Characterization of sodium caseinate-based edible films incorporated with cinnamon or ginger essential oils

Film-forming emulsions were formulated with sodium caseinate and two essential oils (cinnamon or ginger) and films were obtained by casting. At the low oil proportion being tested (maximum ratio protein:oil 1:0.100), the lipid did not affect the mechanical behaviour of the protein films. The water vapour permeability was slightly reduced by both oils. Cinnamon oil greatly affected the optical properties of the films. Ginger oil resulted in lipid droplet aggregation observable by Scanning Electron Microscopy in dried films, surface irregularities and gloss decrease. Neither of the oils improved the ability of sodium caseinate films to act as protection against lipid oxidation, despite the fact that, in a spectrophotometric method, isolated cinnamon oil proved to be very a strong antioxidant.     

酪蛋白酸钠溶液粘度变化的数学模型

研究了浓度为１２－２０％酪蛋白酸钠溶液在６６－９０℃的粘度变化。在ＰＨ值为６．８－７．５的范围内，ＰＨ值对酪蛋白酸钠的粘度没有显著的影响。酪蛋白酸钠溶液粘度的和与溶液的浓度和温度都叶线性关系（Ｒ＾２〉９５％）。酪蛋白酸钠溶液的粘度浓度方程的斜率和截距都与温度呈二次方程的关系（Ｒ＾２＝９４．９１％，Ｒ＾２＝９３．５９％），并由此推导出关于浓度和温度对酪蛋白酸钠溶液粘度相互 半对数方程（Ｒ＾２＝９４．     

混合蛋白酶水解酪朊酸钠工艺的研究

以酪软酸钠为原料,采用混合蛋白酶水解,本文对酶水解工艺参数,小分子肽得率变化进行了系统的研究。本文得出结论:碱性蛋白酶和中性蛋白酶混合使用酶解酪朊酸钠的最适宜条件为:温度为45,pH为6.5,酶解时间为24小时,底物浓度为10%,酶用量为1.55?04u/g.     

Physical properties of edible films made from mixtures of sodium caseinate and WPI

The physical properties of thin films (25–30 μm) made from mixtures of sodium caseinate (NaCas) and whey protein isolate (WPI) were investigated. Films were formed by mixing solutions of NaCas (2.5% w/w protein), plasticised with glycerol (NaCas–gly) at a glycerol:protein ratio of 0.32, with WPI solutions (2.3% w/w protein), plasticised (WPI-gly) at a glycerol:protein ratio 0.37. Tensile and water barrier properties of films formed from mixtures of NaCas–gly and WPI-gly were similar to films containing NaCas–gly only. Films containing only WPI-gly had higher maximum load and elastic modulus values than the mixed films. Increasing the NaCas–gly content of the films from 25 to 100% greatly increased solubility. This increased film solubility may increase the number of food applications for protein-based films.     

酪朊酸钠磷酸化结果验证方法研究

酪朊酸钠是一种天然乳化剂，具有良好的乳化，发泡，粘着等功能症，但由于其蛋白质的疏水性度高，影响了其乳化功能性，在总结前人经验的基础上，对其进行了三聚磷酸钠改性。通过对磷酸酪朊 酸钠的差热分析曲线和等电点的测定结果的分析讨论，证明了酪朊酸钠在ＰＨ７－９之间三聚磷酸钠进行改性是成功的，通过三聚磷酸钠改性，发迹了酪朊酸的蛋白质酸结构，酪朊钠分子中加入磷酸酪键是有可能的。     

微生物转谷氨酰胺酶催化酪蛋白酸钠聚合物的功能特性研究

研究了微生物转谷氨酰胺酶(TGase)催化酪蛋白酸钠聚合对其功能特性的影响。结果显示,随着催化时间的增加,其各组份含量不断减少,同时生成的聚合物含量不断增加,比较了TGase催化不同酪蛋白的聚合速率,结果显示转谷氨酰胺酶较易催化α-和β-酪蛋白,而不易催化κ-酪蛋白TGase催化聚合酪蛋白酸钠能明显改善其乳化性能,聚合时间越长,乳化指数越高,而乳化稳定性随聚合时间先升后降,4h时最高TGase催化酪蛋白酸钠还可提高其热稳定性,然而对其起泡性影响不大     

Use of sodium caseinate/glycerol edible films to reduce lipid oxidation in sliced turkey meat

The objective of this study was to investigate the influence of sodium caseinate films containing glycerol [glycerol:protein ratio 0.32 (w/w)] on lipid oxidation in cooked turkey breast meat slices. Slices were wrapped in films of different thickness (22, 42, and 58 μm) and were stored at 4 °C for 1, 2, 3 and 4 days. Lipid oxidation was measured using TBARS and hexanal assays on each day of storage while an olfactory sensory analysis was carried out on all the samples after 4 days of storage. TBARS values and hexanal levels of unwrapped samples (~6.0 mg MDA/kg and ~8.0 mg hexanal/kg) were significantly (P ≤ 0.05) higher than those of the casein film wrapped samples (~3.0 mg MDA/kg and ~3.0 mg hexanal/kg). Sensory analysis also showed significant (P ≤ 0.05) differences between wrapped samples and unwrapped samples, the former being perceived as less rancid. Thus wrapping in caseinate films may help reduce lipid oxidation in cooked turkey meat.     

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.     

Rheological Properties and Phase Separation of Xanthan-Sodium Caseinate Mixtures Analyzed by a Response Surface Method

Effects of xanthan and sodium caseinate concentrations on the rheological properties of their mixture in an aqueous medium were investigated at neutral pH. It was deduced from the use of an experimental design methodology, the existence of a critical concentration of sodium caseinate, which depends on the xanthan quantity, and beyond which repulsive segregation interactions occur, generating a weakening of the elastic modulus and an embitterment of the colloidal system structure. In addition, it was observed that when the Casson viscosity value of the aqueous solution was above 0.1 Pa.s, phase separation of the system was observed. The phase diagram of the solution was established using a polynomial fit.     

Production and stabilization of a flaxseed oil multi-layer emulsion containing sodium caseinate and pectin

The purpose of this research is the evaluation of a flaxseed oil-in-water emulsion, stabilized by a multi-layer structure consisting of sodium caseinate (Na-caseinate) and pectin to provide a basis for the combination of these materials for future studies. In the first step, the o/w emulsion (10 g oil, 90 g aqueous phase, and a pH 6.8) with varying concentration of Na-caseinate was investigated. Second, the pectin solution (0.05–1.5 g/100 g solution) was added to the primary emulsions and the pH was adjusted to 3.0. The emulsions were characterized by mean particle size (dynamic light scattering and static light scattering techniques), ζ-potential, turbidity value, creaming index, and the visualization of the microstructure. A clear separation of the oil phase at low protein contents and destabilizing by depletion flocculation at high protein content were observed. Extensive droplet flocculation and coalescence were determined until the pectin concentration reached 0.5 g/100 g solution for the secondary emulsion. After 7 days of storage, a 1.5 g/100 g solution pectin content had good stability with a relatively small size distribution, high turbidity value, and no cream phase separation.     

Antimicrobial Activity of Nisin and Natamycin Incorporated Sodium Caseinate Extrusion‐Blown Films: A Comparative Study with Heat‐Pressed/Solution Cast Films

Antimicrobial edible films based on sodium caseinate, glycerol, and 2 food preservatives (nisin or natamycin) were prepared by classical thermomechanical processes. Food preservatives were compounded (at 65 °C for 2.5 min) with sodium caseinate in a twin‐screw extruder. Anti‐Listeria activity assays revealed a partial inactivation of nisin following compounding. Thermoplastic pellets containing food preservatives were then used to manufacture films either by blown‐film extrusion process or by heat‐press. After 24 h of incubation on agar plates, the diameters of K. rhizophila growth inhibition zones around nisin‐incorporated films prepared by solution casting (control), extrusion blowing or heat pressing at 80 °C for 7 min of nisin‐containing pellets were 15.5 ± 0.9, 9.8 ± 0.2, and 8.6 ± 1.0 mm, respectively. Since heat‐pressing for 7 min at 80 °C of nisin‐incorporated pellets did not further inactivate nisin, this indicates that nisin inactivation during extrusion‐blowing was limited. Moreover, the lower diameter of the K. rhizophila growth inhibition zone around films prepared with nisin‐containing pellets compared to that observed around films directly prepared by solution casting confirms that nisin inactivation mainly occurred during the compounding step. Natamycin‐containing thermoplastic films inhibited Aspergillus niger growth; however, by contrast with nisin‐containing films, heat‐pressed films had higher inhibition zone diameters than blown films, therefore suggesting a partial inactivation of natamycin during extrusion‐blowing.     

Amaranth protein films from thermally treated proteins

The usefulness of amaranth protein isolates, native and thermally treated, in edible films preparation was studied. Protein films were prepared by casting using glycerol as plasticizer. Films from amaranth native protein isolates showed low water vapor permeability (WVP) but poor mechanical properties. In order to improve this functionality, proteins were treated at 70 and 90 °C which corresponds to the denaturation temperature of the protein fractions present in the isolates. The unfolded conformation of these thermally treated proteins, when partially or totally denatured, favors the interactions between polypeptide chains during the film formation. These interactions lead to a greater cross-linking degree, which was reflected in the lower amount of water-soluble free peptides that were linked to the matrix. In these thermally treated protein films, a greatest contribution of disulfide and hydrogen bonds to the films stabilization was observed. These changes in the films structural properties would confer them a greater tensile strength and lower water solubility but higher thickness and WVP.     

In vitro lipolysis of fish oil microcapsules containing protein and resistant starch

Microencapsulated fish oil powders (50% oil:25% protein:25% starch) were prepared using a physical blend or a heated mixture of sodium caseinate and pre-processed resistant starch as encapsulants. The in vitro digestibility of microcapsules by lipase, amylase and proteases were examined. Heat treatment of the encapsulants and exposure of microcapsules to simulated gastric fluid (SGF) prior to addition of lipase, trypsin and amylase altered the susceptibility of the microcapsules to digestion. Lipolysis of microcapsules occurred in the presence of lipase alone and was increased in the presence of amylase and/or trypsin. Pre-exposure of microcapsules to SGF had different effects on lipolysis, which depended on the nature of the encapsulant material. Lipolysis in the presence of lipase alone was due to the displacement of the interfacial layer. Increased lipolysis in the presence of amylase and/or trypsin was attributed to the digestion of the encapsulant, which facilitated displacement of the interface of oil droplets by bile salts.     

Structure and Property Changes of Transglutaminase-Induced Modification of Sodium Caseinate in the Presence of Oligochitosan of 5 kDa

Sodium caseinate was modified by transglutaminase-catalyzed reaction in the presence of oligochitosan of 5 kDa at two different levels, aiming to generate two glycated and crosslinked caseinate products (GC-caseinate I and II) and to clarify their respective structure and property changes. Electrophoretic analysis with aid of protein and saccharide staining confirmed that both GC-caseinate I and II were glycated and crosslinked protein products, while high-performance liquid chromatrography analysis demonstrated that both GC-caseinate I and II contained glucosamine (12.8 and 30.8 g/kg protein, respectively). In comparison with sodium caseinate, GC-caseinate I and II also contained less reactable –NH₂ groups (0.50 and 0.52 versus 0.62 mol/kg protein), more –OH groups in their molecules, but they had more ordered secondary structure than sodium caseinate. In addition, GC-caseinate I and II showed higher water-binding capacity, larger hydrodynamic radius (173.9 and 168.2 versus 145.3 nm), and larger negative zeta-potential (–32.9 and –30.9 versus –27.6 mV) in aqueous dispersions, but they exhibited lower thermal stability (namely, greater mass loss) at temperature higher than 286ºC. Oligochitosan-glycated sodium caseinate at lower and higher extents was observed to be unfavorable and favorable to the in vitro digestibility of GC-caseinate I and II, respectively. It is concluded that application of transglutaminase and the oligochitosan can modify structure and property of sodium caseinate to generate new protein ingredients with good hydration and colloidal stability.     

Transglutaminase cross-linking kinetics of sodium caseinate is changed after emulsification

Enzymatic cross-linking is an important method of modifying the structure of food products to control their texture and stability. In this paper we look at the effect that adsorption to the oil–water interface of triglyceride oil-in-water emulsion has on rates of cross-linking of sodium caseinate by microbial transglutaminase. The kinetics of cross-linking has also been assessed for the individual casein proteins within the caseinate. In solution the rates were α_s2-casein > β-casein > α_s1-casein > κ-casein. This order is not as expected given the rheomorphic nature of the proteins and the number of glutamine and lysine residues in each protein. In particular, the α_s1-casein was cross-linked much more slowly than expected. When sodium caseinate was adsorbed to an emulsion the rates for all constituent caseins were decreased but the cross-linking rate for α_s1-casein was markedly reduced, indicating the most significant change in accessibility following adsorption. This knowledge will facilitate optimal production of cross-linked emulsions for use in future studies aimed at engineering emulsions with improved nutritional quality.     

Characterization of biodegradable films prepared with hake proteins and thyme oil

Hake protein biodegradable films containing different thyme oil levels (0.025, 0.05, 0.1 and 0.25 ml oil/g protein) were prepared and their physical, mechanical and antioxidant properties were studied. Dried proteins were solubilized at pH 11 with NaOH and glycerol (59% of protein content) was added as plasticizer.The addition of thyme oil levels reduced both the film thickness and water vapor permeability. Films were homogeneous and transparent with a yellowish color. The optical properties of films were not generally affected by the thyme oil addition. Any clear trend between the mechanical properties of biodegradable films and thyme oil added was observed. Hake protein films exhibited some antioxidant activity, which was improved by the addition of 0.25 ml of thyme oil/g of protein.     

酪蛋白酸钠美拉德反应产物的制备及其乳化特性

利用小型超高温设备制备酪蛋白酸钠与葡萄糖、乳糖、低聚半乳糖、聚葡萄糖的美拉德反应产物,对比分析不同分子质量糖在不同热处理时间的美拉德反应进程及产物的乳化特性。结果表明,小分子质量的糖更易发生美拉德反应,褐变指数与反应程度呈正相关,乳化活性与接枝度均呈现先增大后减小的趋势,但两者并不成线性关系,酪蛋白酸钠与葡萄糖、乳糖、低聚半乳糖、聚葡萄糖乳化活性达到的最大值分别为0.63、0.51、0.55和0.48,其中130?℃热处理15?s的酪蛋白酸钠-葡萄糖溶液乳化活性最大,高于其他组,与水浴90?℃热处理90?min相当,并且乳化稳定性也呈现较高的水平,为123.88?min,将其用作乳化剂制备的DHA藻油乳状液稳定性动力学指数为1.5,显著小于其他组（P＜0.05）;由此可见,葡萄糖可作为美拉德反应的优良糖基配体制备新型高效的乳化剂,并且此方法可实现连续化生产,极大缩短了反应时间,提高了生产效率,对工业化生产具有指导意义。     

Biodegradable sunflower protein films naturally activated with antioxidant compounds

The aim of this work was to study the formation of biodegradable films from sunflower protein isolates having different concentrations of phenolic compounds, which are present in sunflower seeds and are retained during the isolation of proteins from the residual pellet of the oil industry. Films were obtained by casting from aqueous dispersions of the isolates, using glycerol as plasticizer. Although proteins from different sunflower protein isolates presented different structural properties, such as surface hydrophobicity, the films obtained did not differ significantly regarding thickness (64–80 μm), density (∼1.47 g/cm⁻³), water content (∼25%), water vapor permeability (∼1.4 × 10⁻¹⁰ g H₂O/Pa.s.m), mechanical properties (traction), glass transition temperature, or type of interactions involved in the protein network, which in all cases were mainly hydrogen bonds, hydrophobic interactions, and disulfide bonds. Sunflower protein films contained phenolic compounds had antioxidant activity. As the concentration of these compounds increased the films also presented increasing opacity and greenish tones, with absorption maximums at wavelengths similar to those of chlorophyll (which suggests their potential use in mulching for impeding weed growth).     

Physical properties and antilisterial activity of bioactive edible films containing Lactobacillus plantarum

Bioactive polymeric films were developed from the incorporation of Lactobacillus plantarum into polysaccharide or protein edible films. Lactic acid bacteria (LAB) were added directly to the film forming solution and films were obtained by casting. Four different biopolymers were tested: sodium caseinate, pea protein, methylcellulose and hydroxypropylmethylcellulose. In order to study the impact of the incorporation of the protective culture into the biopolymer matrix, the water vapour permeability (WVP), optical and mechanical properties of the dry films were evaluated. Furthermore, survival of L. plantarum and the antimicrobial potential of bioactive films against Listeria innocua were studied. Whereas optical and mechanical properties of the films were not notably altered by the LAB incorporation, WVP values increased for all biopolymers. Viability of the strain was lower in cellulose derivative matrices than in protein films, although bacteriocin production in the newly prepared films was greater in these matrices. As a result, a significant antimicrobial activity against L. innocua was observed for polysaccharide matrices, which was not observed for protein films, where the bacteriocin production is delayed. In pea protein films the maximum bacteriocin production occurs at 15 storage days and afterwards decreases. So, the nature of the biopolymer and the knowledge of time when an adequate bacteriocin concentration is produced are key to use bioactive films in an effective way.     

酪蛋白酸钠-葵花籽油协同对乳化肠品质特性的影响

以猪后腿肉为原料肉,酪蛋白酸钠、葵花籽油预乳化液替代猪背膘制备乳化肠,研究不同比例（0、25%、50%、75%、100%）预乳化液替代对乳化肠蒸煮损失率、物理化学组成、色泽、质构、脂肪酸组成及硫代巴比妥酸值的影响。结果显示：随着预乳化液替代比例增加,乳化肠中蛋白质、水分的含量显著增加（P＜0.05）,灰分含量变化差异不显著,脂肪含量显著下降（P＜0.05）,从18.58%降低到10.17%;蒸煮损失率降低;乳化肠的亮度值随预乳化液代替猪背膘比例的增加呈上升趋势,红度值和黄度值呈下降趋势;预乳化液替代组乳化肠的质构特性优于对照组;预乳化液替代猪背膘制备乳化肠还可以改变乳化肠的脂肪酸组成,随替代比例的增大,乳化肠中必需脂肪酸亚油酸在总脂肪酸中所占的比例显著增加（P＜0.05）,多不饱和脂肪酸所占的比例增加,高达55.92%,饱和脂肪酸从39.72%降低到13.52%,满足消费者对低脂多不饱和脂肪酸肉制品的需求;随替代比例的增大,乳化肠的TBARS值逐渐减小,用预乳化液替代猪背膘可增强乳化肠的氧化稳定性。因此,酪蛋白酸钠、葵花籽油预乳化液替代猪背膘可显著改善乳化肠的品质及营养特性。