Interfacial dynamic properties of whey protein concentrate/polysaccharide mixtures at neutral pH

The effect of two non-surface active polysaccharides (sodium alginate, SA, and λ-carrageenan, λ-C) in the aqueous phase on the surface dynamic properties (dynamic surface pressure and surface dilatational properties) of a commercial milk whey protein concentrate (WPC) adsorbed film at the air–water interface has been studied. A whey protein isolate (WPI) was used as reference. The WPC and WPI concentration (at 1.0% wt), temperature (at 20 °C), pH (7), and ionic strength (at 0.05 M) were maintained constant, while the effect of polysaccharide (PS) was evaluated within the concentration range 0.0–1.0% wt. The surface dynamic properties of the adsorbed films were measured in an automatic pendant drop tensiometer. At short adsorption time and in the presence of PS, the rate of diffusion of WPC to the interface was affected by the interactions with PS in the aqueous phase, which could limit protein availability for the adsorption. On the other hand, at long-term adsorption, the magnitudes of the molecular penetration and configurational rearrangement rates of WPC in mixed systems (WPC/PS) reflected the viscoelastic characteristics of the adsorbed films. The attractive interactions between WPC and PS and/or the WPC aggregation in the presence of PS, which depend on the proper polysaccharide and its concentration in the aqueous phase, have an effect on the adsorption kinetic parameters, the amount of WPC adsorbed at the air–water interface, and the dilatational viscoelastic characteristics of WPC/PS mixed systems.     

Preparation and properties of dialdehyde carboxymethyl cellulose crosslinked gelatin edible films

Glycerol-plasticized gelatin edible films with a new kind of dialdehyde polysaccharide, dialdehyde carboxymethyl cellulose (DCMC) as crosslinking agent are successful prepared using casting techniques. The mechanical properties, thermal stability, light barrier properties, swelling behavior as well as water vapor permeability (WVP) of the gelatin-DCMC films are investigated. The results indicate that the addition of DCMC causes tensile strength (TS) and thermal stability to increase and elongation at break (EB) to decrease, suggesting the occurrence of crosslinking between gelatin and DCMC. The light barrier measurements present high values of transparency at 280 nm and low values of transparency at 600 nm of the gelatin-DCMC films, indicating that gelatin-DCMC films are very transparent (lower in transparency value) while they have excellent barrier properties against UV light. Moreover, the values of transparency at 280 nm increase with the increased DCMC and glycerol content, suggesting the potential preventive effect of gelatin-DCMC films on the retardation of product oxidation induced by UV light. Furthermore, the addition of DCMC can greatly decrease the water vapor permeability (WVP) and equilibrium swelling ratio (ESR) down to values about 1.5 × 10⁻¹⁰ g m/m² s Pa and 150%, revealing the potential of DCMC in reducing the water sensitivity of gelatin-based films. In common for hygroscopic plasticizer in edible films, the addition of glycerol gives increase of EB and WVP and decrease of thermal stabilities and ESR of the gelatin-DCMC films.     

转谷氨酰胺酶对乳清浓缩蛋白-纳米微晶纤维素复合膜性能的影响

为了研究转谷氨酰胺酶(TG)对乳清浓缩蛋白(WPC)-纳米微晶纤维素(NCC)复合膜性能和结构的影响,本研究以WPC和NCC为原料,利用TG酶处理对WPC-NCC复合膜的机械性能和屏障性能进行优化,并探究TG酶的交联作用对乳清蛋白分子二级结构和复合膜成膜微观结构的作用情况。结果表明,在TG酶的添加量达到12 U/g_蛋白时,WPC-NCC复合膜的抗拉强度达到2.25 MPa,断裂伸长率达到86.75%,水蒸气透过率为4.40×10-12 gmPa-1s-1m-2,有效改善了WPC-NCC复合膜的机械性能性和水蒸气屏障性能。经过TG酶的处理,乳清蛋白结构向稳定有序的方向转变,减少了复合膜的孔洞数量和孔径,使成膜表面结构更加致密,促进了复合膜的机械性能和水蒸气屏障性能的提升。     

The water vapour permeability,mechanical properties and solubility of fish gelatin–chitosan films modified with transglutaminase or 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and plasticized with glycerol

The effect of glycerol on the mechanical and water barrier properties, as well as on the water solubility, of fish gelatin–chitosan films (4:1, w/w) cross-linked with TGase or EDC was determined. The addition of glycerol in concentrations up to 30% (of the substrate mass) to the fish gelatin–chitosan films modified with TGase or EDC did not change their solubility in buffers of pH 3 and 6 at 25 °C or during heating at 100 °C for 60 min. The chemical and enzymatic cross-linking of the components did not increase the water barrier properties of the films. WVP of the films modified with EDC and TGase was not affected by glycerol at concentrations up to 25% of the substrate mass. Tensile strength of the films decreased after modification of the components with TGase or EDC, respectively, by about 25% and 40%. The elongations of the enzymatically modified films containing 20% of glycerol and of chemically modified films containing 15% of glycerol were, respectively, about 8 and 13 times higher than those of unplasticized films; however, the tensile strengths of plasticized films were, respectively, 2.5 and 5 times lower.     

Physical assessment of composite biodegradable films manufactured using whey protein isolate,gelatin and sodium alginate

Composite films were manufactured using whey protein isolate (WPI), gelatin (G) and sodium alginate (SA) using a simplex centroid design. Tensile strength (TS), puncture strength (PT), percentage elongation at break point (E), tear strength (TT), water vapour permeability (WVP) and oxygen permeability (OP) of films were evaluated. The interactions between biopolymers showed quadratic effects (P < 0.01) on TS, E, PT, TT and WVP values. Scanning electron microscopy (SEM) was performed to investigate the microstructures of composite films. The proportion of ingredients required to produce the optimum composite films was determined to be: WPI (g):G (g):SA (g) = 8.0:12.0:5.0. Overall, films (WPIGSA-9) produced using the combination of WPI (g):G (g):SA (g) = 10.0:16.0:14.0 demonstrated the best barrier to oxygen (8.00 cm³ μm/m² d kPa); while films (WPIGSA-1) showed the best barrier to water vapour (48.04 g mm/kPa d m²); films (WPIGSA-6) using the combination of WPI (g):G (g):SA (g) = 10.0:17.5:22.5 had the best mechanical properties of all of the experimental composite films tested.     

Manufacture and characterization of gelatin films derived from beef,pork and fish sources using twin screw extrusion

Gelatin films derived from beef, pork and fish sources were manufactured by twin-screw, co-rotating extrusion. The effect of extrusion processing parameters, namely; screw speed (100–400 rpm) and temperature (90, 90, 90, 90 °C and 90, 120, 90, 90 °C) on the mechanical and barrier properties of gelatin films were studied. Increasing screw speed up to 300 rpm improved (P < 0.05) tensile strength (TS) and reduced (non-significantly) water vapour permeability (WVP) values for all manufactured gelatin films. However, the WVP of various gelatin film types was reduced (P < 0.05) when a screw speed of 400 rpm was employed. Increasing the speed of extrusion promoted (P < 0.05) increased solubility of films in water. Manufacture of films using a higher temperature profile resulted in films possessing higher puncture strengths (PS), increased water barrier properties with higher water solubility.     

OPTIMIZATION OF GLYCEROL EFFECT ON THE MECHANICAL PROPERTIES AND WATER VAPOR PERMEABILITY OF WHEY PROTEIN-METHYLCELLULOSE FILMS

Biopolymer films and coatings are generally designed using biological materials such as proteins, polysaccharides, lipids and their derivatives. The use of plasticizers is also required to improve the mechanical properties (tensile strength and elongation) of the films. For application of films to food systems, it is important for the developed films to possess favorable mechanical and permeability characteristics. Therefore, knowledge of optimum conditions where the water vapor permeability (WVP) is minimized while the mechanical properties are enhanced would be significant depending on the application of the edible films. In this study, the effects of glycerol, as a plasticizer, and methylcellulose (MC) ratios on WVP and mechanical properties of the whey protein films were investigated. Optimum properties of edible films were obtained by applying the complex method optimization algorithm to this multiobjective function problem, and glycerol to total polymer ratio (MC and whey protein concentrate [WPC]) of 0.356 and 0.45 was found for the films with MC : WPC ratios of 0.3 and 0.8, respectively. With respect to the results of this study, it might be concluded that optimum conditions for different edible film‐forming agents can be determined via the use of a good experimental design.     

Development of antimicrobial whey protein-based film containing silver nanoparticles biosynthesised by Aspergillus Niger

Applications of whey protein concentrate (WPC)-based films have been limited in the food industry due to their poor mechanical properties. This research aims to evaluate the effect of silver nanoparticles (AgNPs) synthesised by Aspergillus niger on the mechanical and antimicrobial properties of WPC-based films. The biosynthesised AgNPs solution was added into the WPC film formula at the concentration of 0, 0.25 and 1.25 mm . The film samples containing AgNPs inhibited the growth of Staphylococcus aureus, Escherichia coli O157:H7, Salmonella Enteritidis, Listeria monocytogenes, Williopsis saturnus or Aspergillus sydowii with zones of inhibition ranging from 13 to 19.7 mm. Incorporation of AgNPs improved tensile strength and water barrier properties of the films by 84% and 67%, respectively. However, per cent elongation at the break of the film decreased from 37% to 11% by the addition of 1.25 mm AgNPs. This work provides a protocol for preparing improved antimicrobial WPC films with AgNPs.     

Edible oxygen barrier bilayer film pouches from corn zein and soy protein isolate for olive oil packaging

An edible oxygen barrier film pouch was fabricated from a heat sealable corn zein (CZ) layer laminated on soy protein isolate (SPI) film and used to package olive oil condiments for use with instant noodles. The mechanical, barrier, and physical properties of the CZ/SPI bilayer films were then investigated and the oxidative stability of olive oil in the pouches was measured during storage under dry and intermediate relative humidity conditions. When compared to the SPI film, lamination with an additional layer of CZ film led to increased tensile strength and water barrier properties, while it had a lower elongation at break and decreased oxygen barrier properties. Nevertheless, the oxygen permeability of the CZ/SPI film (0.81 × 10⁻¹⁸ m³ m/m² s Pa) was lower than that of nylon-metalocene catalyzed linear low-density polyethylene (NY/mLLDPE) film (3.51 × 10⁻¹⁸ m³ m/m² s Pa) which is the material usually used for such condiments. The CZ/SPI bilayer films generated here were heat sealable at 120-130 °C and produced a seal strength greater than 300 N/m. The higher oxygen barrier property of the CZ/SPI bilayer films resulted in reduced oxidative rancidity of olive oil packaged in the CZ/SPI film when compared to olive oil packaged in NY/mLLDPE films.     

High hydrostatic pressure modification of whey protein concentrate for improved functional properties

Whey protein concentrate (WPC) has many applications in the food industry. Previous research demonstrated that treatment of whey proteins with high hydrostatic pressure (HHP) can enhance solubility and foaming properties of whey proteins. The objective of this study was to use HHP to improve functional properties of fresh WPC, compared with functional properties of reconstituted commercial whey protein concentrate 35 (WPC 35) powder. Fluid whey was ultrafiltered to concentrate proteins and reconstituted to equivalent total solids (8.23%) as reconstituted commercial WPC 35 powder. Solutions of WPC were treated with 300 and 400 MPa (0- and 15-min holding time) and 600 MPa (0-min holding time) pressure. After HHP, the solubility of the WPC was determined at both pH 4.6 and 7.0 using UDY and BioRad protein assay methods. Overrun and foam stability were determined after protein dispersions were whipped for 15 min. The protein solubility was greater at pH 7.0 than at pH 4.6, but there were no significant differences at different HHP treatment conditions. The maintenance of protein solubility after HHP indicates that HHP-treated WPC might be appropriate for applications to food systems. Untreated WPC exhibited the smallest overrun percentage, whereas the largest percentage for overrun and foam stability was obtained for WPC treated at 300 MPa for 15 min. Additionally, HHP-WPC treated at 300 MPa for 15 min acquired larger overrun than commercial WPC 35. The HHP treatment of 300 MPa for 0 min did not improve foam stability of WPC. However, WPC treated at 300 or 400 MPa for 15 min and 600 MPa for 0 min exhibited significantly greater foam stability than commercial WPC 35. The HHP treatment was beneficial to enhance overrun and foam stability of WPC, showing promise for ice cream and whipping cream applications.     

Comparison of the properties of multi-composite fish gelatin films with that of mammalian gelatin films

Four types of films viz. gelatin, gelatin–MMT, gelatin–chitosan and gelatin–MMT–chitosan prepared from redsnapper and grouper bone gelatin were compared with the mammalian gelatin films, for their mechanical and barrier properties. Grouper gelatin films had higher tensile strength (TS) and Young’s modulus (YM), but lower elongation at break (EAB) than redsnapper films. Incorporation of MMT and chitosan improved the TS (p < 0.05) of the films. Water solubilities were lower (p < 0.05) in films incorporated with chitosan compared to simple gelatin film. Protein solubilities were lower in gelatin–MMT films, irrespective of the type of solvent used. The water vapour transmission rates (WVTR) of fish and mammalian gelatin films were similar, but addition of MMT had reduced WVTR (p < 0.05). SEM micrographs depicted smoother surface for gelatin–MMT and gelatin–MMT–chitosan films. Thus, composite fish gelatin films made with MMT and chitosan could be the good natural biodegradable films due to their better mechanical and barrier properties.     

Properties of biodegradable blend films based on fish myofibrillar protein and polyvinyl alcohol as influenced by blend composition and pH level

Effects of the ratios of fish myofibrillar protein (FMP) from bigeye snapper (Priacanthus tayenus) to polyvinyl alcohol (PVA) (FMP:PVA; 10:0, 8:2, 6:4, 5:5, 4:6, 2:8, 0:10) and pH levels (3 and 11) on the properties of resulting films were investigated. Both tensile strength (TS) and elongation at break (EAB) of films increased with increasing PVA content (p < 0.05). When PVA was incorporated up to 40%, films prepared at pH 11 had the higher TS than did those prepared at pH 3 (p < 0.05). However, as PVA content was greater than 40%, films prepared at pH 3 exhibited the higher TS than did those prepared at pH 11 (p < 0.05). Water vapor permeability (WVP) of the films prepared at pH 3 increased when PVA content increased up to 40% and decreased with further increases in PVA content (p < 0.05). PVA films had the higher TS, EAB and WVP than did FMP films and FMP/PVA blend films prepared at both pHs. Films exhibited the increased L∗ and a∗ values but decreased b∗ value with increasing PVA content at both pHs. Films prepared at pH 11 showed higher b∗ value than did those prepared at pH 3 when PVA content was greater than 40% (p < 0.05). FMP/PVA blend films exhibited the negligible transmission to the UV light. At pH 3, light transmission of the films increased as PVA content increased (p < 0.05). At all FMP/PVA ratios, films prepared at pH 11 were less transparent than those prepared at pH 3 (p < 0.05). Therefore, blend composition and pH level influenced the properties of FMP/PVA blend films.     

Antimicrobial effect and physicochemical properties of bioactive trilayer polycaprolactone/methylcellulose-based films on the growth of foodborne pathogens and total microbiota in fresh broccoli

Bioactive trilayer films were prepared using methylcellulose (MC) and polycaprolactone (PCL). Two antimicrobial formulations named as A (organic acids, extract of rosmarinic acid and Asian essential oil (EO) mixture) and B (organic acids, extract of rosmarinic acid and Italian EO mixture) were added in MC films during casting and the trilayer composite films (PCL/MC/PCL) were fabricated using compression molding. These films were inserted into packages containing broccoli and the packages were kept at 4 °C during 12 days storage to determine the antimicrobial capacity of the films and the physico-chemical properties of the films. Bioactive films showed a significant reduction of Escherichia coli in broccoli from Day 4 and a total inhibition at Day 12. Similarly, these films showed a significant reduction of Salmonella typhimurium from Day 2 and a total inhibition at Day 7. Moreover, the films controlled the growth of total aerobic microbiota (TAM) in broccoli up to 10 days. Encapsulation of antimicrobial compounds in films allowed decrease of barrier properties of films. Tensile strength of films was not affected by the presence of formulation B. These results demonstrated the potential application of trilayer antimicrobial on controlling food pathogens and total flora in pre-cut vegetables.     

High methoxyl pectin–methyl cellulose films with antioxidant activity at a functional food interface

The effect of using increasing proportions of methylcellulose (MC) for the development of glycerol plasticized films based on high methoxyl pectin (HMP) (30:70, 50:50 and 70:30 w/w HMP:MC) and carrying l-(+)-ascorbic acid (AA) was studied with the purpose of achieving higher stability of AA and localized antioxidant activity at food interfaces. MC and 30:70 HMP:MC systems could not be casted. The shelf-life of the other AA-active films was assessed by storage at 25 °C, constant relative humidity (RH: 33.3%, 57.7% and 75.2%) and vacuum conditions. The rate constant for AA hydrolysis increased with the RH and, hence, with water mobility. Browning and AA degradation rates were directly related. When stored at 75.2% RH, both decreased as MC proportion increased. Compared to HMP film, the highest proportion of MC (50:50 HMP:MC) showed the highest AA stabilization under vacuum and greater performance under air atmosphere. They also developed localized antioxidant activity preserving the tocopherol content of walnut oil.     

Functional properties of gelatin-based films containing Yucca schidigera extract produced via casting,extrusion and blown extrusion processes: A preliminary study

Gelatin-based films containing both Yucca schidigera extract and low concentrations of glycerol (0.25–8.75 g per 100 g protein) were produced by extrusion (EF) and characterized in relation to their mechanical properties and moisture content. The formulations that resulted in either larger or smaller elongation values were used to produce films via both blown extrusion (EBF) and casting (CF) and were characterized with respect to their mechanical properties, water vapor permeability, moisture content, solubility, morphology and infrared spectroscopy. The elongation of the EF films was significantly higher than that of the CF and EBF films. The transversal section possessed a compact, homogeneous structure for all of the films studied. The solubility of the films (36–40%) did not differ significantly between the different processes evaluated. The EBF films demonstrated lower water vapor permeability (0.12 g mm m⁻² h⁻¹ kPa⁻¹) than the CF and EF films. The infrared spectra did not indicate any strong interactions between the added compounds. Thermoplastic processing of the gelatin films can significantly increase their elongation; however, a more detailed assessment and optimization of the extrusion conditions is necessary, along with the addition of partially hydrophobic compounds, such as surfactants.     

Influence of plasticizers on the water sorption isotherms and water vapor permeability of chicken feather keratin films

Biodegradable films from many protein sources have in recent decades attracted a lot of attention for their potential use in food protection because they have several advantages over synthetic films, including those related to the environment. The effects of type and concentration of plasticizers on microstructure, sorption isotherms and water vapor permeability (WVP) of films obtained from chicken feather keratin (CFK) were investigated. Keratins were extracted with an aqueous solutions of urea, 2-mercaptoethanol and surfactant. The protein was dosed and the maximum concentration achieved was 12 g/100 ml. The protein concentration in the keratin film solution was standardized at 7 g/100 ml for the preparation of the films by casting. The results showed that increasing the plasticizer concentration caused a decrease in barrier properties and favored water adsorption by the polymeric network, increasing the moisture content of the films. The monolayer moisture content was 8.76 times higher for films made with glycerol than films made without plasticizer and 12 times higher than films plasticized with PEG 4000. The same behavior was observed for the water solubility coefficient, which increased with increasing plasticizer concentration.     

Physical and mechanical properties of peanut protein films

The properties of peanut protein films were modified using physical and chemical treatments, and their effects on color, mechanical strength, water solubility and barrier to water vapor and oxygen of the films were investigated. Physical treatments consisted of heat denaturation of film-forming solution for 30 min at 60°C, 70°C, 80°C and 90°C, ultraviolet irradiation of films for up to 24 h, and three ultrasound processes of film-forming solution. Chemical treatments consisted of addition of aldehydes and anhydrides. Heat curing at 70°C, ultraviolet irradiation for 24 h, ultrasound for 10 min in a water-bath, and formaldehyde and glutaraldehyde addition caused a significant increase in the tensile strength of the films. The water vapor permeability (WVP) and oxygen permeability (OP) of the films decreased after heat denaturation and aldehyde treatment. OP also decreased with UV treatment. Heat curing was the most effective treatment, making the films stronger, more resistant to water and less permeable to water vapor and oxygen.     

Mechanical and barrier properties of biodegradable soy protein isolate-based films coated with polylactic acid

Polylactic acid (PLA)-coated soy protein isolate (SPI) films were prepared by dipping SPI film into PLA solution. The effects of coating on improvements in mechanical and water barrier properties of the film were tested by measuring selected film properties such as tensile strength (TS), elongation at break (E), water vapor permeability (WVP), and water solubility (WS). TS of SPI films increased from 2.8±0.3 up to 17.4±2.1 MPa, depending on the PLA concentration of the coating solution, without sacrificing the film's extensibility. In contrast, the extensibility of SPI film coated with solution containing more than 2 g PLA/100 ml solvent, increased. WVP of PLA-coated SPI films decreased from 20 to 60 fold, depending on the concentration of PLA coating solution. Water resistance of SPI films was greatly improved as demonstrated by the dramatic decrease in WS for PLA-coated films. The improvement in water barrier properties was mainly attributed to the hydrophobicity of PLA.     

Film and pharmaceutical hard capsule formation properties of mungbean,waterchestnut, and sweet potato starches

Biodegradable films were developed using mungbean, waterchestnut and sweet potato starches as base raw materials. The physical and mechanical properties of the films were compared with gelatin and HPMC films. The same starches were used to develop hard capsules for utilization in the pharmaceutical industry as a substitute for gelatin or animal based products. Starches with high amylose content had excellent film and hard capsule forming abilities and properties compared to the starches with low amylase content. The starch films also had excellent oxygen barrier properties (0.048 ± 0.008 to 0.070 ± 0.009 fl m/m² s Pa), but water barrier properties (1.1 ± 0.5 to 1.8 ± 0.4 ng m/m² s Pa) were higher than LDPE (0.00064 ng m/m² s Pa) synthetic polymer films. The tensile strength values of starch films (12.1 ± 0.7 to 19.0 ± 2.2 MPa) were not significantly different from gelatin (19.5 ± 1.6 MPa) and HPMC (19.9 ± 1.2 MPa) films. In the case of elongation properties, starch films had lower values (42.2 ± 7.7 to 79.4 ± 9.2%) than gelatin film (122.0 ± 14.6%), but higher than HPMC film (13.8 ± 4.2%). Molecular (SEC-MALLS) and physical (viscosity) characterization of vegetable starches, indicated that the starches with high amylose content produced better biopolymer films and capsules compared to the starches with low amylose and high amylopectin content. Biodegradable films and hard capsules for pharmaceutical applications could be developed from vegetable starches with similar physical and mechanical properties as synthetic and gelatin products.