高氧气调对鲜切莲藕包装质量的影响

试验研究了高氧气调(O2的体积分数＞70%)对鲜切莲藕包装质量的影响,并与低氧气调(体积分数为2%的O2 体积分数为6%的CO2)包装鲜切莲藕的比较.结果表明:高氧气调包装对鲜切莲藕有保鲜作用,适当的高氧气调包装能够抑制鲜切莲藕的软化、营养成分损失等.氧气含量对鲜切莲藕表面亮度、酸含量和Vc含量影响不明显,但氧气含量越高,鲜切莲藕的重量、硬度保持越好.当包装内氧气浓度下降到70%的时候,其保鲜效果也随之明显下降.     

复合吸湿剂对高氧气调包装香菇品质的影响

考察了5种吸湿剂(硅胶、CaCl2、山梨酸、活性炭和皂土)的吸湿能力,并筛选出了最佳复合方式。将复合吸湿剂以不同质量添加到香菇高氧气调包装中,探讨其对香菇贮藏期间质量损失率、呼吸强度、可溶性固形物含量、硬度和颜色的影响。结果表明,吸湿剂的使用会增加香菇质量损失率,但延缓了其可溶性固形物含量及硬度值的下降。其中采用5 g复合吸湿剂处理,降低了香菇的呼吸强度并明显推迟了其呼吸高峰,而5 g和10 g复合吸湿剂处理均能有效延缓香菇白度值的下降。     

Roll‐to‐Roll Production of Graphene Hybrid Electrodes for High‐Efficiency,Flexible Organic Photoelectronics

Despite nearly two decades of research, the absence of ideal, flexible, and transparent electrodes has been the biggest bottleneck for realizing flexible and printable electronics via roll‐to‐roll (R2R) method. A fabrication of poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate):graphene:ethyl cellulose (PEDOT:PSS:G:EC) hybrid electrodes by R2R process, which allows for the elimination of strong acid treatment. The high‐performance flexible printable electrode includes a transmittance (T) of 78% at 550 nm and a sheet resistance of 13 Ω sq⁻¹ with excellent mechanical stability. These features arise from the PSS interacting strongly with the ethyoxyl groups from EC promoting a favorable phase separation between PEDOT and PSS chains, and the highly uniform and conductive G:EC enable rearrangement of the PEDOT chains with more expanded conformation surrounded by G:EC via the π–π interaction between G:EC and PEDOT. The hybrid electrodes are fully functional as universal electrodes for outstanding flexible electronic applications. Organic solar cells based on the hybrid electrode exhibit a high power conversion efficiency of 9.4% with good universality for active layer. Moreover, the organic light‐emitting diodes and photodetector devices hold the same level to or outperform those based on indium tin oxide flexible transparent electrodes.     

Use of Sodium Lactate and Modified Atmosphere Packaging for Extending the Shelf Life of Ready‐to‐Cook Fresh Meal

In this work, the combined effects of sodium lactate and modified atmosphere packaging (MAP) in extending the shelf life of a ready‐to‐cook fresh skewer, made up of raw pork chops and semi‐dried vegetable mix (i.e. zucchini, peppers and tomatoes), were investigated. In the first experimental step, a sodium lactate solution was used to dip pork chops at three different concentrations: 20, 40 and 60% w/w. The second part of the work was focused on the use of MAP. In particular, the following MAPs were tested: MA1 (50%O₂/30%CO₂/20%N₂), MA2 (70%O₂/30%CO₂), MA3 (30%O₂/70%CO₂) and MA4 (30%O₂/30%CO₂/40%N₂). Finally, the optimal concentration of sodium lactate and the best gas composition were combined. The samples were stored at 4 °C; their microbial and sensory qualities were monitored along the entire observation period. The results indicate that the shelf life of the investigated ready‐to‐cook meal can be extended by approximately 83%, if compared with the control skewer packaged in air. The best preservation strategy is the combination of dipping of meat pieces in 40% sodium lactate solution and packaging under MA1. Copyright © 2014 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.     

A Multi‐functional Biofilm Used as an Active Insert in Modified Atmosphere Packaging for Fresh Produce

We developed a multi‐functional agar‐based biofilm for fresh produce packaging by modulating its CO₂ absorption and water vapour absorption functions. The film was prepared from solutions containing agar as a matrix and a water vapour absorbent, glycerol as a plasticizer, and sodium carbonate (SC) and/or sodium glycinate (SG) as a CO₂ absorbent. The optical, mechanical, and CO₂ and water vapour absorption properties of SC, SG, and SC/SG films were investigated. Multi‐functional films tended to show poor mechanical properties, with a hard texture and an opaque and yellowish colour. The three films had different CO₂ absorption capacities and coefficients, with SC film showing the highest absorption, followed by SC/SG and SG films. The water absorption coefficients were much higher than those of CO₂, with the opposite dependence on the absorbent compound. The multi‐functional benefits of the developed film were shown by using the film for modified atmosphere packaging (MAP) of shiitake mushrooms as an insert label. A tailored MAP design for shiitake mushrooms was produced based on mass transfer mathematical models. The package attached with SC film label was capable of generating the desired internal atmosphere and thus showed the best quality preservation in terms of colour, firmness, flavour score, and bacterial growth after 5‐day storage. A tailored MAP system with our multi‐functional film can provide an optimal modified atmosphere for CO₂‐sensitive fresh commodities, preserve their quality, and extend their shelf life. Copyright © 2015 John Wiley & Sons, Ltd.     

Roll‐to‐Roll Production of Layer‐Controlled Molybdenum Disulfide: A Platform for 2D Semiconductor‐Based Industrial Applications

A facile methodology for the large‐scale production of layer‐controlled MoS₂ layers on an inexpensive substrate involving a simple coating of single source precursor with subsequent roll‐to‐roll‐based thermal decomposition is developed. The resulting 50 cm long MoS₂ layers synthesized on Ni foils possess excellent long‐range uniformity and optimum stoichiometry. Moreover, this methodology is promising because it enables simple control of the number of MoS₂ layers by simply adjusting the concentration of (NH₄)₂MoS₄. Additionally, the capability of the MoS₂ for practical applications in electronic/optoelectronic devices and catalysts for hydrogen evolution reaction is verified. The MoS₂‐based field effect transistors exhibit unipolar n‐channel transistor behavior with electron mobility of 0.6 cm² V^?1 s^?1 and an on‐off ratio of ≈10³. The MoS₂‐based visible‐light photodetectors are fabricated in order to evaluate their photoelectrical properties, obtaining an 100% yield for active devices with significant photocurrents and extracted photoresponsivity of ≈22 mA W^?1. Moreover, the MoS₂ layers on Ni foils exhibit applicable catalytic activity with observed overpotential of ≈165 mV and a Tafel slope of 133 mV dec^?1. Based on these results, it is envisaged that the cost‐effective methodology will trigger actual industrial applications, as well as novel research related to 2D semiconductor‐based multifaceted applications.     

An Unusual Strong Visible‐Light Absorption Band in Red Anatase TiO2 Photocatalyst Induced by Atomic Hydrogen‐Occupied Oxygen Vacancies

Increasing visible light absorption of classic wide‐bandgap photocatalysts like TiO₂ has long been pursued in order to promote solar energy conversion. Modulating the composition and/or stoichiometry of these photocatalysts is essential to narrow their bandgap for a strong visible‐light absorption band. However, the bands obtained so far normally suffer from a low absorbance and/or narrow range. Herein, in contrast to the common tail‐like absorption band in hydrogen‐free oxygen‐deficient TiO₂, an unusual strong absorption band spanning the full spectrum of visible light is achieved in anatase TiO₂ by intentionally introducing atomic hydrogen‐mediated oxygen vacancies. Combining experimental characterizations with theoretical calculations reveals the excitation of a new subvalence band associated with atomic hydrogen filled oxygen vacancies as the origin of such band, which subsequently leads to active photo‐electrochemical water oxidation under visible light. These findings could provide a powerful way of tailoring wide‐bandgap semiconductors to fully capture solar light.     

Roll‐to‐Roll Cohesive,Coated, Flexible,High‐Efficiency Polymer Light‐Emitting Diodes Utilizing ITO‐Free Polymer Anodes

This paper reports solution‐processed, high‐efficiency polymer light‐emitting diodes fabricated by a new type of roll‐to‐roll coating method under ambient air conditions. A noble roll‐to‐roll cohesive coating system utilizes only natural gravity and the surface tension of the solution to flow out from the capillary to the surface of the substrate. Because this mechanism uses a minimally cohesive solution, the roll‐to‐roll cohesive coating can effectively realize an ultra‐thin film thickness for the electron injection layer. In addition, the roll‐to‐roll cohesive coating enables the fabrication of a thicker polymer anode film more than 250 nm at one time by modification of the surface energy and without wasting the solution. It is observed that the standard sheet resistance deviation of the polymer anode is only 2.32 Ω/□ over 50 000 bending cycles. The standard sheet resistance deviation of the polymer anode in the different bending angles (0 to 180°) is 0.313 Ω/□, but the case of the ITO‐PET is 104.93 Ω/□. The average surface roughness of the polymer anode measured by atomic force microscopy is only 1.06 nm. Because the surface of the polymer anode has a better quality, the leakage current of the polymer light‐emitting diodes (PLEDs) using the polymer anode is much lower than that using the ITO‐PET substrate. The luminous power efficiency of the two devices is 4.13 lm/W for the polymer anode and 3.21 lm/W for the ITO‐PET. Consequently, the PLEDs made by using the polymer anode exhibited 28% enhanced performance because the polymer anode represents not only a higher transparency than the ITO‐PET in the wavelength of 560 nm but also greatly reduced roughness. The optimized the maximum current efficiency and power efficiency of the device show around 6.1 cd/A and 5.1 lm/W, respectively, which is comparable to the case of using the ITO‐glass.     

Roll‐to‐Roll Production of Transparent Silver‐Nanofiber‐Network Electrodes for Flexible Electrochromic Smart Windows

Electrochromic smart windows (ECSWs) are considered as the most promising alternative to traditional dimming devices. However, the electrode technology in ECSWs remains stagnant, wherein inflexible indium tin oxide and fluorine‐doped tin oxide are the main materials being used. Although various complicated production methods, such as high‐temperature calcination and sputtering, have been reported, the mass production of flexible and transparent electrodes remains challenging. Here, a nonheated roll‐to‐roll process is developed for the continuous production of flexible, extralarge, and transparent silver nanofiber (AgNF) network electrodes. The optical and mechanical properties, as well as the electrical conductivity of these products (i.e., 12 Ω sq^?1 at 95% transmittance) are comparable with those AgNF networks produced via high‐temperature sintering. Moreover, the as‐prepared AgNF network is successfully assembled into an A4‐sized ECSW with short switching time, good coloration efficiency, and flexibility.     

Development of an analyser to determine the oxygen and carbon dioxide levels in the head‐space of packages

This paper describes the development of an analyser intended to measure the concentrations of CO₂ and O₂ present as part of the gas mixture in the head‐space of food packages. The efficiency of the measuring device was evaluated by analysing the atmosphere of packages containing the following food products: grated Parmesan cheese, milk powder and fresh pasta. A comparison between the results of the analysis performed with the newly developed analyser and those obtained by gas chromatography showed good correlation between the two methods. The O₂ and CO₂ analyser presented satisfactory accuracy (absolute error smaller than 2.5%, v/v) and precision (relative standard deviation varying from 0.2% to 8.5%). In addition, final results of the levels of both gas types present in the atmosphere submitted to analysis are obtained after about 2 min. The proposed analyser constitutes an alternative solution for the analysis of gases present in the head‐space of packages, especially when gas samples of very small volumes—about 200 μl—are to be used. Copyright © 1999 John Wiley & Sons, Ltd.     

Porous Ultrahigh Gas‐Permeable Polypropylene Film and Application in Controlling In‐pack Atmosphere for Asparagus

Porous polypropylene (PP) films with greater gas permeability and lower permeability ratios (β) than existing commercial films were developed for fresh produce packaging. PP containing high content of beta‐form crystal was biaxially stretched under controlled conditions. Resulting porous films with uniquely high oxygen transmission rate (OTR) of 2 659 000 cm³?m^?2?d^?1, water vapor transmission rate of 67 g?m^?2?d^?1, and β value of 0.76 was used as a “breathable window” attached to the less permeable commercial BOPP (biaxially oriented PP) lidding film. Various sizes/areas of the breathable windows were designed and tested on packaging asparagus of 400 g, at 5°C. Results demonstrated that in‐pack O₂ and CO₂ concentrations could be practically controlled and modified by changing areas of the breathable windows. Altered porous high OTR area directly affected total gas permeation of the package. Optimum gas composition of Ο₂ and CΟ₂ within the recommended controlled atmosphere for asparagus, stored at 5°C, was effectively created and maintained in the package containing 25 cm² breathable window (15% of total film lid's area). The shelf life of asparagus under optimum modified atmosphere was extended to 29 days, as compared with <3 days in the normal, low OTR tray sealed with BOPP lidding film. Clearly, these developed porous ultrahigh permeable PP films can be useful materials in designing high OTR package with desirable in‐pack O₂ and CO₂ concentrations. Copyright © 2013 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.