Physical Properties of Gelatin Films Plasticized by Blends of Glycerol and Sorbitol

ABSTRACT: The addition of plasticizers increases the flexibility and workability of films based on biopolymers. However, the use of some plasticizers cause undesirable results, such as the migration of these additives out the film or crystallization during shelf life. Thus, the aim of this study was to evaluate the effect of blends with different ratios of sorbitol and glycerol, at 2 plasticizer concentrations, on mechanical, viscoelastic, and water vapor barrier properties of films based on gelatin. The films were prepared with 2 g gelatin/100 mL of water and with 25 or 55 g plasticizer/100 g gelatin. The ratio, glycerol to sorbitol, was studied as 0:100, 20:80, 40:60, 60:40, 80:20, and 100:0. The increase of plasticizer concentration from 25 to 55 g plasticizer/100 g gelatin caused an increase of flexibility and reduction of resistance and water vapor barrier as expected. In relation to the effect of the mixture, the increase in the proportion of glycerol caused a reduction of the puncture force, tensile strength, modulus of elasticity, and an increase of the puncture deformation, elongation at break, and water vapor permeability due to the higher plasticizing effect of glycerol. This behavior was explained in terms of molecular weight of the plasticizers, which demonstrated that the studied properties could be considered as functions of the number of molecules of plasticizers in the films.     

Lipid Addition to Improve Barrier Properties of Edible Starch-based Films and Coatings

ABSTRACT: Effects of formulation (lipid presence, type of starch, and plasticizer) on microstructure, water vapor (WVP) and gas (GP) permeabilities of films and coatings were analyzed. Plasticizer was necessary to maintain film and coating integrity and to avoid pores and cracks. Films made from high amylose starch showed lower WVP and GP than regular corn starch films; permeabilities of films with sorbitol (20 g/L) were lower than those with glycerol. The addition of 2g/L sunflower oil to the formulations decreased WVP of starch-based films; X-ray diffraction and Differential Scanning Calorimetry experiments demonstrated that films with plasticizer and lipid showed lower crystalline-amorphous ratio compared to films without additives. Microstructural observations helped explain the decrease of the film permeabilities during storage.     

Edible Packaging Films Based on Fish Myofibrillar Proteins: Formulation and Functional Properties

Biopackaging materials based on fish myofibrillar proteins have been developed. The effects of protein concentration, pH, temperature and storage time before casting on the apparent viscosity of the film forming solution (FFS) were evaluated using experimental design methodology. The first objective was to determine a feasible experimental range for film-forming. The pH and protein concentration had strong interactive effects on FFS viscosity. During FFS storage before casting, partial degradation of high molecular weight protein components led to decreased viscosity, allowing thin layer casting. In the experimental range for film-forming, none of the conditions affected film functional properties. Standard conditions were determined at: pH 3.0, 2.0g protein/100g FFS, 25°C and 6 hr storage. The functional properties of the standard biopackaging were slightly better than those that determined for known protein-based films, with tensile strength close to those of low density polyethylene films.     

Development and Characterization of Edible Films from Cranberry Pomace Extracts

The feasibility of using cranberry pomace extract as a new film‐forming material was studied. Cranberry pomaces were extracted using hot water. Low methoxyl pectin (LMP) or high methoxyl pectin (HMP) at a concentration of 0.50% or 0.75% (w/w) and 0.25% (w/w) sorbitol or glycerol was incorporated into film‐forming solutions (FFSs) for improving film functionality. Proximate compositions of cranberry pomace and its extract were determined. The pH and total soluble solid content (SSC) of FFSs, physical and mechanical properties, water vapor permeability, and microstructure of dried films were analyzed. About 1.4% (w/w) of solids was obtained from cranberry pomace water extracts, of which about 93% was carbohydrate. Dried films had bright red color and strong cranberry flavor. Films plasticized with sorbitol were denser in matrix structure and had higher color intensity than those of glycerol plasticized films. In general, LMP and sorbitol incorporated films had higher tensile strength and lower elongation at break and lower water vapor permeability than other films. The higher (0.75%) pectin concentration resulted in increased tensile strength, but decreased elongation at break. Scanning electron microscopy images revealed that sorbitol added films had more regular and compact cross‐section structure than those of glycerol added films. This study demonstrated that it is feasible to create natural colorful and fruit flavor edible films from fruit pomace water extracts. Depending on specific applications of the films, targeted film functionality can be achieved by incorporating proper pectin type and concentration and plasticizer into pomace extracts.     

壳聚糖明胶可食用复合膜的制备与抗菌性能研究

以壳聚糖和明胶为复合膜骨架材料,通过加入0.3%(体积比)甘油增塑剂,制备具有显著抗菌性能的可食用复合膜。以较高的抗拉强度、较大的断裂伸长率、较低的水蒸气透过系数为主要性能指标,对成膜骨架材料壳聚糖和明胶的配比进行优化。研究结果表明,当壳聚糖浓度为1.5%、明胶浓度为1.25%时,以6∶4的体积比混合,制备获得机械性能良好(抗拉强度为13.24 MPa,断裂伸长率为112.45%),水蒸气透过系数较低(0.4032 mg·mm·kPa-1·h-1·m-2)的最优化复合膜。通过红外光谱、X射线衍射、扫描电镜等手段对复合膜进行表征。结果表明,与壳聚糖膜和明胶膜相比,复合膜的内部分子之间有较强的氢键和分子间作用力,膜内部致密且水蒸气不易通过,同时复合膜液对大肠杆菌、金黄色葡萄球菌和枯草芽孢杆菌均具有显著的抑制效果。     

Properties of Edible Films from Total Milk Protein

The mechanical properties and water vapor permeability of edible films made from various total milk proteins (TMPs) were investigated. Two TMPs obtained from nonfat dry milk (NDM) by removing lactose and three TMPs obtained from a commercial source were studied. Lactose was extracted from NDM by ultrafiltration or suspension in ethanol followed by filtration. TMP concentrate obtained by ultrafiltration (UF) produced films with the lowest water vapor permeability (WVP) and the highest tensile strength at break. Commercial TMP concentrates produced films more ductile than those from the UF-TMP or retentate from ethanol extraction. Further research is needed to improve mechanical properties of UF-TMP films without increasing the WVP.     

Physicochemical,Water Vapor Barrier and Mechanical Properties of Corn Starch and Chitosan Composite Films

Biodegradable flexible films were developed from corn starch (CS) and chitosan (CH); their microstructure, mechanical and barrier properties were evaluated. Chitosan and starch blend filmogenic suspensions showed a pseudoplastic behavior, similar to that of chitosan solutions. Smooth surfaces, homogeneous and compact film structures were observed from microstructure studies using scanning electron microscopy (SEM). The addition of glycerol reduced film opacity and increased film solubility of both CS and composite CS‐CH films. Water vapor permeability values of composite CS‐CH films plasticized with glycerol ranged between 3.76 and 4.54× 10⁻¹¹ g s⁻¹ m⁻¹ Pa⁻¹, lower than those of the single component films. CS‐CH films were resistant and their flexibility increased with glycerol addition. Tensile strength values of CS‐CH films were comparable to those of low‐density and high‐density polyethylenes but lower than that obtained for cellophane, however, composite biodegradable films showed lower elongation at break values than the synthetic commercial ones. In conclusion, CS‐CH films can be described as biofilms with a homogeneous matrix, stable structure and interesting water barrier and mechanical properties, with great possibilities of utilization, and with the advantage of biodegradability.     

热处理温度对明胶-魔芋粉复合膜性质的影响

为考察热处理温度对明胶-魔芋粉复合膜理化性质的影响,测定和比较了复合膜的溶解性、接触角、微观结构和热稳定性等指标。结果发现,未经热处理的复合膜在30?℃温水中的膜溶解率（film solubility,FS）和蛋白溶解率（protein solubility,PS）分别为45.62%和28.83%,而在90?℃热水中分别为74.32%和71.44%。当复合膜经热处理后,膜的FS和PS随着热处理温度的升高逐渐下降。30?℃温水中溶出的α和β链蛋白条带浓度随热处理温度升高逐渐降低,而90?℃热水中溶出的蛋白受热处理温度影响不明显。复合膜明胶侧的接触角为107.14°,而魔芋粉侧的接触角为88.53°,经过热处理后均出现上升的趋势。伴随热处理温度的升高,膜的水蒸气透过率出现一定程度的下降,而b*值和透明度均出现上升的趋势。根据扫描电子显微镜分析和差示扫描量热法检测的结果,可以发现随热处理温度的升高,复合膜的明胶层和魔芋粉层逐渐融合在一起,而且膜的热稳定性逐渐上升。以上结果表明,提高热处理温度可以改善明胶-魔芋粉复合膜的耐水性、表面疏水性、阻水性和热稳定性。     

Plasticized Whey Protein Edible Films: Water Vapor Permeability Properties

Heat treatment, protein concentration, and pH effects on water vapor permeability (WVP) of plasticized whey protein films were examined. The best film formation conditions were neutral pH, aqueous 10% (w/w) protein solutions heated for 30 min at 90°. Isoelectric point adjustment of whey protein with calcium ascorbate buffer increased WVP with increasing buffer concentration, The importance of vacuum application to minimize film pore size was identified using scanning electron microscopy. Polyethylene glycol, glycerol and sorbitol plasticizer concentration affected film WVP. Determining the effects of relative humidity on WVP for plasticized whey protein films enabled prediction of film behavior under any water vapor partial pressure gradient.     

食品胶对甘薯淀粉膜性能的响应面法优化实验

以机械性能(抗张强度、断裂拉伸应变)和透湿性为指标,研究食品胶对甘薯淀粉膜性能的优化。结果表明：羟丙基羧甲基纤维素(HPCMC)添加量为3.5～4.0g/100g 淀粉、甘油添加量小于2.0g/100g 淀粉及黄原胶添加量小于2.0g/100g 淀粉时,膜的机械性能较好;HPCMC 添加量小于2.0g/100g 淀粉、甘油添加量大于4.0g/100g 淀粉和黄原胶添加量小于1.5g/100g 淀粉时,膜的透湿性较小。由于不同性能的优化值范围不完全相同,在实际应用中可根据对不同性能的要求进行选择。     

Mechanical and Barrier Properties of Egg Albumen Films

Films were cast and dried from heated, alkaline aqueous egg albumen solutions containing glycerin (GLY) at 30, 40, or 50% w/w of protein, polyethylene glycol (PEG) at 50 or 60%, or sorbitol (S) at 50 or 60% as plasticizers. PEG-plasticized (60%) films also were prepared by substituting 10, 30, 50, or 70% of albumen with yolk solids. Film tensile strength (TS), elongation at break (E), water vapor permeability (WVP), and Hunter color values were measured. At a plasticizer content of 50%, films with S had the lowest WVP while films with PEG had the greatest E. S- and PEG-plasticized films had greater TS than GLY-plasticized films. Yolk solids decreased film TS, E, and WVP while increasing film yellowness.     

纤维素纳米晶体/聚苯乙烯复合薄膜的制备及性能研究

通过Pickering乳液法一步实现亲水性纤维素纳米晶体（CNC）和疏水性聚苯乙烯（PS）的高效复合,经溶液浇筑成膜与热压耦合制得力学性能优异的CNC/PS复合薄膜。结果表明,尽管CNC的添加会降低PS薄膜的透明度,但当CNC添加量≤10%时,CNC/PS复合薄膜仍能保持良好的透明度。当CNC添加量为8%时,CNC/PS复合乳液中的乳滴尺寸和乳滴分布均一性最佳,此时CNC/PS复合薄膜的力学性能最佳,其拉伸强度为33.8 MPa,远优于纯PS薄膜（18.9 MPa）,韧性和杨氏模量分别为408.1 kJ/m3和1.9 GPa,是纯PS薄膜的1.8倍和1.5倍。当CNC添加量增至20%时,CNC/PS复合薄膜出现发白现象,透光率显著下降,但仍具有与纯PS薄膜相当的力学性能（拉伸强度为20.9 MPa,杨氏模量为1.6 GPa）。     

Tensile and Barrier Properties of Edible Films Made from Whey Proteins

ABSTRACT: Whey protein isolate (WPI)-based edible biopolymer films were prepared using a film-forming stage designed to provide heat-induced gelation. Effects of whey-protein ratios, calcium, glycerol (plasticizer), and emulsion droplet incorporation on film tensile and barrier properties were investigated. Protein ratios had less influence on tensile strength, elongation, and water vapor permeability than glycerol and calcium ion concentrations. Semitransparent films with reasonably high tensile and UV-light barrier properties and moderate water vapor barrier properties were prepared from WPI:20% glycerol:10 mM calcium solutions. Microstructure analysis revealed the influence of glycerol and calcium concentrations on gel networks, which could be related to film tensile properties.     

可食性膜阻水特性的研究

本实验采用拟杯子法,以CaCl2为吸水材料,以棉布为膜载体,在温度25±2 ℃、相对湿度为90%±2%的条件下,测定了各种膜的水蒸气透过率,并比较了它们的阻水特性.结果表明,海藻酸钠膜是具有最佳阻水性的多糖膜;明胶膜比大豆蛋白膜阻水性更优;脂质膜的阻水率按以下顺序依次增大:月桂酸＜棕榈酸＜硬脂酸＜石蜡＜蜂蜡,乙酰化单甘酯的阻水性优于单甘酯;增塑剂山梨醇、甘油及乙二醇的加入会使膜的阻水性降低;在三元膜中,脂质膜用作被膜剂比用作乳化剂具有更好的效果.     

Effects of Extrusion Temperature and Plasticizers on the Physical and Functional Properties of Starch Films

Cornstarch, at 20% moisture content (dry basis, d.b.), was mixed with glycerol at 3:1 ratio to form the base material for extruded starch films. Stearic acid, sucrose and urea, at varying concentrations, were tested as secondary plasticizers for the starch‐glycerol mixture. The ingredients were extruded at 110 and 120°C barrel temperatures to determine the effects of extrusion temperature, plasticizer type and their concentrations on the film‐forming characteristics of starch, as well as their effects on selected physical and functional properties of the films. The physical and mechanical properties of the films were studied by scanning electron microscopy (SEM) and tensile testing, while the glass transition and gelatinization properties were analyzed using differential scanning calorimetry (DSC). The interactions between the functional groups of starch and plasticizers were investigated using Fourier‐transform infrared (FTIR) spectroscopy. The water vapor permeability (WVP) properties of starch films were determined using ASTM standard E96‐95. Scanning electron micrographs exhibited the presence of native and partially melted starch granules in the extruded films. The tensile stress, strain at break and Young's modulus of starch films ranged from 0.9 to 3.2 MPa, 26.9 to 56.2% and 4.5 to 67.7 MPa, respectively. DSC scans displayed two glass transitions in the temperature ranges of 0.1 to 1°C and 9.6 to 12°C. Multiple melting endotherms, including that of amylose‐lipid complexes, were observed in the thermoplastic extrudates. The gelatinization enthalpies of the starch in the extruded films varied from 0 to 1.7 J/g, and were dependent largely on the extrusion temperature and plasticizer content. The shift in the FTIR spectral bands, as well as the appearance of double‐peaks, suggested strong hydrogen bonding interactions between the starch and plasticizers. The WVP of starch films ranged from 10.9 to 15.7 g mm h^‐1 m^‐2 kPa^‐1, depending on the extrusion temperature and the type of plasticizer used.     

Physical and Mechanical Properties of Pea Starch Edible Films Containing Beeswax Emulsions

ABSTRACT:  Hydrophobic beeswax emulsions were incorporated into hydrophilic starch films to modify physical, mechanical, and thermal properties of the films. Beeswax was added in the film-forming solution of high-amylose pea starch (35% to 40% amylose w/w) at the level of 0%, 10%, 20%, 30%, and 40% w/w of starch with glycerol as a plasticizer (40/60 of glycerol/starch). Addition of beeswax affected mechanical properties, significantly reducing tensile strength and elongation and increasing elastic modulus. Beeswax addition decreased water vapor permeability and increased oxygen permeability. However, the addition of hydrophobic wax particles in starch films marginally affected these physical properties below 30% beeswax in the films. Beeswax addition at the 40% concentration formed amylose–lipid complex that caused the dramatic changes of physical and thermal properties of the films.     

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.     

Physical Properties of WPI Films Plasticized with Glycerol, Xylitol, or Sorbitol

ABSTRACT: Effects of glycerol, xylitol, and sorbitol on selected physical properties of whey protein isolate (WPI) films were examined. Increasing glycerol or sorbitol content led to increases in moisture content, water vapor permeability, and % elongation; and decreases in tensile strength, elastic modulus, and glass transition temperatures of the films. Increasing levels of xylitol had no effect on permeability, moisture content, or glass transition temperature of the films, but decreased % elongation, tensile strength, and elastic modulus. Moisture content of the films correlated well with glass transition temperatures. Differences in measured physical properties of films with plasticizer type and concentration may be attributed to differences in the hygroscopic and crystalline properties of the plasticizers.