Biopolymer Ratio Research Articles

Mixing behaviour of WPI-pectin-complexes in meat dispersions: impact of biopolymer ratios.

Particulated complexes composed of oppositely charged biopolymers were incorporated into highly concentrated protein matrices as potential fat replacers and structuring agents. A multistep procedure was therefore utilized to generate process-stable complexes, which were subsequently embedded into emulsion-type sausages, whereas macro- and microstructural properties were then assessed. Firstly, stock WPI and sugar beet pectin solutions were mixed under neutral conditions (pH 7) at various biopolymer ratios r (2 : 1, 5 : 1, 8 : 1). Secondly, the pH of the biopolymer mixture was decreased to 3.5 to promote associative complexation. Thirdly, electrostatically attracted biopolymer particles were subjected to a heat treatment (ϑ = 85 °C, 20 min) to enhance their stability against superimposed stresses. Finally, fat-reduced emulsion-type sausages were fabricated containing stable WPI-pectin complexes. The results revealed that the heat treatment increased the pH-stability of the biopolymer complexes. In addition, textural and sensorial analysis demonstrated that the meat products became increasingly soft as the biopolymer ratio r increased. This effect was attributed to thermodynamic incompatibility between meat proteins and beet pectin. The results obtained from this study might have important implications for the fabrication of processed meat products with reduced fat levels.

Gelation of soybean protein and polysaccharides delays digestion.

Xanthan gum and carrageenan, representing the medium and highly negatively charged polysaccharides, were heated respectively together with soybean protein isolate (SPI) at different biopolymer ratios. Upon mixing with simulated stomach juice (SSJ), the xanthan-SPI and carrageenan-SPI at biopolymer ratios higher than 0.01 leads to self-assembled gelation immediately. Stronger gel is formed under higher biopolymer ratios. Highly negatively charged carrageenan forms a stronger gel than that composed with xanthan gum. SDS-PAGE results show the digestibility of SPI is delayed after incorporation with the polysaccharides, which is enhanced with the increase of the biopolymer mass ratios. And the polysaccharide with higher negative charge has stronger potential in delaying the digestion of SPI. Furthermore, the microstructure of the xanthan-SPI and carrageenan-SPI gel before and after simulated stomach digestion was characterized by scanning electron microscope (SEM), which also confirms that the gel delays the digestion of soybean protein.

Physico-chemical and microstructural properties of fish gelatin/agar bio-based blend films

This study was conducted with the aim of improving the physico-chemical properties of fish gelatin (FG) based films. For this purpose, FG was blended with agar (AG) in different compositions to acquire biodegradable films (100:0, 80:20, 60:40, 50:50 & 0:100, FG:AG). The obtained results showed that the AG addition strongly increased the film rigidity and resistance to fracture, while reducing the film stretchability, mainly at 50FG: 50AG ratio. AG incorporation greatly reduced the water vapor permeability (WVP) and solubility of gelatin films, as this decline for the blend film with a 50:50 ratio of biopolymers has been about 41% and 66%, respectively (p<0.05). Additional advantages of AG inclusion to FG films are the reduction of the UV-transmittance. Both polymers showed good compatibility, as demonstrated by scanning electron microscopy (SEM) and atomic force microscopy (AFM) images. Therefore, the blend composition influenced the properties of FG/AG bio-based films.

Improving the emulsifying properties of β-lactoglobulin-wild almond gum (Amygdalus scoparia Spach) exudate complexes by heat.

The present study aims to investigate the advantageous effects of wet heating, BLG (β-lactoglobulin)/Ang (Angum gum) ratio, and pH (normal pH of mixed BLG and Ang solutions, pHc > pH > pHΦ1 ) on the emulsifying properties of wet-heated β-lactoglobulin-wild almond gum exudate (Amygdalus scoparia Spach) mixture over those of electrostatic counterparts. Covalent linkage of BLG-Ang conjugates was confirmed by SDS-PAGE and FTIR analysis. Emulsion activity (EA), emulsion stability (ES), and droplet size characteristics of emulsions were significantly (P < 0.05 and P < 0.01) affected by electrostatic/wet-heating, biopolymer ratio, pH, and their interactions. The electrostatic complexes with pHc > pH > pHΦ1 exhibited higher EA and ES values for all the biopolymer ratios investigated than their electrostatic counterparts with pH after mixing. However, these values for the wet-heated samples at pH after mixing were found to be higher than those of the samples subjected to heat treatment at pHc > pH > pHΦ1 . Based on the results obtained, it was concluded that E/1:2/3.80 and W/1:2/6.69 were the two complexes with finer droplet size distributions after preparation (26.72 ± 3.71 and 15.27 ± 1.01 µm, respectively) and after one week of storage at 4 °C (30.71 ± 1.57 and 28.79 ± 0.56 µm, respectively) than others. Apparent viscosities of electrostatic and wet-heated complexes and emulsions made with the complexes were measured. Protein-polysaccharide interactions can be used as an efficient way for producing novel emulsifiers/stabilisers after heat treatment. © 2016 Society of Chemical Industry.

Aggregation and gelation properties of preheated whey protein and pectin mixtures at pH 1.0–4.0

The objective of this work was to understand aggregation and gelation properties of mixtures with preheated whey protein (hWP) and pectin at 1:0–5:1 mass ratios quickly acidified to pH 1.0–4.0 with HCl under agitation. Aggregation properties were studied by measuring turbidity and zeta-potential of hWP–pectin mixtures at pH 1.0–4.0. Gelation properties were characterized for visual inspection of gel formation in vials and small strain oscillation tests. Temperature and time sweeps, also with addition of 5 mM N-ethylmaleimide or 10% urea, were used in rheological tests to understand molecular forces causing gelation. The quickly-acidified gels had less homogenous microstructures and lower strengths than those using slow acidification enabled with glucono-delta-lactone and without agitation. hWP, pectin, and their mixtures had different gelation properties at pH 1.0–4.0. At the studied conditions, pectin neutralized positive charges of hWP, induced gelation at pH 1.5–3.0, and changed properties of hWP gels. hWP gelled at pH 3.5–4.0, while the hWP–pectin mixtures did not. Gelation of hWP alone and its mixture with pectin involved different molecular interactions. Both physical forces (hydrophobic attraction and hydrogen bonds) and disulfide bonds were important to the gelation of hWP at pH 3.5–4.0, while physical forces dominated the gelation of hWP–pectin mixtures, with electrostatic attraction between the two polyelectrolytes playing a significant role. The findings suggest the gelation properties of hWP–pectin mixtures at pH 1.0–4.0 are dependent on the biopolymer ratio and composition.

Encapsulation of Lactococcus lactis subsp. lactis on alginate/pectin composite microbeads: Effect of matrix composition on bacterial survival and nisin release

Alginate/pectin hydrogel microspheres were prepared by extrusion based on a vibrating technology to encapsulate bacteriocin-producing lactic acid bacteria. Effects of both alginate/pectin (A/P) biopolymers ratio and physiological state of Lactococcus lactis subsp. lactis (exponential phase, stationary phase) were examined for nisin release properties, L. lactis survival and beads physico-chemical properties. Results showed that A/P composites were more efficient to increase beads properties than those formulated with pure alginate or pectin. Association of alginate and pectin induces synergistic effect which improves microbeads mechanical properties. FTIR spectroscopy confirms possible interactions between alginate and pectin during inter-penetrating network formation. Physiological state of bacteria during encapsulation process and microbeads composition (A/P ratio, enrichment of internal medium with nutrients) were determining factors for both bacteria viability and bacteriocin release. Of the several matrices tested A/P (75/25) with glucose-enriched M17 gave the best results when L. lactis was encapsulated in exponential state.

Effect of CMC Molecular Weight on Acid-Induced Gelation of Heated WPI-CMC Soluble Complex.

Acid-induced gelation properties of heated whey protein isolate (WPI) and carboxymethylcellulose (CMC) soluble complex were investigated as a function of CMC molecular weight (270, 680, and 750 kDa) and concentrations (0% to 0.125%). Heated WPI-CMC soluble complex with 6% protein was made by heating biopolymers together at pH 7.0 and 85 °C for 30 min and diluted to 5% protein before acid-induced gelation. Acid-induced gel formed from heated WPI-CMC complexes exhibited increased hardness and decreased water holding capacity with increasing CMC concentrations but gel strength decreased at higher CMC content. The highest gel strength was observed with CMC 750 k at 0.05%. Gels with low CMC concentration showed homogenous microstructure which was independent of CMC molecular weight, while increasing CMC concentration led to microphase separation with higher CMC molecular weight showing more extensive phase separation. When heated WPI-CMC complexes were prepared at 9% protein the acid gels showed improved gel hardness and water holding capacity, which was supported by the more interconnected protein network with less porosity when compared to complexes heated at 6% protein. It is concluded that protein concentration and biopolymer ratio during complex formation are the major factors affecting gel properties while the effect of CMC molecular weight was less significant.

Fabrication and characterization of curcumin-loaded albumin/gum arabic coacervate

In this study, gum arabic (GA) and bovine serum albumin (BSA) were used for encapsulation of poorly water-soluble curcumin (CN) by complex coacervation method. To optimize coacervate formulation, three factors including pH (3.7–4.2), BSA/GA weight ratio (3:1, 2:1, 1:1) and CN content (1000–5000 μg), at three levels were examined in central composite design (CCD) using response surface methodology (RSM). A quadratic polynomial equation was used for encapsulation efficiency (EE) optimization. The complex coacervation between GA and BSA was restricted to a narrow pH range, where both molecules carry maximum opposite charges. Optimum conditions were found at BSA/GA weight ratio of 2:1 and pH 3.7. Encapsulation efficiency in this condition was found to be around 92%. Scanning electron microscopy (SEM) revealed a sponge-like coacervate phase and showed the size in the range of 40–80 μm. Further characterization of dried coacervates was performed using XRD and DSC. Penetration test showed that among three mentioned variables, biopolymers ratio had a dominant effect on texture. This study showed that the BSA/GA emulsification-coacervation is an efficient and promising technique for CN encapsulation according to encapsulation efficiency and facility of the method.

Multifilament cellulose/chitin blend yarn spun from ionic liquids

Cellulose and chitin, both biopolymers, decompose before reaching their melting points. Therefore, processing these unmodified biopolymers into multifilament yarns is limited to solution chemistry. Especially the processing of chitin into fibers is rather limited to distinctive, often toxic or badly removable solvents often accompanied by chemical de-functionalization to chitosan (degree of acetylation, DA, <50%). This work proposes a novel method for the preparation of cellulose/chitin blend fibers using ionic liquids (ILs) as gentle, removable, recyclable and non-deacetylating solvents. Chitin and cellulose are dissolved in ethylmethylimidazolium propionate ([C2mim]+[OPr]−) and the obtained one-pot spinning dope is used to produce multifilament fibers by a continuous wet-spinning process. Both the rheology of the corresponding spinning dopes and the structural and physical properties of the obtained fibers have been determined for different biopolymer ratios. With respect to medical or hygienic application, the cellulose/chitin blend fiber show enhanced water retention capacity compared to pure cellulose fibers.

Acid-Induced Aggregation and Gelation of Sodium Caseinate-Guar Gum Mixtures

The aim of this work was to study the formation of bovine sodium caseinate (NaCAS) acid gels induced by addition of glucono-δ-lactone (GDL) in the presence of guar gum (GG). At low biopolymer’s concentrations, a one-phase system was observed, whereas at higher mixture concentrations two-phase systems were formed. Aggregation (at low NaCAS concentrations) and gelation (at high NaCAS concentrations) processes were analyzed through the use of full and fractional factorial experiment designs, using turbidimetric and rheological techniques. Finally, the gel images were obtained by confocal laser scanning microscopy and the images were analyzed. Results showed that at low NaCAS concentrations, the presence of GG affects the pH at which aggregation begins but was not significant for the time at which aggregation begins. On the other hand, at high NaCAS concentrations, the concentration of GG only affected significantly the elastic character of acid gels. As polysaccharide concentration increases, the gels obtained were weaker and with larger pores. Also, the formation of NaCAS droplet-shaped structures at certain biopolymer ratio was observed. The presence of GG affects both the rate of gelation and phase separation, which, in turn, determine the type of gel microstructure. Phase separation seems to occur prior to protein gelation because the protein gel network is discontinued, hindering the gel compactness and reducing gel strength. In summary, GG modifies NaCAS stabilization (self-association and phase separation) and the viscoelasticity and microstructure of NaCAS acid gels. The control of such processes and properties would allow obtaining mixture gels with different textures.

Complex Coacervation of O-Carboxymethylated Chitosan and Gum Arabic

The effects of O-carboxymethylation modification on the coacervation of chitosan with gum arabic (GA) were investigated. O-carboxymethylated chitosan (O-CMC) carried less net positive charge in acidic solutions and its optimum pH and biopolymer ratio for coacervation with GA were lower than those of native chitosan. O-carboxymethylation modification decreased the optimum coacervation temperature from 45 to 25°C and greatly increased the sensitivity to ionic strength. Meanwhile, insoluble O-CMC–GA coacervates were formed in relative lower critical total biopolymer concentration than chitosan–GA coacervates. It was concluded that the O-carboxymethylation modification markedly influenced the electrostatic interaction of chitosan with GA.

Preparation and characterization of O-carboxymethyl chitosan–sodium alginate polyelectrolyte complexes

O-carboxymethyl chitosan (O-CMC) is a water-soluble derivative of chitosan. In this work, the formation of polyelectrolyte complex (PEC) between O-CMC and sodium alginate (SAL) was explored by investigating the effects of medium pH, polyelectrolytes mixing ratio, and ionic strength on the yield of O-CMC–SAL PECs. Meanwhile, the rheological, thermal, and microstructural properties of the PECs prepared at various medium acidities were characterized as well. The results indicated that the strongest complexation between O-CMC and SAL occurred in medium pH 6.5 and biopolymer ratio (RO-CMC/SAL) 1.5:1 (w/w) in the absence of added NaCl. Fourier transform infrared (FTIR) spectroscopy analysis revealed that both electrostatic interaction and hydrogen bonding were involved in PEC formation. The PECs possessed the porous structure and displayed predominately the elastic property with the highest moduli values being recorded at medium pH 3.5. It was concluded that the O-CMC–SAL PECs have potential biomedical applications due to the nearly neutral complexation pH and the porous structure for drug inclusion.

Interaction of cationic antimicrobial (ɛ-polylysine) with food-grade biopolymers: Dextran, chitosan, carrageenan, alginate, and pectin

The cationic biopolymer ε-polylysine (ε-PL) is a food-grade antimicrobial that is highly effective against food pathogens and spoilage organisms. In compositionally complex environments, the antimicrobial activity of cationic ε-PL is likely to be impacted by its interactions with other charged species. The purpose of this study was to characterize the interactions of cationic ε-PL with various food grade biopolymers with different charge characteristics: anionic (carrageenan, alginate, pectin), neutral (dextran), and cationic (chitosan). Isothermal titration calorimetry (ITC), micro-electrophoresis (ME) and turbidity measurements were used to characterize the interactions and the nature of any aggregates formed. Our measurements suggested that there was little interaction or complex formation between cationic ε-PL and cationic or neutral biopolymers, but that strong electrostatic interactions and complex formation occurred between cationic ε-PL and anionic biopolymers. The solubility of the aggregates formed depended on biopolymer type and the mass ratio of biopolymers to ε-PL. The results of this study have important implications for the application of ε-PL in compositionally complex systems.

Investigations of the Effects of Salt and Biopolymer Ratio on Sodium Caseinate-Xanthan Interactions in Aqueous Solution and Emulsions

The aim of this work was to investigate interactions that can take place between, proteins and polysaccharides, in the presence of electrolytes. Thus, our objective was to study the influence of NaCl addition on the associative and/or segregative interactions in the case of biopolymer mixtures and fine emulsions stabilized by sodium caseinate, by analysis of the rheological properties and zeta potential. From the experimental results, it was shown that the presence of salt affects the rheological and physicochemical properties of the aqueous phase and consequently the emulsion stability. Indeed, the electrolytes can modify the conformation of proteins and polysaccharides, by electric neutralization of their charge, as they can generate a complex coacervation or increase their incompatibility.

Effect of charge density of polysaccharides on self-assembled intragastric gelation of whey protein/polysaccharide under simulated gastric conditions.

This study focuses on the behavior of mixed protein and polysaccharides with different charge densities under simulated gastric conditions. Three types of polysaccharides, namely, guar gum, xanthan gum and carrageenan (neutral, medium negatively, and highly negatively charged, respectively) were selected for heating together with whey protein isolate (WPI) at a biopolymer ratio ranging from 0.01 to 0.1. Upon mixing with simulated gastric fluid (SGF), all WPI-guar gum samples remained soluble, whereas WPI-xanthan gum and WPI-carrageenan at biopolymer ratio higher than 0.01 led to self-assembled intragastric gelation immediately after mixing with SGF. The mechanism behind the intragastric gelation is believed to be the cross-linking between oppositely charged protein and polysaccharides when pH was reduced to below the pI of the protein. Higher biopolymer ratio led to a higher degree of intermolecular interaction, which tends to form stronger gel. More negatively charged carrageenan also formed a stronger gel than xanthan gum. SDS-PAGE results show that the digestibility of protein was not affected by the presence of guar gum as well as xanthan gum and carrageenan at biopolymer ratio lower than 0.02. However, intragastric gel formed by WPI-xanthan gum and WPI-carrageenan at biopolymer ratio higher than 0.02 significantly slows down the digestion rate of protein, which could potentially be used to delay gastric emptying and promote satiety.

Intragastric gelation of whey protein–pectin alters the digestibility of whey protein during in vitro pepsin digestion

The aim of this work is to investigate the effect of pectin on in vitro digestion of whey protein. Digestion of heated whey protein isolate (WPI) and pectin solutions (WPI-pectin) as influenced by pectin concentration and pH was studied under simulated gastric conditions. Electrophoresis, dynamic light scattering, colorimetric measurements, and gel microstructures were used to study the digestion pattern. At low pectin concentration (0.25% w/w), pectin did not significantly influence the degradation of whey protein. Increasing the pectin concentration to 1% led to extensive intragastric gelation immediately after mixing with simulated gastric fluid. The microstructure of intragastric gel from WPI-pectin at pH 6.0 showed a more interconnected and denser gel network than that at pH 7.0. More protein and pectin were involved in the gelation at pH 6.0 than pH 7.0. The digesta of samples at pH 6.0 was mainly composed of peptides, while that at pH 7.0 mostly consisted of aggregates and crosslinked peptides. This study suggests that WPI-pectin at high biopolymer ratio formed intragastric gel in simulated gastric models, which could delay protein digestion and potentially slow gastric emptying and promote satiety.

Preparation of microcapsules by complex coacervation of gum Arabic and chitosan

Gum Arabic–chitosan microcapsules containing a commercially available blend of triglycerides (Miglyol 812 N) as core phase were synthesized by complex coacervation. This study was conducted to clarify the influence of different parameters on the encapsulation process, i.e. during the emulsion formation steps and during the shell formation, using conductometry, zeta potential, surface and interface tension measurement and Fourier-transform infrared spectroscopy. By carefully analyzing the influencing factors including phase volume ratio, stirring rate and time, pH, reaction time, biopolymer ratio and crosslinking effect, the optimum synthetic conditions were found out. For the emulsion step, the optimum phase volume ratio chosen was 0.10 and an emulsion time of 15min at 11,000rpm was selected. The results also indicated that the optimum formation of these complexes appears at a pH value of 3.6 and a weight ratio of chitosan to gum Arabic mixtures of 0.25.

Ovalbumin–gum arabic interactions: Effect of pH, temperature, salt, biopolymers ratio and total concentration

The formation of soluble and insoluble complexes between ovalbumin (OVA) and gum arabic (GA) polysaccharide was investigated under specific conditions (pH 1.0–7.0; temperature 4–55°C; NaCl concentration 0–60mM; total biopolymer concentration 0.05–3.0wt%) by turbidimetric analysis. For the 2:1 OVA:GA ratio and in the absence of NaCl, soluble and insoluble complexes were observed at pH 4.61 (pHφ1) and 4.18 (pHφ2), respectively, with optimal biopolymer interactions occurring at pH 3.79 (pHopt). Under the same conditions, OVA alone gave only a weak turbidity intensity (turbidity <0.03), whereas GA had none. As the temperature increased, critical pH values shifted toward lower pH, and the maximum turbidity value occurred at 25°C. The region between pHφ1 and pHφ2 was narrowed and the electrostatic interactions became weaker with increasing NaCl concentration. The maximum turbidity value increased as the total biopolymer concentration increased until reaching a critical value (2.0%), afterwards becoming a constant value.

The effects of compressibility, hydrodynamic interaction and inertia on two-point, passive microrheology of viscoelastic materials

In two-point passive microrheology, a modification of the original one-point technique the cross-correlations of two micron-sized beads embedded in a viscoelastic material are used to estimate the dynamic modulus of a material. The two-point technique allows for sampling of larger length scales which means that it can be used in materials with a coarser microstructure. An optimal separation between the beads exists at which the desired length and time scales are sampled while keeping an acceptable signal-to-noise-ratio in the cross-correlations. A larger separation can reduce the effect of higher-order reflections, but will increase the effects of medium inertia and reduce the signal-to-noise-ratio. The modeling formalisms commonly used to relate two-bead cross-correlations to the dynamic modulus and the complex Poisson ratio neglect inertia effects and underestimate the effect of reflections. A simple dimensional analysis suggests that for a model viscoelastic solid there exists a very narrow window of bead separation and frequency range where these effects can be neglected. In a recent work [Phys. Fluids, 2012, 24, 073103] we proposed an analysis formalism that accounts for medium inertia and high-order hydrodynamic reflections and therefore significantly increases the versatility of the two-point microrheology technique. In this paper we extend our analysis to compressible viscoelastic solids. There has been a recent interest in using two-point microrheology to measure the complex Poisson ratio of biopolymers [Das and MacKintosh, Phys. Rev. Lett., 2010, 105, 138102] however a rigorous analysis of the sensitivity of the technique to the static and dynamic properties of the Poisson ratio is still lacking. There are two decoupled statistics that can be followed with such a technique: motion parallel and perpendicular to the line of centers of the probe beads. We show that the cross-correlation in the direction parallel to the line of centers is insensitive to compressibility, so may reliably be used to determine G* (dynamic modulus) alone. Although, the cross-correlation in the perpendicular direction may then be used to extract a constant Poisson ratio, it is relatively insensitive to its frequency dependence. We consider the example of a composite actin/microtubule network.

Complex coacervation of pea protein isolate and alginate polysaccharides

Complex coacervation between pea protein isolate (PPI) and alginate (AL) was investigated as a function of pH (1.50–7.00) and mixing ratio (1:1–20:1 PPI:AL) by turbidimetric analysis and electrophoretic mobility during an acid titration. Conformational changes to the secondary structures during coacervation were also studied by Raman spectroscopy. Critical structure-forming events associated with the formation of soluble (pH 5.00) and insoluble (pH 2.98) complexes were found for a 1:1 PPI–AL mixture, with optimal biopolymer interactions occurring at pH 2.10 (pHopt). As mixing ratios increased between 4:1 and 8:1, critical pHs shifted towards higher pH. Maximum coacervate formation at pHopt occurred at a mixing ratio of 4:1. Electrophoretic mobility measurements showed a shift in net neutrality from pH 4.00 in homogenous PPI solutions, to pH 1.55 for the 1:1 mixture. As biopolymer ratios increased towards 8:1 PPI:AL, net neutrality shifted to higher pHs (∼3.80). Raman spectroscopy revealed minimal complexation-induced conformational changes. Findings could aid in the design of pH-sensitive biopolymer carriers for use in functional food and bio-material applications.