Complex coacervation between flaxseed protein isolate and flaxseed gum

Flaxseed protein isolate (FPI) and flaxseed gum (FG) were extracted, and the electrostatic complexation between these two biopolymers was studied as a function of pH and FPI-to-FG ratio using turbidimetric and electrophoretic mobility (zeta potential) tests. The zeta potential values of FPI, FG, and their mixtures at the FPI-to-FG ratios of 1:1, 3:1, 5:1, 10:1, 15:1 were measured over a pH range 8.0–1.5. The alteration of the secondary structure of FPI as a function of pH was studied using circular dichroism. The proportion of ɑ-helical structure decreased, whereas both β-sheet structure and random coil structure increased with the lowering of pH from 8.0 to 3.0. The acidic pH affected the secondary structure of FPI and the unfolding of helix conformation facilitated the complexation of FPI with FG. The optimum FPI-to-FG ratio for complex coacervation was found to be 3:1. The critical pH values associated with the formation of soluble (pHc) and insoluble (pH_ɸ1) complexes at the optimum FPI-to-FG ratio were found to be 6.0 and 4.5, respectively. The optimum pH (pH_opt) for the optimum complex coacervation was 3.1. The instability and dissolution of FPI–FG complex coacervates started (pHɸ₂) at pH 2.1. These findings contribute to the development of FPI–FG complex coacervates as delivery vehicles for unstable albeit valuable nutrients such as omega-3 fatty acids.     

Simplified optimization for microcapsule preparation by complex coacervation based on the correlation between coacervates and the corresponding microcapsule

A close correlation between coacervates and the corresponding microcapsule was established using gelatin and gum arabic as a model system. Through turbidimetric titration and zeta-potential measurement, the optimum coacervates were obtained at pH 4.1 with the mixing ratio of 1:1 (w/w). Comparisons on morphology, yield and internal characteristic of heat-resistance were performed to testify the correlation between coacervates and the corresponding microcapsule. A simplified method for optimization of microcapsule preparation by complex coacervation was then proposed, in which the zeta-potential measurement helps to establish the approximate mixing ratios of wall materials; the turbidity analysis facilitates the finding of suitable pH corresponded to the highest turbidity to make the perfect microcapsule. Then, gelatin and sodium carboxymethyl cellulose was provided as a new combination of wall materials for the verification.     

Rheological and Microstructural Characteristics of Canola Protein Isolate−Chitosan Complex Coacervates

Wastage of byproducts such as canola meal is a pressing environmental concern, and canola protein isolate (CPI)?chitosan (Ch) coacervates have a good potential to utilize and convert the wastes into a high value added product. Yet so far, there is very limited rheological and microstructural information to assist in proper utilization of CPI ‐Ch complex coacervates. The rheological and microstructural properties of the complex coacervates formed from CPI and chitosan Ch at various CPI‐to‐Ch mixing ratios (1:1, 16:1, 20:1, and 30:1) and pH values (5.0, 6.0, and 7.0) were therefore investigated. These CPI?Ch complex coacervate phases were found to exhibit elastic behavior as evidenced by significantly higher elastic modulus (G?) compared to viscous modulus (G″) in all the tested ratios and pH ranges. They also exhibited shear‐thinning behavior during viscous flow. The complex coacervates formed at the optimum CPI‐to‐Ch ratio of 16:1 and pH of 6.0 demonstrated the highest G?, G″, and shear viscosity, which correlated well with the high strength of electrostatic interaction and thick‐walled, sponge‐like, less‐porous microstructure at this condition. The higher shear viscosity of the coacervate at pH 6.0 was most likely induced by stronger attractive electrostatic interactions between CPI and Ch molecules, due to the formation of a rather densely packed complex coacervate structure. Hence, it can be concluded that the microstructural observations of denser structure correlated well with the rheological findings of stronger intermolecular bonds at the optimum CPI‐to‐Ch ratio of 16:1 and pH of 6.0. The complex coacervate phase formed at a CPI‐to‐Ch ratio of 16:1 and pH of 6.0 also showed glassy consistency at low temperatures and rubbery consistency above its glass‐transition temperature. This study identified the potential for the newly developed CPI–Ch complex coacervate to be used as an encapsulating material due to its favorable strength. This would drastically reduce the wastage of byproducts, provide a solution to tackle the pressing global issue of wastage of byproducts, and bring about a more environmentally friendly paradigm.     

The effect of ionic strength on the rheology of pH-induced bovine serum albumin/κ-carrageenan coacervates

Protein/polysaccharide coacervates are frequently applied to food products to control the rheology. This study investigated the effect of ionic strength (I) on the rheology of pH-induced protein/polysaccharide coacervates. Bovine serum albumin (BSA) and κ-carrageenan were used as a model protein and a polysaccharide, respectively. As the formation of BSA/κ-carrageenan coacervates increased the turbidity of an aqueous mixture, pH_c, pH_?, and pH_max values were identified corresponding to the pH of the formation of soluble coacervates, insoluble coacervates, and large insoluble coacervates respectively. Based on pH_c, pH_?, and pH_max, a state diagram of BSA/κ-carrageenan coacervation versus pH and I was constructed. Involvement of salt in coacervation screened out the electrostatic interaction between BSA and κ-carrageenan coacervation, resulting in the shift of pH_c, pH_?, and pH_max to lower pH. The shift was linearly changed to 1/I^1/2 that corresponded to the Debye length. BSA/κ-carrageenan coacervates were more elastic than viscous. The transition from insoluble coacervates to large insoluble coacervates contributed to enhancement of the rheology, especially in elasticity. An increase in the I of a BSA/κ-carrageenan mixture reduced the degree of coacervation and the elasticity, and the viscosity of BSA/κ-carrageenan coacervates.     

Complex coacervation of soybean protein isolate and chitosan

The formation of coacervates between soybean protein isolate (SPI) and chitosan was investigated by turbidimetric analysis and coacervate yield determination as a function of pH, temperature, time, ionic strength, total biopolymer concentration (TB(conc)) and protein to polysaccharide ratio (R(SPI/Chitosan)). The interaction between SPI and chitosan yielded a sponge-like coacervate phase and the optimum conditions for their coacervation were pH 6.0-6.5, a temperature of 25 °C, and a R(SPI/Chitosan) ratio of four independently of TB(conc). NaCl inhibited the complexation between the two biopolymers. Fourier transform infrared spectroscopy (FTIR) revealed that the coacervates were formed through the electrostatic interaction between the carboxyl groups of SPI (-COO(-)) and the amine groups of chitosan (-NH(3)(+)), however hydrogen bonding was also involved in the coacervation. Differential scanning calorimetry (DSC) thermograms indicated raised denaturation temperature and network thermal stability of SPI in the coacervates due to SPI-chitosan interactions. Scanning electron microscopy (SEM) micrographs revealed that the coacervates had a porous network structure interspaced by heterogeneously sized vacuoles.     

阿拉伯木聚糖与壳聚糖复凝聚物的制备及表征

研究了不同因素对壳聚糖-阿拉伯木聚糖复凝聚的影响,通过测定平衡相的浊度和复凝聚相收率确定玉米阿拉伯木聚糖（CAX）和壳聚糖（CS）间复合物形成的条件。采用红外光谱、热重分析、扫描电子显微镜和流变学特性对复凝聚物进行表征。研究结果表明,在CAX/CS配比为9:1,体系pH值为4.0,总固形物浓度为3%（m/m）,室温下反应10 min,最大复凝聚相产率达76.04%。红外光谱和热重分析结果表明,CAX/CS复凝聚物是通过CS中的-NH3+和CAX中-COO-之间的相互吸引形成的。用SEM扫描成像显示复凝聚物具有规则且分布均匀的多孔网络结构。CAX/CS复凝聚物粘弹特性取决于发生复凝聚的pH值。在pH值3.5和4.0时,复凝聚物为液体粘弹行为;在pH值5.0时,复凝聚物为固体粘弹性行为。pH值5.0下形成的复凝聚物的G’最高,说明除静电作用外,其他因素也可能对CAX/CS复凝聚物粘弹特性起重要作用。CAX/CS复凝聚物可以作为包封营养素和功能性因子的微囊化壁材。     

Complex coacervates obtained from interaction egg yolk lipoprotein and polysaccharides

Protein–polysaccharide coacervates formation was evaluated under influence of pH (3.0, 4.0, 6.5, 8.5 and 10.0), temperature (10, 20, 30, 40 and 50 °C) and polysaccharide mass (0.025, 0.033 and 0.050 g). It was possible to observe that solutions with lower turbidity values were found in pH band 3.0 to 4.0. Statistical analysis of turbidity data have shown that for all polymers pH was meaningful in coacervate formation, although for some, besides pH, temperature and polymer concentration could also influence significantly (p < 0,05) in coacervate formation. Encapsulates morphology made by coacervation was directly linked to the kind of polymer used and its interactional degree. Dehydrated coacervates have presented heterogeneous morphology, different from their original structures.     

Complex coacervation of pea protein isolate and tragacanth gum: Comparative study with commercial polysaccharides

The ability of pea protein isolates (PPI) to form complex coacervates with tragacanth gum was investigated. The coacervate formation was structurally compared to three other PPI-polysaccharide interaction models: arabic gum and sodium alginate (known to form coacervates with PPI) and tara gum, a galactomannan. The effects of the pH and protein/polysaccharide ratio were mainly investigated using turbidity and zeta potential measurements. Regarding the pH of soluble complex formation, the pH of complex coacervates increased with the increase in protein-anionic polysaccharide mixture ratio. SEM images revealed the ability of the spray-drying process to form spherical particles of pea protein-polysaccharide complexes. The specificity of the microparticle surface was protein-dependent. FTIR analyses of coacervates showed the electrostatic interaction between the PPI and the polysaccharides. The results showed that tragacanth gum could be used as an alternative to gum arabic to form complex coacervates with PPI based on zeta potential measurements and coacervation yield studies.     

银耳多糖与大豆分离蛋白的相互作用及流变性能

研究银耳多糖（Tremella fuciformis polysaccharide,TFP）与大豆分离蛋白（soybean protein isolate,SPI）的相互作用,利用浊度、纳米粒度仪、激光共聚焦扫描显微镜、流变仪、荧光光谱法和傅里叶变换红外光谱法等对TFP与SPI的复合凝聚过程进行表征。结果表明：pH值、SPI与TFP质量比和盐离子浓度对凝聚体的形成影响较大,当SPI∶TFP＞1时,与复合物形成相关的关键pH值（pHc和pHφ1）向高pH值方向移动。当SPI∶TFP＜1时,pHφ1向低pH值方向移动。随着体系中TFP比例的增大,浊度的最大吸收峰逐渐降低（pHopt逐渐减小）。当SPI∶TFP＝1∶1时,两者在pH 3.0处的相互作用最强,此时体系总体的黏度最大（约为1.30 Pa·s）,形成的聚集体最多且粒径最大。NaCl浓度较低（＜20 mmol/L）时能促进SPI-TFP凝聚体形成,NaCl浓度较高（≥20 mmol/L）时由于屏蔽作用会抑制凝聚体的形成。当剪切频率10 Hz、NaCl浓度20 mmol/L、SPI与TFP质量比1∶1时,体系具有最高的黏弹性模量,储能模量为9.24 Pa,损耗模量为3.40 Pa。本研究为TFP在植物蛋白饮料中的开发和应用提供了一定理论基础。     

Associative interactions between chitosan and soy protein fractions: Effects of pH,mixing ratio,heat treatment and ionic strength

The objective of this paper is to explore the complexation between the soy protein fractions (glycinin and β-conglycinin) and chitosan (CS) and to investigate the influence of pH, mixing ratio, heat treatment and ionic strength. Phase behavior and microstructure showed that soluble complex and coacervate were obtained in glycinin/CS and β-conglycinin/CS mixtures at specific pHs, following a nucleation and growth mechanism. Moreover, the coacervates showed higher thermal stability than protein alone. Specially, the glycinin/CS mixture displayed a gel-like network structure at pH 5.5 and 6.0, and this structure kept the mixture soluble at a long pH region. The turbidity versus ζ-potential pattern showed that, independent of protein, the self aggregation of soy protein fractions and the coacervation of glycinin/CS and β-conglycinin/CS mixtures were all obtained at charge neutralization pH, indicating that the ζ-potential is the most critical parameter to understand the stability of soy protein/chitosan mixture. This predictive parameter was less affected by mixing ratio and heating but was significantly affected by ionic strength because mixing ratio and heating only changed the equilibrium between repulsive and attractive forces in colloid system while sodium chloride destroyed the predictability of colloidal stability via shielding charged reactive sites on both biopolymers to disrupt electrostatic interactions.