Mixed aqueous chitin nanocrystal–whey protein dispersions: Microstructure and rheological behaviour

Chitin nanocrystals (ChN) and whey protein isolate (WPI) aqueous dispersions (at pH 3.0) of different polymer concentrations were mixed and examined with small deformation oscillatory measurements and polarized optical microscopy, under different conditions of ionic strength and temperature. The ChN–WPI mixed dispersions displayed a gel-like behaviour with increasing either the ChN or the WPI concentration. The network formation could be attributed to phase separation phenomena, as evidenced by the micrographs obtained, due to thermodynamic incompatibility between the two components; i.e. the addition of WPI, as a globular biopolymer mixture, in a dispersion of rod-like particles (ChN) leads to the formation of ChN-rich and ChN-poor domains. Increasing ionic strength did not significantly affect the viscoelastic properties of the network. However, heating of the ChN–WPI mixed dispersions resulted in further increase of the elastic modulus, which was irreversible upon cooling.     

Core-Shell Biopolymer Nanoparticles Produced by Electrostatic Deposition of Beet Pectin onto Heat-Denatured β-Lactoglobulin Aggregates

ABSTRACT:  The purpose of this study was to produce and characterize core-shell biopolymer particles based on electrostatic deposition of an anionic polysaccharide (beet pectin) onto amphoteric protein aggregates (heat-denatured β-lactoglobulin [β-lg]). Initially, the optimum conditions for forming stable protein particles were established by thermal treatment (80 °C for 15 min) of 0.5 wt%β-lg solutions at different pH values (3 to 7). After heating, stable submicron-sized ( d = 100 to 300 nm) protein aggregates could be formed in the pH range from 5.6 to 6. Core-shell biopolymer particles were formed by mixing a suspension of protein aggregates (formed by heating at pH 5.8) with a beet pectin solution at pH 7 and then adjusting the pH to values where the beet pectin is adsorbed (< pH 6). The impact of pH (3 to 7) and salt concentration (0 to 250 mM NaCl) on the properties of the core-shell biopolymer particles formed was then established. The biopolymer particles were stable to aggregation from pH 4 to 6, but aggregated at lower pH values because they had a relatively small ζ-potential. The biopolymer particles remained intact and stable to aggregation up to 250 mM NaCl at pH 4, indicating that they had good salt stability. The core-shell biopolymer particles prepared in this study may be useful for encapsulation and delivery of bioactive food components or as substitutes for lipid droplets.     

Microfluidic production of monodisperse biopolymer particles with reproducible morphology by kinetic control

Microdroplets of phase separating and gelling gelatin-maltodextrin mixtures were produced by a microfluidic technique. The microstructures observed inside the gelled particles were highly reproducible. This resulted from both the controlled production of monodisperse droplets in a microfluidic device and the tuning of gelation and phase separation kinetics.We showed that the internal particle microstructure can be tailored by varying the cooling rate (90 °C/min, 55 °C/min, 5 °C/min), the biopolymer composition (4% gelatin and 6%-7.3% maltodextrin) and the gelatin type (lime hide, pig skin). The particles were analyzed using confocal scanning laser microscopy and image analysis. Microstructures with smaller domain sizes were formed at the fastest cooling rate (90 °C/min), and microstructures with large domain sizes were obtained at the slowest cooling rate (5 °C/min). Furthermore, differences in particle morphology were observed at this slowest cooling rate. In particles containing pig skin gelatin, maltodextrin was located in the core, whereas gelatin was present at the water-oil interface. The opposite was observed for particles consisting of lime hide gelatin where the maltodextrin was found toward the oil phase. The results also showed that a higher concentration of maltodextrin formed larger bicontinuous microstructures compared to the ones obtained with lower concentrations.     

The importance of glassy biopolymer components in food

The glassy state is not just important in low moisture and frozen foods, where it influences the physical and chemical stability and the crispness of some foodstuffs: glassy biopolymer components affect the physical properties of most food systems and low moisture biological systems. Glassy foods are not always fragile and crispy in texture. Therefore, the relationship between mechanical behaviour and molecular dynamics in low-moisture biopolymer systems will be considered. Vitrification of a macromolecular system only requires a mutual fixation of a certain proportion of the chain segments. The higher the rigidity of the chains, the lower the number of the chain segments which must be mutually fixed to vitrify the system. Mechanical stress can help the thermal movement to re-activate the motion of mutually fixed segments and involves a long deformation of glassy material. The stress required to effect long deformation presumably increases up to the strength of the material as the temperature decreases from the glass transition to the temperatures of brittleness (crispness). Vitrification of a loaded viscoelastic system results in an accumulation of mechanical energy (memory effect), which can be released (elastic recovery) above the glass transition temperature due to heating and or addition of a plasticizer. The effects of memory and elastic recovery could be of particular importance for producing foodstuffs which change their form, e.g. self-stirring dry foods and drinks on re-hydration in hot water. The importance of glassy biopolymer ingredients from the viewpoint of food formulation and processing is discussed.     

Effect of polysaccharide charge on formation and properties of biopolymer nanoparticles created by heat treatment of β-lactoglobulin–pectin complexes

Biopolymer nanoparticles can be formed by heating globular protein/polysaccharide mixtures above the thermal denaturation temperature of the protein under pH conditions where the two biopolymers are weakly electrically attracted to each other. In this study, the influence of polysaccharide linear charge density on the formation and properties of these biopolymer nanoparticles was examined. Mixed solutions of globular proteins (β-lactoglobulin) and anionic polysaccharides (high and low methoxyl pectin) were prepared. Micro-electrophoresis, dynamic light scattering, turbidity and atomic force microscopy (AFM) measurements were used to determine the influence of protein-to-polysaccharide mass ratio (r), solution pH, and heat treatment on biopolymer particle formation. Biopolymer nanoparticles (d < 500 nm) could be formed by heating protein–polysaccharide complexes at 83 °C for 15 min at pH 4.75 and r = 2:1 in the absence of added salt. The biopolymer particles formed were then subjected to pH and salt adjustment to determine their stability. The pH stability was greater for β-lactoglobulin-HMP complexes than for β-lactoglobulin-LMP complexes. The addition of 200 mM sodium chloride to heated complexes greatly improved the pH stability of HMP complexes, but decreased the pH stability of LMP complexes. The biopolymer particles formed consisted primarily of β-lactoglobulin, which was probably surrounded by a pectin coating at low pH values. AFM measurements indicated that the biopolymer nanoparticles formed were spheroid in shape. These biopolymer particles may be useful as delivery systems or fat mimetics.     

微胶囊化生姜、枸杞、栀子提取物的ACE抑制率、苦味及稳定性研究

本文通过粉碎、超声获得生姜、枸杞、栀子的混合醇提物,以麦芽糊精、变性淀粉、两者混合分别与明胶作为复合包埋壁材,利用喷雾干燥制成微胶囊,测定其包埋率、ACE（angiotensin-convertion enzyme）抑制率、吸湿性、总酚含量（TPC）、苦味程度,并利用红外光谱（FTIR）、扫描电镜（SEM）、热重分析仪（TGA）对微胶囊化颗粒的结构、热稳定性进行研究。结果表明,微胶囊的最佳壁材为麦芽糊精和变性淀粉质量比1:1混合,此时包埋率为75.24%（P<0.05）,红外光谱分析表明,提取物被壁材包埋成功并形成了淀粉/糊精-酚类-明胶聚合体。与未包埋及单一麦芽糊精、变性淀粉包埋相比,以麦芽糊精和变性淀粉质量比1:1混合作为壁材包埋后的微胶囊苦味显著（P<0.05）降低,吸湿性由未包埋时的52.83 g/(100 g)降为16.04 g/(100 g)。该微胶囊经胃肠消化后其中的酚类释放率为69.64%,ACE抑制率为49.64%（P<0.05）。由此可见,以麦芽糊精和变性淀粉质量比1:1混合作为壁材的微胶囊化药食同源提取物,能明显降低苦味并提高产品稳定性,在室温保存7 d后,ACE抑制率仍高达22.36%。     

Influence of carbohydrates on self‐association of mung bean protein hydrolysate in the presence of amphiphilic asiatic acid

This study investigated the influence of surface‐inactive carbohydrates on association characteristics of amphiphilic mung bean protein hydrolysate (MPH) and asiatic acid (AA) in aqueous suspension (11.72–11.94% total solids). The carbohydrates investigated were trehalose, maltodextrin, mixed trehalose–maltodextrin and mixed maltodextrin–starch. The presence of low‐molecular‐weight carbohydrates enhanced micellisation of AA to form micrometre‐sized particles due to depletion flocculation. Nonetheless, the presence of starch retained the submicrometre size of AA. In contrast, the presence of starch enhanced self‐association of MPH via segregative phase separation. However, the mixed suspensions containing MPH, AA and carbohydrate in a ratio of 1:0–0.072:2.34, respectively, retained particle sizes of around 300 nm regardless of the carbohydrate used. It was found that the MPH–AA co‐aggregates were stable against the osmotic effect of carbohydrates. The results suggest that carbohydrates regulated the aggregate size and surface hydrophobic region of MPH and MPH–AA by controlling surface‐induced aggregation.     

Rheological and thermal properties of an enteral nutrition formula for nutritional support patients using a combined mixture of gelatin and maltodextrin

Enteral nutrition is a type of nutritional support that provides the necessary sources of energy and protein for patients who suffer from dysphagia, chronic disease, and loss of appetite. In this study, a gelatin-maltodextrin binary biopolymer system has been incorporated into a semi-solid formula. The I-optimal combination design approach was used to create 19 formulations, and the dynamic rheological properties, dynamic laser scattering, and zeta potential responses were evaluated over 30 days of storage at 5°C. Solid viscoelastic behavior has been approved since G′ > G″ in the frequency sweep test with no cross-over point. Maltodextrin may interfere within the gelatin network, and increasing the maltodextrin to gelatin (from 0.14 to 1) may lead to a wider linear viscoelastic (LVE) strain range (2.16%), a lower storage modulus at LVE (52%), a lower yield stress (46%), and a lower glass transition temperature (34%). The presence of maltodextrin may reduce the temperature of the sol-to-solid transformation by 48% and enhance its flexibility. In contrast, increasing the gelatin-to-maltodextrin ratio following melting at 37°C led to an increase in the cumulant mean and polydispersity index, indicating a relatively unstable system. The range of zeta potential values between −4.4 and 1.7 mV confirmed a tendency toward coagulation. Microscopic images revealed instability because of irregular or compact chains formed in the gelatin matrix by using higher amounts of maltodextrin. Finally, the best formula had the best rheological stability and was suitable for tube-feeding patients, with a gelatin-to-maltodextrin ratio of 4.35:3.64% w/w on day 17.4.     

Structural properties of single and mixed milk/soya protein systems

Single-component gels were prepared by cold-setting aqueous preparations of thermally processed milk and soya proteins. Small deformation mechanical measurements on soya protein samples showed a strong elastic response (G′) even at the hydration temperature (50°C). Both proteins produced an initial monotonie increase in G′ on cooling, followed by a relatively constant modulus during a subsequent time sweep at the setting temperature (5°C). Networks were fully reversible on heating; the milk protein gels melting out completely at temperatures >60°C, whereas the soya protein gels maintained significant structure even at the highest accessible temperature (95°C). The lack of thermal hysteresis or of sharp, cooperative melting was also confirmed by differential scanning calorimetry. Further investigation of the macromolecular properties of the gels, comprising G′ dependence as a function of frequency of oscillation and creep experiments, suggests that gels remain stable within the time scale of the measurements (90 min). Finally, under increasing amplitude of oscillation, networks withstood structural breakdown up to strain levels of ~70%; behaviour anticipated for biopolymer gels. Mixed gels were studied using a fixed amount of milk protein (10% w/w) with soya protein concentrations from 6 (minimum gelling requirement) to 16% w/w (solubility limit). Comparison of melting profiles (G′ vs. T) for the phase separated systems with those obtained for the individual components indicated phase-inversion from a milk protein continuous network to a soya continuous system at a soya protein concentration of ~11%. Analysis of solvent partition between the constituent phases utilized classical theory of network deswelling for polymer combinations below the phase inversion point and phase equilibria treatment for the soya continuous network with milk protein inclusions. In the case of equilibrium separation of the two components, results were expressed in terms of a single adjustable parameter, p (the ratio of solvent to polymer in one phase divided by the corresponding ratio in the other phase), indicating a soya hydrophilicity of ~1.25 times that of milk protein.     

共混改性改善高低黏度PET并列复合纤维性能的研究

选取高黏度PET、低黏度PET添加PBT的混合物作为并列纺丝的两种组分进行复合纺丝,并对其可纺性进行研究;采用与不经改性的高低黏度PET并列复合纤维的力学性能对比进行研究。结果表明,高黏度PET/(低黏度PET混合PBT)并列复合纺丝具有良好的可纺性及后加工性能,纺制的复合纤维具有较好的力学性能及自卷曲性能。     

Biopolymer Nanoparticles from Heat-Treated Electrostatic Protein–Polysaccharide Complexes: Factors Affecting Particle Characteristics

ABSTRACT: Biopolymer nanoparticles can be formed by heating globular protein–ionic polysaccharide electrostatic complexes above the thermal denaturation temperature of the protein. This study examined how the size and concentration of biopolymer particles formed by heating β-lactoglobulin–pectin complexes could be manipulated by controlling preparation conditions: pH, ionic strength, protein concentration, holding time, and holding temperature. Biopolymer particle size and concentration increased with increasing holding time (0 to 30 min), decreasing holding temperature (90 to 70 °C), increasing protein concentration (0 to 2 wt/wt%), increasing pH (4.5 to 5), and increasing salt concentration (0 to 50 mol/kg). The influence of these factors on biopolymer particle size was attributed to their impact on protein–polysaccharide interactions, and on the kinetics of nucleation and particle growth. The knowledge gained from this study will facilitate the rational design of biopolymer particles with specific physicochemical and functional attributes.     

不同壁材选择对姜油树脂微胶囊化的影响

测定麦芽糊精(DE=7)与大豆蛋白、麦芽糊精(DE=14)与大豆蛋白、麦芽糊精与明胶、麦芽糊精与酪蛋白等不同壁材组合的黏度及壁材不同配比时包埋率和溶解性,研究不同壁材对姜油树脂微胶囊化的影响。结果表明,在不同的壁材组合中,在大豆蛋白与麦芽糊精比例一定的情况下,高DE值的麦芽糊精与大豆蛋白混合壁材的水溶液黏度值较小,且当麦芽糊精:大豆蛋白为2∶1时,得到的微胶囊产品具有较高的包埋率和溶解性。     

Spray Drying Formulation of Polyphenols-Rich Grape Marc Extract: Evaluation of Operating Conditions and Different Natural Carriers

The efficiency of maltodextrin, whey protein isolate, and pea protein isolate to formulate a polyphenol-enriched grape marc extract by spray drying has been compared. Different inlet (120–140 °C ) and outlet (81–89 °C ) temperatures have been evaluated, as well as the amount of carrier expressed as carrier/extract ratio (0.1:1–1:1). The particles obtained were characterized in terms of their chemical composition, morphology, cytotoxicity, and cellular antioxidant activity. Outlet temperature was observed to have a higher influence on the particles than inlet temperature. A 22 % loss in total phenolic content was observed when the extract was spray dried without any carrier material, whereas the addition of the lowest amount of carrier lowered this value (<12 %). While all the carriers tested showed high phenolic retention results, whey and pea protein outperformed maltodextrin in terms of total phenolic and anthocyanin content; in particular, the particles obtained with the lowest carrier/extract ratio presented the highest phenolic and anthocyanin concentrations per gram of product while maintaining a high phenolic recovery (>87 %). Whey protein showed an enhancement of the chemical and cellular antioxidant activity per unit mass of gallic acid equivalent when compared to the other carriers.     

The modification of the molecular and thermodynamic parameters of the low-DE potato maltodextrin in an aqueous medium through the interactions with anionic small-molecule surfactants

We present the modification of the molecular and thermodynamic parameters of the low-DE (DE <3; where DE is the dextrose equivalent) maltodextrin in an aqueous medium that is induced by the interactions with anionic surfactants over a wide range of the surfactant concentrations both below and above their critical micelle concentrations. As the main objects of our investigation we have chosen the industrially important low-DE maltodextrin (Paselli SA-2, DE=2) and the anionic surfactants, SSL and CITREM, which represent generally the mixtures of the esters of the stearic and palmitic acids with a lactic acid or a citric acid, respectively (i.e., these surfactants have the close lengths of the hydrocarbon “tails”, but are different in chemical structure of polar “heads” (charge, size)). Measurements have been made by static and dynamic multiangle laser light scattering of the weight—average molar mass (M_w); the radius of gyration (R_G) and the hydrodynamic radius (R_h), as well as their ratio (ρ=R_G/R_h), reflecting the specific architecture of the scattering particles; and the thermodynamic affinity for an aqueous medium (the second virial coefficient (A₂)) of the maltodextrin+surfactant complexes in an aqueous medium. The pronounced maltodextrin association, which is attended with the change in both the shape of the maltodextrin particles and hydrophilic/lipophilic balance of the maltodextrin molecular properties, has been found as a result of the maltodextrin modification induced by the interactions with the surfactants. The revealed correlations between the light scattering data and the values of the intrinsic viscosity allowed to get a more understanding of the structural peculiarities of the surfactant-modified maltodextrin associates formed in an aqueous medium. In addition, the plausible contribution of the specific character of the maltodextrin–surfactant interactions into the way of the maltodextrin modification in an aqueous medium has been found using the mixing calorimetry data.     

Mechanical α-relaxations and stickiness of milk solids/maltodextrin systems around glass transition

BACKGROUND: Stickiness correlates with changes in mechanical α‐relaxation properties and often results from glass transition and plasticisation of amorphous food components. In this study, milk solids with maltodextrins with different dextrose equivalents (DE9 and DE17) were analysed for glass transition (T_g), α‐relaxation (T_α) and sticky point (SPT) temperatures using differential scanning calorimetry, dynamic mechanical analysis and a sticky point test respectively. RESULTS: At the same maltodextrin contents, T_g and T_α were lower for milk solids with the higher‐DE maltodextrin. Increasing maltodextrin contents gave T_g, T_α and SPT at higher temperatures, and the magnitudes of α‐relaxations with high maltodextrin (DE9 and DE17) contents were less pronounced. CONCLUSION: Stickiness was governed by glass transition and affected by skim milk/maltodextrin composition. Stickiness was reduced with increasing maltodextrin content as a result of maltodextrin miscibility with skim milk solids, particularly lactose, which changed the relaxation behaviour above the glass transition. The mixes of milk solids with low‐DE maltodextrin may show improved dehydration characteristics and powder stability resulting from increased T_g, T_α and SPT. Copyright © 2011 Society of Chemical Industry     

胶原蛋白与壳聚糖复合膜的机械性能

以鮰鱼皮胶原蛋白与壳聚糖为原料制备可食用复合膜。通过正交试验考察胶原蛋白与壳聚糖的质量比、增塑剂种类及添加量、热处理温度及时间等工艺参数对可食用复合膜性能的影响。结果表明：胶原蛋白与壳聚糖质量比和热处理温度对拉伸强度影响较大;甘油添加量对复合膜断裂伸长率影响显著,而热处理时间对复合膜断裂伸长率有较小的影响。最佳机械性能复合膜制备工艺为：胶原蛋白与壳聚糖质量比为6∶4,甘油添加量（以总溶质计）20%、热处理温度为70 ℃、热处理时间为30 min。在此条件下,得到的复合膜表面光滑无气泡,拉伸强度为（21.98±0.33）MPa,断裂伸长率为（127.35±3.03）%。     

Acid-induced gelation of aqueous WPI–CMC solutions: Effect on orange oil aroma compounds retention

Electrostatic gelation under benign conditions of mixed whey protein isolate–carboxymethylcellulose aqueous solutions of relatively low biopolymer concentration was effected following pH reduction from neutral to values between the protein pI and the polysaccharide pK. Small deformation dynamic rheometry (time and frequency sweep measurements) was applied to determine the gel point and characterize the gel structure. State diagrams of biopolymer solutions in absence or presence of Tween 40 were also constructed to assess the contribution of interactions other than ionic ones to the development of the mixed gel structure. The findings are discussed in terms of the attainment of a stoichiometric electrical charge equivalence as the pH was moved towards acidity. As a consequence, the biopolymer molecules carried equal but opposite charges and protein–polysaccharide interactions took place. Retention of selected orange aroma compounds as a result of gel matrix formation was also investigated by applying the Headspace Solid Phase Microextraction technique, followed by gas chromatography–mass spectrometry analysis. The measurements indicated that a number of terpenic constituents of the orange oil were better retained in the matrix while the same was not observed in the case of the aldehydes.     

Development of an in-vitro mouth model to quantify salt release from gels

In the present study, an in-vitro mouth model to quantify salt release from food structures has been developed. In this instance biopolymer gels were used as model food systems. The model aimed to reproduce key phenomena occurring during oral processing, such as diffusion through the sample and compression. Salt release profiles from different gels (gelatin, gellan and alginate), under quiescent conditions and compression, were determined at temperatures of 25 and 37 °C. In-vitro results indicated that salt release is affected both by the type of gelling agent and by temperature. When melting took place, release occurred within seconds. However, when diffusion through the biopolymer matrix was the controlling parameter, the time scale was in the order of hours. It has been shown that compression of the gel only affects release when fractures occur. This is believed to be a consequence of increased surface area. Finally, a mathematical model has been compiled to predict release profiles when diffusion is the controlling mechanism.     

Mixed biopolymers at interfaces: Competitive adsorption and multilayer structures

Mixed biopolymer layers are commonly involved in the stabilization of food emulsions and foams. The interfacial composition and structure of mixed layers are predominantly determined by two mechanistic phenomena—competitive adsorption from mixed solution and cooperative adsorption into multilayers. The surface-active protein components typically dominate primary layers around droplets and bubbles, and the interacting polysaccharides form outer secondary stabilizing layers. This article reviews progress in understanding the factors controlling the nanoscale structure and physico-chemical properties of adsorbed layers in colloidal systems containing mixtures of biopolymers. Contributions from different experimental techniques are described, with particular attention directed towards the role of surface shear rheology in providing information on competitive adsorption of proteins and macromolecular interactions at fluid interfaces. We also consider here the phenomenon of phase separation in mixed protein monolayers, the balance of thermodynamic and kinetic factors in determining biopolymer layer properties, and the involvement of electrostatic interactions in the stabilization of emulsions by protein–polysaccharide complexes.     

Hydrogel microspheres for encapsulation of lipophilic components: Optimization of fabrication & performance

Filled hydrogel microspheres consisting of small oil droplets trapped within biopolymer matrices are useful for encapsulating and delivering lipophilic bioactive agents. The aim of this study was to improve the current method of microsphere fabrication by increasing lipid loading capacity and microsphere yields, reducing the number of processing steps involved in fabrication, and creating microspheres that resist gravitational separation during storage. Filled hydrogel microspheres were fabricated from a phase separated mixture of pectin, caseinate, and emulsified oil to form an oil-in-water-in-water (O/W₁/W₂) emulsion. This system was then acidified and the resulting microspheres were cross-linked with transglutaminase. The order in which the biopolymer phases (W₁ and W₂) and oil droplets (O) were mixed together did not impact the lipid loading capacity. Decreasing the proportion of the continuous biopolymer phase (W₂) used in the preparation procedure increased microsphere yields; however too low proportions (60–70%) caused excessive foaming and protein coagulation. Alternative methods of fabricating filled hydrogel particles using free oil (rather than emulsified oil) proved unsuccessful, resulting in the formation of large non-encapsulated oil droplets (d ∼ 10 μm). Hydrogel microspheres (d₃₂ ∼ 3 μm) with high stability to gravitational separation could be produced by fabricating microspheres with an oil-to-biopolymer ratio of ∼2.6, since this ratio formed particles with a density that nearly matched the surrounding aqueous phase.