Effect of freezing on physical properties of whey protein emulsion films

The objective of this work was to study the effect of the freezing process on physical properties of whey protein emulsion films with different beeswax content dried at 5 °C. Thickness, microstructure, water vapour permeability, solubility in water, sorption isotherms and mechanical properties were measured in Control and Frozen films. The freezing process did not cause fractures or perforations in films, but films with beeswax showed a change in the appearance of the lipids after freezing. Only films with 40% of beeswax showed a significant increase in the water vapour permeability after freezing. The freezing process did not affect film solubility in water but produced small differences in the equilibrium moisture content values. In the puncture test, the freezing process increased puncture strength and deformation of films without beeswax but those parameters were not affected in films with beeswax. In tensile test, tensile strength and elastic modulus decreased, but elongation was not affected by freezing process. Principal component analysis accomplished an adequate condensation of the date grouping samples according to film formulation and treatment (Control and Frozen films). Indeed, the relationships of sample grouping and measured parameters were enlightened by principal component analysis. In conclusion, whey protein emulsion films were resistant to the freezing process (freezing, frozen storage and thawing) and could be a good alternative as a treatment to preserve the quality of frozen foods.     

Water Vapor Permeability, Solubility, and Tensile Properties of Heat-denatured versus Native Whey Protein Films

Whereas native whey protein films were totally water soluble, heat denatured films were insoluble. Heat-denatured whey protein films had higher tensile properties than native whey protein films. However, native and heat-denatured films had similar water vapor permeability (WVP). The pH of the film-forming solution did not have any notable effect on film solubility, mechanical properties, or WVP. Results suggest that covalent cross-linking due to heat denaturation of the whey protein is accountable for film water insolubility and higher tensile properties but does not affect WVP of the films.     

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.     

Physical and Mechanical Properties of Pea-Protein-based Edible Films

ABSTRACT: Edible films produced from denatured pea protein concentrate (PPC) solution possessed the strength and elasticity to resist handling. Increasing the concentration of the plasticizer (glycerol) in the film decreased tensile strength and elastic modulus, and increased elongation and water vapor permeability (WVP). Very strong and stretch-able films were obtained from 70/30 and 60/40 of PPC/glycerol composition, respectively. The low WVP value was maintained over a range of glycerol concentration from 20% to 40%, in the dry film. Film solubility was not affected significantly by the amount of the plasticizer. The physical and mechanical properties of the PPC films were comparable with those of soy protein and whey protein films.     

Physical Properties of WPI Films Plasticized with Glycerol, Xylitol, or Sorbitol

ABSTRACT: Effects of glycerol, xylitol, and sorbitol on selected physical properties of whey protein isolate (WPI) films were examined. Increasing glycerol or sorbitol content led to increases in moisture content, water vapor permeability, and % elongation; and decreases in tensile strength, elastic modulus, and glass transition temperatures of the films. Increasing levels of xylitol had no effect on permeability, moisture content, or glass transition temperature of the films, but decreased % elongation, tensile strength, and elastic modulus. Moisture content of the films correlated well with glass transition temperatures. Differences in measured physical properties of films with plasticizer type and concentration may be attributed to differences in the hygroscopic and crystalline properties of the plasticizers.     

单宁酸对鸢乌贼肌原纤维蛋白膜性能的影响

采用葡聚糖接枝的肌原纤维蛋白,以及酸、碱提取等电点沉淀方法提取的鸢乌贼（Symplectoteuthis oualaniensis）蛋白为原料,分别制得酸提、碱提、糖基化肌原纤维蛋白膜,研究不同浓度的单宁酸对蛋白膜物理性能的影响。结果表明：接枝反应后肌原纤维蛋白中自由氨基含量明显降低。成膜液中的自由氨基和巯基的含量随单宁酸添加量增大而显著降低（P＜0.05）。3 种蛋白膜中,糖基化蛋白膜含水量最低,同时具有较高的水溶性和机械强度。在碱性环境下由于单宁酸氧化交联导致蛋白膜颜色明显变深,表面粗糙度增大。此外,单宁酸的引入使得蛋白膜的拉伸强度增加,而断裂伸长率降低。其中,添加1%的单宁酸的糖基化蛋白具有较高的膜拉伸强度和断裂伸长率,分别为1.26 MPa和118%,同时具有较低的水蒸气透过率。此研究对鸢乌贼蛋白用于可食用包装膜的制备以及延长食品货架期具有重要意义。     

Milk Protein-based Edible Film Mechanical Strength Changes due to Ultrasound Process

The effects of ultrasound frequency, acoustic power, and exposure time on the functional properties of whey protein concentrate and sodium caseinate films were examined. Average tensile strength of the ultrasound treated caseinate films was 224% higher than that of the control. The ultrasonic process was more effective on sodium caseinate than whey protein concentrate film. Resistance to puncture was improved for both types of films treated at an acoustic power of 5.22W. Increased exposure time resulted in stronger films. Elongation at break, water vapor permeability, and moisture content of films were not affected by the treatment. Ultrasound showed potential for improving mechanical strengths of milk protein films.     

麦麸纤维/小麦麸质蛋白复合膜碱性乙醇成膜体系影响因素研究

将小麦麸质蛋白(wheat gluten,WG)和麦麸纤维(wheat-bran cellulose,WC)通过溶液共混于碱性乙醇系统,采用流延成膜法制备复合膜。探讨成膜体系中料液比、麦麸纤维含量、甘油添加量、乙醇浓度、体系pH值及黄原胶添加量对复合膜物理性能抗拉强度(tensile strength,TS)、断裂伸长率(elongation at break,EAB)、水蒸气透过系数(water vapor permeability,WVP)、水溶性和透光性等的影响。结果表明:添加麦麸纤维能明显增强小麦麸质蛋白膜的抗拉强度,降低其水蒸气透过系数和水溶性,抗拉强度最高为20.44 MPa,比纯小麦麸质蛋白膜(TS=8.65 MPa)提高了140%;成膜体系各因素对复合膜各物理性能都存在不同程度的影响,其中甘油添加量影响最大,其次为麦麸纤维含量,黄原胶添加量影响最小。该研究可为进一步制备性能优异的小麦麸质蛋白复合膜提供技术参考。     

Physical and mechanical properties of chitosan films as affected by drying methods and addition of antimicrobial agent

Incorporation of an antimicrobial agent into a biopolymer matrix not only affects the antimicrobial property, but also the physical, mechanical and barrier properties of the resulted films. In addition to the effect of antimicrobial agent different drying methods that are used to prepare the films should also be considered. The aim of this study was to investigate the combined effects of drying methods, namely, hot air drying and low-pressure superheated steam drying (LPSSD), and addition of a natural antimicrobial agent, namely, galangal extract, at concentrations of 0%, 0.6%, 0.9%, 1.2% and 1.5% (w/w film forming solution) on selected physical properties (thickness, moisture content, color and opacity), mechanical properties (tensile strength and percent elongation), barrier properties (water vapor and oxygen permeabilities), degree of crystallinity and degree of swelling of antimicrobial films prepared from chitosan. X-ray diffraction (XRD) analysis, Fourier-transform infrared (FTIR) spectroscopy as well as dynamic mechanical analysis (DMA) were also performed and their results used to explain the observed combined effects. The combined effects were noted to have a statistically insignificant influence on the moisture content, thickness and water vapor permeability of the films. On the other hand, the combined effects had a statistically significant influence on the color, degree of crystallinity, degree of swelling, tensile strength, percent elongation and oxygen permeability of the films. Only the galangal extract concentration had a statistically significant influence on the film opacity. The DMA patterns and FTIR spectra confirmed the formation of crosslinkage interactions between the galangal extract and chitosan matrix.     

4种改性淀粉与明胶共混膜的制备与性质比较

该研究对4种改性淀粉（羟丙基二淀粉磷酸酯、羟丙基淀粉、氧化淀粉、氧化羟丙基淀粉）的溶解度、膨胀势、糊化特性、老化值进行了分析和比较。溶解度高、膨胀势小、糊化特性好、老化值低的淀粉,较适宜作为制备共混膜的原料。在此基础上加入甘油或聚乙二醇400（Polyethylene Glycol,PEG400）作为增容剂,并对配方中水和甘油加入量进行了初步摸索,运用紫外、扫描电镜和拉伸试验机测定共混膜的透光性、透水气性、微观形貌和机械性能。结果表明：羟丙基淀粉溶解度最高,为86.42%;膨胀势最低,为0.086%,稳定性更好;黏度较低,老化值较大,流动性高,易于成膜。为4种改性淀粉中最适宜和明胶共混的原料。利用紫外分光光度计进行全波长扫描测量透光率;利用不同时间水保留质量反应透水汽性;用扫描电镜放大500~6 000倍对微观形貌观察,用拉伸材料试验机对机械性能进行测试。通过比较,发现以羟丙基淀粉为原料的共混膜,具有较好的透明度（优于纯明胶样品的透光度）,良好的透水汽性和机械性能。微观形貌也是呈现出相容性较好的形态（SEM显示）,相较于PEG400,甘油作为增容剂时共混膜的微观形貌横截面均匀光滑,内容物相容性好。明胶:甘油:水质量比为1:9:3:13制得共混膜透光性、透水气性、机械性能最佳,具有较好的实际应用价值。     

Characteristics of edible films made from dairy proteins and zein hydrolysate cross-linked with transglutaminase

The main objectives of this research were to develop whey protein or casein films incorporating zein hydrolysate and also cross‐linked by transglutaminase as to well as characterize the physical and mechanical properties of the film. Zein hydrolysate decreased the solubility of the whey protein film (P < 0.05), while treatment with transglutaminase did not change the solubility of the film significantly. Electrophoresis patterns demonstrated that casein molecules were cross‐linked by transglutaminase and the extent of this cross‐linkage was further increased when zein hydrolysate was added. In addition, the use of zein hydrolysate decreased the tensile strength of the whey protein film by 35–45%. The elongation of the casein film was increased by 41% because of the action of transglutaminase and zein hydrolysate (P < 0.05). The water vapour permeability of the films was not significantly different. As the addition of zein hydrolysate and treatment with transglutaminase improved the flexibility of the films, the level of plasticizer required to maintain film flexibility could be reduced without sacrificing their water vapour permeability.     

静态超高压处理对抗菌复合蛋白薄膜的改性研究

本研究以乳清分离蛋白和酪蛋白酸钠为成膜基材,甘油为增塑剂,山梨酸钾为抗菌剂制备复合蛋白成膜溶液,在其流延成薄膜之前对成膜溶液分组并进行了静态超高压处理:压力分别为200、300、400 MPa,处理时间分别为5、10、20、30 min,未经超高压处理的为对照组。通过对13组薄膜样品的机械性能、光学性能、水溶性、微观结构、阻隔性能等参数的分析,结果表明,超高压处理的薄膜表面更光滑和均匀,有较少的孔洞。超高压处理对薄膜的机械性能、阻隔性能均有显著性(p<0.05)影响,超高压压力300 MPa,处理20 min后,薄膜抗拉强度达到最大值4.86 MPa;C₄组薄膜的水蒸气透过系数降低到1.177×10-9 g·cm/cm2·s·Pa;超高压压力200 MPa,处理10 min后氧气渗透系数降低到0.93×10-9 cm3·cm/cm2·s·cmHg。超高压处理对组B₁、C₁、D₄水溶性均有显著性(p<0.05)影响,能够使薄膜水溶性降低。不同超高压处理后的薄膜可适应不同包装食品的货架期要求。     

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。     

Preparation and characterization of proteinous film from lentil (Lens culinaris): Edible film from lentil (Lens culinaris)

This study was conducted to extract protein from lentil seed and prepare edible film from the protein and to determine mechanical, optical and barrier properties of lentil protein concentrate (LPC) film. The film was prepared from LPC (5 g/100 ml water) and glycerine (50%, w/w of LPC). Hunter color value (L, a and b), tensile strength, percentage elongation at break (E), puncture strength, water vapor permeability (WVP), moisture content after conditioning at 50% RH and 25 °C for 48 h and total soluble matter after immersion in water, were measured. In regarding to WVP, in spite of difference in film thickness and relative humidity of experiment in different studies, lentil protein film is comparable with other protein films. Characteristics of the lentil protein-based edible films were comparable with other edible protein films. LPC film had more red and less yellow color; it seems that the film had good mechanical properties and water vapor permeability in concomitant with good solubility.     

Reducing fat uptake in cassava product during deep-fat frying

The present study aimed at investigating the influence of the use of edible coatings from three different hydrocolloids during the deep-frying of a pre-fried, frozen product preformed from cassava. Three hydrocolloids (pectin, whey protein and soy protein isolate) were used as coatings in the deep-fat frying of preformed products made from cassava flour and from cassava purée. The water vapor permeability, water solubility and film thickness were measured. The cassava products were characterized with respect to their moisture and lipid contents. The water vapor permeability, water solubility and film thickness were directly proportional to the concentration of the films. Whey protein showed the best results with respect to fat absorption, presenting a reduction of 27% for the cassava purée product. The coating treatments were not efficient for the fingers preformed from cassava flour, indicating that different products can show different responses with the same type of coating material.     

酪蛋白磷酸肽钙- 乳清蛋白复合膜物理性质的研究

在乳清分离蛋白(WPI)基础膜中引入酪蛋白磷酸肽钙(CPPs)制备成富钙的单层复配膜和双层复合膜,并对膜的有关物理性质(机械强度、含水量、水蒸气透过系数)进行评价。单层复配膜中CPPs 与WPI 的最大百分比为8%,总钙含量最高为0.59%。CPPs 的添加量对所测膜的物理性质没有显著影响(P ＞ 0.05)。双层复合膜可使总钙含量高达28% 以上,但同时也使膜的机械强度较单层复配膜降低近一半,且含水量显著降低(P ＜ 0.05)。     

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。     

肉桂醛浓度对浓缩乳清蛋白/壳聚糖复合膜性能的影响

为了研究新型高性能抗菌包装材料,本文将肉桂醛添加到浓缩乳清蛋白/壳聚糖复合膜中制成抗菌复合膜,采用FT-IR对复合膜的微观结构进行表征,研究了肉桂醛浓度对复合膜厚度、透光率、机械性能、水蒸气透过系数、氧气透过率等性质的影响,以及其对复合膜抗菌性能的影响。肉桂醛与浓缩乳清蛋白/壳聚糖复合膜有很好的相容性。结果表明:随着肉桂醛浓度的增加,膜的透光率和抗拉强度减小,当肉桂醛浓度为0.3%时,膜的水蒸气透过系数最小,为1.15×10-13 g/(cm·s·Pa),当肉桂醛浓度为0.4%时,膜的厚度和氧气透过率最小,氧气透过率为1.1×10-5 cm3/(m2·d·Pa),当肉桂醛浓度为0.5%时,膜的断裂伸长率最大,为57.5%,膜的抑菌效力随着肉桂醛浓度的增大而显著增大。该研究可为肉桂醛/浓缩乳清蛋白/壳聚糖复合抗菌膜的生产工艺参数的优化提供新的参考。     

含微米颗粒的乳清蛋白复合膜物理性质的研究

乳清蛋白具有一定的营养价值和良好的凝聚造粒及成膜性能。使用喷雾干燥技术制备乳清蛋白微米颗粒,并将上述颗粒以1.0%、1.7%、2.5% 及3.3% 的质量分数添加到乳清蛋白成膜液中,制备含微粒的乳清蛋白复合膜。利用质构仪、扫描电镜(SEM)及差示热量扫描仪(DSC)测定颗粒对乳清蛋白膜性能的影响。结果表明,在上述实验浓度范围内,加入的颗粒对乳清蛋白膜的机械性能、水蒸气透过率、透明度及透光率值、膜的玻璃化温度及熔点均未产生显著影响,乳清蛋白基础膜的性能得到很好的保持。     

环境湿度对植物蛋白膜的影响研究

研究了环境湿度对小麦蛋白膜、大豆蛋白膜以及小麦-大豆复合膜机械性能、通透性等的影响。结果表明,由于蛋白腹为亲水性膜,受环境湿度的影响,其水分含量、分子间作用力有所不同,从而导致蛋白膜的机械性能、透湿性和吸湿率也随之发生变化。膜的阻止水蒸汽渗透的能力下降,吸湿率降低,透氧率呈上升趋势。