Physico-mechanical properties of chitosan films with carvacrol and grape seed extract

The physico-mechanical properties of 3 films composed by carvacrol, grape seed extract (GSE) and chitosan in different proportions were studied. The films, prepared by solvent casting technique with the following compositions of the casting solutions in carvacrol, GSE and chitosan: film-1: 9.6 ppm–684 ppm–1.25% w/v, film-2: 60 ppm–400 ppm–1.2% w/v and film-3: 90 ppm–160 ppm–1.24% w/v and were compared to a control (1.25% w/v chitosan) film. Mechanical, structural, barrier and colour properties of the films were evaluated. Film-3 presented the lowest water vapour and carbon dioxide permeabilities (WVP and CO₂P) and tensile strength (TS) values and the highest oxygen permeability (O₂P), whereas film-1 presented the highest water content and the lowest crystallinity, CO₂P, TS and luminosity. These results suggest that in the range studied, carvacrol and GSE affect the film structure and its mechanical properties due to hydrophilic (GSE) and hydrophobic (carvacrol) compounds. This work will help the development of edible films, based on physico-mechanical properties, contributing to food preservation and shelf-life extension.     

Antimicrobial activity against foodborne pathogens of chitosan biopolymer films of different molecular weights

Antimicrobial activity against Listeria monocytogenes, Escherichia coli 0157:H7 and Samonella typhimurium of chitosan biopolymer films (CBFs) prepared with four different viscosities of chitosans (10, 40, 100 and 200 mPa s) were investigated by agar diffusion assay. The films were also characterized with measurements of color, tensile strength (TS), % elongation (EL), water vapor permeability and oxygen permeability. CBFs prepared with 100 mPa s chitosan showed an antimicrobial effect only on 10⁴ cfu/mL inoculation of L. monocytogenes while other viscosities showed an antilisterial effect on all concentrations (10⁴-10⁶ cfu/mL) of L. monocytogenes. CBFs prepared with 10 mPa s (CBF-10) and 40 mPa s (CBF-40) chitosans showed an inhibitory effect against E. coli 0157:H7 and S. typhimurium only at the 10⁴ cfu/mL concentration. CBFs prepared with the two higher viscosity chitosans did not show any effect regardless of bacterial level. TS and EL of the CBFs increased with increasing viscosity up to 100 mPa s. Molecular weight distribution was found to be positively correlated with viscosity. The oxygen permeability of the CBFs increased with increasing viscosity of chitosans, but water vapor transmission rate was not similarly affected. In conclusion, CBFs were more effective at inhibition of L. monocytogenes than S. typhimurium and E. Coli O157:H7. Molecular weight of chitosan must be chosen selectively to control the target foodborne pathogens.     

花生抗真菌蛋白的纯化及活性鉴定

利用亲和色谱Affi-gel和葡聚糖凝胶色谱SephadexG-75从花生种子中分离出一种抗真菌蛋白。试验结果表明:此种纯化的抗真菌蛋白对植物致病菌苹果轮纹病菌(Physalosporapiricola)、棉花枯萎病菌(Fusariumoxysporum)、瓜果腐霉病菌(PythiumapHanidermatum)的生长具有明显抑制作用。通过SDS-聚丙烯酰胺凝胶电泳鉴定达到电泳纯,分子质量为34.4kDa。还原和非还原状态下的此抗真菌蛋白均显示单一区带,说明该抗真菌蛋白为单倍体蛋白。     

Composite and bi-layer films based on gelatin and chitosan

The aims of this work were: to develop composite, bi-layer and laminated biodegradable films based on gelatin and chitosan, to determine film barrier and mechanical properties and to characterize their microstructure.Gelatin and chitosan concentrations used were 7.5% and 1% (w/w), respectively. Glycerol (0.75%) was added as plasticizer.Physicochemical properties such as moisture content, transparency and color were analyzed. Composite and bi-layer systems showed a compact structure indicating a good compatibility between components.Water vapor permeability (WVP) was independent of film thickness up to 120 μm for gelatin films and 60 μm for chitosan ones. Both, bi-layer and laminated systems resulted effective alternatives to reduce WVP of composite films (at least 42.5%). Bi-layer systems showed better mechanical properties than laminated ones. The resistance at break increased from 54.3 for composite to 77.2 MPa for bi-layer films, whereas elongation at break values of both composite and bi-layer films were similar (2.2–5.7%).     

不同粒度甲壳素对所制备壳聚糖脱乙酰度和相对分子质量影响的研究

研究不同粒度甲壳素制备壳聚糖时,在不同反应时间对壳聚糖脱乙酰度和壳聚糖相对分子质量的影响,并求得不同粒度甲壳素脱乙酰反应的动力学公式.又采用凝胶过滤色谱测定不同脱乙酰度壳聚糖的相对分子量分布,结果表明：脱乙酰反应10 h所得壳聚糖的相对分子质量较反应8 h所得壳聚糖的小,脱乙酰反应14 h时,多糖主链的糖苷键已经发生断裂.     

Antifungal properties of Zinc‐compounds against toxigenic fungi and mycotoxin

Antifungal and antimycotoxin properties of zinc (Zn) compounds were evaluated against toxigenic strains of Fusarium graminearum, Penicillium citrinum and Aspergillus flavus. In addition, was verified the activity of these Zn‐compounds on conidia production, hyphae morphological alterations, mortality and reactive oxygen species (ROS) production. The Zn‐compounds treatments utilised were zinc oxide nanoparticles (ZnO‐NPs), zinc oxide (ZnO), zinc sulphate (ZnSO₄) and zinc perchlorate (Zn(ClO₄)₂). The Zn‐compounds effect on growth diameter of fungal colony was concentration dependent. Two treatments (ZnSO₄ and Zn(ClO₄)₂) completely inhibited the fungal growth and their ability to produce mycotoxins. The conidia production of all fungi also was reduced after the treatment with Zn‐compounds. Morphological alterations occurred in the treated fungi showing hyphae damage. The treatments led to cell death and ROS production observed in the fungi hyphae. ZnSO₄ and Zn(ClO₄)₂ were the compounds that showed better results as antifungal, presenting antimycotoxin activity and caused alterations in the fungi cell structure.     

Study on the degradation of chitosan by pulsed electric fields treatment

Chitosan solution was processed by applying pulsed electric fields (PEF) with different strengths up to 25 kV cm^− 1. Changes of the physicochemical properties of chitosan, such as molecular weight and crystallinity degree, were measured by analyses of scanning electron microscopy (SEM), viscosity molecular weight (M_v), X-ray diffractometry (XRD), FTIR and UV spectra. The results showed that after being treated at 25 kV cm^− 1, the chitosan granules were significantly deformed with many pits and cracks appeared on the surface. M_v was decreased with the increasing electric field strength, for example, the M_v was decreased from 2.81 × 10⁵ Da (initial chitosan) to 1.54 × 10⁵ Da after the PEF treatment at 25 kV cm^− 1. Meanwhile, the crystalline region of the treated sample was significantly damaged from XRD patterns. All results showed that the PEF technique is a possible method to obtain low molecular-weight chitosan.

Industrial Relevance

Chitosan solution was treated by using pulsed electric fields (PEF) with different strengths up to 25 kV·cm^-1. Changes of the physicochemical properties of chitosan were measured by analyses of scanning electron microscopy (SEM), viscosity molecular weight (M_v), X-ray diffractometry (XRD), FTIR and UV spectra. The results showed that the PEF technique is a promising method for scale-up industrial manufacture of low-molecular-weight chitosan.     

壳聚糖对芒果炭疽病菌、蒂腐病菌的拮抗作用

以芒果炭疽病菌、蒂腐病菌为实验菌株，研究了不同pH、酸溶剂的种类对壳聚糖抗菌活性及其抗菌稳定性的影响。结果表明：壳聚糖的抑菌率随着壳聚糖浓度的提高而提高；在pH4．8和pH6．0的环境中，壳聚糖的抗菌能力较强；壳聚糖的乳酸溶液对芒果蒂腐病菌有很强的抑制力；壳聚糖连续刺激诱导40代后，芒果炭疽病菌、蒂腐病菌的EC50值均有所提高，其中以芒果球二孢霉蒂腐病菌和芒果褐色蒂腐病菌变化最显著，说明壳聚糖对其抗菌稳定性最差。     

Functional packaging properties of chitosan films

 The barrier properties of chitosan and cross-linked chitosan films with respect to water vapour at three water activities, oxygen transmission rates and grease resistance values have been determined. Other properties evaluated include tensile strength, tear resistance and burst strength. In general, the cross-linked chitosan films possessed greater permeabilities and lesser values for mechanical properties. The water vapour permeabilities were found to be influenced by water activity, obeying non-Fickian behaviour characteristic of hydrophilic polymers. Received: 1 July 1997     

Effects of chitosan molecular weight and degree of deacetylation on the properties of gelatine-based films

The effect of chitosan molecular weight (MW) and degree of deacetylation (DD) on the physicochemical properties of gelatine-based films was studied with the goal of improving the films. Determination of the dynamic viscoelastic properties (elastic modulus G′ and viscous modulus G″) of the film-forming solutions revealed that the interactions between gelatine and chitosan were stronger in the blends made with chitosan of higher molecular weights or higher degrees of deacetylation than the blends made with lower molecular weights or degrees of deacetylation. Fish gelatine films modified with chitosan of higher molecular weights or higher degrees of deacetylation had higher tensile strengths (TS, 72.4 MPa for 550 kDa vs. 62.2 MPa for 200 kDa; 63.2 MPa for 93.6% DD vs. 38.0 MPa for 76.5% DD) and higher glass transition temperatures (T_g, 130 °C for 550 kDa vs. 108 °C for 200 kDa; 108 °C for 93.6% DD vs. 103 °C for 76.5% DD). Fourier transform infrared spectra (FTIR) and X-ray diffraction (XRD) studies indicated that gelatine and chitosan interactions determined the properties of the film. Thus, combining gelatine and chitosan may be a method for improving the physicochemical properties of gelatine films, especially when using chitosan of higher molecular weights and higher degrees of deacetylation.     

Properties of wheat starch film-forming dispersions and films as affected by chitosan addition

In order to evaluate the impact of chitosan on the physical properties of wheat starch–glycerol films, part of the wheat starch was replaced by chitosan, and the effect of composition on the properties of both the films and the film-forming dispersions was studied. The latter became more stable and viscous as the chitosan proportion was increased in the mixture. Both polymers appeared to integrate homogeneously in the film matrix. The combined effect of the glycerol and chitosan proportions affected the mechanical and barrier properties of the films. The tensile strength and elastic modulus of the films were improved as chitosan ratio increased. The oxygen and water vapor permeability slightly increased in line with the amount of chitosan in the blend although the induced differences were very small. Chitosan ratio directly affected the antimicrobial properties of the films, which showed a significant bactericide activity when the chitosan–starch ratio in the film was 50%. Nevertheless, at a starch:chitosan ratio of 80:20, counts of coliforms did not exceed the initial value in the meat after 7 storage days.     

Antioxidative activity of chitosans with varying molecular weights

Antioxidant activity of chitosans of different molecular weights (30, 90 and 120 kDa chitosan) in salmon (Salmo salar) was investigated. The progress of oxidation was monitored by employing the 2-thiobarbituric acid-reactive substances (TBARS) and 2, 2-diphenyl-1-picrylhydrazyl (DPPH) scavenging assays. In general, all chitosans exhibited antioxidative activities in salmon. The addition of chitosans to salmon reduced lipid oxidation for seven days of storage. The TBARS values of salmon containing chitosan were significantly lower than those of the control (p < 0.01). At 0.2% (w/v) and 0.5% (w/v) concentrations, the TBARS with chitosan addition was decreased by 75% and 45%, respectively, over 15 days. At 1% concentration, the TBARS value with native chitosan addition was decreased by 32% after 15 days of storage. 90 kDa chitosan showed an increased DPPH free radical-scavenging activity with increasing concentration in the range of 0.2–1% (w/v). The free radical-scavenging activity of the 0.2 mM DPPH solution was saturated by 30 kDa chitosan at a concentration of ?0.7% (w/v), resulting in a strong antioxidant activity of approximately 85%. This was comparable to the DPPH free radical-scavenging activity of BHT.     

Effect of the presence of glycerol and Tween 20 on the chemical and physical properties of films based on chitosan with different degree of deacetylation

Chitosans with two different deacetylation degree (DD) (60.9% and 96%) were used to elaborate edible films. The influence of the degree of deacetylation and the presence of glycerol and Tween 20 in the formulation on the surface tension of the film forming solutions as well as on the chemical structure, optical and mechanical properties and water vapor permeability (WVP) of the resulting films were studied.IR spectra showed no significant differences on the chemical structures of chitosan of the different films. However, X-ray diffraction analysis indicated that the use of chitosan with higher DD and the use of glycerol as additive resulted in higher crystallinity. Films made of chitosan with the lower DD (60.9%) were found to have higher tensile strength (TS) and elongation (E) in a tensile test. Degree of deacetylation did not have any effect on WVP. The presence of glycerol resulted in less resistant, more elastic and more permeable films.The presence of Tween 20 improved the wettability of film solutions and affected significatively mechanical, optical and barrier properties of the films. A positive interaction between glycerol and Tween 20 was observed for WVP.     

Effects of chitosan on the physicochemical and antimicrobial properties of PLA films

Films based on polylactic acid (PLA) and different amounts of chitosan powder (CH), were prepared by extrusion. The effects of CH particle size (715 and 180 μm) and the amount of chitosan incorporated in the PLA matrix (5% or 10% on PLA basis) were investigated in terms of physicochemical characteristics and antimicrobial activity of the films. The incorporation of CH particles led to less rigid and less stretchable films. Thermal properties of PLA were not affected by chitosan addition. Water vapor permeability of the composite films was higher than pure PLA films. PLA:CH composite showed significant antimicrobial activity against total aerobial and coliform microorganisms, especially when the particle size of CH was reduced.     

Study of optimization of the synthesis and properties of biocomposite films based on grafted chitosan

Acrylic acid (AcAc) and 2-hydroxyethyl methacrylate (HEMA) were graft copolymerized onto the chitosan backbone using radical initiation under different experimental conditions. The grafted products were then characterized by FTIR, TGA, grafting and swelling index (%G and Q, respectively), Mechanical properties and biodegradability were determined. The study of the properties of the grafted films demonstrated a marked influence of the concentration of acrylic monomers, time and temperature on the %G. In addition, both grafted films (CH-g-HEMA and CH-g-AcAc) showed a noticeable difference in their mechanical behavior. CH-g-HEMA stands the highest deformation for longer periods in relation to smaller strain values, whereas CH-g-AcAc shows better tension strain but lower deformation. Therefore, CH-g-HEMA films have a vast potential for food biodegradable covering characterized by their mechanical properties, non-toxicity and biodegradability.     

Hypocholesterolaemic effects of different chitosan samples in vitro and in vivo

This study determined the hypocholesterolaemic effects of chitosan preparations with different physicochemical properties. Chitosans with smaller particle size had better cholesterol-binding capacities. Chitosans exhibited potent hypocholesterolaemic effect in rats; those with higher degree of deacetylation and molecular weight seemed to reduce plasma triglyceride, total cholesterol and low-density-lipoprotein cholesterol levels and elevate the high-density-lipoprotein cholesterol level more effectively, although not all differences were significant. We concluded that the hypocholesterolaemic mechanism of chitosan was by adsorption, electrostatic force and entrapment.     

Electrically treated composite FILMS based on chitosan and methylcellulose blends

Films obtained from chitosan (CH) and methylcellulose (MC) can reduce environmental problems associated with synthetic packaging. The objective of the present work was to analyze the effect of an electrical field applied during drying on microstructure and macroscopic properties of films obtained with different mixtures of CH and MC.     

Preparation of molecular imprinted film based on chitosan/nafion/nano-silver/poly quercetin for clenbuterol sensing

A useful molecular imprinted film (MIP-CNSQ/WGE) based on chitosan/nafion/nano-silver/poly quercetin compound was prepared by a compound electrochemical method at paraffin-impregnated graphite electrode for clenbuterol (CLB) sensing, which was characterised by means of field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy spectra (XPS), infrared spectra (IR) and electrochemical techniques to confirm the formation. The molecular imprinted film modified electrode was successfully applied to the determination of CLB with a reliable result. In optimum conditions, CLB at concentrations of 0.3–50.0 μM could be determined with a detection limit of 0.01 μM (3σ). Determination of CLB in practical samples of pork liver showed good recovery.     

Fragmentation of chitosan by microfluidization process

Fragmentation of chitosan in 0.1 M acetic acid (HAc) by microfluidization was investigated. The degree of fragmentation was followed by viscometry and size exclusion chromatography. The chemical structure of chitosan and its fragments was examined by elemental analysis and ¹H NMR spectroscopy. Fragmentation of chitosan was affected by pressure or intensity of turbulence, exposure time, and hydrodynamic parameters such as molecular weight and polymer concentration in solution; but temperature had only a negligible effect. Chain scission increased bi-linearly with pressure, increased with molecular weight of chitosan but decreased with its concentration. Continuous microfluidization appeared to be more effective in fragmentation than volume pass mode. Molecular weight distribution of fragments was narrower than that of the original polymer indicating that large macromolecules were preferentially fragmented. Degree of acetylation of fragments increased when 0.1 M HAc was used as solvent for chitosan but not in 0.04 M HCl. The fragmentation of chitosan by microfluidization process was described by a parametric model relating chain scission to mechanical action and hydrodynamic parameters of the polymer. It was concluded that microfluidization can be a useful method for moderate fragmentation of chitosan.     

In vitro evaluation of antifungal activity of soybean (Glycine max) seed coat proteins

Proteins in the soybean seed coat have previously been characterized; however, the function of these proteins is unknown. We show that a soybean seed coat protein fraction was able to inhibit the growth of Fusarium lateritium and Fusarium oxysporum phytopathogenic fungi. The antifungal fraction isolated by DEAE-Sepharose chromatography revealed the presence of peroxidase, vicilin and a 24 kDa protein homologous to acid phosphatases. Germination experiments revealed that both acid phosphatase and peroxidase were exuded during seed imbibition. We suggest that the set of seed coat antifungal proteins may help protect seeds from colonization by phytopathogenic fungi.