Mechanical and Barrier Properties of Edible Chitosan Films as affected by Composition and Storage

Oxygen permeability coefficients (OP), water vapor permeability coefficients (WVP), ethylene permeability coefficients (EP), tensile strength (TS) and percent elongation (%E) at break values were determined for chitosan films plasticized with glycerin at two concentrations (0.25 and 0.50 mL/g chitosan). Film samples were tested after 0, 2, 4, 8 and 12 wk of storage. After an initial drop in permeability during the first 2 wk of storage, mean OP (4.6 × 10^?5 cc/m-day-atm) and mean EP (2.3 × 10^?4 cc./m.day.atm) remained constant while mean WVP (2.2 × 10^?1 g/m-day-atm) decreased with respect to storage time. TS values (15–30 MPa) decreased and %E values (25%–45%) increased with respect to storage time. The stability of OP and EP values with storage was not expected, while the change in mechanical properties was as expected.     

Development of Soybean Protein-Isolate Edible Films Incorporated with Beeswax,Span 20, and Glycerol

Abstract: The effect of the beeswax, Span 20, and glycerol content on qualities of soybean-protein-isolate edible films was evaluated. Beeswax and Span 20 were selected to improve qualities of soybean-protein-isolate films from 11 emulsifiers. The content of beeswax, Span 20, and glycerol was further optimized by response surface analysis. The optimal composite emulsifier was beeswax (1.87% of soybean protein-isolate), Span 20 (10.25% of soybean protein-isolate), and glycerol (29.12% of soybean protein-isolate) with tensile strength of 908 MPa, percentage elongation at break of 25.8%, water vapor permeability of 19.2 g/m·d·MPa, and oxygen permeability of 0 cm³/m·d·MPa. The quality of soybean-protein-isolate films incorporated with the optimal composite emulsifier was 2.34 times higher than that of the control. Furthermore, the disulfide bond content of soybean-protein-isolate films showed a positive correlation with their quality, which provided a simple and rapid way to rank quality of soybean-protein-isolate films. Therefore, our result will not only give an instruction to soybean-protein-isolate-film production, but also give a simple and rapid way to rank film qualities. Practical Application: Our results give the optimal composite emulsifiers for the soybean-protein-isolate-film production. The soybean-protein-isolate films based on the optimal composite emulsifiers show their tensile strength of 908 MPa, percentage elongation at break of 25.8%, water vapor permeability of 19.2 g/m·d·MPa, and oxygen permeability of 0 cm³/m·d·MPa, being stronger than the control. Moreover, our results give a simple and rapid way to rank film qualities, because the disulfide bond content of soybean-protein-isolate films showed a positive correlation with their quality. Hence, the disulfide bond content was an indicator to rank qualities of soybean-protein-isolate films.     

Modified Atmosphere Packaging of Fresh, "Ready-to-use" Grated Carrots in Polymeric Films

“Ready-to-use” grated carrots were packaged in different films (oxygen permeability from 950 to 22,000 cc/m²/day/atm at 25°C) and stored at 2, 6 or 10°C for 10 days. Gaseous atmosphere in packs and the following were monitored: lactic acid bacteria, yeast counts, exudate and potassium ion released, sugars, carotene, ethanol and lactic acid. The respiration rate of the packaged carrots was measured. Films with very low oxygen permeability resulted in anaerobic respiration, high leakage of potassium, and high lactic acid bacteria. With high-permeability films (between 10,000 and 20,000 cc/m²/day/atm at 25°C), grated carrots showed aerobic respiration and retained good quality. At 10°C, in carrots packed in the most permeable film, sucrose decreased markedly during storage. The gas permeabilities required for packaging grated carrots were evaluated in relation to storage temperature.     

Development and Characterization of Biodegradable/Edible Wheat Protein Films

Biodegradable and edible films were prepared from three types of wheat flours: commercial bread, hard red winter, and soft white. Films were produced at two pH values (4 and 11) and tested for oxygen permeability as related to temperature. Films were also produced with a cross-linked agent and tested for tensile strengths. Oxygen permeability was 5.9 × 10^?20 to 18.5 × 10^?20 m³O₂ m m^?2 s^?1 Pa^?1 similar to values for commercial nylon. The oxygen permeability activation energy varied from 9.1 to 14.5 kcal mol^?1, depending on type of flour and pH did not affect oxygen permeability. Presence of the cross-linking agent increased the strength of films and elongation at break ranged from 490% to 640%, while tensile stress at break ranged from 25.8 × 10^?3 kg m^?2 to 44.1 × 10^?3 kg m^?2, lower than commercial nylon.     

Biodegradable Poly(butylene adipate-co-terephthalate) Films Incorporated with Nisin: Characterization and Effectiveness against Listeria innocua

ABSTRACT: Biodegradable poly(butylene adipate-co-terephthalate) (PBAT) films incorporated with nisin were prepared with concentrations of 0, 1000, 3000, and 5000 international units per cm² (IU/cm²). All the films with nisin inhibited Listeria innocua, and generated inhibition zones with diameters ranging from 14 to 17 mm. The water vapor permeability and oxygen permeability after the addition of nisin ranged from 3.05 to 3.61 × 10¹¹ g m m⁻² s⁻¹ Pa⁻¹ and from 4.80 × 10⁷ to 11.26 × 10⁷ mL·m·m⁻²·d⁻¹·Pa⁻¹, respectively. The elongation at break (ɛ_b) was not altered by the incorporation of nisin (P > 0.05). Significant effect was found for the elastic modulus (E) and the tensile strength (σ_s) (P < 0.05). The glass transition and melting temperatures with the presence of nisin ranged from −36.3 to −36.6 °C and from 122.5 to 124.2 °C, respectively. The thermal transition parameters such as the crystallization and melting enthalpies and crystallization temperature were influenced significantly (P < 0.05) by incorporation of nisin into films. The X-ray diffraction patterns exhibited decreasing levels of intensity (counts) as the concentration of nisin increased in a range of 2θ from 8° to 35°. Formation of holes and pores was observed from the environmental scanning electron microscopy images in the films containing nisin, suggesting interaction between PBAT and nisin.     

Preparation and Characterization of an Olive Flounder (Paralichthys olivaceus) Skin Gelatin and Polylactic Acid Bilayer Film

Olive flounder skin gelatin (OSG) was used as a film base material. A bilayer film of OSG and polylactic acid (PLA) was prepared using solvent casting method to enhance the film properties. Physical properties of the OSG–PLA film were increased compared with the nonaugmented OSG film. In particular, the PLA lamination decreased water vapor permeability from 2.17 to 0.92 × 10^?9 g·m/m²·s·Pa, as well as of the water solubility from 16.62% to 9.27%, in the bilayer film relative to the OSG film. The oxygen permeability of the OSG–PLA bilayer film was held low by the OSG film, compensating for the high oxygen permeability of the PLA layer. Therefore, the OSG–PLA bilayer film with its enhanced physical properties and high water and oxygen barrier properties can be applied as a food packaging material.     

Sodium Chloride Diffusion in Low‐Acid Foods during Thermal Processing and Storage

This study aimed at modeling sodium chloride (NaCl) diffusion in foods during thermal processing using analytical and numerical solutions and at investigating the changes in NaCl concentrations during storage after processing. Potato, radish, and salmon samples in 1% or 3% NaCl solutions were heated at 90, 105, or 121 °C for 5 to 240 min to simulate pasteurization and sterilization. Selected samples were stored at 4 or 22 °C for up to 28 d. Radish had the largest equilibrium NaCl concentrations and equilibrium distribution coefficients, but smallest effective diffusion coefficients, indicating that a greater amount of NaCl diffused into the radish at a slower rate. Effective diffusion coefficients determined using the analytical solution ranged from 0.2 × 10^–8 to 2.6 × 10^?8 m²/s. Numerical and analytical solutions showed good agreement with experimental data, with average coefficients of determination for samples in 1% NaCl at 121 °C of 0.98 and 0.95, respectively. During storage, food samples equilibrated to a similar NaCl concentration regardless of the thermal processing severity. The results suggest that sensory evaluation of multiphase (solid and liquid) products should occur at least 14 d after processing to allow enough time for the salt to equilibrate within the product.     

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.     

Assessment of Different Packaging Structures in the Stability of Frozen Fresh Brazilian Toscana Sausage

The aim of this work was to evaluate the effect of different package conditions on the characteristics of Toscana fresh sausage stored for 150?days under freezing. The analyses of lipid oxidation, moisture, pH, acidity, water activity, and counting of psychotrophic microorganisms were carried out along with the storage time for each package (low-density polyethylene with and without vacuum and oxygen permeability of 500?cm³ O₂/m² day atm at 23 ??C; nylon polyester with and without vacuum and permeability of 100?cm³ O₂/m² day atm at 23 ??C; and formal copolymer of ethylene and vinyl alcohol with and without vacuum and oxygen permeability of 5?cm³ O₂/m² day atm at 23 ??C). Results showed that from 60?days of storage, the samples stored using polyethylene without vacuum and nylon 100?cm³ O₂/m² day atm, without vacuum, presented a slight rancidity flavor, statistically different (p?<?0.05) from the other tested ones. After 151?days of storage, a relationship between 2-thiobarbituric acid reactive substances analysis and sensory characteristics could be observed. In this case, the packages without application of vacuum presented higher values in the sensory and oxidative rancidity analyses, configuring flavor of slight to moderate rancidity.     

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.     

The effects of the rate of addition of formic acid and sulphuric acid on the ensilage of perennial ryegrass in laboratory silos

Perennial ryegrass was ensiled in laboratory silos after addition of formic acid (850 g kg^?1) or sulphuric acid (906 g kg^?1) at rates of 0, 2, 4 and 6 litres t^?1 fresh grass. Silos were opened after 6, 18 and 90 days and the silage subjected to chemical and microbiological analysis. The untreated control was poorly fermented with a final pH of 4.7, a butyric acid concentration of 19 g kg^?1 dry matter (DM) and an NH₃-N content of 275 g kg^?1 total nitrogen (TN). For the formic acid treatments the 2 litre t^?1 and 6 litre t^?1 levels both produced well-preserved silages but they were of different types. The silage treated with 2 litre t^?1 had a pH of 4.0, a lactic acid concentration of 92 g kg^?1 DM and 161 g NH₃-N kg^?1 TN, whereas with the 6 litre t^?1 treatment, fermentation had been severely restricted. The pH was 4.2, the lactic acid concentration was only 8 g kg^?1 DM and the NH₃-N content was 80 g kg^?1 TN. However, formic acid at 4 litre t^?1 produced a badly fermented silage of final pH 5.0 with lactic acid and butyric acid concentrations of 16 and 15 g kg^?1 DM, respectively, and an NH₃-N content of 149 g kg^?1 TN. Sulphuric acid at 2 and 4 litres t^?1 produced silages of low lactic acid contents, 36 and 24 g kg^?1 DM, and they also contained butyric acid in concentrations of 13 and 11 g kg^?1 DM; respective NH₃-N contents were 206 and 114 g kg^?1 DM. When sulphuric acid was added at 6 litres t^?1, despite a reduction in the pH of the grass to 3.5, fermentation was not restricted as it was with the equivalent level of formic acid. Lactic acid was present at 27 g kg^?1 DM and the ethanol concentration was very high at 66 g kg^?1 DM; the sulphuric acid-treated silages were characterised by high yeast counts. At the higher rates of addition, formic acid reduced the.     

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.     

Preparation and characterization of kafirin‐quercetin film for packaging cod during cold storage

This study mainly evaluated the physical properties of kafirin‐quercetin (KQ) edible films and their application on the quality of cod fillets during cold storage. The results showed that the addition of quercetin significantly increased mechanical properties of KQ films, while decreased water vapor permeability, water solubility, and transparency. As quercetin was 0.4% (wt/vol), the film had the highest tensile strength (4.96 ± 1.23 MPa), the lowest water vapor permeability (1.08 ± 0.09 g·mm·m^?2·h·KPa^?1) and water solubility (22.02 ± 0.45%). Moreover, compared with the pure kafirin and polythylene films, KQ films could effectively inhibit the cod meat deterioration by restraining the growth of microorganisms and decreasing TVB‐N and TBARs. The KQ_0.4% film was the best to prolong the shelf life of cod fillets during cold storage. Therefore, KQ edible films could be used as a potential food packaging material to protect and retain the quality of aquatic products.     

Effect of storage time and temperature on structure,mechanical and barrier properties of chitosan-based films

The mechanical (tensile strength, elongation at break, mechanical work of deformation) and barrier (water vapor permeability and water vapor uptake) properties of chitosan films produced with acetic and lactic acids have been studied as a function of storage time, molecular weight of chitosans, concentration of plasticiser and the storage temperature. It was demonstrated that mechanical properties of chitosan-based films can be improved to a great extent during storage at low temperatures in freezer and refrigerator. Transition of chitosan molecules during storage in the solid state to more extended conformations and free volume changes are considered as mechanisms for the improvement of mechanical and barrier properties of chitosan films. The best mechanical properties are achieved for chitosan films produced with acetic acid and plasticized by the addition of 20% of glycerol. Sharp decrease in water vapor permeability has been demonstrated for thinner chitosan films and related to more dense packing and orientation of linear chitosan macromolecules.     

Hardaliye: fermented grape juice as a traditional Turkish beverage

Twenty-six aged hardaliye samples, collected from different spots of the Kirklareli province of Turkey and hardaliye produced in laboratory conditions using the traditional method were investigated in this study. The pH ranged from 3·21 to 3·97. Red colour (Hunter Lab a_Lvalue) of samples ranged from 1·33 to 9·66. The total bacterial count ranged from 3·5×10²to 8×10⁵cfu ml⁻¹. The lactic acid bacteria counts of the samples were found to be between 1·0×10²and 4·0×10⁴cfu ml⁻¹. Yeasts and moulds, which were found in 21 samples out of 26, ranged from 1·0×10²to 8·1×10⁴cfu ml⁻¹. Coliforms and Escherichia coli were found in none of the samples. The changes of some microbiological and chemical properties of hardaliye during fermentation were investigated. The pH of hardaliye dropped from 3·86 to 3·39. The ethanol content of the end product was determined as 595·50 mg dl⁻¹. During the fermentation process, the total bacteria count, lactic acid bacteria count and yeast count changed from 2·1×10⁵, 6·0×10⁴and 1·2×10⁵cfu ml⁻¹to 1·3×10², 1·2×10³and 1·1×10³cfu ml⁻¹, respectively.Lactobacilli isolated from hardaliye samples were characterized by API 50 CH and other phenotypic criteria. A succession of Lactobacillus species, dominated by L. paracasei subsp. paracasei and L. casei subsp. pseudoplantarum were found during the fermentation process.     

Characterization of red ginseng residue protein films incorporated with hibiscus extract

An edible film was prepared from red ginseng residue protein (RGRP) and incorporated with hibiscus extract (HE). RGRP was extracted from red ginseng residue, which is an inexpensive by-product of the red ginseng processing industry. Different concentrations of HE were added to an RGRP film-forming solution as a natural antioxidant. The prepared RGRP films without HE had a tensile strength of 16.9 MPa and an elongation at break of 25.1%. The antioxidant activity of the RGRP film increased with increasing concentration of HE. In addition, the RGRP film with 1% HE exhibited the lowest value of water vapor permeability (1.88×10^?9 g·m/m²·s·Pa), which indicates that the film has high water barrier property. The results present the production of edible films from discarded red ginseng residue, and the antioxidant activity of RGRP films as a packaging material can prevent lipid oxidation and quality loss of food products.     

Usage of Capillary Isotachophoresis and Antioxidant Capacity Measurement in Analysis of Changes in Coffee Properties After Roasting,Steaming and Decaffeination

The aim of the study was to optimise and validate the method for quantitation of short-chained organic acids in coffee brews by capillary isotachophoresis (ITP). The linearity of the method was satisfactory with R ² from 0.9924 for lactic acid to 0.9998 for acetic acid. The limit of detection (LOD) was from 4.9 μmol L^?1 for acetic acid to 24.8 μmol L^?1 for lactic acid. Precision of the method was from 0.20 to 2.69 %. This method was successfully applied to determine six organic acids (tartaric, formic, citric, malic, lactic and quinic) in Arabica and Robusta green and roasted coffee brews. The roasting as well as steaming and decaffeination processes of beans influenced degradation of acids (citric and malic) and their formation (quinic, tartaric, lactic and formic) in coffee brews. The influence of coffee processing on the antioxidant capacity of coffee brews was also tested by using the 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), Folin-Ciocalteu and chelating Fe(II) assays. The roasted coffee brews possessed higher antioxidant capacity than unprocessed coffee brews, excluding chelating activity.     

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.     

Organic acids as browning inhibitors on harvested “Baby” lettuce and endive

The effects of different organic acid solutions on enzymatic browning of “Baby” lettuce and “Geante Maraichiere” endive were assayed by quantitative measurement of colour changes. Acetic, formic, propionic, malonic, oxalic and lactic acid solutions (10 g l^–1) were the most effective at preventing discoloration in stem discs taken from the vegetables. Among the above treatments, acetic, propionic, malonic and oxalic acid solutions (50 g l^–1) were selected and applied with the help of cotton wool to the butt end of lettuce and endive heads. The browning process was evaluated during 7 days of storage at 2°C, plus an additional commercial handling period of 2 days at 13°C. Acetic and propionic acid treatments were the most effective at reducing lettuce-butt discoloration during storage and commercial handling. In general, treatments with organic acid solutions were less effective on endive than on lettuce.     

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.