Fundamental understanding of polysaccharide lubrication and large-strain rheological behaviors is... more Fundamental understanding of polysaccharide lubrication and large-strain rheological behaviors is needed for targeted design of foods with more desirable texture and sensory attributes. Thus, the objective of this study was to investigate large amplitude oscillatory shear (LAOS) behavior and tribo-logical properties of Alyssum homolocarpum seed gum aqueous dispersions at different concentrations (1-3% w/v) and temperatures (5-50 C). Dispersions prepared at higher concentrations showed greater stability to permanent deformation under LAOS and lower friction coefficients. These results were attributed to greater molecular connectivity and structure development at higher concentrations. Increased temperature did not have strong effects on the tribological behavior of the dispersions; however, less permanent deformation at large strain was observed at higher temperatures. These results provide a more complete picture of Alyssum homolocarpum rheological behavior, which can be used to design foods with more desirable textures.
Concentrated emulsions stabilized by proteins, polysaccharides, or a combination are the basis fo... more Concentrated emulsions stabilized by proteins, polysaccharides, or a combination are the basis for many food products such as mayonnaise and heavy cream. However, fundamental influences of protein epolysaccharide interactions on concentrated emulsion tribological properties and large deformation behavior are often poorly understood, leading to difficulties in targeted development of concentrated food emulsions with palatable textures and good stability. Thus, the objective of this study was to characterize the effects of fish gelatin (FG)egum arabic (GA) complexation on the large amplitude oscillatory shear (LAOS) and tribological behaviors of concentrated emulsions. Concentrated emulsions (oil phase volume fraction ¼ 0.7) were prepared using FGeGA mixtures at different aqueous phase pH (3.6, 5.0, and 9.0) and characterized by rheometry and tribometry. Samples prepared with FGeGA mixtures at higher pH showed lower critical strains, increased extent of nonlinear behavior under LAOS (higher G 0 3 /G 0 1 and G 00 3 /G 00 1 values), increased strain hardening and shear thinning under LAOS (G 0 L /G 0 M and h 0 L /h 0 M values further from unity, respectively), and higher friction coefficients. These results were attributed to reduced FGeGA electrostatic complexation as pH increased from 3.6 to 9.0. Complexes formed at lower pH induced higher droplet monodispersity, greater network extension, and smaller oil droplets, resulting in greater structural stability to deformation. These stability differences would likely contribute to differences in food textures and stability under food processing and storage conditions.
Concentrated emulsions containing both proteins and polysaccharides are the basis for many commer... more Concentrated emulsions containing both proteins and polysaccharides are the basis for many commercial products ; however, the effects of protein–polysaccharide interactions on the functional properties of these complex systems are often poorly understood from a fundamental standpoint. Hence, the objective of this study was to determine the effects of fish gelatin (FG)-gum arabic (GA) complexation at different aqueous phase pH (3.6, 5.0, and 9.0) on concentrated emulsion structure–function relationships. Concentrated emulsions were prepared using FG-GA mixtures and characterized by rheometry and confocal scanning laser microscopy (CSLM). CSLM images showed that all samples were O/W emulsions; emulsions with lower pH showed smaller oil droplets, greater homogeneity in size distribution, and higher stability. This was attributed to an increased number of FG-GA complexes in the emulsification. Electrostatic attractive interactions and charge neutralization created biopolymer associations with increased emulsification capacity. Samples with FG-GA mixtures at lower pH showed higher elastic moduli under small deformation and exhibited greater deviation between apparent and complex viscosities under the Cox-Merz rule, indicating increased gel network extension and greater inter-molecular connectivity between adsorbed layers of adjacent oil droplets. These results can be used to incorporate protein–polysaccharide complexes as a suitable emulsifier in materials comprising concentrated emulsions.
Chemical composition, rheological properties and antioxidant activities of Althaea officinalis fl... more Chemical composition, rheological properties and antioxidant activities of Althaea officinalis flower gum were studied as a new source of thickening agent for application in food systems. The isolated gum comprised mainly carbohydrates (52.6 ± 0.8%), uronic acids (37.5 ± 0.5%), and proteins (7.1 ± 0.1%). Rhamnose (57.7%) was the major sugar; the polysaccharide backbone was chiefly composed of 1,2-linked rhamnose. The average molar mass of the polysaccharide was 33.3 Â 10 6 g/mol. Rheological behavior was determined as a function of concentration (0.5e5.0% w/v) and temperature (5.0e50 C). Polysaccharide solution steady-shear flow behavior was pseudoplastic and well-described with the Carreau model (R 2 ¼ 0.99). The degree of pseudoplasticity (N) of the solutions increased with increased concentration and decreased with increased temperature. Frequency sweeps indicated weak gel behavior at higher concentrations or lower temperatures. Moderate DPPH radical scavenging activity and ferric reducing power was observed for the extracted polysaccharide.
Since concentrated emulsions are the basis for many commercial products, conducting comprehensive... more Since concentrated emulsions are the basis for many commercial products, conducting comprehensive studies on structureefunction relationships of emulsion systems is necessary for targeted product design. Hence, the objectives of this study were to 1) characterize the effects of fish gelatin concentration and oil phase volume fraction on the rheological, tribological and microstructural properties of concentrated emulsions and 2) determine structureefunction relationships based on the measured parameters. Emulsions were prepared using different amounts of oil and fish gelatin, and characterized by rheometry and microscopy. Emulsions containing higher oil or fish gelatin concentrations had greater stability to creaming, larger critical strains, and lower friction profiles. However, they exhibited increased nonlinear behavior under large amplitude oscillatory shear. These results were ascribed to increased homogeneity, higher network extension, and smaller oil droplets in emulsions with higher protein or oil concentrations. These results can be used to incorporate concentrated emulsions in emulsion-based formulations.
The objective of this study was to characterize influence of different cooling and heating rates ... more The objective of this study was to characterize influence of different cooling and heating rates on gelation of fish gelatin (FG)-gum arabic (GA) complex coacervate phase using rheological measurements. For the coacervate phase prepared at 10 • C, the gelling temperature, melting temperature, gel strength, and stress relaxation decreased with increasing cooling or heating rate, however, no gelation was observed at the highest cooling rate of 0.05 • C/min. Similar trends were obtained for the coacervates phase prepared at 30 • C, but the gelation did not occur at a cooling rate of 0.033 or 0.05 • C/min. The results indicated that rheological properties of FG-GA coacervate gels were highly dependent to the cooling process, where more thermos-stable and stronger gels formed at slower cooling. This was probably because of higher degree of molecular rearrangements, more hydrogen bindings, and formation of greater junction zones into the gel network at slower cooling rates. However, all of the FG-GA coacervate gels obtained at different cooling rates were classified as a weak physical gel.
Keywords: Fish gelatin e gum arabic coacervate gel Tannic acid Cross-linker Gel strength Rheology... more Keywords: Fish gelatin e gum arabic coacervate gel Tannic acid Cross-linker Gel strength Rheology Fourier transform infrared a b s t r a c t The propose of this study was to investigate the rheological and structural properties of fish gelatin (FG) egum arabic (GA) complex coacervate gels treated with oxidized or non-oxidized tannic acid (OX-TA or NO-TA, respectively) at different concentrations ranged from 0.0 to 0.3% (v/v), using compositional, dynamic oscillatory rheological, and Fourier transform infrared (FTIR) analyses. The results revealed that the degree of NO-TA incorporation for cross-linking with FG via hydrogen bindings into the system was more pronounced than affinity of OX-TA for reaction through covalent bindings as evidenced by greater loss in volume fraction, moisture content, and biopolymer content values into the FGeGA coacervate phase. FTIR analysis showed addition of NO-TA led to more molecular disorder into the system, so that higher concentrations (0.2 and 0.3%) of the cross-linker disrupted electrostatic interactions through formation of stronger hydrogen bindings with proteins. Rheological results mentioned that addition and enhancement of (NO-or OX-) TA concentration improved gelling ability and mechanical properties of the FGeGA coacervate gels. However, frequency sweep test results implied that all the gels obtained can be classified as weak gels with shear-thinning behavior. Based on weak gel model, the gels obtained by treated FGeGA coacervates with NO-TA had more developed network structures and stronger inter-molecular connectivities than those of obtained by the coacervates modified by OX-TA. The results of the current study provide basic knowledge necessary for the use of reinforced FGeGA complex coacervate gels in many useful applications, such as microencapsulation and hydrogel formation, in food and pharmaceutical industries.
Compositional and rheological properties of Alyssum homolocarpum seed gum, as a new source of thi... more Compositional and rheological properties of Alyssum homolocarpum seed gum, as a new source of thickening agent for application in food industries, were investigated in this study. The extracted gum primarily comprised carbohydrates (61.0 ± 0.6%), proteins (17.9 ± 1.0%) and uronic acids (10.9 ± 0.8%); the main carbohydrates were galactose (65.7%) and rhamnose (18.3%). The polysaccharide backbone was chiefly composed of 1,2-rhamnose, 1,3- and 1,3,6-galactose glycosidic linkages. The average molecular weight of the polymer was 122.5 × 106 g mol-1. Attenuated total reflectance-Fourier transform infrared spectroscopy and ζ-potential measurements revealed that Alyssum homolocarpum seed gum with multiple carboxylic groups was negatively charged in water in the pH range 3–11. Rheological behaviors of the extracted gum were investigated between 0.5–5.0% (w/w) concentrations and temperatures of 5–50°C. Viscosity profile showed shear thinning behavior at all concentrations and temperatures. The pseudoplasticity degree (N) of the extracted polymers increased with concentration while temperature changes did not show any specific trend on N values. The flow activation energy, quantified using an Arrhenius equation decreased from 11.00 to 5.17 (kJ/mol) as shear rate increased, which implied that the aqueous solutions flowed more easily at higher shear rates. The mechanical spectra derived from strain sweep and frequency sweep measurements indicated viscoelastic behavior in all of samples. Frequency sweep data showed that aqueous solutions of gum, displayed weak gel behavior over the range of tested concentrations and temperatures: as dynamic moduli increased with the increased frequency and storage modulus was always greater than loss modulus.
The rheological and structural characteristics of fish gelatin (FG)–gum arabic (GA) complex coace... more The rheological and structural characteristics of fish gelatin (FG)–gum arabic (GA) complex coacervate phase, separated from an aqueous mixture of 1% FG and 1% GA at pH 3.5, were investigated as influenced by phase separation temperature. Decreasing the phase separation temperature from 40 to 10 °C lead to: (1) the formation of a coacervate phase with a larger volume fraction and higher biopolymer concentrations, which is more viscous, more structural resistant at low shear rates, more shear-thinning at high shear rates, and more condensed in microstructure, (2) a solid-like elastic behavior of the phase separated at 10 °C at a high oscillatory frequency, (3) the increase in gelling and melting temperatures of the coacervate phase (3.7−3.9 °C and 6.2−6.9 °C, respectively), (4) the formation of a more rigid and thermo-stable coacervate gel. The coacervate phase is regarded as a homogeneously networked biopolymer matrix dispersed with water vacuoles and its gel as a weak physical gel reinforced by FG–GA attractive electrostatic interactions.
Effect of nisin on biochemical and microbial quality and shelf life of vacuum packaged rainbow tr... more Effect of nisin on biochemical and microbial quality and shelf life of vacuum packaged rainbow trout (Oncorhynchus mykiss) during 16 days storage at 4 °C was investigated. According to the obtained results, nisin treated fish showed lower (p < 0.05) and acceptable biochemical (Peroxide value, thiobarbituric acid-index, pH, and total volatile base nitrogen) and bacteriological (total viable counts, psychrotrophic viable counts, and lactic acid bacteria) attributes up to 16 days storage at 4 °C compared with those treated without nisin. Furthermore, FAs composition analysis indicated that presence of the nisin preserved nutritional quality of fish lipid, so that nisin treated samples contained higher percentage (p > 0.05) of essential FAs such as eicosapentaenoic acid and docosahexaenoic acid. This study concluded that treatment of the vacuum packaged rainbow trout with nisin resulted in improvement of quality and extension of shelf life of the fish from 12 to 16 days at 4 °C.
"Chemical and microbiological changes in vacuum-packaged slices of rainbow trout (Onchorynchus my... more "Chemical and microbiological changes in vacuum-packaged slices of rainbow trout (Onchorynchus mykis) treated or not treated (controls) with nisin (0.2 % w/w) samples were evaluated for 16 days at 4 °C. The peroxide value (PV), thiobarbituric acid value (TBA) and total volatile basic nitrogen (TVB-N) remained within standard acceptable levels of 6.21 meqkg-1, 0.71 mgkg-1 and 24.81mg100g-1, respectively, whereas the same values were exceeded in untreated control samples. Nisin significantly (p<0.05) lowered the number of psychrotrophic, mesophilic and lactic acid bacteria (LAB) compared with controls (5.35 log, 1.57 log, and 6.3 log vs. 6.82 log, 5.35 log and 7.84 log, respectively). The results suggest that nisin could be used to extend the shelf-life of filleted rainbow trout.
"
The interactions between fish gelatin (FG) and gum arabic (GA) in aqueous solutions were investig... more The interactions between fish gelatin (FG) and gum arabic (GA) in aqueous solutions were investigated by turbidimetry, methylene blue spectrophotometry, zeta potentiometry, dynamic light scattering, protein assay, and state diagram at 40 °C and a total biopolymer concentration (CT) of 0.05%. FG underwent complex coacervation with GA, possibly via its conformational change, depending on pH and FG to GA ratio (FG:GA). The formation of FG–GA complexes was the most intense when pH 3.55 and FG:GA = 50:50 (6.6:1 M ratio), however, the coacervate phase was found to be composed of a much higher FG fraction. The pH range of complex formation shifted to a higher pH region with increasing FG:GA. Soluble and insoluble FG–GA complexes were formed even in a pH region where both biopolymers were net-negatively charged. Varying CT significantly influenced not only the formation of FG–GA complexes but also the development and composition of coacervate phase.► Fish gelatin (FG) undergoes complex coacervation with gum arabic (GA). ► A state diagram is created by plotting phase boundary pHs against FG to GA ratio. ► The most intensive FG–GA complex formation at pH 3.55 and FG to GA ratio of 50:50. ► Complex formation occurs even between net-negatively charged FG and GA. ► The composition of coacervate phase is affected by total biopolymer concentration.
Compositional and rheological properties ofAlyssum homolocarpumseed gum, as a new source of
thick... more Compositional and rheological properties ofAlyssum homolocarpumseed gum, as a new source of thickening agent for application in food industries, were investigated in this study. The extracted gum primarily comprised carbohydrates (61.0±0.6%), proteins (17.9±1.0%) and uronic acids (10.9±0.8%); the main carbohydrates were galactose (65.7%) and rhamnose (18.3%). The polysaccharide backbone was chiefly composed of 1,2-rhamnose, 1,3- and 1,3,6-galactose glycosidic linkages. The average molecular weight of the polymer was 122.510 6 gmol 1 . Attenuated total reflectance-Fourier transform infrared spectroscopy and z-potential measurements revealed that A. homolocarpumseed gum with multiple carboxylic groups was negatively charged in water in the pH range 3e11. Rheological behaviors of the extracted gum were investigated between 0.5 and 5.0% (w/w) concentrations and temperatures of 5 e50
C. Viscosity profile showed shear thinning behavior at all concentrations and temperatures. The pseudoplasticity degree (N) of the extracted polymers increased with concentration while temperature changes did not show any specific trend onNvalues. Theflow activation energy, quantified using an Arrhenius equation decreased from 11.00 to 5.17 (kJ/mol) as shear rate increased, which implied that the aqueous solutionsflowed more easily at higher shear rates. The mechanical spectra derived from strain sweep and frequency sweep measurements indicated viscoelastic behavior in all of samples. Frequency sweep data showed that aqueous solutions of gum, displayed weak gel behavior over the range of tested concentrations and temperatures: as dynamic moduli increased with the increased frequency and storage modulus was always greater than loss modulus.
Fundamental understanding of polysaccharide lubrication and large-strain rheological behaviors is... more Fundamental understanding of polysaccharide lubrication and large-strain rheological behaviors is needed for targeted design of foods with more desirable texture and sensory attributes. Thus, the objective of this study was to investigate large amplitude oscillatory shear (LAOS) behavior and tribo-logical properties of Alyssum homolocarpum seed gum aqueous dispersions at different concentrations (1-3% w/v) and temperatures (5-50 C). Dispersions prepared at higher concentrations showed greater stability to permanent deformation under LAOS and lower friction coefficients. These results were attributed to greater molecular connectivity and structure development at higher concentrations. Increased temperature did not have strong effects on the tribological behavior of the dispersions; however, less permanent deformation at large strain was observed at higher temperatures. These results provide a more complete picture of Alyssum homolocarpum rheological behavior, which can be used to design foods with more desirable textures.
Concentrated emulsions stabilized by proteins, polysaccharides, or a combination are the basis fo... more Concentrated emulsions stabilized by proteins, polysaccharides, or a combination are the basis for many food products such as mayonnaise and heavy cream. However, fundamental influences of protein epolysaccharide interactions on concentrated emulsion tribological properties and large deformation behavior are often poorly understood, leading to difficulties in targeted development of concentrated food emulsions with palatable textures and good stability. Thus, the objective of this study was to characterize the effects of fish gelatin (FG)egum arabic (GA) complexation on the large amplitude oscillatory shear (LAOS) and tribological behaviors of concentrated emulsions. Concentrated emulsions (oil phase volume fraction ¼ 0.7) were prepared using FGeGA mixtures at different aqueous phase pH (3.6, 5.0, and 9.0) and characterized by rheometry and tribometry. Samples prepared with FGeGA mixtures at higher pH showed lower critical strains, increased extent of nonlinear behavior under LAOS (higher G 0 3 /G 0 1 and G 00 3 /G 00 1 values), increased strain hardening and shear thinning under LAOS (G 0 L /G 0 M and h 0 L /h 0 M values further from unity, respectively), and higher friction coefficients. These results were attributed to reduced FGeGA electrostatic complexation as pH increased from 3.6 to 9.0. Complexes formed at lower pH induced higher droplet monodispersity, greater network extension, and smaller oil droplets, resulting in greater structural stability to deformation. These stability differences would likely contribute to differences in food textures and stability under food processing and storage conditions.
Concentrated emulsions containing both proteins and polysaccharides are the basis for many commer... more Concentrated emulsions containing both proteins and polysaccharides are the basis for many commercial products ; however, the effects of protein–polysaccharide interactions on the functional properties of these complex systems are often poorly understood from a fundamental standpoint. Hence, the objective of this study was to determine the effects of fish gelatin (FG)-gum arabic (GA) complexation at different aqueous phase pH (3.6, 5.0, and 9.0) on concentrated emulsion structure–function relationships. Concentrated emulsions were prepared using FG-GA mixtures and characterized by rheometry and confocal scanning laser microscopy (CSLM). CSLM images showed that all samples were O/W emulsions; emulsions with lower pH showed smaller oil droplets, greater homogeneity in size distribution, and higher stability. This was attributed to an increased number of FG-GA complexes in the emulsification. Electrostatic attractive interactions and charge neutralization created biopolymer associations with increased emulsification capacity. Samples with FG-GA mixtures at lower pH showed higher elastic moduli under small deformation and exhibited greater deviation between apparent and complex viscosities under the Cox-Merz rule, indicating increased gel network extension and greater inter-molecular connectivity between adsorbed layers of adjacent oil droplets. These results can be used to incorporate protein–polysaccharide complexes as a suitable emulsifier in materials comprising concentrated emulsions.
Chemical composition, rheological properties and antioxidant activities of Althaea officinalis fl... more Chemical composition, rheological properties and antioxidant activities of Althaea officinalis flower gum were studied as a new source of thickening agent for application in food systems. The isolated gum comprised mainly carbohydrates (52.6 ± 0.8%), uronic acids (37.5 ± 0.5%), and proteins (7.1 ± 0.1%). Rhamnose (57.7%) was the major sugar; the polysaccharide backbone was chiefly composed of 1,2-linked rhamnose. The average molar mass of the polysaccharide was 33.3 Â 10 6 g/mol. Rheological behavior was determined as a function of concentration (0.5e5.0% w/v) and temperature (5.0e50 C). Polysaccharide solution steady-shear flow behavior was pseudoplastic and well-described with the Carreau model (R 2 ¼ 0.99). The degree of pseudoplasticity (N) of the solutions increased with increased concentration and decreased with increased temperature. Frequency sweeps indicated weak gel behavior at higher concentrations or lower temperatures. Moderate DPPH radical scavenging activity and ferric reducing power was observed for the extracted polysaccharide.
Since concentrated emulsions are the basis for many commercial products, conducting comprehensive... more Since concentrated emulsions are the basis for many commercial products, conducting comprehensive studies on structureefunction relationships of emulsion systems is necessary for targeted product design. Hence, the objectives of this study were to 1) characterize the effects of fish gelatin concentration and oil phase volume fraction on the rheological, tribological and microstructural properties of concentrated emulsions and 2) determine structureefunction relationships based on the measured parameters. Emulsions were prepared using different amounts of oil and fish gelatin, and characterized by rheometry and microscopy. Emulsions containing higher oil or fish gelatin concentrations had greater stability to creaming, larger critical strains, and lower friction profiles. However, they exhibited increased nonlinear behavior under large amplitude oscillatory shear. These results were ascribed to increased homogeneity, higher network extension, and smaller oil droplets in emulsions with higher protein or oil concentrations. These results can be used to incorporate concentrated emulsions in emulsion-based formulations.
The objective of this study was to characterize influence of different cooling and heating rates ... more The objective of this study was to characterize influence of different cooling and heating rates on gelation of fish gelatin (FG)-gum arabic (GA) complex coacervate phase using rheological measurements. For the coacervate phase prepared at 10 • C, the gelling temperature, melting temperature, gel strength, and stress relaxation decreased with increasing cooling or heating rate, however, no gelation was observed at the highest cooling rate of 0.05 • C/min. Similar trends were obtained for the coacervates phase prepared at 30 • C, but the gelation did not occur at a cooling rate of 0.033 or 0.05 • C/min. The results indicated that rheological properties of FG-GA coacervate gels were highly dependent to the cooling process, where more thermos-stable and stronger gels formed at slower cooling. This was probably because of higher degree of molecular rearrangements, more hydrogen bindings, and formation of greater junction zones into the gel network at slower cooling rates. However, all of the FG-GA coacervate gels obtained at different cooling rates were classified as a weak physical gel.
Keywords: Fish gelatin e gum arabic coacervate gel Tannic acid Cross-linker Gel strength Rheology... more Keywords: Fish gelatin e gum arabic coacervate gel Tannic acid Cross-linker Gel strength Rheology Fourier transform infrared a b s t r a c t The propose of this study was to investigate the rheological and structural properties of fish gelatin (FG) egum arabic (GA) complex coacervate gels treated with oxidized or non-oxidized tannic acid (OX-TA or NO-TA, respectively) at different concentrations ranged from 0.0 to 0.3% (v/v), using compositional, dynamic oscillatory rheological, and Fourier transform infrared (FTIR) analyses. The results revealed that the degree of NO-TA incorporation for cross-linking with FG via hydrogen bindings into the system was more pronounced than affinity of OX-TA for reaction through covalent bindings as evidenced by greater loss in volume fraction, moisture content, and biopolymer content values into the FGeGA coacervate phase. FTIR analysis showed addition of NO-TA led to more molecular disorder into the system, so that higher concentrations (0.2 and 0.3%) of the cross-linker disrupted electrostatic interactions through formation of stronger hydrogen bindings with proteins. Rheological results mentioned that addition and enhancement of (NO-or OX-) TA concentration improved gelling ability and mechanical properties of the FGeGA coacervate gels. However, frequency sweep test results implied that all the gels obtained can be classified as weak gels with shear-thinning behavior. Based on weak gel model, the gels obtained by treated FGeGA coacervates with NO-TA had more developed network structures and stronger inter-molecular connectivities than those of obtained by the coacervates modified by OX-TA. The results of the current study provide basic knowledge necessary for the use of reinforced FGeGA complex coacervate gels in many useful applications, such as microencapsulation and hydrogel formation, in food and pharmaceutical industries.
Compositional and rheological properties of Alyssum homolocarpum seed gum, as a new source of thi... more Compositional and rheological properties of Alyssum homolocarpum seed gum, as a new source of thickening agent for application in food industries, were investigated in this study. The extracted gum primarily comprised carbohydrates (61.0 ± 0.6%), proteins (17.9 ± 1.0%) and uronic acids (10.9 ± 0.8%); the main carbohydrates were galactose (65.7%) and rhamnose (18.3%). The polysaccharide backbone was chiefly composed of 1,2-rhamnose, 1,3- and 1,3,6-galactose glycosidic linkages. The average molecular weight of the polymer was 122.5 × 106 g mol-1. Attenuated total reflectance-Fourier transform infrared spectroscopy and ζ-potential measurements revealed that Alyssum homolocarpum seed gum with multiple carboxylic groups was negatively charged in water in the pH range 3–11. Rheological behaviors of the extracted gum were investigated between 0.5–5.0% (w/w) concentrations and temperatures of 5–50°C. Viscosity profile showed shear thinning behavior at all concentrations and temperatures. The pseudoplasticity degree (N) of the extracted polymers increased with concentration while temperature changes did not show any specific trend on N values. The flow activation energy, quantified using an Arrhenius equation decreased from 11.00 to 5.17 (kJ/mol) as shear rate increased, which implied that the aqueous solutions flowed more easily at higher shear rates. The mechanical spectra derived from strain sweep and frequency sweep measurements indicated viscoelastic behavior in all of samples. Frequency sweep data showed that aqueous solutions of gum, displayed weak gel behavior over the range of tested concentrations and temperatures: as dynamic moduli increased with the increased frequency and storage modulus was always greater than loss modulus.
The rheological and structural characteristics of fish gelatin (FG)–gum arabic (GA) complex coace... more The rheological and structural characteristics of fish gelatin (FG)–gum arabic (GA) complex coacervate phase, separated from an aqueous mixture of 1% FG and 1% GA at pH 3.5, were investigated as influenced by phase separation temperature. Decreasing the phase separation temperature from 40 to 10 °C lead to: (1) the formation of a coacervate phase with a larger volume fraction and higher biopolymer concentrations, which is more viscous, more structural resistant at low shear rates, more shear-thinning at high shear rates, and more condensed in microstructure, (2) a solid-like elastic behavior of the phase separated at 10 °C at a high oscillatory frequency, (3) the increase in gelling and melting temperatures of the coacervate phase (3.7−3.9 °C and 6.2−6.9 °C, respectively), (4) the formation of a more rigid and thermo-stable coacervate gel. The coacervate phase is regarded as a homogeneously networked biopolymer matrix dispersed with water vacuoles and its gel as a weak physical gel reinforced by FG–GA attractive electrostatic interactions.
Effect of nisin on biochemical and microbial quality and shelf life of vacuum packaged rainbow tr... more Effect of nisin on biochemical and microbial quality and shelf life of vacuum packaged rainbow trout (Oncorhynchus mykiss) during 16 days storage at 4 °C was investigated. According to the obtained results, nisin treated fish showed lower (p < 0.05) and acceptable biochemical (Peroxide value, thiobarbituric acid-index, pH, and total volatile base nitrogen) and bacteriological (total viable counts, psychrotrophic viable counts, and lactic acid bacteria) attributes up to 16 days storage at 4 °C compared with those treated without nisin. Furthermore, FAs composition analysis indicated that presence of the nisin preserved nutritional quality of fish lipid, so that nisin treated samples contained higher percentage (p > 0.05) of essential FAs such as eicosapentaenoic acid and docosahexaenoic acid. This study concluded that treatment of the vacuum packaged rainbow trout with nisin resulted in improvement of quality and extension of shelf life of the fish from 12 to 16 days at 4 °C.
"Chemical and microbiological changes in vacuum-packaged slices of rainbow trout (Onchorynchus my... more "Chemical and microbiological changes in vacuum-packaged slices of rainbow trout (Onchorynchus mykis) treated or not treated (controls) with nisin (0.2 % w/w) samples were evaluated for 16 days at 4 °C. The peroxide value (PV), thiobarbituric acid value (TBA) and total volatile basic nitrogen (TVB-N) remained within standard acceptable levels of 6.21 meqkg-1, 0.71 mgkg-1 and 24.81mg100g-1, respectively, whereas the same values were exceeded in untreated control samples. Nisin significantly (p<0.05) lowered the number of psychrotrophic, mesophilic and lactic acid bacteria (LAB) compared with controls (5.35 log, 1.57 log, and 6.3 log vs. 6.82 log, 5.35 log and 7.84 log, respectively). The results suggest that nisin could be used to extend the shelf-life of filleted rainbow trout.
"
The interactions between fish gelatin (FG) and gum arabic (GA) in aqueous solutions were investig... more The interactions between fish gelatin (FG) and gum arabic (GA) in aqueous solutions were investigated by turbidimetry, methylene blue spectrophotometry, zeta potentiometry, dynamic light scattering, protein assay, and state diagram at 40 °C and a total biopolymer concentration (CT) of 0.05%. FG underwent complex coacervation with GA, possibly via its conformational change, depending on pH and FG to GA ratio (FG:GA). The formation of FG–GA complexes was the most intense when pH 3.55 and FG:GA = 50:50 (6.6:1 M ratio), however, the coacervate phase was found to be composed of a much higher FG fraction. The pH range of complex formation shifted to a higher pH region with increasing FG:GA. Soluble and insoluble FG–GA complexes were formed even in a pH region where both biopolymers were net-negatively charged. Varying CT significantly influenced not only the formation of FG–GA complexes but also the development and composition of coacervate phase.► Fish gelatin (FG) undergoes complex coacervation with gum arabic (GA). ► A state diagram is created by plotting phase boundary pHs against FG to GA ratio. ► The most intensive FG–GA complex formation at pH 3.55 and FG to GA ratio of 50:50. ► Complex formation occurs even between net-negatively charged FG and GA. ► The composition of coacervate phase is affected by total biopolymer concentration.
Compositional and rheological properties ofAlyssum homolocarpumseed gum, as a new source of
thick... more Compositional and rheological properties ofAlyssum homolocarpumseed gum, as a new source of thickening agent for application in food industries, were investigated in this study. The extracted gum primarily comprised carbohydrates (61.0±0.6%), proteins (17.9±1.0%) and uronic acids (10.9±0.8%); the main carbohydrates were galactose (65.7%) and rhamnose (18.3%). The polysaccharide backbone was chiefly composed of 1,2-rhamnose, 1,3- and 1,3,6-galactose glycosidic linkages. The average molecular weight of the polymer was 122.510 6 gmol 1 . Attenuated total reflectance-Fourier transform infrared spectroscopy and z-potential measurements revealed that A. homolocarpumseed gum with multiple carboxylic groups was negatively charged in water in the pH range 3e11. Rheological behaviors of the extracted gum were investigated between 0.5 and 5.0% (w/w) concentrations and temperatures of 5 e50
C. Viscosity profile showed shear thinning behavior at all concentrations and temperatures. The pseudoplasticity degree (N) of the extracted polymers increased with concentration while temperature changes did not show any specific trend onNvalues. Theflow activation energy, quantified using an Arrhenius equation decreased from 11.00 to 5.17 (kJ/mol) as shear rate increased, which implied that the aqueous solutionsflowed more easily at higher shear rates. The mechanical spectra derived from strain sweep and frequency sweep measurements indicated viscoelastic behavior in all of samples. Frequency sweep data showed that aqueous solutions of gum, displayed weak gel behavior over the range of tested concentrations and temperatures: as dynamic moduli increased with the increased frequency and storage modulus was always greater than loss modulus.
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Papers by Mohammad Anvari
"
thickening agent for application in food industries, were investigated in this study. The extracted gum
primarily comprised carbohydrates (61.0±0.6%), proteins (17.9±1.0%) and uronic acids (10.9±0.8%); the
main carbohydrates were galactose (65.7%) and rhamnose (18.3%). The polysaccharide backbone was
chiefly composed of 1,2-rhamnose, 1,3- and 1,3,6-galactose glycosidic linkages. The average molecular
weight of the polymer was 122.510
6
gmol
1
. Attenuated total reflectance-Fourier transform infrared
spectroscopy and z-potential measurements revealed that A. homolocarpumseed gum with multiple
carboxylic groups was negatively charged in water in the pH range 3e11. Rheological behaviors of the
extracted gum were investigated between 0.5 and 5.0% (w/w) concentrations and temperatures of 5
e50
C. Viscosity profile showed shear thinning behavior at all concentrations and temperatures. The
pseudoplasticity degree (N) of the extracted polymers increased with concentration while temperature
changes did not show any specific trend onNvalues. Theflow activation energy, quantified using an
Arrhenius equation decreased from 11.00 to 5.17 (kJ/mol) as shear rate increased, which implied that the
aqueous solutionsflowed more easily at higher shear rates. The mechanical spectra derived from strain
sweep and frequency sweep measurements indicated viscoelastic behavior in all of samples. Frequency
sweep data showed that aqueous solutions of gum, displayed weak gel behavior over the range of tested
concentrations and temperatures: as dynamic moduli increased with the increased frequency and
storage modulus was always greater than loss modulus.
"
thickening agent for application in food industries, were investigated in this study. The extracted gum
primarily comprised carbohydrates (61.0±0.6%), proteins (17.9±1.0%) and uronic acids (10.9±0.8%); the
main carbohydrates were galactose (65.7%) and rhamnose (18.3%). The polysaccharide backbone was
chiefly composed of 1,2-rhamnose, 1,3- and 1,3,6-galactose glycosidic linkages. The average molecular
weight of the polymer was 122.510
6
gmol
1
. Attenuated total reflectance-Fourier transform infrared
spectroscopy and z-potential measurements revealed that A. homolocarpumseed gum with multiple
carboxylic groups was negatively charged in water in the pH range 3e11. Rheological behaviors of the
extracted gum were investigated between 0.5 and 5.0% (w/w) concentrations and temperatures of 5
e50
C. Viscosity profile showed shear thinning behavior at all concentrations and temperatures. The
pseudoplasticity degree (N) of the extracted polymers increased with concentration while temperature
changes did not show any specific trend onNvalues. Theflow activation energy, quantified using an
Arrhenius equation decreased from 11.00 to 5.17 (kJ/mol) as shear rate increased, which implied that the
aqueous solutionsflowed more easily at higher shear rates. The mechanical spectra derived from strain
sweep and frequency sweep measurements indicated viscoelastic behavior in all of samples. Frequency
sweep data showed that aqueous solutions of gum, displayed weak gel behavior over the range of tested
concentrations and temperatures: as dynamic moduli increased with the increased frequency and
storage modulus was always greater than loss modulus.