmission rates of film B more than film A. This work provides a basic guideline to select the right headspace for a given type of packaged food whenever heat and pressure are used simultaneously.     

Sorption Phenomena in Packaged Foods: Factors Affecting Sorption Processes in Package–Product Systems

Sorption process can readily occur from many foods. The sorption behaviours result in loss of food quality and shelf life of the packaged foods by altering the aroma compound profile. Although the intensity of the aroma of a packaged foodstuff depends on the vapour pressure, the interaction of the volatile organic moieties with other food constituents and the aroma barrier characteristics of the package, the nature of the aroma is also imperative in determining the extent of sorption. Sorption properties are largely determined by packaging characteristics, flavour molecules properties, food matrix composition and environmental conditions. The chemical composition, chain stiffness, morphology, polarity and crystallinity of the polymer influence flavour absorption as much as the chemical composition, concentration and polarity of the flavour compounds, as well as the presence of other chemical constituents. External factors such as duration of storage, relative humidity, temperature and the presence of other food components can also affect the solubility of aroma compounds in packaged foods. Factors relating to both chemical and physical structure of flavour, food and packaging influence the degree of sorption and also the sorption pattern. Sorption from the packaged foods is of major concern in the selection and use of plastic packaging materials for food packaging. The present review highlights some of the major factors influencing the sorption process. The scientific principles related to sorption are reviewed and distinguished. Copyright © 2011 John Wiley & Sons, Ltd.     

Studies on functional barriers to migration. 3. Migration of benzophenone and model ink components from cartonboard to food during frozen storage and microwave heating

Studies of the migration of benzophenone from inks and of model ink components incorporated deliberately into cartonboard have been carried out at low temperature and during microwave heating. Benzophenone was found in the packaging of four of seven frozen foods examined and this was attributed to its use as a photoinitiator for UV‐cured ink. Benzophenone was found to migrate to the packaged food even from polyethylene‐coated board, and this was attributed in part to the fact that polyethylene is rather permeable to low molecular weight substances and is not a good barrier to migration. Additional studies were conducted with two other frozen foods by incorporating model ink components into their cartonboard packaging. The substances were benzophenone, benzylbutyl phthalate, butyl benzoate, chlorodecane and dimethyl phthalate. Migration was readily detected after storing the food at −20°C for 1 week in the impregnated cartonboard. Migration levels in the food increased only slowly thereafter, up to 1 year, except for the most volatile substances used. Subsequent heating of the frozen food using a microwave oven decreased the concentration of some migrants by volatilization, but increased the concentration of other, less volatile substances by heat‐accelerated migration. It is concluded that for inks used to print food contact materials, if the content of low molecular weight volatiles is controlled and if transfer of higher molecular weight components via set‐off is controlled also, then migration levels could be kept low in these conditions. Copyright © 2000 Crown Copyright. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.     

基于阻隔性的卷烟内衬材料应用性能研究

为探讨不同阻隔性能卷烟内衬材料的实际应用性能,模拟了卷烟包装条件,采用烘箱法和静态顶空-气质联用法,分别评价了不同存储条件下内衬材料对烟丝含水率和2种外加致香成分含量的影响。结果显示,内衬材料的透氧透湿性能与烟丝含水率及致香成分含量之间没有明显的对应关系,实际应用性能基本不受透湿透氧性能的影响。     

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.     

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.     

Discriminative detection of volatile sulfur compound mixtures with a plasma-polymerized film-based sensor array installed in a humidity-control system

We demonstrated the discrimination of volatile sulfur compound mixtures with different mixing ratios by using an array of the plasma-polymerized film (PPF)-coated quartz crystal resonators. The PPF sensor array, which contains PPFs prepared from amino acids and synthetic polymers, exhibited different response patterns to mono or mixed volatile sulfur compounds (VSCs) (hydrogen sulfide and methanethiol) under a dry environment. The sensor array was installed in a desktop-size relative humidity controller. The relative humidity and temperature conditions of the sample flow to the sensor cell were equalized to those of the inner atmosphere of the sensor cell based on the concept of the two-separate-temperatures method. In this way, the baseline drift of PPF sensor response caused by the introduction of a highly humid sample was successfully suppressed. We compared the sensor array responses under the controlled humidity conditions. Presorption of water molecules by PPFs caused a decrease of sensor sensitivity, but the films still had the ability to discriminate sub-ppmv VSC mixtures having 6:1, 1:1, and 1:6 mixture ratios of hydrogen sulfide and methanethiol.     

Single column trapping/separation and chemiluminescence detection for on-site measurement of methyl mercaptan and dimethyl sulfide

A simple, automated method for the measurement of methyl mercaptan (CH3SH) and dimethyl sulfide (DMS) has been investigated. These two sulfur gases have strong and unpleasant odors. The collection and separation are performed in sequence with a single short column packed with silica gel powder. CH3SH and DMS are separated according to their desorption temperatures and introduced into a chemiluminescence cell in this order. These two gases emit strong chemiluminescence by reaction with ozone. The calibration curves obtained are linear, which is superior to flame photometric detection of these substances. The whole system, including a small cylinder for the carrier nitrogen, can be set in a portable box. The instrument is applicable to breath odor analysis, and automated measurement of room air can also be performed. In toilet air analysis, it was observed that levels of the sulfur gases increased after dark. With this instrument, sulfur gases at a ppbv level are successfully measured by a simple procedure without much interference.     

Oxygen and its reactions in beer

This review examines contemporary literature available on the deteriorative reactions of oxygen in beer and packaged beer. It attempts to identify the shelf‐life factors affected by oxygen, discussing both the reactions and resultant compounds and their role in decreasing the shelf‐life of the product. It attempts to determine whether lowering the total package oxygen to near‐zero in packaged beer would result in an increased shelf‐life. Copyright © 2005 John Wiley & Sons, Ltd.     

Package Headspace Composition Changes of Chill‐Stored Perishable Foods in Relation to Microbial Spoilage

In order to find a convenient way to monitor and control the microbial quality and shelf life of chill‐stored perishable foods, microbial growth and package headspace gas concentration changes were measured during storage of three foods (seasoned pork meat, Manila clam and seasoned spinach) at 10°C, and their interrelationship was investigated. Aerobic bacterial count was the highest among the measured counts of microbial groups including specific spoilage organisms and thus may be potentially used as an index of microbial spoilage of the foods. Spoilage bacterial growth on the foods accompanied O₂ depletion and CO₂ build‐up in package headspace with some delay. There was a wide variation among the foods in the headspace package atmospheric change resulting from or related to microbial spoilage. Except for CO₂ production of Manila clam, lag times of the O₂ and CO₂ changes, determined by applying logistic function, amounted to 10^5.1–10^7.3 CFU/g, which is in the range of the microbial quality limit commonly used for shelf life determination. Overall, lag times of gas concentration changes may be used as an indicator of shelf life periods of perishable foods to a limited extent. Copyright © 2011 John Wiley & Sons, Ltd.     

Sampling and determination of formaldehyde using solid-phase microextraction with on-fiber derivatization

Gaseous formaldehyde is sampled by derivatization with o-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA) adsorbed onto poly (dimethylsiloxane)/divinylbenzene solid-phase microextraction fibers. The product of the reaction is an oxime which is thermally very stable and insensitive to light. The oxime can be analyzed by gas chromatography with flame ionization detection and other detectors. Loading PFBHA on the fiber is by room-temperature headspace extraction from aqueous solutions of PFBHA. The process of loading and desorption of unreacted PFBHA, and oxime formed, is both highly reproducible and reversible, with more than 200 loading, sampling, and analysis steps possible with one fiber. The standard formaldehyde gas concentrations studied ranged from 15 to 3200 ppbv with sampling times from 10 s to 12 min. Quantification can be achieved via interpolation from calibration curves of area counts as a function of formaldehyde concentration for a fixed sampling time. Sampling for 10 s yields a method detection limit of 40 ppbv and at 300 s the method detection limit is 4.6 ppbv. This is equal to or better than all other conventional grab sampling methods for gaseous formaldehyde employing sampling trains or passive sampling techniques. Alternatively, gaseous formaldehyde can be quantified with an empirically established apparent first-order rate constant (0.0030 ng/(ppbv s) at 25 °C) for the reaction between sorbed PFBHA and gaseous formaldehyde. This first-order rate constant allows for quantitative analyses without a calibration curve, only requiring detector calibration with the oxime. This new method was used for the headspace sampling of air known to contain formaldehyde, as well as other carbonyl compounds, and from various matrixes such as cosmetics and building products.     

Catalytic oxidation of gaseous reduced sulfur compounds using coal fly ash

Activated carbon has been shown to oxidize reduced sulfur compounds, but in many cases it is too costly for large-scale environmental remediation applications. Alternatively, we theorized that coal fly ash, given its high metal content and the presence of carbon could act as an inexpensive catalytic oxidizer of reduced sulfur compounds for "odor" removal. Initial results indicate that coal fly ash can catalyze the oxidization of H(2)S and ethanethiol, but not dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) at room temperature. In batch reactor systems, initial concentrations of 100-500 ppmv H(2)S or ethanethiol were reduced to 0-2 ppmv within 1-2 and 6-8 min, respectively. This was contrary to control systems without ash in which concentrations remained constant. Diethyl disulfide was formed from ethanethiol substantiating the claim that catalytic oxidation occurred. The presence of water increased the rate of adsorption/reaction of both H(2)S and ethanethiol for the room temperature reactions (23-25 degrees C). Additionally, in a continuous flow packed bed reactor, a gaseous stream containing an inlet H(2)S concentration of 400-500 ppmv was reduced to 200 ppmv at a 4.6s residence time. The removal efficiency remained at 50% for approximately 4.6h or 3500 reactor volumes. These results demonstrate the potential of using coal fly ash in reactors for removal of H(2)S and other reduced sulfur compounds.     

Gas-phase analysis of trimethylamine, propionic and butyric acids, and sulfur compounds using solid-phase microextraction

Complaints due to odors are an important problem for the wastewater, composting, and animal agriculture industries. Accurate, objective measurement techniques are needed to monitor emissions, to develop new waste handling procedures, and to reduce the production of these volatile gases. Solid-phase microextraction was investigated as a technique for the determination of representative odorous gases. A flow-through Teflon chamber was used to expose the fibers to certified gas standards. A 75-microm carboxen-poly(dimethylsiloxane) (Car-PDMS) coating was used for trimethylamine (TMA), carbon disulfide (CS2), dimethylsulfide (DMS), and dimethyl disulfide (DMDS), and an 85-microm polyacrylate coating was used for propionic acid (PA) and butyric acid (BA). Using a 1-h fiber exposure time and a flow rate through the chamber of 72 mL/min, method detection limits were 2.38, 0.074, 0.150, 0.063, 1.85, and 1.32 ppbv for TMA, DMS, CS2, DMDS, PA, and BA, respectively. Enhanced detector signal was observed for all analytes under flow conditions, as compared to static conditions, and the porous nature of the Car-PDMS coating appears to increase the time needed for analytes to reach equilibrium under flow conditions.     

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.     

Evaluation of a Non‐destructive High‐voltage Technique for the Detection of Pinhole Leaks in Flexible and Semi‐rigid Packages for Foods

This study evaluated the capabilities of a high‐voltage technique for the detection of pinhole leaks by using flexible pouches and semi‐rigid cups for foods. This evaluation was performed by measuring the discharge voltage when high voltages ranging from 0.25 to 10 kV were applied to sample packages. The results showed that package contact surface area, film thickness, food type and electrical conductivity are significant factors affecting the detection of pinhole leaks in flexible pouches by a high‐voltage leak detection (HVLD) system within the ranges tested (p < 0.05). For plastic cups with plastic‐laminated and foil‐laminated lids, the headspace inside a cup had the greatest effect followed by dielectric constant of lid films, electrical conductivity of foods and pinhole diameter (p < 0.01). In general, the HVLD system can detect pinholes as small as 10 µm in both plastic‐laminated and foil‐laminated pouches and lid cups, even at worst‐case scenario conditions, including liquid, semi‐solid and solid foods with 0.85 a_w. Because of high voltages applied, however, delamination in foil‐laminated films occurred when an applied voltage was greater than 3.5 kV, which resulted in increased oxygen permeability. Statistical z‐test analysis of results from blind studies showed that the HVLD technique is significantly effective in determining defective pouches and cups with pinhole leaks as small as 10 µm (p < 0.05). Therefore, it can be concluded that the HVLD technique is a promising non‐destructive and on‐line method to detect pinhole defects, which may be applicable to a wide range of hermetically sealed packages. Copyright © 2013 John Wiley & Sons, Ltd.     

食品软包装复合膜

本文在大量参考国内外食品包装的基础上,讨论各类食品包装中存在的问题,分析各类食品用复合膜的结构特性,并介绍了两种新的复合膜。