Gelation, oxygen permeability, and mechanical properties of mammalian and fish gelatin films

The objective of this study was to evaluate the gelation, thermal, mechanical, and oxygen permeability properties of different mammalian, warm- and cold-water fish gelatin solutions and films. Mammalian gelatin solutions had the highest gel set temperatures, followed by warm-water fish and then cold-water fish gelatin solutions. These differences were related to concentrations of imino acids present in each gelatin, with mammalian gelatin having the highest and cold-water fish gelatin having the lowest concentrations. Mammalian and warm-water fish gelatin films contained helical structures, whereas cold-water fish gelatin films were amorphous. This was due to the films being dried at room temperature (23 °C), which was below or near the gelation temperatures of mammalian and warm-water fish gelatin solutions and well above the gelation temperature of cold-water fish gelatin solutions. Tensile strength, percent elongation, and puncture deformation were highest in mammalian gelatin films, followed by warm-water fish gelatin film and then by cold-water fish gelatin films. Oxygen permeability values of cold-water fish gelatin films were significantly lower than those for mammalian gelatin films. These differences were most likely due to higher moisture sorption in mammalian gelatin films, leading to higher oxygen diffusivity.     

Starch-gelatin edible films: Water vapor permeability and mechanical properties as affected by plasticizers

Physical and mechanical properties of edible films based on blends of sago starch and fish gelatin plasticized with glycerol or sorbitol (25%, w/w) were investigated. Film forming solutions of different ratios of sago starch to fish gelatin (1:0, 2:1, 3:1, 4:1, and 5:1) were used and cast at room temperature. Amylose content of sago starch was between 32 and 34% and the protein content of the fish gelatin was found to be 81.3%. The findings of this study showed that the addition of fish gelatin in starch solutions has a significant effect (p < 0.05), resulting in films with lower tensile strength (TS) and higher water vapor permeability (WVP). On the other hand, increasing protein content (from 10.9% to 21.6%) in film samples plasticized with sorbitol showed significantly lower (p < 0.05) TS but no trend was observed in % elongation-at-break (EAB) and no differences in WVP. However, TS decreased with higher protein content in the samples when either plasticizers were used in general, but no significance differences was observed among the samples (p < 0.05) with glycerol with exception to film with high protein content (21.6%) only and no trend was observed in % EAB among samples as well. Significant difference (p < 0.05) was observed in TS and viscosity between different formulations with sorbitol. The morphology study of the sago starch/fish gelatin films showed smoother surfaces with decreasing protein in the samples with either plasticizer. DSC scans showed that plasticizers and protein content incorporated with sago starch films reduced the glass transition temperature (T_g) and melting temperature (T_m) and the melting enthalpy (ΔH_m). In this study, observation of a single T_g is an indication of the compatibility of the sago starch and fish gelatin polymers to form films at the concentration levels used.     

Alginate-calcium films: Water vapor permeability and mechanical properties as affected by plasticizer and relative humidity

Alginate films containing dissimilar amounts of guluronate (G) and mannuronate (M): M/G∼0.45 and M/G∼1.5, soaked in a calcium chloride solution up to 20 min were evaluated for water vapor permeability (WVP). M/G∼0.45 films proved to be better moisture barriers at all calcium immersion times compared to M/G∼1.5. WVP of M/G∼0.45 and M/G∼1.5 films decreased as time of immersion in calcium increased; after 3 min, a decrease in WVP was observed. M/G∼0.45 films soaked for 1 min in calcium were further analyzed to determine the effect of plasticizer and relative humidity (RH) on their mechanical properties and WVP, using fructose, glycerol, sorbitol, and polyethylene glycol (PEG-8000). Films without plasticizer showed a lower capacity to adsorb water compared to those with plasticizer. As RH increased, tensile strength (TS) decreased and elongation (E) increased for all films. This effect was more pronounced on films containing plasticizer, which had lower TS at all RHs. Plasticizer did not increase E at 58% RH. At 78% and 98% RH, glycerol, sorbitol and fructose showed a significant increase in E compared to PEG-8000 and no-plasticizer. PEG-8000 provided lower TS and E, while glycerol showed the highest among all plasticizers. There was no difference on WVP between no-plasticizer and glycerol. Fructose and sorbitol showed the lowest WVP while PEG-8000 showed the highest.     

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.     

Preparation and mechanical properties of edible rapeseed protein films

Edible films were manufactured from rapeseed oil extraction residues. To prepare rapeseed protein (RP) films, various concentrations of plasticizers and emulsifiers were incorporated into the preparation of a film-forming solution. The optimal conditions for the preparation of the RP film were 2% sorbitol/0.5% sucrose as plasticizer and 1.5% polysorbate 20 as an emulsifier. In addition, RP blend films were prepared. Gelidium corneum or gelatin was added to improve the physical properties of the RP film, and the highest tensile strength value of the films was 53.45 MPa for the 3% RP/4% gelatin film. Our results suggest that the RP-gelatin blend film is suitable for applications in food packaging. PRACTICAL APPLICATION: Edible RP films prepared in the present investigation can be applied in food packaging.     

Comparative analysis of mechanical properties of size films

The advent of very high speed shuttleless looms has increased the importance of sizing. Starch has been the most popular and economic size material. Synthetic binders are also being blended with starch to improve weaving loom efficiency. Some synthetic size materials have got restrictions in use mainly because of ecological reasons. In the recent years, many modifications have come up in the starch as a sizing agent. Different modifications give different properties, which can be suited for particular application. In the present study, a comparative analysis of different varieties of natural starch, modified starch and synthetic size materials have been carried out for their cohesion power, adhesion power, abrasion resistance and bending rigidity. Comparison is made between various varieties and also among different blends to see the effect of blending on different mechanical properties of size film. The effect of lubricant on properties of size film is also examined. In general, it is observed that paste characteristics and film properties of synthetic and modified starch are better than the natural starch.     

Effect of carp (Cyprinus carpio) oil incorporation on water vapour permeability,mechanical properties and transparency of chitosan films

The effect of carp oil incorporation on properties of chitosan films was evaluated. Chitosan and carp oil were obtained from shrimp wastes and viscera respectively. Tests were performed with different values of chitosan: oil ratios, agitation rates, homogenisation times and pH. The optimum conditions for stability of the film–forming dispersions were of 20,000 rpm at 10 min, and 10:1 ratio of chitosan:oil. The highest values of tensile strength and elongation percentage (%E) of films were obtained at pH 3.5. The addition of carp oil in the chitosan films (10:1 ratio) showed an increase in the resistance to diffusion of water vapour (1.7 g mm m^?2 day^?1 kPa^?1) in relation to pure chitosan films (4.1 g mm m^?2 day^?1 kPa^?1). However, pure chitosan films showed better mechanical properties (38 MPa and%E 18%) and transparency than films of chitosan:oil (20.4 MPa and 8.8%).     

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.     

提高玉米醇溶蛋白膜机械性能的研究进展

玉米醇溶蛋白膜的阻隔性能强于其他植物蛋白膜,但机械性能较差,使其应用受到了限制.影响玉米醇溶蛋白膜机械性能的主要因素有成膜液中各组分性质、制膜工艺及贮藏条件等.通过添加增塑剂、交联剂和改进成膜工艺,可提高玉米醇溶蛋白膜的机械性能.     

Whey protein-okra polysaccharide fraction blend edible films: tensile properties, water vapor permeability and oxygen permeability

BACKGROUND: A hot‐buffer‐soluble‐solid fraction (HBSS) and an alkaline‐soluble‐solid fraction (ASS) of okra polysaccharides (OKP) were obtained using sequential extraction. These fractions were combined with whey protein isolate (WPI) and glycerol (Gly) plasticizer to form blend edible films. Effects of OKP fraction and content on tensile properties, water vapor permeability (WVP) and oxygen permeability (OP) were determined. RESULTS: HBSS film had significantly higher percent elongation (%E) and lower elastic modulus (EM), WVP and OP than ASS film. Increasing HBSS or ASS content in blend films with WPI significantly reduced film tensile strength and EM and increased film %E and WVP. OP values for WPI–HBSS blend films were significantly lower than OP for WPI or HBSS film. WPI–HBSS and WPI–ASS blend films had lower WVP and OP than WPI films with equivalent tensile properties. CONCLUSIONS: WPI–HBSS blend films have higher WVP and lower OP than WPI film or HBSS film, indicating unique interactions between WPI and HBSS. Compared to WPI film, WPI–HBSS blend films have improved flexibility, stretchability and oxygen barrier. Different HBSS and ASS compositions and structures are responsible for property differences between HBSS and ASS films and between WPI–HBSS and WPI–ASS blend films. Copyright © 2010 Society of Chemical Industry     

Variations in banana properties

Samples prepared from different bananas and from different parts of a banana may vary in their properties, which may cause variations in the final results in experiments. Therefore, assessment of variation in the samples’ properties is necessary, and it can be evaluated using statistical analysis. In this work, the variation in banana properties—colour, texture, moisture and sugar contents—within and between bananas were assessed statistically using a two-stage nested design test and the two-sample t-test. Results show that the variation of properties is significant for bananas with different degrees of ripeness. This finding suggests that samples can be prepared from different parts of the bananas provided that the bananas are at the same degrees of ripeness. It was also found that the location of sample in the drying chamber did not affect the measured properties of the drying bananas, significantly. The tests performed for banana texture using a laboratory apparatus produced results that were similar to those performed using a dynamic mechanical analyzer. This suggests that the use of highly-sophisticated instruments in the texture analysis of dried fruit in terms of the apparent modulus is not crucial.     

香蕉粘胶纤维的结构与理化性能

采用扫描电镜、傅里叶红外光谱、热重分析、差示扫描量热分析等手段,研究了香蕉粘胶纤维的形态结构、化学结构、力学性能和热学性能.结果表明:香蕉粘胶纤维纵向形态平直,为带有平直纵条纹的柱体,表面有沟槽和裂缝,表面粗糙;香蕉粘胶纤维和普通粘胶纤维的红外光谱吸收图谱相似;纤维的湿断裂强度仅为干断裂强度的42%;纤维有较高的耐热性能.     

香蕉纤维结构及其染色性能

采用扫描电镜、红外光谱分析了香蕉纤维的理化特征.通过分析3种活性染料对香蕉纤维的上染速率、上染率和固色率,并与亚麻纤维的染色性能进行比较,发现香蕉纤维的染色性能与亚麻纤维相似,但比亚麻纤维更易染色.试验采用的3种活性染料染香蕉纤维时,元明粉质量浓度为30～60g/L,纯碱质量浓度为10～20g/L时,染色效果最好.     

Effect of copper nanoparticles on permeability, physical, and mechanical properties of particleboard

Effects of a 200 ppm nanocopper suspension, with size range from 10 to 80 nm, on the physical and mechanical properties of particleboard made on an industrial scale at the Iran-Choob Factory were studied. Nanocopper suspension was added to the mat at two levels of 100 and 150 ml/kg dry weight wood particles and compared with control boards. Results showed that hot-pressing time was reduced by 5.7 and 3.4 % when 100 and 150 ml of nanocopper were used, respectively. Also, both levels of nanocopper consumption had improving effects on physical and mechanical properties, although in some cases not significant. Permeability was significantly decreased to its lowest value in 150 ml/kg treatment. It can be concluded that 150 ml of nanocopper/kg may be used to improve the physical and mechanical properties, to reduce press time, and to decrease permeability in particleboards. For industrially accepted outcome, 150 ml/kg of nanocopper is recommended.     

浆料混溶性对共混浆膜力学性能的影响

针对浆料混溶性对共混浆膜力学性能的影响,以变性淀粉/聚乙烯醇(PVA)共混物为研究对象,探讨了变性淀粉/PVA间的共混比、PVA醇解度对共混物浆膜性能和浆液黏附力的影响,并通过扫描电子显微镜和X射线衍射仪对共混浆膜的织态结构进行了微观表征,分析了浆料组分数与浆膜性能的关系。结果表明,当PVA1799与变性淀粉的共混比为40∶60时,共混浆膜的断裂强力、断裂伸长达到最大值,纯棉粗纱的浆液黏附力较理想;低醇解度的PVA会使共混浆膜的相畴增大,结晶性变差,削弱了共混膜的各项力学性能。为提高浆料的混溶性,增强共混膜的力学性能,浆料配方组分宜尽可能少。     

Implication of water activity and glass transition on the mechanical and optical properties of freeze-dried apple and banana slices

The interactions between water content, matrix structures and chemical and physical events in complex foods are usually regarded in terms of water activity and glass transition. In this work, the water content and water activity values that define important changes in the textural and optical properties of freeze-dried banana and apple slices have been related to the critical water content and water activity that cause the glass transition in both products. From the obtained results, it may be concluded that both approaches, glass transition and water activity, may be considered to prevent changes in the mechanical properties, while only the concept of water activity is needed to control the browning reactions that take place in the fruits.     

增塑剂对甘薯淀粉膜机械及渗透性能的影响

鉴于塑料食品包装带来的严重环境问题,研究可食、可降解的包装薄膜非常必要.本文以抗张强度、断裂伸长率、透湿性和透氧性为指标,研究增塑剂对甘薯淀粉膜性能的影响.结果表明,甘油和山梨醇的增塑效果优于聚乙二醇和蔗糖,使膜的断裂伸长率和透湿性更大,透氧性更小.甘油(浓度>5g/100g淀粉)可以显著降低甘薯淀粉膜的抗张强度,较高浓度甘油(浓度>10g/100g淀粉)可以显著改善甘薯淀粉膜的断裂伸长率.甘油的添加使甘薯淀粉膜的透湿性增加.较低浓度甘油(浓度≤7g/100g淀粉)的添加降低甘薯淀粉膜的透氧性,高浓度甘油(浓度>10g/100g淀粉)又使透氧性有所增加,但总体上用甘油增塑的淀粉膜的透氧性均比未增塑的对照膜的透氧性小.     

可食性生物聚合膜的微观结构与透气性

可食性生物聚合膜是一类由多糖和蛋白质等天然大分子构成的复合膜,其透气性与其微观结构密切相关。论述了可食膜的晶体结构、大分子链的流动性、膜的完整性以及增塑剂和环境湿度等因素对其透气性的影响,并对示差扫描量热法、X-射线衍射及扫描电镜等在分析可食膜的微观结构与透气性关系方面的应用进行综述,对其发展趋势提出展望。