Physical and mechanical properties of peanut protein films

The properties of peanut protein films were modified using physical and chemical treatments, and their effects on color, mechanical strength, water solubility and barrier to water vapor and oxygen of the films were investigated. Physical treatments consisted of heat denaturation of film-forming solution for 30 min at 60°C, 70°C, 80°C and 90°C, ultraviolet irradiation of films for up to 24 h, and three ultrasound processes of film-forming solution. Chemical treatments consisted of addition of aldehydes and anhydrides. Heat curing at 70°C, ultraviolet irradiation for 24 h, ultrasound for 10 min in a water-bath, and formaldehyde and glutaraldehyde addition caused a significant increase in the tensile strength of the films. The water vapor permeability (WVP) and oxygen permeability (OP) of the films decreased after heat denaturation and aldehyde treatment. OP also decreased with UV treatment. Heat curing was the most effective treatment, making the films stronger, more resistant to water and less permeable to water vapor and oxygen.     

Optimization of the biocide properties of chitosan for its application in the design of active films of interest in the food area

The influence on biocide performance of some unprecedented physicochemical features of chitosan cast films such as film thickness, pH of the nutrient broth, film neutralization, film autoclave sterilization and temperature exposure were analyzed against Staphylococcus aureus and in some experiments also against Salmonella spp. The work demonstrates for the first time the influence of the release or positive migration of protonated glucosamine fractions from the biopolymer into the microbial culture as the responsible event for the antimicrobial performance of the biopolymer under the studied conditions. From the results, a reliable and reproducible method for the determination of the bactericidal activity of chitosan-based films was developed in an attempt to standardize the testing conditions for the optimum design of active antimicrobial food packaging films and coating applications.     

Tensile and water barrier properties of cassava starch composite films reinforced by synthetic zeolite and beidellite

Composites films were prepared by the casting method using native cassava starch plasticized with glycerol and 3D or 2D synthetic fillers i.e. Beta zeolite and Na-beidellite type 2:1 phyllosilicate. Special attention was paid to the effect of the filler contents and type on the mechanical and barrier properties. It was shown that films reinforced with lyophilized Beta zeolite presented both high water solubility (WS) and water vapor permeability (WVP) values than the pristine starch whereas an improvement on the WVP was found for composites prepared from Na-beidellite or from non lyophilized Beta zeolite. For the two types of fillers, a drastic increase of the mechanical properties (especially in the Young’s modulus) was observed.     

Effect of the unsaturation degree and concentration of fatty acids on the properties of WPI-based edible films

The incorporation of lipids into hydrophilic protein films allows the modification of their barrier properties, improving its commercial application as preservation medium on different foods. The main objective of this study was to develop films from Whey Protein Isolate (WPI) together with saturated and unsaturated fatty acids and to determine the effect of concentration and unsaturation degree on surface tension of the coating solution and on water vapor permeability (WVP), mechanical properties (tensile strength and elongation at break), and opacity, of the films. The results obtained showed that surface tension was significantly decreased by adding unsaturated fatty acids (oleic and linoleic acid), whereas the greatest effect on WVP reduction was achieved with stearic acid. The addition of stearic acid resulted in a decrease of elongation and an increase of tension strength; however unsaturated fatty acid content did not modify the elongation and slightly reduce a tensile strength.     

Mechanical and water vapor barrier properties of tapioca starch/decolorized hsian-tsao leaf gum films in the presence of plasticizer

The objectives of this research were to examine the mechanical and water vapor barrier properties of the starch/decolorized hsian-tsao leaf gum (dHG) films as a function of dHG and glycerol concentration. Edible film-forming solutions were prepared by mixing tapioca starch with dHG at different starch/dHG ratios to make a total solid content of 2%. In total, 15–40% glycerol was then added based on the dry film matter. Starch/dHG films were obtained by casting. It was found that the puncture strength, tensile strength, and modulus as well as the inverse of relaxation coefficient of starch/dHG films pronouncedly increased with increasing dHG, accompanied with a decreasing tendency in puncture deformation and tensile strain at break. Such results implied that starch interacted with dHG synergistically, resulting in the formation of a new network to improve the mechanical properties of tapioca starch/dHG films. Mechanical strengths of starch/dHG films decreased and water vapor permeability (WVP) at 75% RH increased with increasing glycerol concentration. However, the plasticizing effect of glycerol became less significant at high dHG concentration, particularly for the puncture deformation and tensile strain at break of the films. Water sorption isotherm results indicated that significant water sorption would only occur at high water activity (about 0.75), and generally became more pronounced with increasing glycerol and dHG concentration, but to a lesser extent for the latter. Dynamic mechanical analysis revealed that the major glass transition of starch/dHG films occurred at about −50 °C.     

Effect of cellulose fibers addition on the mechanical properties and water vapor barrier of starch-based films

Starch-based films have promising application on food packaging, because of their environmental appeal, low cost, flexibility and transparency. Nevertheless, their mechanical and moisture barrier properties should be improved. The aim of this work was to enhance these properties by reinforcing the films with cellulose fibers. Besides, the influences of both the solubility coefficient of water in the films (β) and the diffusion coefficient of water vapor through the films (D^w) on the films' water vapor permeability (K^w) were investigated. Films were prepared by the so-called casting technique, from film-forming suspensions of cassava starch, cellulose fibers (1.2 mm long and 0.1 mm of diameter), glycerol and water. The influence of fibers addition on K^w was determined at three relative humidity gradient ranges, ΔRH (2–33%, 33–64% and 64–90%). Films reinforced with cellulose fibers showed higher tensile strength and lower deformation capacity, and presented lower K^w than films without fibers. K^w showed strong dependency of β and D^w, presenting values up to 2–3 times greater at ΔRH = 64–90% than at ΔRH = 33–64%, depending on the film formulation. Therefore, adding cellulose fibers to starch-based films is a viable alternative to improve their mechanical and water barrier properties. Besides, this work showed the importance of determining film's water vapor permeability simulating the real environmental conditions the film will be used.     

Simplex lattice mixture design approach on the rheological behavior of glucomannan based salep-honey drink mixtures: An optimization study based on the sensory properties

The rheological properties of salep drink sweetened with different honeys were measured using a controlled-stress rheometer. Mixture design experiments were used to study the effect of interactions among pine, flower and highland honeys on the rheological properties of salep-honey drink mixture (SHDM) samples. In addition, product optimization was carried out using the ridge analysis to determine the optimum mixture proportions based on sensory properties of SHDM samples. Flower honey was the component showing the highest effect on the consistency coefficient values of SHDM samples. The preference of panelists was more prominent for the SHDM samples including the higher concentrations of highland honey with respect to odour and overall preference parameters. Optimum values of pine, flower and highland honeys in the mixture were found to be 0–85%, 0–40% and 15–100%, respectively, with respect to sensory properties. In addition, ridge analysis results revealed that the SHDM should include 65% highland honey, 35% pine honey and no flower honey to obtain the maximum overall preference score (7.24). The consistency coefficient and flow behavior index values of the sample to get maximum overall preference score (7.24) were predicted to be 3.650 Pa sⁿ and 0.435, respectively.     

Miniaturization of cellulose fibers and effect of addition on the mechanical and barrier properties of hydroxypropyl methylcellulose films

Cellulose fibers were miniaturized by microfluidics technology to decrease their size and incorporated in hydroxypropyl methylcellulose (HPMC) films to study the effect of addition of such fibers on the mechanical and barrier properties of HPMC films suitable for application in food packaging. The particle size of fibers and the mechanical properties, water vapor and oxygen permeabilities, total pore volume, and light and electron microscopy micrographs of films were analyzed. Incorporation of cellulose fibers in the films improved their mechanical and barrier properties significantly. This study is the first to investigate the use of microfluidics technology for the purpose of decreasing the size of cellulose fibers and the addition of reduced size microfibers to improve physical properties of HPMC films.     

Experimental design and response surface modeling applied for the optimisation of pectin hydrolysis by enzymes from A. niger CECT 2088

Optimisation of pectin hydrolysis using pectolytic enzymes produced by Aspergillus niger CECT 2088 was carried out. The effect of enzyme concentration (0.018–0.072%, w/v), substrate concentration (0.004–0.896%, w/v), pH (4.49–5.91), temperature (32.2–67.8 °C) and reaction time (18.2–71.8 min) on the enzymatic process was studied. The experiments were arranged according to a central composite statistical design. Response surface methodology (RSM) was used to assess factor interactions and empirical models regarding four product response variables (i.e., reactor conversion, reducing sugar concentration, endopectolytic productivity and enzymatic depolymerization productivity). Multi-response optimisation was also performed on the reactor and endopectolytic productivity data set of the factorial design. The highest reactor conversion (61%) and endopectolytic productivity (7.2 cSt mg⁻¹ ml⁻¹) were achieved with 1 h reaction time at 46 °C and pH 4.8 at a substrate/enzyme ratio of 11.6.     

Classification,modeling and prediction of the mechanical behavior of starch-based films

The starch-based film properties database was created with 8 variables and 322 observations collected from the literature. The selected variables were: (1) the starch origin (potato, cassava (tapioca), corn (maize), wheat, yam), (2) the starch concentration, (3) the amylose content, (4) the glycerol concentration, (5) the ambient relative humidity during storage, (6) the aging time of films and two mechanical properties of the starch films at break, (7) tensile strength at break (s_b) and (8) strain at break (e_b). The main objective of this work was to classify the data set and to predict mechanical properties (tensile strength (s_b) and strain at break (e_b) of starch-based films using a Rival Penalized Competitive Algorithm to find the clusters and, for each class, an artificial neural network (ANN) model from 6 parameters (starch origin, starch concentration (%), amylose content (%), glycerol content, ambient relative humidity (RH) and the aging of films). Each ANN was optimized using a genetic algorithm. The root-mean square error (RMSE) and the coefficient of determination B allowed to choose the best ANN. The results showed that it was possible to distinguish five classes where the composition of each class C_i could be described accurately and connected with the mechanical behavior of the films. This work also showed that it was useful firstly to classify the database before attempting to predict the mechanical properties of the starch-based films.     

Comparative study on the properties of flour and starch films of plantain bananas (Musa paradisiaca)

Biodegradable films were prepared by using the flour and starch isolated from plantain bananas of the variety “Terra” (Musa paradisiaca). Since the non-starchy fraction present in the banana flour represents 29.4% (on dry basis) of its composition, we considered it would be interesting to compare the properties of the film elaborated from this natural blend with that of the film produced from the banana starch only. Both films were characterized on the basis of their mechanical, barrier, optical, structural, and thermal properties. The banana flour film was less mechanically resistant but more flexible than the banana starch film. Despite the differences in the microstructure of the flour and starch films, the former was slightly soluble in water, and its water vapor permeability was similar to that of the starch film. Regarding the optical properties, the flour film was yellowish, which can be attributed to its protein content and the presence of phenolic compounds. The starch film, on the other hand, was lighter and less opaque. The FTIR spectra revealed the presence of the amide I group related to proteins only in the case of the flour film. Both plantain banana films displayed a C-type X-ray pattern and one glass transition temperature each, which was higher for the starch film (46.4 °C) as compared to the flour film (30.2 °C). The presence of other components (protein, lipids, and fiber) in the flour film had important effects on its properties. In general, the banana flour and starch are very promising materials for the formulation of coatings and films.     

轻游戏的设计与实现

以寓教于乐的设计思想为指导,采用Java和数据库技术设计开发了一款基于网络的教育游戏.该款游戏以一般游戏的激励机制为手段、以教学内容为载体,实践了轻游戏的内涵.     

Effect of montmorillonite clay and biopolymer concentration on the physical and mechanical properties of alginate nanocomposite films

Alginate-based nanocomposites at different montmorillonite clay (MMT) loadings were produced by solvent casting method. The combined effect of biopolymer and MMT content on the mechanical and physical properties of the obtained nanocomposites was investigated. The MMT weight percent relative to alginate was varied from 1% to 5% and polymer concentration was 1 and 1.5% w/v. Films containing 5% (wt/wt) of MMT show, with respect to neat alginate, reduced water permeability of about 19% and 22% and an increased water solubility of about 36% and 40%, for 1% and 1.5% alginate films, respectively. The tensile strength of neat alginate films increased significantly with increasing alginate concentration (about 36%) but slightly increased with increasing clay content up to 3%. The values of elongation decreased with increasing the both of clay content and polymer concentration. Results on X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed well developed exfoliated nanocomposite films especially at low level of nanoclay addition.     

Effect of pH on the formation of edible films made from the muscle proteins of Blue marlin (Makaira mazara)

Whole meat of Blue marlin (Makaira mazara) was used to prepare edible films. Protein solubility in film-forming solutions was high at acidic and alkaline pHs, while that at neutral pH was close to zero. Acidic and alkaline pHs improved the tensile strength while the effects of pH, on elongation at break, water vapour permeability and light transmission of the films, were not significant. From the film solubility in various protein denaturants it was revealed that the main interaction responsible for the formation of acidic and alkaline pH films was hydrophobic interaction, while that for neutral pH films was ionic bonding.     

Simplex lattice mixture design approach on physicochemical and sensory properties of wheat chips enriched with different legume flours: An optimization study based on sensory properties

In this study, physicochemical and sensory characteristics of wheat chips enriched with different legume flours were investigated. Wheat chips formulations were composed with the mixture of wheat flour and the mixture of three different legume flours (wheat–legume ratio 80:20). Mixture design approach was used to determine the effect of interactions between pea, chickpea and soy flour on the physicochemical and sensory properties of chips produced with wheat–legume flour mixture. In addition, product optimization was carried out by using ridge analysis to determine the optimum legume flour mixture proportions based on sensory properties of chips samples. Chickpea flour was found to be highest desired component depending on the general acceptability scores of chips. Protein content of chips increased significantly with the addition of soy flour. Optimum limit values of chickpea, pea and soy flour in the legume flour mixture used for the enrichment of the wheat chips were found to be 50–100 g/100 g, 0–60 g/100 g and 0–45 g/100 g legume flour, respectively, with respect to sensory properties. Additionally, ridge analysis results showed that the wheat chips should include only chickpea flour in the legume flour fraction to obtain maximum overall preference score (6.08).     

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.     

Physical properties and sensory evaluation of WPI films of varying thickness

The effect of varying thickness on the water barrier properties, tensile properties and sensory characteristics of glycerol-plasticised whey protein isolate (WPI) films was investigated. Thickness was varied by preparing films with increasingly dilute film forming WPI solutions in the range 9.5-2.3 g protein/100 g. All films had a glycerol to protein ratio of 0.37 (Gly: Pro). Tensile strength (TS), elastic modulus (EM) and film permeance were unaffected by film thickness but maximum load (ML) and % elongation (E) decreased (P<0.05) with decreasing thickness. In a sensory test with crackers and melted cheese, panelists could readily detect the thickest films (79 μm) but not the thinnest films (23 μm) (P<0.05). The results indicate that reducing the thickness of glycerol plasticised WPI films makes them less perceptible in a food system while maintaining moisture barrier and certain tensile properties.     

Mechanical properties of contact lenses: The contribution of measurement techniques and clinical feedback to 50 years of materials development

Purpose

This review summarises the way in which mechanical property measurements combined with clinical perception have influenced the last half century of materials evolution in contact lens development.

Stability of the mechanical properties of edible films based on whey protein isolate during storage at different relative humidity

Formulations for whey protein isolate (WPI)-based films include low molecular weight plasticizers, which implies certain degree of instability of films properties due to plasticizer migration. The aim of this work was to study the effect of storage time on the mechanical properties of WPI films plasticized with two low molecular weight polyols: glycerol (Gly) and sorbitol (Sor). Films were stored inside cabins at 50% or 75% relative humidity (RH) and at room temperature. Mechanical properties and moisture content were measured at regular intervals for 30 weeks. The effect of plasticizer type and content and RH on mechanical properties right after equilibrium (1 week) was also included in this study.     

Structural and functional properties of soy protein isolate and cod gelatin blend films

The structure-function relationship of composite films obtained from soybean-protein isolate (SPI) and cod gelatin was studied. Films with different ratios of SPI:gelatin (0, 25, 50, 75, 100% [w/w]) and plasticized by a mixture of glycerol and sorbitol were prepared by casting. Regardless of the soybean-protein concentration, the thickness and water-vapor permeability of the composite films diminished significantly as compared to pure-gelatin films. The formulation containing 25% SPI: 75% cod-skin gelatin had the maximum force at the breaking point, which was 1.8-fold and 2.8-fold greater than those of 100% gelatin and 100% SPI films, respectively. Moreover, this formulation offered high percent-deformation values lower than those of gelatin but higher than all other films containing SPI-, and the same relatively low water-vapor permeability as the 100% SPI film. While all the films exhibited high water solubility, a slight reduction in film solubility and soluble protein was observed with increasing SPI concentration. Differential-scanning calorimetry analyses revealed that gelatin was completely denatured in all films, while soy proteins largely maintained their native conformation. Analysis by fourier-transform–infrared spectroscopy revealed that the presence of 25% SPI produced gelatin conformational changes, self-aggregation of gelatin chains, and intermolecular associations via CO bonds between gelatin and SPI proteins. All films were translucent in appearance, but the yellowish color increased with increasing proportions of the soybean proteins.