TiO2/壳聚糖纳米复合涂料制备及其在抗菌纸中的应用

以纳米TiO2、壳聚糖双胍盐酸盐为抗菌剂,加以胶黏剂羧基丁苯胶乳、分散剂六偏磷酸钠、消泡剂叔丁醇,制备了TiO2/壳聚糖纳米复合涂料,利用SEM、FT-IR对涂料的微观形貌和基本结构进行了表征。以表面涂布方式将TiO2/壳聚糖纳米复合涂料施涂于纸张表面,制得涂布抗菌纸,对涂布抗菌纸的微观结构及抗菌性能进行了研究。结果表明,经TiO2/壳聚糖纳米复合涂料涂布后,纸张具备较强的抗菌性能;而且,实验发现,随着涂料体系中壳聚糖组分的不断增加,涂布纸的抗菌性能逐渐提高。当纳米TiO2/壳聚糖的加入比例为1∶1时,双层涂布后的纸张对大肠杆菌和金黄色葡萄球菌的抗菌率分别达到86.55%和92.19%。     

Packaging‐related properties of protein‐ and chitosan‐coated paper

The mechanical and gas‐barrier properties of paper and paperboard coated with chitosan–acetic acid salt (chitosan), whey protein isolate, whey protein concentrate and wheat gluten protein were studied. Paper sheets were solution‐coated using a hand applicator. In addition, bi‐layer composites of wheat gluten and paper or paperboard were produced by compression moulding, and the chitosan solution was also applied on paperboard using curtain coating. Young's modulus, fracture stress, fracture strain, tearing strength, air permeance and oxygen permeability were assessed. The mechanical and air permeance measurements of solution‐coated paper showed that chitosan was the most effective coating on a coat weight basis. This was due to its high viscosity, which limited the degree of penetration into the paper. The proteins, however, also enhanced the strength and toughness of the paper. Compression‐moulded wheat gluten/paper or paperboard, as well as curtain‐coated chitosan paperboard laminates, showed oxygen barrier properties comparable to those of paper and paperboard coated with commercial barrier materials. None of the composites could be delaminated without fibre rupture, indicating good adhesion between the coatings and the substrates. Copyright © 2005 John Wiley & Sons, Ltd.     

Antimicrobial Activity of Cinnamaldehyde and Eugenol and Their Activity after Incorporation into Cellulose‐based Packaging Films

Cinnamaldehyde and eugenol were investigated for their antimicrobial activity against 10 pathogenic and spoilage bacteria and three strains of yeast, using an agar‐well diffusion assay. The minimum inhibitory concentrations (MICs) of these compounds were determined using an agar dilution method. Finally, cinnamaldehyde‐incorporated and eugenol‐incorporated methyl cellulose films were prepared to obtain active antimicrobial packaging materials. These antimicrobial cellulose‐based packaging films were investigated for antimicrobial activity against target microorganisms using both an agar‐disc diffusion technique and a vapour diffusion technique. At a concentration of 50 µl/ml, cinnamaldehyde and eugenol revealed antimicrobial activity against all test strains. They showed zones of inhibition, ranging from 8.7 to 30.1 mm in diameter. Eugenol and cinnamaldehyde possessed ‘moderate?strong inhibitory’ and ‘strong?highly strong inhibitory’ characteristics, respectively. With MICs of 0.78?50 µl/ml, cinnamaldehyde and eugenol also inhibited the growth of all test microorganisms. Among the test microorganisms, Aeromonas hydrophila and Enterococcus faecalis were the most sensitive to cinnamaldehyde and eugenol. Cinnamaldehyde showed lower MICs against all test strains than those of eugenol. In an agar‐disc diffusion assay, cellulose‐based film containing cinnamaldehyde or eugenol totally failed to exhibit a clear inhibitory zone. However, it showed positive activity against all selected test strains in terms of size and enumeration of microbial colonies in a vapour diffusion assay. This study shows the potential use of cinnamaldehyde and eugenol for application in antimicrobial packaging film or coating. Copyright © 2011 John Wiley & Sons, Ltd.     

Effect of chitosan‐propolis edible coatings on stability of refrigerated cachama (Piaractus brachypomus) vacuum‐packed fish fillets

The effect of chitosan‐based coatings containing ethanolic extracts of propolis (EEPs) on the quality of chill‐stored, vacuum‐packed fillets of cachama, an emerging aquaculture species of fish native to the Amazon basins, was evaluated. Coatings were prepared by adding propolis to chitosan following two different strategies: (1) incorporation of microencapsulated EEP and (2) direct incorporation of EEP. Fillets were dip‐coated, vacuum‐packed in medium‐oxygen barrier bags, stored at 4°C, and their quality was evaluated during 20 days, by monitoring lipid oxidation indexes, physicochemical parameters, microbiological quality indicators, texture profile, and sensory acceptance. Chitosan‐EEP coatings significantly increased the time stability of physicochemical, microbiological, and sensory quality indicators of the fish meat compared with control treatments (uncoated vacuum‐packed fillets). In particular, the secondary lipid oxidation of the coated muscles was 12% to 15% lower compared with uncoated samples after 12 days; pH and total volatile base nitrogen (TVB‐N) presented a slower increase in the coated samples; and a greater inhibition of coliforms was observed between days 8 and 16. The chitosan‐EEP coatings had a positive effect in both texture stability and sensory acceptance of the products during storage. Moreover, chitosan coatings with encapsulated EEP had better impact on the evaluated sensory quality parameters. The results indicate that the combination of the barrier properties of chitosan with the bioactive properties of propolis compounds against oxidative free radicals and microbiological deterioration allowed for the edible coatings to extend the shelf life of this aquaculture product with respect to conventionally vacuum‐packed fillets.     

Release behavior of 1‐methylcylopropene coated paper‐based shellac solution in response to stepwise humidity changes to develop novel functional packaging for fruit

1‐Methylcyclopropene (1‐MCP) has been shown to be a suitable inhibitor of ethylene production in fruit and vegetables during preservation and distribution. In this study, a 1‐MCP controlled‐release system on coated paper was produced using shellac as the coating material. The effect of humidity and temperature on the release of 1‐MCP from the coated paper was investigated using a dynamic sorption system (DVS) with stepwise humidity changes (initial 20% relative humidity (RH) for 2 h, then increased to 40%, 50%, 60%, and 80% RH for 2 h, respectively). The release rate kinetic data were simulated using an Avrami equation with a mechanism release number n of 1.26. The results showed that the dynamic release of 1‐MCP from the coated paper was mainly affected by humidity, for which the release rate constant could be correlated with moisture concentration in humid air. The highest humidity condition (80% RH) resulted in the highest apparent activation energy of 46.8 kJ/mol. The effect of 1‐MCP coated paper on apple storage was evaluated by measuring the ethylene production rate, flesh firmness, and titratable acidity (TA) of apple. Ethylene production rates of apple were significantly affected with 1‐MCP coated paper. The values were 0.22 nL/g FW/h at 50 mg of 1‐MCP powder and 44.7 nL/g FW/h at 0 mg of 1‐MCP powder after 15 days at 4°C and 15 days at 20°C. The other properties of apple such as flesh firmness and TA also indicated that 1‐MCP coated paper could delay fruit softening during storage time. Based on these results, the release of 1‐MCP could be controlled by coating paper with shellac solution and promising to produce functional packaging for fruit.     

Use of Allyl Isothiocyanate‐containing Sachets to Reduce Aspergillus flavus Sporulation in Peanuts

Peanuts are oilseed crops that are frequently infected by fungi (including Aspergillus flavus) that may produce aflatoxin, a highly carcinogenic mycotoxin. Conventional food packaging techniques can only prevent aflatoxin production to a certain extent. Therefore, the development of novel active packaging strategies to control post‐harvest sporulation by A. flavus is important. Essential oils from plants have antimicrobial potential, and one of the most powerful components is allyl isothiocyanate (AITC), the major component of mustard essential oil. Here, we aimed to evaluate the antifungal effect of AITC against A. flavus, develop an AITC‐containing sachet to control A. flavus sporulation in peanuts and quantify residual AITC in grains and package headspaces during a 90 day period. Diffusion and volatile susceptibility tests showed the in vitro effectiveness of AITC at 0.215 ppb against A. flavus. Because in vitro and real food assays may provide distinct antimicrobial efficiencies due to different compositions, sachets incorporated with AITC were stored with peanuts for 90 days at 25°C. A 10‐fold reduction in A. flavus survival was observed in 1 week, and after 60 days, survival was reduced by 4.81 log cycles. No residual AITC was detected in grains throughout the storage period, whereas volatile AITC within the package headspaces decreased with time: 92.4% of volatile AITC was reduced within the first 15 days, and AITC was no longer detected after 30 days. We proved that AITC retards A. flavus sporulation and that sachets are a promising delivery system for AITC to act as an antimicrobial agent for peanuts. Copyright © 2014 John Wiley & Sons, Ltd.     

Covalent attachment of functional protein to polymer surfaces: a novel one-step dry process.

The attachment of bioactive protein to surfaces underpins the development of biosensors and diagnostic microarrays. We present a surface treatment using plasma immersion ion implantation (PIII) to create stable covalent binding sites for the attachment of functional soya-bean peroxidase (SBP). Fourier transform infrared spectra of the surfaces show that protein is retained on the surface after boiling in sodium dodecyl sulphate and sodium hydroxide, which is indicative of covalent attachment. The activity of SBP on the treated surfaces remains high in comparison with SBP attached to control surfaces over the course of 11 days. Surface plasmon resonance was used to show that the surface coverage of the attached protein is close to a monolayer. We describe the potential of the PIII treatment method to be used as a one-step dry process to create surfaces for large-scale protein micro- or nanopatterning.     

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.     

High‐pressure processing effects on the mechanical,barrier and mass transfer properties of food packaging flexible structures: a critical review

Food products can be high‐pressure processed (HPP) either in bulk or prepackaged in flexible or semi‐rigid packaging materials. In the latter case the packaging material is subjected, together with the food, to high‐pressure treatment. A number of studies have been performed to quantify the effects of high‐pressure processing on the physical and barrier properties of the packaging material, since the integrity of the package during and after processing is of paramount importance to the safety and quality of the food product. This article reviews the results of published research concerning the effect of HPP on packaging materials. Copyright © 2004 John Wiley & Sons, Ltd.     

Chitosan tailor‐made films: the effects of additives on barrier and mechanical properties

With the aim of achieving ‘tailor‐made’ chitosan films, the effects of several variables on the properties of chitosan films were studied. These variables were chitosan concentration and molecular weight of thermally depolymerized chitosan, addition of lipids (palmitic acid, beeswax or carnauba wax) and plasticizer (glycerol). The water vapour transmission rate (WVTR) and mechanical properties of these films were measured. The innovative feature of this study is that it provides specific information to support the design of tailor‐made films. These can only be formulated when the effects of the important variables are well understood. It was found that WVTR was reduced by 57% in film made from chitosan that had been thermally treated for 7 h at 100°C (molecular mass 13.7 kDa), while in the emulsion films, the WVTR was increased by incorporation of palmitic acid, beeswax or carnauba wax incorporation. The mechanical properties (tensile strength and elongation at break) were improved when glycerol was used as plasticizer, resulting in more elastic films (increasing the elongation at break by 62%). Copyright © 2008 John Wiley & Sons, Ltd.     

Laser‐Raman and Nuclear Magnetic Resonance (NMR) studies on plasma‐sprayed hydroxylapatite coatings: Influence of bioinert bond coats on phase composition and resorption kinetics in simulated body fluid

The structure and phase composition of HAp coatings deposited onto Ti6Al4V coupons (50x20x2mm) by atmospheric plasma spraying (APS) were studied by laser‐Raman spectroscopy, ³¹P‐ and ¹H‐MAS‐NMR and 2D‐³¹P/¹H HETCOR‐CP‐NMR spectroscopy, and XRD with Rietveld refinement. The samples investigated comprised APS HAp coatings with and without a TiO₂ bond coat as well as coatings incubated for different lengths of time (up to 12 weeks) in simulated body fluid (SBF) under physiological conditions. In APS coatings the presence of a bond coat increased the proportion of well‐ordered crystalline HAp at the expense of distorted apatite‐like structures such as oxyHAp and oxyapatite, and thermal decomposition products such as tricalcium phosphate (TCP) and tetracalcium phosphate (TTCP), and also decreased the amount of amorphous calcium phosphate (ACP). Incubation in SBF further advanced the proportion of crystalline HAp since the disordered structures, the thermal decomposition products, and ACP exhibit substantially higher solubility.     

Global parameterization of a topological surface defined as a collection of trimmed bi‐parametric patches: Application to automatic mesh construction

We describe a new geometric algorithm to map surfaces into a plane convex area. The mapping transformation is bijective; it redefines the whole surface as a unique bi‐parametric patch. Thus this mapping provides a global parametrization of the surface. The surfaces are issued from industrial CAD software; they are usually described by a large number of patches and there are many shortcomings. Indeed, the decomposition into patches depends on the algorithm of the geometric modelling system used for design and usually has no meaning for any technological application. Moreover, in many cases, the surface definition is not compatible, i.e. patches are not well connected, some patches are self‐intersecting or intersect each other. Many applications are hard to address because of these defects. In this paper we show how patch‐independent meshing techniques may be easily automated using a unique metric in a plane parametric space. Thus we provide an automatic procedure to build valid meshes over free‐form surfaces issued from industrial CAD software (Computer Aided Design: this terminology should refer to a large amount of software. For the scope of this paper we only refer to geometric modelling systems. Indeed geometric modelling systems remain the kernel of many CAD software). Copyright © 2002 John Wiley & Sons, Ltd.     

Strong materials – a structural view of material strength down to a molecular scale: Concept of a novel strong and extremely light weight molecular space frame‐polymer

The paper presents the concept of a novel very low density polymer with a rather high stiffness and possibly a high strength. The polymer molecular structure is related to a macroscopic structural engineering principle, a static (over‐) determined space frame. Before describing the molecular space frame in detail, it is discussed how and when macroscopic mechanical principles can be applied to molecular structures. It will be made plausible that this can be done to a large extent. In that way a material with an extremely fine aerogel‐like structure can be created, showing a very low density and a high stiffness to density‐ratio.