改性纳米TiO2-大豆分离蛋白抑菌保鲜膜的制备及其性能

选取表面改性的纳米TiO2制备大豆分离蛋白（soy protein isolate,SPI）膜,以复合膜的抗拉强度、断裂伸长率、水蒸气透过率、透光性、透氧性、透二氧化碳性为评价指标,通过单因素试验和正交试验优化制膜最佳工艺。结果表明,复合膜的最佳成膜工艺条件为SPI添加量4.5?g/100?mL、改性TiO2添加量2.0?g/100?mL、甘油添加量1.5?g/100?mL,其接触角为115.3°。傅里叶变换红外光谱仪实验结果表明,改性纳米TiO2-SPI复合膜与纳米TiO2-SPI复合膜、普通SPI膜在4 000～600 cm－1波数范围内呈现出相似的红外光谱,且由扫描电子显微镜以及原子力显微镜扫描结果可以看出,与纳米TiO2-SPI复合膜及普通SPI膜相比,改性纳米TiO2-SPI复合膜表面更为致密平整,表面性能表现更佳,改性纳米TiO2-SPI复合膜的结构性质要优于纳米TiO2-SPI复合膜及普通SPI膜。当改性TiO2添加量为2?g/100?mL、365?nm波长紫外灯照射6?h时,复合膜对大肠杆菌和李斯特菌的抑菌性能最强,抑菌率达到91.14%和92.81%。改性纳米TiO2-SPI复合膜具有一定的机械性能和良好的抑菌性能,在食品包装应用方面具有巨大潜力。     

环境温度对明胶-普鲁兰多糖可食性膜性能的影响

研究环境温度对明胶-普鲁兰多糖膜机械性能、氧气透过率、水蒸气透过率、油脂透过率、颜色和溶水性的影响,并比较温度对明胶膜、明胶-普鲁兰多糖膜和普鲁兰多糖膜的影响。结果表明：环境温度升高提高了明胶-普鲁兰多糖膜的机械性能,而对其阻水性、阻氧性、阻油性和溶水性没有显著的影响,明胶-普鲁兰多糖膜有轻微的黄化。明胶-普鲁兰多糖膜的抗拉强度、阻水性、阻氧性能优于明胶膜和鲁兰多糖膜。     

Mechanical,Physical, Antioxidant,and Antimicrobial Properties of Gelatin Films Incorporated with Thymol for Potential Use as Nano Wound Dressing

The aim of this study was to determine the properties of gelatin films incorporated with thymol. Gelatin films were prepared from gelatin solutions (10% w/v) containing thymol (1, 2, 4, and 8% w/w), glycerol (25% w/w) as plasticizer, and glutaraldehyde (2% w/w) as cross‐linker. Cross‐likened films showed higher tensile strength, higher elongation at break, lower Young's modulus, lower water solubility, lower swelling, lower water uptake, and lower water vapor permeability. Incorporation of thymol caused a significant decrease in tensile strength, increase in elongation at break, decrease in Young's modulus, increase in water solubility, decrease in swelling and water uptake, and increase in water vapor permeability slightly. The films incorporated with thymol exhibited excellent antioxidant and antibacterial properties. The antibacterial activity of the films containing thymol was greatest against Staphylucoccus aureus followed by Bacillus subtilis followed by Escherichia coli and then by Pseudomonas aeruginosa. Thus, gelatin films‐containing thymol can be used as safe and effective source of natural antioxidant and antimicrobial agents with the purpose of evaluating their potential use as modern nano wound dressing. Practical Application : This study clearly demonstrates the potential of gelatin films incorporated with thymol as natural antioxidant and antimicrobial nano film. Such antimicrobial films exhibited excellent mechanical, physical, and water activities and could be used as antibacterial nano wound dressing against wounds burn pathogens.     

海藻酸钠对鱼皮明胶膜理化特性的影响

采用罗非鱼皮明胶与海藻酸钠混合制备可食性复合膜,研究海藻酸钠含量对复合膜理化性质的影响。结果显示：单一罗非鱼皮明胶具有良好的成膜能力,但是机械性能差,将海藻酸钠添加到明胶膜中得到的复合膜抗拉强度和断裂伸长率有明显改善,海藻酸钠添加量在40%时,抗拉强度达最大值6.6?MPa,相对于纯明胶膜（5.5?MPa）和纯海藻酸钠膜（4.6?MPa）分别增加20%和43%,断裂伸长率也在此时达到最大值120%,比纯明胶膜（64%）和纯海藻酸钠膜（88%）分别增加87.5%和26.7%。海藻酸钠水溶性和吸湿率分别高达100%和48.7%,经共混后复合膜的水溶性降低至55%以下,吸湿率介于25%～40%之间,有较大的改善。流变学特性和X射线衍射分析结果表明：明胶和海藻酸钠具有良好的相容性,二者共混可制得性质稳定的复合膜,海藻酸钠与明胶的复合膜液为非牛顿流体,黏度和增稠能力较单一明胶膜有所增加。     

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.     

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.     

Improved microstructure and properties of the gelatin film produced through prior cross‐linking induced by horseradish peroxidase,glucose oxidase and glucose

The effects of prior enzymatic cross‐linking of bovine gelatin via horseradish peroxidase, glucose oxidase and glucose on microstructure and properties of the target film (cross‐linked gelatin film) were assessed. The cross‐linked gelatin film exhibited similar film thickness and moisture content, lower water solubility and higher opacity than the gelatin film directly prepared with bovine gelatin. The cross‐linked gelatin film also demonstrated improved thermal stability and mechanical properties, characterised by higher melting point and glass transition temperature, enhanced tensile strength and elongation at break and greater storage modulus. Prior gelatin cross‐linking resulted in 30.2% and 68.6% reductions in water vapour and CO₂ permeability of the cross‐linked gelatin film, respectively, but did not affect oil permeability. Furthermore, the cross‐linked gelatin film possessed smaller cross‐sectional voids (diameter 100?360 nm vs. 200?595 nm) than the bovine gelatin film. This study shows that cross‐linking can efficiently improve film microstructure and properties of the gelatin‐like products.     

添加单宁对明胶可食膜性质的影响

如何提高明胶膜的机械性能和阻隔性能,一直以来是可食膜研究领域的重要内容。本文以不同剂量(0 mg/g、10 mg/g、20 mg/g、30 mg/g和40 mg/g)单宁添加于明胶液并以浇注法成膜,然后对膜的理化性质进行分析。研究结果发现单宁有效提高了明胶膜的拉伸强度,但降低了其断裂伸长率;当单宁添加量为30 mg/g(明胶干基)时,其拉伸强度最大(22.10 MPa),断裂延伸率最小(40.12%)。与对照膜相比,单宁的添加降低了复合膜水溶性,水蒸气透过率和氧气透过率。在单宁含量添加范围内,水蒸气透过性最低为1.49×10-11 g/(Pa·s·m);水溶性最低为27.76%,氧气透过率最低为21.63 meg/kg。同时,DSC分析表明单宁提高了明胶膜的热稳定性。FT-IR图谱表明单宁与明胶之间发生了以氢键和疏水键为主的物理交联作用。所以,单宁-明胶复合膜在食品包装方面具有潜在的开发价值。     

Water Vapor Permeability and Mechanical Properties of Soy Protein Isolate Edible Films Composed of Different Plasticizer Combinations

Water barrier and mechanical properties were measured for soy protein isolate (SPI) films plasticized with glycerol (GLY) and 1 of the plasticizers (propylene glycol [PG], polyethylene glycol [PEG], sorbitol [SOR], or sucrose [SUC]) at a ratio of 25:75, 50:50, 75:25, and 0:100. Plasticizer type as well as the plasticizer ratio in the GLY: plasticizer mixtures affected the film water barrier and mechanical properties. An addition of as little as 25% of a less hygroscopic plasticizer in the mixture induced significant reduction in water vapor permeability (WVP) of SPI films. However, at least 50% of the mixture needs to be GLY to show significant improvement in tensile strength (TS). From our experimental design, 50:50 GLY:SOR was the recommended combination because of its comparatively low WVP value and relatively high flexibility and strength. Incompatibility of GLY:PEG plasticizer mixture in SPI film was observed by surface migration of PEG from the film matrix.     

The impact of anthocyanin-rich red raspberry extract (ARRE) on the properties of edible soy protein isolate (SPI) films

To modify the properties of edible soy protein isolate (SPI) films, 0.5% anthocyanin-rich red raspberry (Rubus strigosus) extract (ARRE) (0.5 g raspberry powder in 95% ethyl alcohol/water/85% lactic acid [80:19:1. v/v/v]) was incorporated into film-forming solutions. ARRE resulted in an SPI film having significantly enhanced tensile strength (P < 0.05) and % elongation at break (P < 0.05), as well as increased water swelling ratio (P < 0.05) and in vitro pepsin digestibility (P < 0.05). The resultant films also showed significantly decreased water solubility and water vapor permeability (P < 0.05). In addition, ARRE increased darkness, redness, and yellowness film appearance as evidenced by a lower L* (P < 0.05), greater positive a* (P < 0.05), and a higher b* (P < 0.05) than the control film. Scanning electron microscopy images revealed that extract-added films had denser and more compact cross-section microstructure. Fourier transform infrared spectra illustrated that ARRE-created hydrogen bonding involved conformational changes of soy protein without destroying its backbone structure. SDS-PAGE electrophoretograms revealed that the extract induced intermolecular interaction of the soy protein monomers. Natural plant extracts would be a promising ingredient to make SPI films with different physicochemical properties and applications. PRACTICAL APPLICATION: This study characterizes the potential physicochemical changes of SPI film with incorporated raspberry extract. Upon the above modification, the resultant film was found to enhance the applications of pure SPI film in food packaging. For example, SPI-ARRE film could prolong the usage life of SPI film due to increased strength, or could be useful as a desiccant (drying agent) such as a water-absorbing sheet for preserving dried foods due to its increased hydrophilic surface and water-swelling ratio. SPI-ARRE film could also be alternately used as a food wrap with unique color.     

桔子精油优化鱼鳞明胶膜性能的作用研究

为改善鱼鳞明胶膜的性能,测定添加明胶质量的0%、25%、50%、75%、100%桔子精油的可食膜的厚度、机械性能、水溶性、水蒸汽透过率、色泽、透明度和透光率、热性能、红外光谱和抑菌活性。结果表明:随着精油浓度的增加,鱼鳞明胶膜的厚度、断裂伸长率增加,拉伸强度、透光率、水溶性降低,水蒸汽透过率呈现先增加后降低的趋势;差示扫描量热法(DSC)和傅里叶变换红外光谱(FTIR)分析结果表明,鱼鳞明胶分子与桔子精油的部分成分发生相互作用,在一定程度上改善了明胶膜的热稳定性;桔子精油的添加还赋予了鱼鳞明胶膜抑菌作用。综合评价得出75%质量浓度的桔子精油添加量对鱼鳞明胶膜各项性能优化效果最好,本实验结果可为生产高性能的鱼鳞明胶膜提供理论基础。     

大豆蛋白基明胶复合膜性能稳定性分析

以大豆蛋白和明胶为主要原料,采用戊二醛溶液交联方式和戊二醛饱和蒸汽交联制备大豆蛋白基明胶复合膜,通过对两种交联方式制备的复合膜机械性能稳定性和降解性测定,比较分析戊二醛不同交联方式对复合膜机械性能稳定性、降解性及微观结构影响。结果表明,在3个月贮藏期内,戊二醛溶液交联改性、蒸汽交联改性处理复合膜拉伸强度稳定性提高了20.58%、38.51%,延伸率稳定性提高了31.71%、54.49%,水蒸气透过系数稳定性提高了31.74%、52.19%,透氧率稳定性提高了0.24%、18.01%,降解实验中降解速率分别为未经改性处理大豆蛋白基明胶复合膜溶液交联改性处理复合膜蒸汽交联改性处理复合膜。同时,蒸汽交联复合膜表面及拉伸断面形成结构致密的三维立体网络结构。因此,戊二醛蒸汽交联制备的大豆蛋白基明胶复合膜机械稳定性能及微观结构均优于戊二醛溶液交联改性处理复合膜。     

Physical properties and internal microstructures of films made from catfish skin gelatin and triacetin mixtures

Gelatin from catfish skin was obtained by thermal extraction. Triacetin was added to the gelatin at 0, 50, 100, and 150% of the gelatin content to improve the hydrophobic properties of the resulting films. Tween 80 (10% of triacetin amount) was also added as an emulsifier. Internal microstructures of the films were examined using a transmission X-ray microscope (TXM). Other film properties, such as thickness, mechanical properties, water vapor permeability, water solubility, light transparency, and thermal properties were also evaluated. Possible relationships between the internal microstructures and the film properties were hypothesized. The triacetin distribution changed from homogeneous to heterogeneous with its increased content in the films. The addition of triacetin resulted in decreased tensile strength (TS) and increased percent elongation (%E), water solubility, UV and visible light barrier properties, and protein denaturation temperature of the films. Water vapor permeability of the films increased in some treatments (100% and 150% triacetin) possibly due to the heterogeneous distribution of the triacetin and also the increased Tween 80 amount in the films.     

Characterization of ‘wet’ alginate and composite films containing gelatin,whey or soy protein

The following study explored how the addition of various proteins (gelatin, soy protein isolate (SPI) and heated/unheated whey protein isolate (WPI)), at two different concentration levels (1% and 2%), affected the mechanical, microstructural and optical properties of calcium cross-linked ‘wet’ alginate films. Additionally, the water holding capacity and textural profile analysis (TPA) properties were determined for the alginate–protein gels. Adding all types of protein significantly (P < 0.05) decreased the force to puncture the ‘wet’ alginate–protein composite films compared to the control alginate film. The tensile test showed significant differences in tensile strength between the various films but interestingly there was no significant difference in the percent elongation at breaks between any of the films. Micrograph images showed that the SPI and heated WPI formed relatively larger protein clumps/regions in the alginate films whereas the gelatin and unheated WPI appeared to be more integrated into the alginate film. The heated WPI films were the least transparent of all the films, followed by the SPI films. Few TPA differences existed between the alginate–protein gels. However, the alginate–gelatin gels did have significantly less water loss than the other alginate–protein gels suggesting that alginate and gelatin may be the most compatible of all the alginate–protein combinations tested.     

Use of beef,pork and fish gelatin sources in the manufacture of films and assessment of their composition and mechanical properties

This study investigated the properties of different types of gelatin films from solutions of varying gelatin concentrations (4–8 wt %). Gelatin derived from beef, pork and fish skin sources was used to manufacture films using a casting approach. Mechanical properties of gelatin films, water vapour permeability (WVP), oxygen permeability, oil permeability and aqueous solubility of films were evaluated. FTIR spectroscopy was utilized to assess the composition of various gelatin sources so as to determine differences in composition of these sources and ultimately, in overall functionality. High concentration gelatin films had good mechanical properties with tensile and puncture strengths being particularly improved. Gelatin films manufactured from fish skin had the lowest WVP values for each concentration used. All gelatin films possessed excellent barriers to oxygen and oil. Films derived from pork gelatin exhibited lowest water solubility compared to those formed using beef and fish gelatin sources, regardless of the concentrations used. FTIR spectra showed that plasticizer and gelatin were well mixed and interacted well together. The use of higher concentrations of gelatin had the effect of increasing the wavenumber of amide-A in films due to greater interaction occurring between gelatin functional groups.     

明胶/普鲁兰酶改性淀粉膜的制备与性能研究

研究了普鲁兰酶对淀粉膜性能的影响及明胶对普鲁兰酶改性淀粉膜性能的影响。结果表明:与原淀粉膜相比,普鲁兰酶改性淀粉膜的表面更平滑;膜的热稳定性增大,热封性能增强;抗拉强度、水蒸气透过率和透光率分别增加了75%、18%和35%,断裂伸长率降低了53%。与未添加明胶的酶改性淀粉膜相比,添加明胶后,膜的表面变粗糙;膜的阻水性能与阻光性能增强,热封性能变差。当明胶添加量为10%时,膜的抗拉强度增加了17.6%;当明胶添加量为25%时,膜的断裂伸长率增加了54.3%;在明胶添加量为15%时,膜的热稳定性最大。     

Preparation and functional properties of fish gelatin–chitosan blend edible films

With the goal of improving the physico-chemical performance of fish gelatin-based films, composite films were prepared with increasing concentrations of chitosan (Ch) (100G:0Ch, 80G:20Ch, 70G:30Ch, 60G:40Ch and 0G:100Ch, gelatin:Ch), and some of their main physical and functional properties were characterised. The results indicated that the addition of Ch caused significant increase (p < 0.05) in the tensile strength (TS) and elastic modulus, leading to stronger films as compared with gelatin film, but significantly (p < 0.05) decreased the elongation at break. Ch drastically reduced the water vapour permeability (WVP) and solubility of gelatin films, as this decline for the blend film with a 60:40 ratio has been of about 50% (p < 0.05). The light barrier measurements present low values of transparency at 600 nm of the gelatin–chitosan films, indicating that films are very transparent while they have excellent barrier properties against UV light. The structural properties investigated by FTIR and DSC showed a clear interaction between fish gelatin and Ch, forming a new material with enhanced mechanical properties.     

Edible films produced with gelatin and casein cross-linked with transglutaminase

In this study, transglutaminase was used to produce cross-linked casein, gelatin and casein–gelatin blend (100:0, 75:25, 50:50, 25:75 and 0:100) edible films. Cross-linking was investigated by SDS–PAGE. Mechanical and water vapor barrier properties of the films were characterized using ASTM procedures, and the film morphology was evaluated using scanning electron microscopy. The casein–gelatin film showed significant greater elongation values (P < 0.05) with or without transglutaminase treatment, as compared to films made from gelatin or casein alone. Mixtures of casein and gelatin produced a synergistic effect only observed in the film elongation, while no improvement was detected for tensile strength and water vapor barrier properties, except for the casein:gelatin (75:25) formulation with transglutaminase, which showed the lowest water vapor permeability value (5.06 ± 0.31 g mm/m² d kPa). Enzymatic cross-linking also induced a substantial increase in the high molecular weight protein components in the film forming solutions.     

Physicochemical,Antioxidant, In Vitro Release,and Heat Sealing Properties of Fish Gelatin Films Incorporated with β-Cyclodextrin/Curcumin Complexes for Apple Juice Preservation

The antioxidant activity of gelatin film is poor. Curcumin is a natural antioxidant, but its main disadvantage is low aqueous solubility. In this study, curcumin was encapsulated by β-cyclodextrin to prepare βCD/CUR complex. Gelatin films incorporated with βCD/CUR complexes (GL-βCD-CUR films) were fabricated. The effects of curcumin content on their properties were investigated. Results showed that the water solubility of curcumin was improved in βCD/CUR complex. The βCD/CUR complex containing 2.5 mg curcumin had smaller size and more homogeneous distribution. The thicknesses of all films were about 87 μm and there were no significant differences (p > 0.05). The optimal tensile strength (TS) and elongation at break (EAB) of GL-βCD-CUR films were observed at the curcumin content of 2.5 mg. With the increase of curcumin concentration, water vapor permeability (WVP) of gelatin-based films decreased from 2.88 to 2.38 × 10^?10 g m^?1 Pa^?1 s^?1 and water content (WC) decreased from 34.64 to 24.72%, but water solubility (WS) increased from 21.22 to 59.75%. GL-βCD-CUR films exhibited lower light transmission in UV light compared with GL-βCD film. SEM provided that there was a good compatibility between gelatin molecules and βCD/CUR complexes. FTIR proved that no functional groups appeared or disappeared. A significant increase in antioxidant activity and the stability of this activity along with a lower release rate of curcumin in food simulant were observed in gelatin films incorporated with βCD/CUR complexes. The heat sealing property of GL-βCD-CUR films containing 1 or 2.5 mg curcumin was better than that of film containing 5 mg curcumin. The L values of red Fuji (Malus pumila mill) apple juice packed by GL-βCD-CUR films reduced slowly. The slowest decline in total polyphenol content was found in GL-βCD-2.5CUR group. Our results indicated that the incorporation of βCD/CUR complex significantly enhanced the antioxidant activity of gelatin film, and the GL-βCD-CUR film can be used in apple juice preservation.