Unsteady‐ and steady‐state gas permeation through active packaging walls

Steady‐ and unsteady‐state gas permeation rates through packaging walls containing active (scavenger) materials are determined as functions of the system's physical parameters and the scavenger load. With the simplifying assumptions of constant scavenger concentration and first‐order reaction kinetics, steady‐state analysis shows that there is a minimum quantity of scavenger that must be added to the packaging wall if any reduction of gas permeation is to be achieved. Unsteady‐state studies have established the dependence of the time needed to reach stationary behaviour on the system's physical parameters. Copyright © 2007 John Wiley & Sons, Ltd.     

PET 瓶装碳酸饮料货架期影响因素研究

目的研究影响碳酸饮料货架期的各种因素。方法以PET瓶装碳酸饮料为研究对象,分析了PET瓶的二氧化碳泄漏的途径,通过4类实验分析了温度、壁厚、二氧化碳阻隔剂、气含量等因素对其泄漏速度的影响。结果常温下瓶体是二氧化碳泄露的主要途径,降低仓储温度、增加瓶子壁厚,在PET料里添加二氧化碳阻隔剂以及增加气体含量都可以有效延长货架期,而高温下气体含量高的饮料的货架期可能更短。结论实验得到了不同仓储温度、瓶子壁厚、不同初始含气量以及添加二氧化碳阻隔剂与产品货架期的关系。     

Effects of weight reduction of packaging material on the mechanical performance of PET bottles for cooking oil

This study compares and evaluates the mechanical performance of two types of PET bottle of different nominal weights but identical design and filled with 900 ml vegetable cooking oil. The air in the headspace of all the bottles was replaced with liquid or gaseous nitrogen upon conclusion of the filling operation and immediately before capping. Two different closures, with an internal or external tamper‐evident feature, were used on the 20 g bottles. The 27 g bottle was closed exclusively with the closure fitted with an external seal. The 20 g PET bottles prior to capping were either flushed with gaseous nitrogen or pressurized with liquid nitrogen. The air contained in the headspace of the 27 g bottle was removed by injection of gaseous nitrogen only. Corrugated fibreboard cases containing 20 bottles each were submitted to a vibration test and all the components of the packaging system were subsequently evaluated with respect to important mechanical properties, such as stacking strength, drop impact strength and package integrity. The results show that the closure with external seal provided considerably better protection against leakage. Also tests conducted with stacks of five corrugated cases each and arranged onto two pallets placed one upon the other demonstrated that reducing total bottle weight by 26% is viable in terms of mechanical performance. On the other hand, the use of pressurized liquid nitrogen was found to be unnecessary. Copyright © 2000 John Wiley & Sons, Ltd.     

吸氧性PET果汁饮料瓶的制备及性能研究

将吸氧剂与聚对苯二甲酸乙二醇酯(PET)共混制得吸氧性PET橙汁饮料瓶。利用扫描电子显微镜、容器透氧仪对共混材料的结构与性能进行测定;利用高效液相色谱和色差仪对瓶装橙汁的质量进行检测。结果表明,吸氧剂能有效提高PET瓶的阻氧性能,减缓橙汁中维生素C的氧化速度,保证其色泽鲜亮,口感纯正。     

Shelf life of vegetable oils bottled in different scavenging polyethyleneterephthalate (PET) containers

The shelf life of extra virgin olive oil (EVOO) and sunflower oil (SO) bottled in containers with different levels of oxygen scavenger (OS) and stored at room temperature under diffuse lighting conditions for 6 months has been evaluated. Four packaging materials were tested: glass, polyethyleneterephthalate (PET), PET including 1% of OS (PET 1%) and PET including 5% of OS (PET 5%). Free acidity, peroxide value (PV), spectrophotometric indices (K₂₃₂, K₂₇₀, ΔK), antioxidant (biophenols and tocopherols) content, pigment (chlorophylls and carotenoids) change and the amount of oxygen dissolved in the oil were monitored during storage. A significant influence of the packaging material on the quality decay was not found. The differences in the shelf life observed between oils bottled in PET and oils bottled in glass are attributable to a difference in the initial content of dissolved oxygen in the oils. The study showed the usefulness of monitoring changes in dissolved oxygen level, antioxidant (phenols and tocopherols) and pigment (chlorophyll and carotenoids) profiles during oil storage. The change of these compounds could in fact supply important information on the oxidation processes that occur in bottled oils and on the effectiveness of the material employed in oil packaging. Copyright © 2007 John Wiley & Sons, Ltd.     

Influence of composition on structure and barrier properties of active PET films for food packaging applications

A very attractive solution in food packaging technology is the functionalization of packaging materials by incorporating an active phase into polymeric matrices. Nowadays, the applications of active substances into flexible packaging are very limited due to difficulties in realizing performing films by common manufactory processes. This work is focused on the production and characterization of monolayer poly(ethylene terephtalate) (PET) active films at different concentrations of an oxygen scavenger by cast extrusion process. Rheological, thermal, morphological analyses and oxygen absorption measurements were carried out on the produced samples to investigate the structure of active PET films and to determine their scavenging properties. Overall migration analyses were performed on active films to asses their safety in use with foodstuff, and finally the produced films were used to package fresh banana slices for evaluating their capability in quality foods preservation. Copyright © 2010 John Wiley & Sons, Ltd.     

Investigating the optimal passive and active vibration controls of adjacent buildings based on performance indices using genetic algorithms

This study proposes the optimal passive and active damper parameters for achieving the best results in seismic response mitigation of coupled buildings connected to each other by dampers. The optimization to minimize the H₂ and H_∞ norms in the performance indices is carried out by genetic algorithms (GAs). The final passive and active damper parameters are checked for adjacent buildings connected to each other under El Centro NS 1940 and Kobe NS 1995 excitations. Using real coded GA in H_∞ norm, the optimal controller gain is obtained by different combinations of the measurement as the feedback for designing the control force between the buildings. The proposed method is more effective than other metaheuristic methods and more feasible, although the control force increased. The results in the active control system show that the response of adjacent buildings is reduced in an efficient manner.     

Long‐time Performance of Bottles Made of PET Blended with Various Concentrations of Oxygen Scavenger Additive Stored at Different Temperatures

Blending of poly(ethylene terephthalate) (PET) with oxygen scavenger additives is a way to reduce ingress of oxygen into PET bottles made of these blends. The objective is to reduce oxidation of packaged beverages and oils. However, few studies were performed about the long‐time influence of temperature on PET bottles with oxygen scavenger additives. Such knowledge is relevant for the development of accelerated tests. In this study, the influence of temperature on oxygen permeation of PET bottles with the oxygen scavenger additives MXD6 or Oxyclear® was examined. PET bottles made of blends of PET with 2, 5 and 8 wt.?% MXD6, respectively, or with 2 wt.?% Oxyclear® were filled with deoxygenated water. The bottles were stored at 5, 23, 38 and 55 °C up to 5 years. Oxygen partial pressure of the water in the bottles was measured regularly. As expected, oxygen partial pressure increased earlier at higher temperature because of faster exhaustion of the oxygen scavenger. Oxygen partial pressure of water in PET bottles with 8 wt.?% MXD6 was below 10 mbar even after 5 years storage time at 5 and 23 °C. Oxygen absorption capacity of activated MXD6 was at least 76 mg/g. This study shows that PET bottles with oxygen scavengers are able to reduce the oxygen ingress for several years, even at elevated temperatures. Copyright © 2017 John Wiley & Sons, Ltd.     

A comparative analysis of the accuracy and dynamic characteristics of two systems for converting the parameters of passive electrical quantities into an active quantity

A comparative analysis of an autocompensation bridge with double conversion of the unbalance signal and a two-channel active converter with additive correction is presented. The advantages of the latter in power and speed of response are pointed out. __________ Translated from Izmeritel’naya Tekhnika, No. 2, pp. 54–57, February, 2007.     

Experimental direct evaluation of functional barriers in PET recycled bottles: comparison of migration behaviour of mono‐ and multilayers

Recycling of used bottles into new bottles is associated with possible migration of pollutants arising from the previous life of the packages. To reduce or delay such migration, the recycled resin is depolluted or a functional barrier layer made of virgin plastics is used. Testing migration from such recycled bottles relies on the use of model pollutants (surrogates). In order to enable modelling of migration kinetics, each step of the use of surrogates is carefully investigated here in the case of PET. First, criteria underlying the selection of surrogates are carefully examined; together with volatility, polarity and diffusion behaviour, it is shown here that their solubility in the food simulant and their chemical stability strongly influence migration results. For aqueous test media, 2,4‐pentanedione and phenol should be used as surrogates. Second, a procedure is developed to impregnate surrogates at very large concentrations (several thousands of mg/kg PET) which are necessary to monitor migration kinetics. This procedure, which uses dichloromethane as solvent, allows a quick and reproducible impregnation, not sensitive to temperatures between 11–23°C, factors which favour its use at a plant scale. Third, flakes impregnated with this procedure are processed into bottles, and their physicochemical properties are compared to those of commercial bottles. Last, monolayer and tri‐layer polluted bottles (model pollutants in inner layer) are tested for migration for more than 1.5 years. With multilayers, the migration lag time of the fastest surrogates is 6 months with 3% acetic acid and 3 months with ethanol as the simulant, due to plasticization of PET by ethanol. The sequence of migration of surrogates is different with monolayer and multilayer bottles, which shows that partition effects (solubility) play an essential role, especially with monolayer materials. Copyright © 2005 John Wiley & Sons, Ltd.     

Production and Application of Active Packaging Film with Ethylene Adsorber to Increase the Shelf Life of Broccoli (Brassica oleracea L. var. Italica)

Broccoli (Brassica oleracea L. var. Italica) florets were packaged in low‐density polyethylene (LDPE) bags with or without ethylene adsorber under passive modified atmosphere and then stored at 4°C for 20 days. LDPE films with (8% Tazetut® masterbatch, M2) or without ethylene adsorber (M1) were tested. The effects of modified atmosphere packaging treatments on gas concentrations (O₂, CO₂ and ethylene) in the headspace, the mass loss, colour, texture, pH, total soluble solids, chlorophyll content, total phenolic content and sensory quality of packaged broccoli were determined by comparing with unpackaged (control) florets. Results revealed that deterioration occurred quickly in control broccoli, manifested mainly by mass loss, chlorophyll degradation and stem hardening. Also, it was found unacceptable by sensory panel after 5 days. Conversely, in those florets packaged under modified atmosphere packaging, especially for LDPE with ethylene adsorber (M2), all changes related with loss of quality were significantly reduced and delayed with time. Additionally, total soluble solids and total phenolic content remained almost unchanged during the whole period. Ethylene concentration was determined as 61.8 ppm in M1 and 0.33 ppm in M2, respectively, at the end of the storage. Thus, broccoli packaged with M2 films had prolonged storability up to 20 days with high quality attributes, this period being only 5 days in unpackaged control broccoli. Oxygen concentration decreased below 1% after 5 days of storage in M1, and the shelf life of broccoli in these bags was limited to 5 days because of risk for anaerobic fermentation. Copyright © 2013 John Wiley & Sons, Ltd.     

Formulation of sage essential oil (Salvia officinalis,L.) monoterpenes into chitosan hydrogels and permeation study with GC-MS analysis

This study deals with the formulation of natural drugs into hydrogels. For the first time, compounds from the sage essential oil were formulated into chitosan hydrogels. A sample preparation procedure for hydrophobic volatile analytes present in a hydrophilic water matrix along with an analytical method based on the gas chromatography coupled with the mass spectrometry (GC-MS) was developed and applied for the evaluation of the identity and quantity of essential oil components in the hydrogels and saline samples. The experimental results revealed that the chitosan hydrogels are suitable for the formulation of sage essential oil. The monoterpene release can be effectively controlled by both chitosan and caffeine concentration in the hydrogels. Permeation experiment, based on a hydrogel with the optimized composition [3.5% (w/w) sage essential oil, 2.0% (w/w) caffeine, 2.5% (w/w) chitosan and 0.1% (w/w) Tween-80] in donor compartment, saline solution in acceptor compartment, and semi-permeable cellophane membrane, demonstrated the useful permeation selectivity. Here, (according to lipophilicity) an enhanced permeation of the bicyclic monoterpenes with antiflogistic and antiseptic properties (eucalyptol, camphor and borneol) and, at the same time, suppressed permeation of toxic thujone (not exceeding its permitted applicable concentration) was observed. These properties highlight the pharmaceutical importance of the developed chitosan hydrogel formulating sage essential oil in the dermal applications.     

Lockout/tagout and optimal production control policies in failure-prone non-homogenous transfer lines with passive redundancy

This paper considers a production problem for a transfer line subject to random failures and repairs, and differs from other studies on transfer lines. It considers a manufacturing system consisting of three machines (two machines with passive redundancy, and one in series with the previous ones) producing one part type. The control problem is subject to non-negative constraints on work-in-process (WIP). The decision variables are the production rates of two main machines and a standby machine, and influence the WIP levels, the inventory levels and the system's capacity, which is assumed to be described by a finite-state Markov chain. The objective of this paper is to minimise WIP and finished goods inventory costs; it also aims to respect the essential space–time during intervention on machine down, in order to minimise the possibility of the circumvention of protection devices or of the retraction of lockout/tagout procedures through a passive redundancy system. This paper therefore verifies the effect of passive redundancy on optimal stock levels. Given that an analytical or even a numerical solution of the problem is very difficult to find, and that we want to have a more realistic model for industries, we present a combined approach, which is presented based on a combination of analytical formalism, simulation modelling, design of experiments, and response surface methodology to optimise a transfer line with passive redundancy, producing one part type. The usefulness of the proposed approach is illustrated through a numerical example and a sensitivity analysis.     

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.     

Advances in piezoelectric thin films for acoustic biosensors,acoustofluidics and lab-on-chip applications

Recently, piezoelectric thin films including zinc oxide (ZnO) and aluminium nitride (AlN) have found a broad range of lab-on-chip applications such as biosensing, particle/cell concentrating, sorting/patterning, pumping, mixing, nebulisation and jetting. Integrated acoustic wave sensing/microfluidic devices have been fabricated by depositing these piezoelectric films onto a number of substrates such as silicon, ceramics, diamond, quartz, glass, and more recently also polymer, metallic foils and bendable glass/silicon for making flexible devices. Such thin film acoustic wave devices have great potential for implementing integrated, disposable, or bendable/flexible lab-on-a-chip devices into various sensing and actuating applications. This paper discusses the recent development in engineering high performance piezoelectric thin films, and highlights the critical issues such as film deposition, MEMS processing techniques, control of deposition/processing parametres, film texture, doping, dispersion effects, film stress, multilayer design, electrode materials/designs and substrate selections. Finally, advances in using thin film devices for lab-on-chip applications are summarised and future development trends are identified.