Gas barrier and wetting properties of whey protein isolate‐based emulsion films

The aim of this research was to investigate the effect of rapeseed oil concentration (1–3% w/w) on the water vapor, oxygen and carbon dioxide permeability, water vapor sorption and surface properties of whey protein isolate emulsion‐based films. The water contact angle as affected by oil content, film side and time was analyzed. The effect of temperature (5 and 25°C) on the water vapor permeability (WVP), water vapor sorption kinetics and diffusion coefficient was also studied. The results showed that the incorporation of a lipid phase to whey protein film‐forming solutions was able to decrease the WVP, water hydrophilicity (increasing water contact angle) and water transfer of whey protein films. However, the films containing oil were more permeable to oxygen and carbon dioxide. Significantly higher values of WVP and diffusion coefficient were obtained at 5°C than at 25°C, indicating that storage temperature should be taken into account when designing the composition of edible films and coatings for food applications. POLYM. ENG. SCI., 59:E375–E383, 2019. © 2018 Society of Plastics Engineers     

Effects of Candelilla and Carnauba Wax Incorporation on the Functional Properties of Edible Sodium Caseinate Films

The aim of this study was to evaluate the effects of candelilla (CAN) or carnauba wax (CAR) incorporation on functional properties of edible sodium caseinate (CAS) films. Glycerol and Tween-80 were used as the plasticizer and the emulsifier, respectively. The results showed that the incorporation of waxes increased film opacity, total color differences (∆E), and mechanical resistance and reduced film lightness, water vapor permeability (WVP), and elongation at break. Scanning electron microscopy showed heterogeneous structure of emulsion films with regular distribution of lipid particles. A different internal arrangement was observed as a function of the film composition with both layered and incorporated film structure. Films containing candelilla wax exhibited more regular lipid reorganization, which resulted in better water vapor barrier efficacy and mechanical resistance in comparison to control films. The presence of Tween-80 resulted in better dispersion of lipid particles in film-forming solutions and lower water solubility, lightness, film opacity, and water vapor permeability, whereas the total color differences (∆E) were significantly larger and the improvement in mechanical properties was also achieved.     

Influence of preparation conditions on the physical properties of zein films

Zein is a hydrophobic protein produced from maize. Biodegradable zein films without additional reagents were prepared using various controlled drying conditions. The zein films were transparent. Mechanical properties (tensile strength and puncture strength), gas permeability, and water vapor permeability (WVP) of the zein films were measured. The tensile strengths of the zein films were between 7 and 30 MPa and the puncture strengths between 37 and 191 MPa. The zein films had higher oxygen permeability than carbon dioxide permeability. The lowest WVP of the zein film was 0.012×10⁻⁹ g·m/m²·s·Pa. We found differences in the WVP between the sides of the zein films; i.e., the air side of the zein film had a higher WVP than the basal side of the zein film when the films were exposed to high humidity during testing. This indicates a relationship between the WVP of the zein film and the contact angle of the zein film. The mechanical properties of the zein film depended on the drying conditions during preparation. Zein films with various useful physical mechanical properties were produced.     

Studies on glass transition temperature of mono and bilayer protein films plasticized by glycerol and olive oil

Thermomechanical and thermal properties of whey protein, maize prolamin protein (zein), and the laminated whey protein–zein films were studied. The dynamic mechanical (thermal) analysis (DMTA) results showed that the single zein film had higher T_g than single whey protein and zein–whey laminated films. The shift in the T_g values of films from 31.2°C in whey protein film and 88.5°C in the zein film to 82.8°C in the laminated whey protein–zein films may be implied some interaction formation between the two polymers. The small tan δ peaks were observed at ?50°C in zein–glycerol films and at ?22.37°C in the whey protein films and can be related to β‐relaxation phenomena or presence of glycerol rich region in polymer matrix. Zein‐olive oil and zein–whey protein–olive oil films showed tan δ peaks corresponded the T_g values at 113.8, and 92.4°C, respectively. Thus, replacing of glycerol with olive oil in film composition increased T_g. A good correspondence was obtained when DSC results were compared with the tan δ peaks in DMTA measurements. DSC thermograms suggested that plasticizers and biopolymers remained a homogeneous material throughout the cooling and heating cycle. The results showed that T_g of zein–glycerol films predicted by Couchman and Karasz equation is very close to value obtained by DSC experiments. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

From acacia honey monosaccharide content to a new external binary plasticizer applicable in aqueous whey protein films

Plasticizer is an essential adjuvant in food and pharmaceutical film coatings affecting the appearance, mechanical and permeation properties of the final coat. In the present study, film formation and plasticization of native whey proteins (potential future “green” coating agents for pharmaceuticals and food products), were studied with free isolated films. Special attention was paid to the effects of plasticizer, preheating and film forming solution pH on the mechanical stress–strain and moisture permeation properties of whey protein films. Glycerol, binary mixtures of fructose and glucose, and non-crystalline acacia honey were studied as external plasticizers. The type and amount of plasticizer affected the mechanical stress–strain properties of the whey protein films. A short preheating treatment of whey proteins prior to film casting resulted in mechanically strong films with a reduced elongation. The film forming properties of aqueous whey proteins could be modified by adjusting the pH above the isoelectric point of β-lactoglobulin prior to film coating. For effective plasticization, whey protein films required a high amount of monosaccharide containing plasticizer ranging from 80% to 120% (calculated from the protein weight). A new external binary plasticizer having the same ratio of monosaccharides as non-crystalline acacia honey (fructose and glucose 1.67:1) was found to be applicable in aqueous whey protein films.     

Edible starch sodium octenyl succinate film formation and its physical properties

Edible starch sodium octenyl succinate (SSOS) films, with or without glycerol as plasticizer, were prepared by solution‐casting method. The effect of SSOS concentration, degree of substitution (DS) of octenyl group, as well as glycerol content, on the properties of SSOS films was studied including tensile strength, water vapor permeability (WVP), and oil permeability (OP). The results indicated that the tensile strength of SSOS film was up to 39.4 ± 1.9 MPa when the concentration of SSOS was 0.05 g/mL and DS was 0.05. The increase of glycerol content resulted in a decrease of film tensile strength. WVP of SSOS films was relatively low. Meanwhile, study in OP showed that SSOS films were oilproof. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

莲藕淀粉/乳清蛋白复合膜的制备、表征及性能

将莲藕淀粉与乳清蛋白按1∶0.3、1∶0.4、1∶0.5、1∶0.6、1∶0的质量比共混得到系列复合膜，探究不同比例乳清蛋白的添加对膜性能的影响。通过SEM、XRD、FTIR、DSC及TG对复合膜进行表征，在常温环境下对复合膜的机械性能和阻隔性能进行测定。结果表明，乳清蛋白的添加对膜的机械性能、阻隔性能均有所改善，特别当莲藕淀粉∶乳清蛋白=1∶0.5时，成膜基质间相互作用，紧密结合，相容性良好，且机械性能及阻隔性能最佳，抗拉强度和断裂伸长率分别达到11.66 MPa和14.71 %，热稳定性好。     

催化剂对复合薄膜用水性聚氨酯胶粘剂性能的影响

采用丙酮法制备了复合薄膜用的水性聚氨酯(WPU)乳液胶粘剂,研究了催化剂用量对WPU反应速率及其性能的影响。研究结果表明,适量的催化剂能明显加快聚氨酯(PU)预聚体的反应速率;当催化剂质量分数为0.1%时,WPU乳液的粘度和复合薄膜的T型剥离强度最大,但WPU胶膜的玻璃化转变温度(Tg)降低,由未加催化剂时的-25.5℃降低到-29.1℃。     

Poly(lactide-co-trimethylene carbonate) and Polylactide/Polytrimethylene Carbonate Blown Films

In this work, poly(lactide-co-trimethylene carbonate) and polylactide/polytrimethylene carbonate films are prepared using a film blowing method. The process parameters, including temperature and screw speed, are studied, and the structures and properties of the P(LA-TMC) and PLA/PTMC films are investigated. The scanning electron microscope (SEM) images show that upon improving the content of TMC and PTMC, the lamellar structures of the films are obviously changed. With increasing TMC monomer or PTMC contents, the elongation at the break is improved, and the maximum is up to 525%. The water vapor permeability (WVP) results demonstrate that the WVP of the PLA/PTMC film increased with the increase in the PTMC content, whereas the WVP of the P(LA-TMC) film decreased. Thermogravimetric (TG) measurements reveal that the decomposition temperatures of the P(LA-TMC) and PLA/PTMC films decrease with increases in the TMC and PTMC contents, respectively, but the processing temperature is significantly lower than the initial decomposition temperature. P(LA-TMC) or PLA/PTMC film can extend the shelf life of apples, for instance, like commercial LDPE film used in fruit packaging in supermarkets.     

Characterization of soybean protein concentrate—stearic acid/palmitic acid blend edible films

The effect of incorporating commercial stearic acid/palmitic acid blend (SA/PA, 63/37 wt %) into hydrophilic soybean protein concentrate (SPC) film‐forming solutions at neutral and alkaline pH on some selected properties of edible cast films was investigated. SA/PA‐added SPC film exhibited a significant increase in translucency, being more relevant for films obtained at pH 7. This was associated with the more heterogeneous morphology of such films as observed by scanning electron microscopy. Calorimetric measurements and X‐ray diffraction studies confirmed the presence of crystalline fatty acids in films at pH 7 and new crystalline structures at pH 10 due to interactions or reactions between SPC and SA/PA blend. Fourier Transform infrared spectroscopy results confirmed the incorporation of fatty acids into SPC and revealed the occurrence of interactions between both components, depending on the film‐forming emulsion pH. Moisture absorption isotherms at high relative humidity (RH) were determined and experimental data were adequately fitted by Peleg's empirical equation. Control SPC films produced at pH 7 were distinctly more moisture resistant than those at pH 10 owing to the more charged protein molecules at alkaline pH. The increased moisture resistance of SA/PA‐added‐SPC film at pH 10 was related to the more homogeneous dispersion of fatty acid particles within the protein matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Influence of sorghum wax,glycerin, and sorbitol on physical properties of soy protein isolate films

Sorghum wax, sorbitol, glycerin, and soy protein isolate (SPI) composite films were prepared. Effects of sorghum wax, sorbitol, and glycerin concentrations on various films were evaluated using response surface methodology. All independent variables significantly (P<0.05) affected film water vapor permeability (WVP), tensile strength (TS), elongation at break (E), total color difference, and total soluble matter (TSM). Increasing the sorghum wax concentration decreased WVP and E. As sorbitol content increased in the composite films, WVP and TS increased. Sorbitol had a critical point of 2–5 g/5 g SPI for low values of TSM. The addition of sorbitol contributed more to the properties of the film than did glycerin.     

Potential of Pinhão husk (Araucaria angustifolia) as a structural reinforcement agent in the properties of edible films of Pinhão flour and gelatin

In this study, the use of Pinhão husk as a source of reinforcement material for development of edible films, where the Pinhão seed flour and bovine gelatin were used as matrices for the films. Mechanical properties, water vapor permeability, solubility and opacity, microstructure, and thermal degradation characterized the films produced. The films presented homogeneous and cohesive structures. Pinhão husk content positively affected film properties by increasing tensile strength (TS) and decreasing water vapor permeability (WVP), with Pinhão flour film formulations (5.0% Pinhão flour, 1.2% glycerol, and 0.4% Pinhão husk) and gelatin (5.0% gelatin, 2.0% glycerol, and 0.4% Pinhão husk) those that presented the best results (5.06 MPa for TS and 0.14 g.mm/kPa.h.m² for WVP) and (3.88 MPa for TS and 0.28 g.mm/kPa.h.m² for WVP), respectively The thermal degradation study revealed that the films are stable at temperatures below 150°C, losing only free water and volatile compounds of low molecular weight. Pinhão husk can reinforce films, making them suitable as biodegradable and edible packaging materials for eco-friendly food products. This contributes to the circular economy, preserves biodiversity, and reduces plastic waste, offering promising sustainable packaging solutions.     

Effects of the incorporation of saturated fatty acids on the mechanical and barrier properties of biodegradable films

The effects of saturated fatty acids at a concentration of 1.5% on the mechanical and barrier properties of starch‐based films were evaluated in films prepared with two concentrations of glycerol, 20 and 25%. The water vapor permeability (WVP) was determined at three ranges of relative humidity, RH, (0–33, 33–64 and 64–97%). In all cases, an increase in WVP values was observed with increasing RH. SEM images showed a more homogeneous and compact structure in the films with caproic and lauric acids. The films with fatty acids showed higher elongation and maximum stress, and they had Young's modulus values close to those of the control; thus, the addition of fatty acids did not impair the mechanical properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Heterogeneous method of chitosan film preparation: Effect of multifunctional acid on film properties

The heterogeneous crosslinking method was applied to chitosan films with citric acid to observe and understand the effect of a multifunctional acid at a low concentration on film properties. Neat and neutralized chitosan films and films containing 15% (w/w) citric acid (denoted as CA films) were characterized by mechanical, water vapor permeability (WVP), and thermogravimetric analysis tests. The CA films displayed a higher tensile strength by 10%, lower WVP by 30%, and higher thermal stability, compared to neutralized films. The crystalline structure converted back from tendon to Type II after the addition of citric acid, as determined by X-ray diffraction. Neat films displayed a lower water contact angle (72°) compared to neutralized and CA films (78°–79°). The heterogeneous method was also applied to incorporate a plasticizer into a neutralized film to potentially observe the glass transition using dynamic mechanical analysis. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48648.     

Development of chitosan/gelatin/starch composite edible films incorporated with pineapple peel extract and aloe vera gel: Mechanical,physical, antibacterial,antioxidant, and sensorial analysis

In this study, chitosan (C)/gelatin(G)/starch(S) composites incorporated pineapple peel extract (PPE) and aloe vera gel (AVG) were prepared by the casting method as antioxidant agents. Mechanical, water vapor permeability (WVP), moisture content, solubility, opacity, and color properties of the effects of PPE and AVG at different concentrations (0%, 10%, and 30%) were investigated. The prepared films were characterized by Fourier transform infrared spectroscopy in attenuated total reflection (ATR-FTIR), X-ray diffraction (XRD), Thermal gravimetric analysis (TGA), Scanning electron microscope (SEM), mechanical, water barrier, opacity, and color. PPE and AVG extract incorporated edible films improved thermal stability of edible films. Tensile strength decreased with the addition of extracts; the maximum tensile strength was 8.15 MPa for CGS film. The WVP of the films increased with the increasing PPE and AVG concentration. As a biological activity, the films inhibited the growth of gram-positive (Staphylococcus aureus) and gram-negative bacteria (Escherichia coli). With the addition of PPE and AVG to the CGS film, its antioxidant properties were enhanced. In addition, the prepared films were applied for strawberry coating both in the refrigerator and at room temperature. Consequently, these edible-coated films can be used for active food packaging/coating to extend the shelf life of fruits.     

Influence of forming method of blending versus casting layer-by-layer on structural properties and packing performances of casein-gelatin composite edible film under different appending proportion

In order to obtain casein edible films with great packing performance, gelatin as the reinforcing additive with different ratios were loaded via two methods including layer- by- layer and blending. A comparative study on structure properties between double layers and blending films made from casein and gelatin was obtained by scanning electron microscopy and Fourier transform infrared spectroscopy. The difference between the films' packing characters were conducted by water vapor permeability (WVP), optical property, and mechanical properties (including tensile strength (TS) and elongation (EAB)). The results showed that the degree of films roughness increased and the structural stability decreased as the increase of gelatin additive ratio in both double layers and blending films. Thickness and WVP both displayed a trend of increasing first then decreasing at the dividing of gelatin instead of casein in 50%. Importantly, WVP values in double layers film with a largest value of 6.95 gm⁻¹Pa⁻¹s⁻¹ was higher than blending films, observably (P < 0.05). Additionally, TS in blending film was increased by 23.44% than double layers film under the gelatin additive proportion of 70%, and EAB value in double layers film was larger by 207.65% than blending film under the gelatin additive proportion of 10%.     

Fabrication of κ-carrageenan and whey protein isolate-based films reinforced with nanocellulose: optimization via RSM

The aim of this study was to prepare nanocomposite films composed of whey protein isolate (W) and carrageenan (C) with nanocellulose (N) for food packaging applications. Response surface methodology was applied to investigate the effect of W concentration (v/v, 0–100%), glycerol/sorbitol (G/S) ratio (0–1), and N concentration (w/w, 0–5%) on the physicomechanical properties of film samples. Higher W and N contents and lower G/S ratios showed positive effect on rigidity of film samples, while introducing high concentration of N increased the water vapor permeability values with increasing plasticizer and C concentration. The highest water uptake values were observed in C based films, while a higher C content resulted in lower opacity values. The addition of nanocellulose into whey protein and carrageenan blend films in the presence of a plasticizer mixture improved the suitability of selected biopolymers for food packaging applications when compared to their neat films. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48902.     

多重改性水性聚氨酯胶粘剂对聚烯烃薄膜的粘接机理

以自制的多重改性水性聚氨酯(WPU)复合乳液为基料,配合适量的消泡剂、润湿剂和偶联剂等,制备出软包装覆膜用多重改性WPU胶粘剂。考察了消泡剂、润湿剂和偶联剂用量对胶粘剂性能的影响,分析了胶粘剂对聚烯烃薄膜的粘接机理。结果表明:该胶粘剂对经过电晕处理的聚烯烃薄膜表面润湿性好、润湿速率快,并且和基材表面存在着广泛的氢键,因此其与聚烯烃薄膜表面有较强的吸附作用;通过外加偶联剂己二酰肼(ADH),强化了胶粘剂对聚烯烃表面的粘接效果;当w(消泡剂)=0.3%、w(润湿剂)=0.5%和w(ADH)=0.5%时,BOPP(双向拉伸聚丙烯)膜和CPP(流延聚丙烯)膜之间的最终粘接强度为264 N/m,可以满足软包装覆膜用胶粘剂的使用要求。     

A rapid method for extraction of total lipids from whey protein concentrates and separation of lipid classes with solid phase extraction

A modified procedure for extraction of total lipids from whey protein concentrates was developed such that stable emulsion with extracting solvents was avoided and the solvent system remained monophasic. Nonlipid contaminants from the extract were removed using gel filtration instead of traditional aqueous washing to prevent any loss of polar lipids. The extraction of total lipids by the modified procedure was complete and comparable with a reference procedure. Traditional thin-layer chromatography is tedious and more qualitative than quantitative for lipid class separation. Total lipids were further separated into free fatty acids, phospholipids, cholesterol ester, triacylglycerol, cholesterol, diacylglycerol, and monoacylglycerol, using modified solid phase extraction procedure. Columns with 2 g amino propyl packing allowed separation of up to 80 mg of total lipids into lipid classes gravimetrically. The values for anhydrous milk fat for all lipid classes agreed with those in the literature. Separation of total lipids into lipid classes with solid phase extraction is easy, quantitative, and can also be performed on a preparative scale.     

Enhancing the Gastrointestinal Stability of Curcumin by Using Sodium Alginate-Based Nanoemulsions Containing Natural Emulsifiers

Curcumin presents interesting biological activities but low chemical stability, so it has been incorporated into different emulsion-based systems in order to increase its bioaccessibility. Many strategies are being investigated to increase the stability of these systems. Among them, the use of polysaccharides has been seen to highly improve the emulsion stability but also to modulate their digestibility and the release of the encapsulated compounds. However, the effect of these polysaccharides on nanoemulsions depends on the presence of other components. Then, this work aimed to study the effect of alginate addition at different concentrations (0–1.5%) on the gastrointestinal fate and stability of curcumin-loaded nanoemulsions formulated using soybean lecithin or whey protein as emulsifiers. Results showed that, in the absence of polysaccharides, whey protein was more effective than lecithin in preventing curcumin degradation during digestion and its use also provided greater lipid digestibility and higher curcumin bioaccessibility. The addition of alginate, especially at ≥1%, greatly prevented curcumin degradation during digestion up to 23% and improved the stability of nanoemulsions over time. However, it reduced lipid digestibility and curcumin bioaccessibility. Our results provide relevant information on the use of alginate on different emulsifier-based nanoemulsions to act as carriers of curcumin.