Chitosan Film Mechanical and Permeation Properties as Affected by Acid, Plasticizer, and Storage

The effects of acid (acetic, formic, lactic, propionic) concentrations, plasticizer concentrations, and storage time (up to 9 wk) on mechanical properties, water vapor permeability, and oxygen permeability of solution-cast chitosan films were determined. Measured water vapor permeability coefficients ranged from 5.35 to 13.20 × 10^?1 g/m·day·atm. Oxygen permeated coefficients ranged from 0.08 to 31.67 × 10^?3 cc O₂ m·day·atm. Neither property was affected by storage time. Tensile strength (6.85–31.88 Mpa) also was not time dependent, but elongation (14–70%) decreased with storage time. Lactic acid solutions produced the lowest oxygen permeability values, formic acid the highest. Films formed with 7.5% lactic acid solutions had uniquely high values for elongation at break.     

Characteristics of Different Molecular Weight Chitosan Films Affected by the Type of Organic Solvents

ABSTRACT: Chitosan films were prepared using 3 chitosan molecular weights and 4 organic acid solvents without plasticizer. Tensile strength (TS) and elongation (E) ranged from 6.7 to 150.2 MPa, and from 4.1 to 117.8%, respectively. Water vapor permeability (WVP) and oxygen permeability (OP) ranged from 0.3 to 0.7 ng-m/m²-s-Pa and OP from 0.4 to 5.8 × 10 ⁻⁸ cc/m²-day-atm, respectively. TS increased with chitosan molecular weight. Acetic acid resulted in the toughest films followed by malic, lactic, and citric acid, respectively. Films prepared with citric acid had the highest E values. WVP was not influenced significantly by the molecular weight of chitosan. OP of films prepared with malic acid was the lowest, followed by acetic, lactic, and citric acid.     

Barrier Properties and Surface Characteristics of Edible, Bilayer Films

Various formulations and methods of fabricating a film consisting of edible hydrocolloids and lipids were investigated. Two formulations consisting of a methylcellulose base layer and a beeswax layer, deposited either from a molten state (Wax-M film) or from an ethanolic solution (Wax-S film), were examined for water vapor permeability (WVP), oxygen permeability and other physical properties. WVP values (g-mil-m^?2-day^?1-mm Hg^?1) for the Wax-M and Wax-S films were 0.5 ± 0.05 and 1.6 ± 0.4, respectively. WVP of the two films did not change significantly after storage for 1 wk at -40°C. Oxygen permeability values (g-cm-cm^?2-sec^?1-mm Hg^?1× 10^?12) for the Wax-M and Wax-S films were 0.021 ± 0.002 and 0.007 ± 0.002, respectively. The Wax-M film had a more uniform surface topography than the Wax-S film.     

Properties of triticale flour protein based films

Triticale flour proteins based films were developed. Solubility in water, water vapor permeability (WVP), and mechanical properties of triticale films are presented. The effects of thermal treatments and glycerol concentration were also evaluated. WVP values were in the range 0.10-4.22 × 10⁻¹⁰ g m⁻¹ s⁻¹ Pa⁻¹. Tensile strength (TS) and percentage of elongation (%E) were in the range 2.9-0.20 MPa and 250-110% respectively. Total soluble matter (TSM), WVP, and %E decreased with the increase in the curing temperature. More plasticized films presented greater TSM, WVP, %E and lower values of TS. At a giving temperature (T) and glycerol concentration, an increase in relative humidity (RH) resulted in higher values of TSM, WVP, %E and lower TS values. It was observed that in films with the same treatments and conditioning, WVP increased with the increase in measurement temperature. Triticale proteins showed suitable film-forming capacity for the formulation of biodegradable films.     

Development and Characterization of Edible Films Based on Mucilage of Opuntia ficus-indica (L.)

Abstract: Mucilage of Opuntia ficus-indica (OFI) was extracted and characterized by its composition and molecular weight distribution. Mucilage film-forming dispersions were prepared under different pHs (3, 4, 5.6, 7, and 8) and calcium concentration (0% and 30% of CaCl₂, with respect to mucilage's weight), and their particle size determined. Mucilage films with and without calcium (MFCa and MF, respectively) were prepared. The effect of calcium and pH on mucilage films was evaluated determining thickness, color, water vapor permeability (WVP), tensile strength (TS), and percentage of elongation (%E). The average molecular weight of the different fractions of mucilage was: 3.4 × 10⁶ (0.73%), 1 × 10⁵ (1.46%), 1.1 × 10³ (45.79%), and 2.4 × 10² Da (52.03%). Aqueous mucilage dispersions with no calcium presented particles with an average size d(0.5) of 15.4 μm, greater than the dispersions with calcium, 13.2 μm. MFCa films showed more thickness (0.13 mm) than the MF films (0.10 mm). The addition of calcium increased the WVP of the films from 109.94 to 130.45 gmm/m²dkPa. Calcium and pH affected the mechanical properties of the films; the largest TS was observed on MF films, whereas the highest %E was observed on MFCa films. The highest differences among MF and MFCa films were observed at pHs 5.6 and 7 for TS and at pHs 4 and 8 for %E. No effect of pH and calcium was observed on luminosity and hue angle. Chroma values were higher for MF when compared with MFCa, and increased as pH of the films increased. Practical Application: In this study mucilage from nopal was extracted and characterized by its ability to form edible films under different pHs, and with or without the addition of calcium. Opuntia ficus-indica mucilage had the ability to form edible films. In general, it can be considered that mucilage films without modification of pH and without the addition of calcium have the best water vapor barrier properties and tensile strength. Mucilage from nopal could represent a good option for the development of edible films in countries where nopal is highly produced at low cost, constituting a processing alternative for nopal.     

Edible Films and Coatings from Soy Protein

A method was developed by which films could be prepared from commercial isolated soy protein (ISP). ISP was treated with alkali (ATISP) to alter film orooerties. Water vapor oermeability (WVP). oxygen‘permeability (O₂P), tensile strength (TS), percent elongatidn (%E), and appearance of ISP and ATISP were compared. Alkali treatment had no effect on WVP. O₂P, and TS, gave hieher %E, and improved film appearance. Films properties were also compared at pH 6, 8, 10, and 12. In general, pH 6 gave higher WVP and O₂P and lower TS and %E; while higher pH gave lower WVP and O₂P and higher TS and %E. ATISP films could not be produced at pH 6. Film appearance generally improved with increased pH.     

Preparation of biopolymer film from chitosan modified with lipid fraction

Films formed from polysaccharides, as chitosan, present a high permeability in water vapour. In order to increase resistance to water vapour for chitosan‐based films, different lipid fractions were incorporated into a filmogenic matrix: fish and vegetable oils, stearic and oleic acids. The chitosan showed a molecular weight of 150 kDa and a deacetylation degree of 86 ± 1%. Results showed that incorporation of different lipid fractions decreased the water vapour permeability (WVP) (1.3–1.8 g mm m^?2 day^?1 kPa^?1) as compared with pure chitosan film (3.8 g mm m^?2 day^?1 kPa^?1). A higher reduction in WVP (65%) was found with the addition of refined fish oil to the continuous matrix of the films than with the addition of refined rice oil, oleic or stearic acid (50–60%). However, pure chitosan films showed better tensile strength (TS = 33 MPa) and elongation percentage (E = 18%) than lipids fraction–chitosan films (7–19 MPa and 7–13%, respectively).     

Whey protein-okra polysaccharide fraction blend edible films: tensile properties, water vapor permeability and oxygen permeability

BACKGROUND: A hot‐buffer‐soluble‐solid fraction (HBSS) and an alkaline‐soluble‐solid fraction (ASS) of okra polysaccharides (OKP) were obtained using sequential extraction. These fractions were combined with whey protein isolate (WPI) and glycerol (Gly) plasticizer to form blend edible films. Effects of OKP fraction and content on tensile properties, water vapor permeability (WVP) and oxygen permeability (OP) were determined. RESULTS: HBSS film had significantly higher percent elongation (%E) and lower elastic modulus (EM), WVP and OP than ASS film. Increasing HBSS or ASS content in blend films with WPI significantly reduced film tensile strength and EM and increased film %E and WVP. OP values for WPI–HBSS blend films were significantly lower than OP for WPI or HBSS film. WPI–HBSS and WPI–ASS blend films had lower WVP and OP than WPI films with equivalent tensile properties. CONCLUSIONS: WPI–HBSS blend films have higher WVP and lower OP than WPI film or HBSS film, indicating unique interactions between WPI and HBSS. Compared to WPI film, WPI–HBSS blend films have improved flexibility, stretchability and oxygen barrier. Different HBSS and ASS compositions and structures are responsible for property differences between HBSS and ASS films and between WPI–HBSS and WPI–ASS blend films. Copyright © 2010 Society of Chemical Industry     

Effects of glycerol,sorbitol, xylitol and fructose plasticisers on mechanical and moisture barrier properties of pullulan–alginate–carboxymethylcellulose blend films

The effects of glycerol, sorbitol, xylitol and fructose plasticisers on water sorption, mechanical properties, water vapour permeability (WVP) and microstructure of pullulan–alginate–carboxymethycellulose (PAC) blend films were investigated. At low plasticiser concentrations (below 7% w/w dry basis), antiplasticisation effect was observed, causing an increase in tensile strength (TS) but a decrease in the equilibrium moisture content. As glycerol concentration increased from 0% to 7%, TS increased from 68.1 to 69.6 MPa, whereas equilibrium moisture contents at 0.84 a_w decreased from 0.37 to 0.3 g H₂O g^?1 dry basis. At higher plasticiser concentrations (14–25% w/w), an opposite trend was observed on the PAC films, resulting in the reduction of TS and elevation of moisture content. Among the four plasticisers tested, the fructose‐plasticised films were the most brittle, showing the highest TS, but had the lowest elongation at break (EAB), WVP and equilibrium moisture content values than films plasticised with other polyols. On the other hand, glycerol resulted in the most flexible film structure, exhibiting opposite materials' properties as compared with the fructose‐plasticised films. For instance, at 25% (w/w) plasticiser concentration, EAB and WVP values of fructose‐plasticised films were 33.5% and 3.48 × 10^?6 g m Pa^?1 h^?1 m^?2, which were significantly lower than that of glycerol‐plasticised films (58.6% and 4.86 × 10^?6 g m Pa^?1 h^?1 m^?2, respectively). Scanning electron microscopy showed that the plasticised PCA films were less homogeneous and more porous than the unplasticised counterparts, indicating that plasticisers had an effect on the microstructural morphology of the film matrix.     

Preparation and characterization of agar/clay nanocomposite films: the effect of clay type

Abstract: Agar‐based nanocomposite films with different types of nanoclays, such as Cloisite Na⁺, Cloisite 30B, and Cloisite 20A, were prepared using a solvent casting method, and their tensile, water vapor barrier, and antimicrobial properties were tested. Tensile strength (TS), elongation at break (E), and water vapor permeability (WVP) of control agar film were 29.7 ± 1.7 MPa, 45.3 ± 9.6%, and (2.22 ± 0.19) × 10^?9 g·m/m²·s·Pa, respectively. All the film properties tested, including transmittance, tensile properties, WVP, and X‐ray diffraction patterns, indicated that Cloisite Na⁺ was the most compatible with agar matrix. TS of the nanocomposite films prepared with 5% Cloisite Na⁺ increased by 18%, while WVP of the nanocomposite films decreased by 24% through nanoclay compounding. Among the agar/clay nanocomposite films tested, only agar/Cloisite 30B nanocomposite film showed a bacteriostatic function against Listeria monocytogenes.     

Peanut Protein Film as Affected by Drying Temperature and pH of Film Forming Solution

Films were made from peanut protein concentrate solution of pH 6.0, 7.5 or 9.0, and dried at 70, 80 or 90°C. Both total solubility and protein solubility of film decreased with increasing temperature but increased with increasing pH. Film color was darker and more yellow when pH increased. Tensile strength (TS) and elongation (E) increased but water vapor permeability (WVP) and oxygen permeability (OP) decreased as temperature increased. At pH 9 and 90°C, film had the lowest WVP and OP, and the highest TS.     

Permeability and Mechanical Properties of Cellulose-Based Edible Films

Factors affecting barrier properties [oxygen permeability (OP) and water vapor permeability (WVP)] and mechanical properties [tensile strength (TS) and elongation (E)] were investigated for methyl cellulose (MC) and hydroxypropyl cellulose (HPC) films. OP, WVP and TS of MC and HPC films increased as the molecular weight (MW) of the cellulose increased. E of MC films increased as MW increased, but E of HPC films was highest for the intermediate MW of 370,000. OP, WVP and TS of MC films were not a function of thickness, but E slowly increased as film thickness increased. OP and WVP of HPC films were not relatable to film thickness, but TS and E of HPC films slowly increased as film thickness increased. TS decreased and E increased for both film types as concentration of plasticizers was increased. Plasticizers enhanced or retarded OP and WVP of cellulose-based films, depending on their concentrations.     

Properties of Chitosan Films as a Function of pH and Solvent Type

ABSTRACT: Two different deacetylated chitosans were dissolved in formic, acetic, lactic, or propionic acid to prepare chitosan films. The pH values of the film-forming solutions were adjusted to 3, 4, and 5. Water vapor permeability (WVP), tensile strength (TS), elongation (E), and total soluble matter (TSM) were significantly ( P < 0.05) affected by acid type, pH, and degree of deacetylation (DA). Low DA (LDA) chitosan films had lower WVP and TSM, higher TS compared with high DA (HDA) chitosan films. The E values were not affected by DA. As pH increased, WVP and TSM of chitosan films tended to increase while TS decreased significantly ( P < 0.05). Chitosan films with acetic and propionic acid solvents had low WVP and TSM and high TS, while films with lactic acid solvent had high E and TSM and the lowest TS. Fourier-transform infrared showed peak shifting in the spectra with different solvents and at different pH values. Chitosan films with lactic acid solvent showed a peak shift to a lower frequency range. The NH₃⁺ band was absent in the pH 5.0 chitosan film spectra.     

Mechanical and Barrier Properties of Lactic Acid and Rennet Precipitated Casein-Based Edible Films

Tensile strength (TS), percent elongation (%E), oxygen permeability (OP), and water vapor permeability (WVP) of lactic acid and rennet precipitated casein-based edible films were studied to determine the effect of protein to plasticizer ratio (0.6:1, 1:1, 1.4:1) and plasticizer type (sorbitol, glycerol) on these properties. TS increased (p<0.05) with increase in protein to plasticizer ratio. Sorbitol plasticized films were stronger (p<0.05) than glycerol plasticized films. However, films plasticized with glycerol were more extensible (p<0.05). Film %E decreased with increase in protein/plasticizer ratio for lactic acid casein films, whereas it increased for rennet casein films. Films plasticized with sorbitol were more effective (p<0.05) moisture and oxygen barriers than glycerol plasticized films. Overall, lactic acid casein films plasticized with sorbitol had the most effective mechanical and barrier properties.     

Physicochemical Changes in Potato Granules During Storage

Physicochemical properties of freeze-thaw (F-T) and add-back (A-B) potato granules, such as swelling power (SP), water-holding capacity (WHC), degree of starch retrogradation, moisture change, and rate of rehydration were monitored over about 100 wk of storage. SP of both types of granules decreased to minima after 40 wk then increased on further storage, while WHC showed an opposite trend, reaching maxima after 52 wk. Degree of starch retrogradation in the granules increased to maxima after 40 wk then declined. Moisture content of the granules also increased slightly during the first 33 wk then decreased on further storage. These changes caused the reduction in the rehydration rate of the granules from 8.3 × 10^?2 see^?1 to 5.5 × 10^?2 set^?1 (F-T) and 5.2 × 10^?2 sec^?1 (A-B) after 36 wk of storage, after which the rate again increased. Addition of Ca⁺⁺ to the granules during precooking and cooling steps of the process appeared to cause similar changes.     

紫外辐照对蜂胶/纳米SiO2复合膜性能的影响

本文以拉伸强度(TS)、断裂伸长率(E)、透光率(T)、溶解度(S)、水蒸气透过性(WVP)和氧气透过性(OP)等为品质指标,研究了紫外辐照对蜂胶/纳米SiO2复合膜品质的影响。研究显示:随着辐照时间的延长,复合膜的TS和S先升高后降低、E和OP先降低后升高、T和WVP先降低后逐渐趋于不变,且紫外处理12 h复合膜的TS达到了最大值,较对照组提高了3.07 MPa,当辐照时间达到16 h时,S达到最大值,较对照组提高了5.68%,E、T、WVP和OP均在16 h时达到最小值,分别较对照组分别降低了2.88%、4.33%、2.13 g/(cm·s·Pa)和0.5 cm3/(m2·24 h·0.1 MPa)。通过主成分聚类分析法对试验结果进行多指标分析,结果显示,当辐照时间为16 h时,复合膜的综合得分最高,即此时复合膜的综合性能最好,这与单因素实验结果一致,因此,可以利用主成分聚类分析确定紫外辐照改性蜂胶/纳米SiO2复合膜的最佳处理时间。     

Effects of Interactions between the Constituents of Chitosan-Edible Films on Their Physical Properties

The main objective of this work was to evaluate the effect of chitosan and plasticizer concentrations and oil presence on the physical and mechanical properties of edible films. The effect of the film constituents and their in-between interactions were studied through the evaluation of permeability, opacity and mechanical properties. The effects of the studied variables (concentrations of chitosan, plasticizer and oil) were analysed according to a 2³ factorial design. Pareto charts were used to identify the most significant factors in the studied properties (water vapour, oxygen and carbon dioxide permeability; opacity; tensile strength; elongation at break and Young’s modulus). When addressing the influence of the interactions between the films’ constituents on the properties above, results show that chitosan and plasticizer concentrations are the most significant factors affecting most of the studied properties, while oil incorporation has shown to be of a great importance in the particular case of transport properties (gas permeability), essentially due to its hydrophobicity. Water vapour permeability values (ranging from 1.62?×?10^?11 to 4.24?×?10^?11 g m^?1 s^?1 Pa^?1) were half of those reported for cellophane films. Also the mechanical properties (tensile strength values from 0.43 to 13.72 MPa and elongation-at-break values from 58.62% to 166.70%) were in the range of those reported for LDPE and HDPE. Based on these results, we recommend the use of 1.5% (w/w) chitosan concentration to produce films, where the oil and plasticizer proportions will have to be adjusted in a case-by-case basis according to the use intended for the material. This work provides a useful guide to the formulation of chitosan-based film-forming solutions for food packaging applications.     

Effect of pH and addition of corn oil on the properties of whey protein isolate-based films using response surface methodology

Response surface methodology (RSM) was used to investigate pH and corn oil (CO) effects on the properties of films formed from whey protein isolate (WPI). Test films were evaluated for tensile strength (TS), puncture strength (PT), percentage elongation at break point (E), water vapour permeability (WVP) and oxygen permeability (OP). TS of WPI films increased with increasing pH, while addition of CO produced no trend. However, when WPI solution pH increased >10.0, film TS generally decreased with CO addition (>11%). E values increased dramatically with increasing levels of CO when pH for WPI solutions were >8.5. However, pH had no effect on E values. WPI solutions possessing high pH values (maximum pH value of 10.62) produced WPI films with the highest PT values. WVP had a quadratic relationship with pH and CO addition. OP had an inversely linear relationship with increasing pH (6.5–10.5) and a quadratic relationship with CO addition. Optimal pH (9.88) and CO level (2.93%), determined from physical test film data, were predicted by RSM.     

Effects of nano‐clay type and content on the physical properties of sesame seed meal protein composite films

Sesame seed meal protein (SSMP)/nano‐clay composite films were prepared, and the physical properties of the films were determined. The SSMP film was prepared with 5 g of SSMP and 2 g of glycerol in 100 mL of film‐forming solution, and the tensile strength (TS), elongation (E) and water vapour permeability (WVP) of the SSMP film were 2.51 MP, 21.84% and 3.23 × 10^?9 g m m^?2s^?1 Pa^?1, respectively. Two types of nano‐clays were incorporated to enhance the physical properties of the SSMP film. The TSs of the SSMP film with 5% Cloisite Na⁺ and 7% Cloisite 10A were 6.32 and 5.76 MPa, respectively, and the WVPs of the SSMP nanocomposite films were 2.04 × 10^?9 g m m^?2s^?1 Pa^?1 compared with the SSMP film without nano‐clay, which was 3.23 × 10^?9 g m m^?2s^?1 Pa^?1. Therefore, these results indicate that the SSMP nanocomposite film can be applied in food packaging.     

Storability of Antimicrobial Chitosan-Lysozyme Composite Coating and Film-Forming Solutions

ABSTRACT:  Chitosan-lysozyme (CL) film and coating solutions were prepared aseptically by incorporating 60% lysozyme (w/w chitosan) into 3% chitosan solution. The solutions were stored at 10, 21, and 37 °C up to 6 mo for monthly evaluation of physicochemical and antimicrobial properties. Solutions were made into films at each sampling time to investigate lysozyme release, water solubility, water vapor permeability (WVP), tensile strength (TS), and elongation (EL) of the films. During the 6-mo storage, the pH and translucency of CL solutions did not change ( P > 0.05) and microorganisms were not detected with total aerobic count media. CL solutions became darker, with a more saturated yellow hue developing with increased storage time and temperature. Storage enhanced the antimicrobial activities of the solutions against E. coli and L. monocytogenes , and films made of solutions stored at 37 °C exhibited higher antimicrobial activities against these 2 pathogens than those stored at 10 and 21 °C. Increased water solubility and lysozyme release and decreased TS and EL were observed in films made from solutions stored at 37 °C. WVP was not significantly affected by storage temperature and time. These changes might be attributed to increased chitosan degradation by lysozyme hydrolysis at a higher storage temperature and longer storage time. Results indicated that with storage at 10 to 20 °C, premade CL solutions are stable and may be distributed as a commercial product for coating or film applications or both in different foods for at least 6 mo.