可食性大豆分离蛋白膜制备与性质

为探索新型生物膜材料的制备,以大豆分离蛋白为基本材料,探究大豆分离蛋白(SPI)、增塑剂(甘油)、还原剂(Na_2SO_3)、乙醇等添加量和处理温度、成膜液pH、成膜介质等条件对膜的完整率、厚度、透光率、水溶率、水蒸气透过系数、透油性等性质的影响。当SPI浓度在2%~6%时,随着添加量的增加,成膜变得容易,但是膜的厚度增加、水蒸气透过系数和透油系数变大、色泽变深。甘油添加量在2%以下可以改善膜的柔韧性,同时降低膜的透气性能和透油性。添加5%的乙醇也可以降低膜的透气性和透油性。添加0.1%的Na_2SO_3可以改善膜的色泽,同时降低膜的透油性。适当提高处理温度和溶液pH可以降低膜的透气性和透油性。     

Development and characterization of cassava starch and soy protein concentrate based edible films

The sensory attributes, mechanical, water vapour permeability (WVP) and solubility properties of cassava starch and soy protein concentrate (SPC)‐based edible films of varying levels of glycerol were studied. Addition of SPC and glycerol up to 30% and 20%, respectively, reduced stickiness and improved colour and appearance of the films. Tensile strength (TS), elastic modulus (EM) and elongation at break (EAB) of films increased, while film solubility (FS) and WVP decreased with SPC and glycerol up to 50% and 20% level, respectively, ranging from 20.33 to 26.94 MPa (TS), 41.33 to 72.76 MPa (EM), 7.90 to 12.28 MPa (EAB), 15.07 to 31.90% (FS) and 2.62 to 4.13 g H₂O mm m^?2 day kPa (WVP). The TS, EAB and WVP were higher for the biofilms than for low‐density polyethylene and cellophane films.     

Physical and mechanical properties of water resistant sodium alginate films

Properties of sodium alginate films were modified using two different methods of CaCl₂ treatment, i.e. the direct addition of CaCl₂ into film making solution (mixing films) and the immersion of alginate films into CaCl₂ solutions (immersion films), and their treatment effects on tensile strength (TS), percentage elongation at break (E), water vapor permeability (WVP), and water solubility (WS) of the films were investigated. TS and E of the mixing films were not changed considerably, but those of the immersion films changed considerably with significant (P<0.05) increase in TS and decrease in E. WVP of the immersion films decreased significantly (P<0.05), but that of the mixing films did not decreased. Water resistance measured by WS was not improved with the mixing films, but the alginate films became water resistant when they treated by immersing in higher than 2 g/100 ml CaCl₂ solutions. Water adsorption by the films also decreased in the immersion films. Swelling ratio (SR) of the immersion film decreased with temperature without affecting WS of the films.     

Mechanical and physical properties of calcium-treated gellan films

The physicochemical properties of Ca²⁺-treated gellan films plasticized with glycerol were investigated as a function of CaCl₂ concentration (0–20%, w/w) in an aqueous soaking solution. Films were examined based on their mechanical properties, water vapor permeability (WVP), swelling index (SI), thickness and opacity. The SI was lower for Ca²⁺-treated films relative to a control, however, above 13% (w/w) CaCl₂ no differences in SI were found. At 13% (w/w) CaCl₂, tensile and puncture strengths reached a maximum. Tensile elongation, puncture deformation, film thickness and WVP were lower for CaCl₂-treated films than untreated, however, all increased with CaCl₂ concentration. Opacity of gellan films increased with the Ca²⁺-treatment relative to the untreated film, however declined as CaCl₂ concentration increased. In general, Ca²⁺-treated gellan films were stronger, acted as better water vapor barriers, swelled less when in contact with water, and became less pliable and transparent.     

Effects of Salts and pH on Heating-Related softening of Snap Beans

The effects of salts and pH on softening during cooking were tested by modifying solutions in which pods were heated. Ca displacement was minimized by soaking heated pods in 0.2M CaCl₂ before measuring firmness. Softening was increased independently by the presence of salts and when pH was raised from 5.2 to 6.2. Cations decreased firmness in the order Li > Na = K > NH4 and Ca > Mg. Anions decreased the firmness in the order SO₄ > acetate > CI > NO₃. Firmness differences persisted at long heating times. The results support the hypothesis that pectin β-elimination was the principal softening reaction.     

Edible Films and Coatings from Soy Protein

A method was developed by which films could be prepared from commercial isolated soy protein (ISP). ISP was treated with alkali (ATISP) to alter film orooerties. Water vapor oermeability (WVP). oxygen‘permeability (O₂P), tensile strength (TS), percent elongatidn (%E), and appearance of ISP and ATISP were compared. Alkali treatment had no effect on WVP. O₂P, and TS, gave hieher %E, and improved film appearance. Films properties were also compared at pH 6, 8, 10, and 12. In general, pH 6 gave higher WVP and O₂P and lower TS and %E; while higher pH gave lower WVP and O₂P and higher TS and %E. ATISP films could not be produced at pH 6. Film appearance generally improved with increased pH.     

Development of bioactive edible film from turmeric dye solvent extraction residue

We developed and characterized turmeric flour films using the turmeric dye solvent extraction residue. We evaluated how the heating temperature and pH affected film properties using a 2² central composite design. Multi-response analysis furnished the film formulation that offered larger resistance to break, as well as lower water solubility, WVP, and opacity. The heating temperature and pH affected the mechanical properties, solubility, moisture content, WVP, and opacity of the resulting film. High heating temperature promoted more interactions between the polymers present in the turmeric flour (starch, protein, lipid, and fiber), affording a more resistant polymeric structure with lower WVP, moisture content, and opacity. Higher pH values also favored a more mechanically resistant and dense matrix with lower water solubility and WVP. The optimized conditions were: T = 86.7 °C and pH = 8.5. The films produced under these conditions displayed high mechanical strength (18 MPa), low solubility (36%), and low WVP (0.167 g mm h⁻¹ m⁻² kPa⁻¹). However, because these films contained lignocellulosic fibers, they presented low elongation at break (1.8%), which elicited a non-continuous structure. HPLC and DPPH assays showed that the turmeric dye solvent extraction residue can be a promising source to develop films with antioxidant activity.     

Structure-modifying alkaline and acidic pH-shifting processes promote film formation of soy proteins

The effect of pH-shifting, a process that induces the molten globule state in proteins, on the film-forming potential of soy protein isolate (SPI) at different temperatures was investigated. Partial unfolding at pH 1.5 or 12, followed by refolding at pH 7.0, was performed to alter the protein structure. Glycerin-plasticised films were prepared from pH-treated SPI at ambient temperature (20 °C), or by heating at 50, 60, 70, or 80 °C (30 min). Tensile strength (TS), elongation at break (EAB), water vapour permeability (WVP), protein solubility (pH 3–7), and non-participating proteins of films were analysed, and the film microstructures were examined. The pH₁₂-treated SPI spontaneously formed a transparent, slightly yellowish film at 20 °C, which had the greatest EAB, while pH_1.5-treated and native SPIs required preheating at 50 and 70 °C, respectively, to form a film. Heating generally decreased solubility and WVP but increased TS. Films formed from both pH₁₂- and pH_1.5-treated SPIs were more elastic (up to 2-fold greater in EAB, P < 0.05) than the film formed from untreated SPI despite slightly reduced TS and WVP. Electrophoresis revealed disulphide bonds between A and B subunits of glycinin being a dominant force in pH₁₂- and pH_1.5-treated SPI films, while noncovalent forces were abundant in untreated SPI films. The pH₁₂-treated SPI film consisted of more interactive protein strands than other SPI films, which seemed to explain its superior elastic properties.     

Migration analysis,antioxidant, and mechanical characterization of polypropylene-based active food packaging films loaded with BHA,BHT, and TBHQ

Polypropylene (PP) based active composite films were prepared by adding butylated hydroxy anisole (BHA), butylated hydroxytoluene (BHT), and tertiary butylated hydroquinone (TBHQ) antioxidants using the extrusion molding process. All concentrations of BHT, 2% to 3% BHA, and 3% TBHQ significantly increased the tensile strength (TS) of the composite films compared with control films. Increasing antioxidant concentration decreased TS values for BHT films, whereas an opposite trend was observed for BHA and TBHQ films. BHA at < 2%, BHT at > 2%, and TBHQ at all added concentrations significantly reduced elongation at break (E_b) of the composite films compared to control films. Water vapor permeability (WVP) of 1% BHT film was not significantly different from control. However, other antioxidants especially at increased concentrations significantly increased WVP values. TBHQ films with 300% to 662% increase had the highest WVP and BHT films with 5% to 81% increase had the lowest WVP among composite films. All three antioxidants had a negative effect on the transparency of the films; however the effect of BHA at higher concentrations was greater. The antioxidants did not change the color attributes of the films. Films containing all antioxidants showed 2,2-diphenyl-1-picrylhydrazyl radical-scavenging activity, which increased with increase in their concentration, especially for those containing 3 wt.% BHT and TBHQ. Overall, incorporating BHA and BHT into a PP matrix improved mechanical, barrier, antioxidant properties, and film appearance and consequently were proposed for the development of antioxidant active PP films. TBHQ film is not recommended for food packaging because of its weak mechanical properties (lower E_b and TS values, higher WVP, and greater migration).     

Effect of Salt and Ethanol Addition on Zein–Starch Dough and Bread Quality

Development of viscoelastic doughs from non‐wheat proteins allows for a wider range of gluten‐free products. Little work has been completed to describe mechanisms of zein functionality in food systems. To identify factors responsible for dough development in zein–starch mixtures and their influence on zein bread quality, a mixture of 20% zein–80% maize starch was mixed with water and various reagents. Salts, NaSCN, NaCl, and Na₂SO₄ were evaluated at concentrations from 0 to 2M for their influence on the properties of zein–starch dough systems. NaSCN at low concentrations produced softer dough. Ethanol treatments produced softer more workable dough in the absence of salts. Increasing concentrations of NaCl and Na₂SO₄ resulted in coalescing of the proteins and no dough formation. The addition of β‐ME had minimal softening effects on zein–starch dough. Specific volumes of zein–starch bread increased with decreasing NaCl addition in bread formulations. Likewise, including 5% ethanol (v/v) in the bread formula increased bread quality.     

Water Solubility, Mechanical, Barrier, and Thermal Properties of Cross-linked Whey Protein Isolate-based Films

Water solubility, hermal properties, tensile strength, percent elongation, oxygen permeability (OP), water‐vapor permeability (WVP) of cross‐linked glycerol plasticized whey protein isolate films were studied to determine the effect of cross‐linkers (glutaraldehyde, formaldehyde, dialdehyde starch, carbonyldiimidazole, and UV irradiation) on film properties. With the exception of UV treatment, solubility of the films decreased (P>0.05) upon treatment of the film‐forming solutions with chemical cross‐linkers. Tensile strength increased (P>0.05), whereas percent elongation was not affected by cross‐linking. Chemical cross‐linking increased (P>0.05) WVP and decreased (P>0.05) OP of the films. UV treatment had no effect on WVP and O P. With the exception of UV‐treated films, both onset temperature and degradation temperatures, as determined by differential scanning calorimetry, were increased upon cross‐linking.     

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.     

The effect of fatty acid content on water vapour and carbon dioxide transmissions of cellulose-based edible films

Water vapour and CO₂ transmissions of methyl cellulose (MC)-based edible films with varying amounts of the fatty acids, stearic acid (SA), palmitic acid (PA) and lauric acid (LA) were studied and the results were compared with those obtained for a film without added fatty acid. Water vapour transmission rate (WVTR), water vapour permeance (WVPN) and water vapour permeability (WVP) values of films were determined by measuring the amounts of water vapour transmitted through the film and then adsorbed on anhydrous CaCl₂ as a function of time, using a static method. A recently-developed static method which utilises ascarite to adsorb carbon dioxide transmitted through the film was employed for the determination of carbon dioxide transmission rate (CO₂TR), carbon dioxide permeance (CO₂PN) and carbon dioxide permeability (CO₂P) of films. Among the three fatty acids studied, SA was found to be the most effective in decreasing both the water vapour and the CO₂ transmissions of films. In general, it was observed that WVTR, WVPN and WVP values of films decreased with increasing fatty acid content in the film composition. CO₂ transmission parameters also decreased with increasing SA and PA contents but increased with increasing LA content of films.     

有机蒙脱土对热塑性氧化淀粉膜性能影响

以不同有机蒙脱土为增强剂,采用熔融挤出流延制膜工艺,研究不同有机蒙脱土对淀粉膜性能影响。结果表明,有机蒙脱土可有效提高淀粉膜拉伸强度和断裂伸长率、增加膜透明度、并降低膜的水蒸气透过率和水溶性。添加不同有机蒙脱土对膜性能有不同影响,DK_1和DK_5蒙脱土可有效提高膜断裂伸长率,DK_4蒙脱土可明显提高膜拉伸强度,DK_3蒙脱土可提高膜透明度,DK_2蒙脱土可有效降低膜的水蒸气透过率。     

Effects of different salts on the gelation behaviour and mechanical properties of citric acid-induced tofu

To elucidate the effects of salts on the properties of citric acid-induced tofu gel, gelation was induced in the presence of KCl, CaCl₂ or CaSO₄, and gypsum tofu was used as a reference. The textural properties, water-holding capacity (WHC), rheological behaviour, aggregate size distribution and microstructure of the tofu were evaluated. The results indicated that the addition of 0.10 g/100 mL KCl,0.05 g/100 mL CaCl₂ and 0.15 g/100 mL CaSO₄ yields more elastic tofu with high water-holding capacity. The WHC of tofu induced in the presence of salts was similar to that of gypsum tofu, while the tofu was firmer and less elastic than gypsum tofu. The maximum elasticity of citric acid-induced tofu was obtained with addition of 0.15 g/100 mL CaSO₄. These results are useful to understand the effects of different salts on soymilk gelation and provide a theoretical base for the quality improvement of citric acid-induced tofu.     

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.     

Effect of flaxseed meal on the dynamic mechanical properties of starch-based films

Starch (S)–flaxseed meal (FM) biofilms were prepared from potato and maize starch by incorporating FM up to 15% (dry solid basis) and using glycerol as plasticizer. The dynamic mechanical properties, tensile properties and water vapor permeability (WVP) of these films were measured. The storage modulus of both the starch (control) and starch–FM films decreased as temperature increased. Tan δ increased initially in all the films with increase in temperature until a peak value was reached which allowed the determination of glass transition temperature (T_g). Both tensile strength and Young’s modulus of the starch–FM films increased with increase in the FM content. The WVP of the potato starch–FM films first increased to 2.261 (×10⁵ g m⁻² h⁻¹ Pa⁻¹) when FM content increased to 5% and decreased down to 1.832 (×10⁵ g m⁻² h⁻¹ Pa⁻¹) with further increase in the FM content to 15%. While the WVP values of the cornstarch and corn starch–FM films were not significantly (p > 0.05) different. The incorporation of FM increased the tensile strength, decreased the % elongation at break and increased the T_g.     

Tensile and water vapour properties of calcium‐crosslinked alginate‐cashew tree gum films

In this study, sodium alginate films were blended with cashew tree gum (CTG) and immersed in CaCl₂ solution. The influence of CTG concentration and immersion time in CaCl₂ on tensile properties, water vapour permeability and water solubility (WS) of alginate films was evaluated. Glycerol‐plasticized alginate/CTG films were cast on glass plates, which were then immersed in a 2% CaCl₂ solution to crosslink alginate. CTG concentration in the film solution and immersion time in CaCl₂ bath were varied according to a central composite design. Tensile strength, Young′s modulus, WS and water vapour barrier of the films were favoured by higher immersion times in CaCl₂ and lower CTG concentrations. The negative CTG effects on such properties have been attributed to competition between the polysaccharides for interactions with calcium ions, reducing crosslinking density and loosening the film structure. On the other hand, this loosening effect resulted in higher film flexibility at higher CTG concentrations.     

Effects of starch acryloylation on the grafting efficiency,adhesion, and film properties of acryloylated starch‐g‐poly(acrylic acid) for warp sizing

In order to enhance the grafting efficiency of graft copolymerization of granular cornstarch with acrylic acid (AA) for improving the adhesion and film properties of starch‐g‐poly(acrylic acid) used as sizing agent, the esterification of hydrolyzed starch with acryloyl chloride was applied before graft copolymerization. The influence of three common initiators on the copolymerization were also studied. The initiators included ceric ammonium nitrate [Ce(NH₄)₂(NO₃)₆], hydrogen peroxide/ferrous ammonium sulfate [H₂O₂/FeSO₄ · (NH₄)₂SO₄], and potassium persulfate/sodium bisulfite [K₂S₂O₈/NaHSO₃]. It was found that acryloylation of starch before the copolymerization was an effective method for substantially enhancing the grafting efficiency and improving the performances such as adhesion‐to‐fibers and mechanical properties of grafted starch film. The acryloylation could increase the efficiency to 67–81% when the degree of substitution (DS) of acryloylated starch ranged from 0.010 to 0.036. The adhesion to polyester and cotton fibers reached their maximum at DS = 0.010 and 0.022, respectively. Strong and tough film was obtained when the DS value was in a range of 0.010–0.022. H₂O₂/FeSO₄ · (NH₄)₂SO₄ redox system was more appropriate for initiating the copolymerization of acryloylated starch with AA.     

Physical and Mechanical Properties of Biobased Materials Starch,Polylactate and Polyhydroxybutyrate

Commercial and semi‐commercial biobased materials (Polylactate, PLA, polyhydroxy‐butyrate, PHB, wheat starch and corn starch) were investigated. Physical and mechanical characterisation (tensile strength, elongation, tear strength, compression, gas permeability (CO₂ and O₂) and water vapour permeability (WVP)) was examined. Tests on both films and cups show potential use of these materials for primary food packaging, especially PLA and PHB. An interesting O₂:CO₂ permeability ratio (1:7 to 1:12) was seen, which make these materials suitable for packaging of food with high respiration. The mechanical properties were comparable to conventional materials such as polyethylene (PE) and polystyrene (PS). The WVP measured on films ranged from 12.6 to 18.6 [g H₂O/(m² ? 24h)], and on cups the range was 2.2 to 10.5 [g H₂O ? 700 μm/(m² ? 24h)]. The WVP for the starch‐based materials seems to be the most crucial parameter, and needs improvement if these materials are to be used as food packaging.