Water Vapor Permeability of Whey Protein Emulsion Films as Affected by pH

The water vapor permeability (WVP) of whey protein isolate-beeswax emulsion films was investigated as related to pH. Lower WVP was observed for films cast from solutions at pH 7.0. When pH of the film-forming solution was lowered, resulting film WVP increased. At the isoelectric point, WVP was the highest. As pH of the emulsion approached pI, a sharp change in viscosity occurred due to an increase in protein aggregation. This increase in viscosity probably lowered lipid mobility and reduced interconnectivity among lipid droplets, resulting in the higher WVP. For minimum WVP, such films should be applied at pH different from pI.     

Hydrophilic Edible Films: Modified Procedure for Water Vapor Permeability and Explanation of Thickness Effects

The ASTM E96 Standard Method for determining water vapor permeability (WVP) was modified for hydrophilic edible films. Accurate measurement of relative humidity conditions and maintenance of 152 m/min air speeds were essential outside the test cups. The WVP Correction Method was developed to account for the water vapor partial pressure gradient in stagnant air layer of the test cup. Errors were as high as 35% without this correction. Applying these guidelines explained commonly observed thickness effects on WVP values of hydrophilic films. Relative humidity was the cause of observed thickness effects.     

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.     

Permeability of d-Limonene in Whey Protein Films

The effects of temperature, relative humidity (%RH) and permeant concentration on aroma permeability were investigated in edible whey protein isolate (WPI) films. An orthogonal regression was performed to ascertain significance of these factors. Temperature and %RH had exponential effects on d-limonene permeability, interacting synergistically to influence aroma transport in WPI polymer films. Permeability of d-limonene in WPI polymer films was not influenced by permeant concentration in the range 62 to 226 ppm (mol/mol). The predictive equation generated by regression analysis could be potentially useful for edible packaging design within the given temperature, %RH, and concentration ranges. The Arrhenius-type format also provided insight into the temperature-sensitivity of WPI films and confirmation of the influence of %RH on permeability activation energy.     

Polarity Homogeneity and Structure Affect Water Vapor Permeability of Model Edible Films

A continuous gravimetric measurement method was perfected to determine with accuracy the water vapor permeability of edible films. Two substances, methylcellulose and paraffin wax, with different physicochemical properties, were used as films. Factors affecting permeability included the polarity of film components, the homogeneity or dispersion of material in the film and the structure which depends on the distribution of paraffin wax in the composite films. The thickness and the Water Vapor Transmission Rate (WVTR) measurement methods resulted in different values for permeability. WVTR increased with hydrophilicity and heterogeneity. Modeling trials con-cerning water vapor transport indicated the major influence that structure had on permeability. Waxlaminated fiIms had a very high barrier efficiency, comparable with that of synthetic films.     

Fatty Acid Concentration Effect on Tensile Strength, Elongation, and Water Vapor Permeability of Laminated Edible Films

Water vapor permeability (WVP), tensile strength (TS), and elongation (E) were investigated in laminated methyl cellulose/corn zein-fatty acid films. They were prepared by casting corn zein-fatty acid solutions onto methyl cellulose films. WVP decreased as chain length and concentration of fatty acids increased. The TS of laminated edible film containing palmitic acid decreased as palmitic acid increased. The TS of films containing stearic-palmitic acid blends showed similar trends but there were no significant differences among blends. The TS of the film containing lauric acid was maximum at 30% lauric acid concentration. The E values for films containing fatty acids varied inversely with TS.     

乳清浓缩蛋白可食用膜成膜工艺的研究

研究了乳清浓缩蛋白可食用膜的成膜工艺,分析了蛋白质浓度、甘油浓度和加热温度对可食用膜透水性和透氧性的影响,并确定了可食用膜阻隔性能的优化工艺参数。研究结果表明,可食用膜的阻水性随蛋白质浓度和甘油浓度的增大而下降,阻氧性随甘油浓度增大而下降。加热温度为70℃时,膜的阻水性和阻氧性达到最佳。响应面分析表明,当蛋白质浓度为100 g/L,甘油浓度为27 g/L,加热温度为69℃时,乳清浓缩蛋白可食用膜的综合通透性能为最佳,其透湿系数为0.004 35 g·mm/(m~2·h·kPa),透氧系数为0.134 cm~3·mm/(m~2·min·kPa)。     

Whey Protein Edible Film Structures Determined by Atomic Force Microscope

Atomic force microscopy was used to study edible films produced from whey proteins. The films were imaged under ambient conditions with no special sample preparation. Low resolution imaging of areas from 10 μm to 150 μm on a side was performed in the contact mode. Higher resolution scans of 350 nm to 2,700 nm required use of the noncontact imaging mode. Features about the same size as the primary protein in whey, beta-lactoglobulin (7 nm), were identified in the film samples. Molecular aggregates in the range of 1 μm, reported in other studies using transmission electron microscopy of whey protein gels, were combined in results from atomic force microscopy.     

Heat Curing of Whey Protein Films

Heat curing of edible whey protein isolate (WPI) films was studied as a means of improving mechanical and water vapor barrier properties. Curing temperature and relative humidity (RH) effects on the rate of change of maximum tensile stress (TS), elongation at break (E), Young's Modulus (Y_m), and water vapor permeability (WVP) were investigated. Cure time linearly affected TS and Y_m, while influencing E and WVP exponentially. Increased cure temperature and reduced RH accelerated TS increase, E and Y_m decrease, and increased improvement in WVP barrier properties. These data support the hypothesis that heat curing may elicit additional cross-linking of protein, yielding increased TS and decreased E and WVP; however, further work is required to confirm this hypothesis.     

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.     

Permeability Properties of Fruit Puree Edible Films

The potential of fruit purees as edible mass transfer barriers was studied. Water vapor and oxygen permeabilities (WVP and O₂P) of peach puree films were evaluated at different relative humidities (RH) and temperatures (T). Peach puree was not a good water barrier. Peach and apricot films exhibited lower WVPs than pear and apple films. Calcium addition, RH increases and T decreases resulted in increased WVP values for peach puree edible films. WVPs of peach films were compared with other edible and synthetic films. Peach puree films were good oxygen barriers. RH increases resulted in exponential increases in O₂P. Most edible and many synthetic polymers showed higher O₂Ps at equivalent conditions.     

乳清蛋白-茁霉多糖-阿魏酸复合可食性膜的研制

以乳清浓缩蛋白、茁霉多糖、阿魏酸为成膜材料,制备乳清浓缩蛋白-茁霉多糖-阿魏酸复合膜。分别对复合膜的厚度、刺穿强度、拉伸强度、水蒸气透过系数、含水量和溶解性等性能进行测试,研究成膜材料添加量和成膜条件与复合膜性能的关系。结果表明:乳清浓缩蛋白中添加茁霉多糖和阿魏酸作为增强剂,可明显提高膜的性能。最优工艺条件为成膜温度80℃,pH9.0,阿魏酸添加量200 mg/100 mL,茁霉多糖添加量150 mg/100 mL。     

TG对大豆蛋白／PVA复合膜透湿性、透气性影响研究

以大豆蛋白和聚乙烯醇（PVA）为主要原料,以透H2 O率、透O2率、透CO2率为评价指标,通过单因素试验和正交试验,研究了谷氨酰胺转氨酶（简称TG）对大豆蛋白/PVA复合膜透湿性、透气性的影响。试验结果表明：当反应pH值为5．0,TG添加质量分数为0．22‰;反应温度为53℃时得到性能最佳的复合薄膜。     

Combined Effects of Proteins and Polysaccharides on Physical Properties of Whey Protein Concentrate-based Edible Films

ABSTRACT: The water-vapor permeability (WVP) and mechanical properties of edible films formed from dry blends or co-dried preparations of protein-polysaccharide powders prepared from whey protein concentrate (WPC)-45 and alginate, pectin, carrageenan, or konjac flour (WPC-45-to-polysaccharide ratio of 95:5 w/w) were investigated. Films were prepared from 8% WPC using WPC-45 (45% protein powder), consisting of 17.76 g of WPC-45 in 82.84 g of water per 100 g solution to give 8% protein w/w. Films formed from co-dried powders had lower WVP and higher tensile strength (TS), elastic modulus (EM) ( P < 0.05), and elongation (EL) than equivalent films formed from the dry blended powders. Films containing alginate had lower WVP and higher TS, EM, and EL than films containing pectin, carrageenan, or konjac flour. There is potential to alter the physical properties of hydrophilic films by combining whey protein and polysaccharide components.     

Water Vapor Permeability of Caseinate-Based Edible Films as Affected by pH, Calcium Crosslinking and Lipid Content

Edible films were cast from solutions of sodium or calcium caseinate and from emulsions of these proteins with acetylated monoglyceride, beeswax, and stearic acid. The water vapor permeabilities of the films were evaluated at 25°C using the ASTM E96–80 method, modified to calculate the % relative humidity at the film underside. Adjustment to pH 4.6 (isoelectric point), calcium ion crosslinking and combined effects of calcium ascorbate buffer (pH 4.6) reduced water vapor permeability of sodium caseinate films by 36%, 42%, and 43%, respectively. Calcium caseinate-beeswax emulsion films had water vapor permeabilities up to 90% lower than pure sodium caseinate films. Water vapor permeability varied by a factor of two depending on emulsion film orientation, indicating nonisotropic structure.     

可食性小麦蛋白膜透氧性的研究

一定的条件下 ,以小麦蛋白为原料可以制得具有良好透氧性的薄膜。文中研究了可食性小麦蛋白膜的透氧性能 ,对影响透氧性的 5种因素的影响效果及机理进行了探讨 ,以期望为改善小麦蛋白膜的透氧性提供参考。     

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.     

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.     

Edible Coatings on Frozen King Salmon: Effect of Whey Protein Isolate and Acetylated Monoglycerides on Moisture Loss and Lipid Oxidation

Whey protein isolate (WPI) and acetylated monoglyceride (AMG) coatings were evaluated for effectiveness against moisture loss and lipid oxidation of frozen King salmon. A model gel material was also used to screen coatings for effectiveness against moisture loss. Coatings of low-melting-point AMG used alone or after applying WPI solution or WPI powder were effective in reducing the rate of moisture loss by 42–65% during the first 3 wk of storage. Onset of lipid oxidation was delayed and peak peroxide values were reduced in samples coated with WPI solution/antioxidant overspray or those containing low-melting-point AMGs. No differences in effectiveness were found among the coating treatments.     

Water Vapor Permeability of Edible Bilayer Films

Edible films composed of a water soluble, carbohydrate layer (hydroxypropyl methylcellulose) and various kinds of lipid layers were tested for resistance to water vapor permeability. Films were tested at 25°C and a relative humidity differential of 85%. Films containing solid lipids, such as beeswax, paraffin, hydrogenated palm oil or stearic acid yielded permeabilities of 0.2 g · mil · day⁻¹· mmHg⁻¹ or less which is a smaller value than that for low density polyethylene.