Fernando Rincon | Willamette University (original) (raw)

Papers by Fernando Rincon

Food Hydrocolloids, 2009

Rheological studies of Cedrela odorata gum aqueous dispersions demonstrated viscoelastic properti... more Rheological studies of Cedrela odorata gum aqueous dispersions demonstrated viscoelastic properties. Mechanical spectra derived from small amplitude oscillatory shear (SAOS) results support the onset of gel-like structure at given conditions (10% w/v, 20 °C). The increase in the storage and loss moduli, along with the drop in their frequency dependence, observed at higher gum concentrations, indicates a slower relaxation mechanism, which may be related to the increasing number and structural complexity of transient junction zones among macromolecules. The transition from gel-like to sol-like structure, at higher temperature, was detected from SAOS results. The flow behaviour of the aqueous gum dispersions under steady shear is highly non-Newtonian and can be modelled by the Sisko equation. The Cox–Merz rule was found to fail at critical gum concentration for the onset of gel-like behaviour and also at a temperature slightly above the gel–sol transition. C. odorata gum aqueous dispersions may have interesting applications as stabilisers of emulsions and suspensions on account of their rheological behaviour.

Food Hydrocolloids, 2000

Venezuela, a tropical country, has many species, widely disseminated, that are able to produce gu... more Venezuela, a tropical country, has many species, widely disseminated, that are able to produce gum in good yield. We have been working on gums from species belonging to many families. It has been demonstrated that 29 species located in different counties of Zulia State, Venezuela, South America, produce gum easily. The gum produced from the studied species was collected a week after the injury was made at trunk level. Most of these gums are very soluble in water and are produced in high yield. The analytical data of gums from Mimosaceae species were determined. The properties of the gums from Acacia macracantha, A. tortuosa, A. glomerosa, Enterolobium cyclocarpum and Samanea saman are very interesting. The gums from A. macracantha and A. tortuosa have high solubility, comparable to that reported for A. senegal. This behavior contrasts with that of A. glomerosa which forms a gel easily. The viscosity of E. cyclocarpum (100 ml/g), comparable to some Combretum gums, is higher than that reported for the Acacia gums studied so far. 13C NMR spectra of the polysaccharides isolated from these gums showed interesting structural features. The properties of these Mimosaceae gums may have potential economical interest. The proven presence of native species, adapted to the precise ecological conditions, capable of yielding good quality gum offers an opportunity for attention to be given to increasing agroforestry development within Venezuela based on those species. The climatological conditions of hot arid areas are suitable for commercial gum production in high yield.

Carbohydrate Polymers, 2008

Acacia macracantha, a Venezuelan Gummiferae species, exudes a soluble gum which has a very high p... more Acacia macracantha, a Venezuelan Gummiferae species, exudes a soluble gum which has a very high polydispersity index (Mw/Mn = 3.75). It consists of carbohydrate predominantly and a proteinaceous material as a minor component. The relatively high nitrogen content (4.98%) led to study the latter material. Fractionation of the gum by atmospheric pressure size exclusion chromatography (APSEC) was monitored by determination of total protein and carbohydrate contents. High pressure exclusion chromatography (HPSEC), coupling on-line with multi-angle light scattering (MALLS) and differential refractive index (DRI) detectors were also used. The elution profiles of the original gum and those of the gum after basic and enzymatic hydrolyses showed a heterogeneous system. Studies of the highest molecular weight fraction, that contain carbohydrate and protein, revealed the presence of hydroxyproline, serine, and lysine. On the other hand, sequential acid hydrolysis study of this fraction demonstrated the presence of rhamnose and arabinose as terminal and internal residues, respectively. The findings suggest that the gum from A. macracantha contains probably AG and AGP.

Food Hydrocolloids, 2000

The polysaccharides isolated from Spondias purpurea var. lutea and Spondias cytherea contain gala... more The polysaccharides isolated from Spondias purpurea var. lutea and Spondias cytherea contain galactose, as main component, arabinose, mannose, xylose and rhamnose residues. On the other hand, glucuronic acid and its 4-0-methyl derivative are present in those polysaccharides in contrast to the presence of galacturonic acid reported for other Spondias gums. S. cytherea gum has the highest intrinsic viscosity (63 ml/g). The values of nitrogen are comparable to those observed for some Acacia included in series Vulgares. Comparison of the specific optical rotation values and the 13 C-NMR spectra of the polysaccharides from S. purpurea var. lutea and S. purpurea, may be very useful to distinguish those two close botanical species. The high solubility of the Spondias gums studied and the absence of tannin may have potential industrial application therefore, it is necessary to do toxicological studies of those Spondias gums. ᭧

Carbohydrate Polymers, 2007

Steady shear flow properties of Acacia tortuosa gum aqueous dispersions at different concentratio... more Steady shear flow properties of Acacia tortuosa gum aqueous dispersions at different concentrations (15–40% w/v) were studied at 20 °C using a controlled shear rate Couette rheometer and Mooney–Ewart sensor systems. Flow curves showed shear thinning non-Newtonian behaviour with a tendency to a Newtonian plateau at high-shear rate. The results obtained fitted the Sisko model very well. The influence of temperature (5–40 °C) on the flow curves was studied at given gum concentration (40% w/v). The infinite-shear rate Newtonian viscosity derived from the Sisko model fitted an Arrhenius-type equation. A controlled stress rheometer was used to conduct small amplitude oscillatory shear tests with the double cone geometry on A. tortuosa gum dispersion (40% w/v). It was clearly observed that the gum dispersion exhibited viscoelastic properties in a given temperature range (5–25 °C). The elastic component was always higher than the viscous one. The frequency dependence of the dynamic moduli and the failure of the Cox–Merz rule supported the existence of a soft gel-like structure which weakened with temperature. The surface tension of A. tortuosa aqueous solutions was measured in a concentration range (0.01–1.5% w/v). The equilibrium value reached at (0.5% w/v) was (42.6 mN/m), which is significantly lower than the corresponding to A. senegal gum (46.9 mN/m). The rheological behaviour and surface tension of A. tortuosa gum suggest that it may compete with arabic gum in some industrial applications.

Carbohydrate Polymers, 2000

The polysaccharide, isolated from Spondias mombin gum exudate, was subjected to acid hydrolysis a... more The polysaccharide, isolated from Spondias mombin gum exudate, was subjected to acid hydrolysis and Smith degradation processes in order to investigate its relevant structural features. Chemical and spectral evidence suggested the existence of small blocks of (1→3)-linked β-d-galactosyl residues, interspersed with 6-O substituted d-galactosyl residues, in the backbone of the investigated structure; these residues are also in the side-chains. In addition, there was arabinose, up to three units long, predominantly in the form of furanosyl residues (terminal, 2-O- and 3-O-linked). Arabinopyranosyl residues (terminal and 2-O-linked) as well as rhamnose and mannose are also present in minor amounts. Uronic acids, β-d-glucuronic acid and its 4-O-methyl analogue, are attached at the C-6 and C-4 positions of the galactose moieties in the backbone. These sugar acid residues were difficult to remove from the core. 13C-NMR spectroscopy confirmed the results obtained by chemical methods, and showed the presence of reducing terminal sugar residues and internal acetyl groups.

Food Hydrocolloids, 2009

Rheological studies of Cedrela odorata gum aqueous dispersions demonstrated viscoelastic properti... more Rheological studies of Cedrela odorata gum aqueous dispersions demonstrated viscoelastic properties. Mechanical spectra derived from small amplitude oscillatory shear (SAOS) results support the onset of gel-like structure at given conditions (10% w/v, 20 C). The increase in the storage and loss moduli, along with the drop in their frequency dependence, observed at higher gum concentrations, indicates a slower relaxation mechanism, which may be related to the increasing number and structural complexity of transient junction zones among macromolecules. The transition from gel-like to sol-like structure, at higher temperature, was detected from SAOS results. The flow behaviour of the aqueous gum dispersions under steady shear is highly non-Newtonian and can be modelled by the Sisko equation. The Cox-Merz rule was found to fail at critical gum concentration for the onset of gel-like behaviour and also at a temperature slightly above the gel-sol transition. C. odorata gum aqueous dispersions may have interesting applications as stabilisers of emulsions and suspensions on account of their rheological behaviour.

Food Hydrocolloids, 2014

Under the geological conditions of wells and during the drilling operation, some of the water-bas... more Under the geological conditions of wells and during the drilling operation, some of the water-based mud compositions are sometimes not effective for the drilling success of the oil wells (case of the oil wells in the south Algeria). For this, the aim of this study is to examine the influence of polymer types [carboxymethylcellulose (CMC) and polyanionic cellulose (PAC)] on the physicochemical and rheological properties of water-based drilling muds. A mud samples were prepared with a polymers (PAC or CMC) according to mud formulations currently used in the wells drilling. The properties are controlled at such values that the mud provides optimum performance. For this purpose, the physico-chemical (pH, Pb: mud alkalinity) and rheological (apparent viscosity, yield point, and behavior rheological) were measured out on the studied muds. According to the obtained results, the rheological characteristics of studied muds (yield point and plastic viscosity) were clearly improved in the polymers presence. However, it should be noted that the PAC has given the better results compared to the CMC at a concentration of 8 g/l. By against in the temperature presence (hot rolling), the CMC is a good controller agent of mud filtrate compared to those containing the PAC for the same concentration.

Carbohydrate Polymers, 2007

Steady shear flow properties of Acacia tortuosa gum aqueous dispersions at different concentratio... more Steady shear flow properties of Acacia tortuosa gum aqueous dispersions at different concentrations (15-40% w/v) were studied at 20°C using a controlled shear rate Couette rheometer and Mooney-Ewart sensor systems. Flow curves showed shear thinning non-Newtonian behaviour with a tendency to a Newtonian plateau at high-shear rate. The results obtained fitted the Sisko model very well. The influence of temperature (5-40°C) on the flow curves was studied at given gum concentration (40% w/v). The infinite-shear rate Newtonian viscosity derived from the Sisko model fitted an Arrhenius-type equation. A controlled stress rheometer was used to conduct small amplitude oscillatory shear tests with the double cone geometry on A. tortuosa gum dispersion (40% w/v). It was clearly observed that the gum dispersion exhibited viscoelastic properties in a given temperature range (5-25°C). The elastic component was always higher than the viscous one. The frequency dependence of the dynamic moduli and the failure of the Cox-Merz rule supported the existence of a soft gel-like structure which weakened with temperature. The surface tension of A. tortuosa aqueous solutions was measured in a concentration range (0.01-1.5% w/v). The equilibrium value reached at (0.5% w/v) was (42.6 mN/m), which is significantly lower than the corresponding to A. senegal gum (46.9 mN/m). The rheological behaviour and surface tension of A. tortuosa gum suggest that it may compete with arabic gum in some industrial applications.

Carbohydrate Polymers, 2008

Acacia macracantha, a Venezuelan Gummiferae species, exudes a soluble gum which has a very high p... more Acacia macracantha, a Venezuelan Gummiferae species, exudes a soluble gum which has a very high polydispersity index (Mw/ Mn = 3.75). It consists of carbohydrate predominantly and a proteinaceous material as a minor component. The relatively high nitrogen content (4.98%) led to study the latter material. Fractionation of the gum by atmospheric pressure size exclusion chromatography (APSEC) was monitored by determination of total protein and carbohydrate contents. High pressure exclusion chromatography (HPSEC), coupling on-line with multi-angle light scattering (MALLS) and differential refractive index (DRI) detectors were also used. The elution profiles of the original gum and those of the gum after basic and enzymatic hydrolyses showed a heterogeneous system. Studies of the highest molecular weight fraction, that contain carbohydrate and protein, revealed the presence of hydroxyproline, serine, and lysine. On the other hand, sequential acid hydrolysis study of this fraction demonstrated the presence of rhamnose and arabinose as terminal and internal residues, respectively. The findings suggest that the gum from A. macracantha contains probably AG and AGP.

Food Hydrocolloids, 2009

Rheological studies of Cedrela odorata gum aqueous dispersions demonstrated viscoelastic properti... more Rheological studies of Cedrela odorata gum aqueous dispersions demonstrated viscoelastic properties. Mechanical spectra derived from small amplitude oscillatory shear (SAOS) results support the onset of gel-like structure at given conditions (10% w/v, 20 °C). The increase in the storage and loss moduli, along with the drop in their frequency dependence, observed at higher gum concentrations, indicates a slower relaxation mechanism, which may be related to the increasing number and structural complexity of transient junction zones among macromolecules. The transition from gel-like to sol-like structure, at higher temperature, was detected from SAOS results. The flow behaviour of the aqueous gum dispersions under steady shear is highly non-Newtonian and can be modelled by the Sisko equation. The Cox–Merz rule was found to fail at critical gum concentration for the onset of gel-like behaviour and also at a temperature slightly above the gel–sol transition. C. odorata gum aqueous dispersions may have interesting applications as stabilisers of emulsions and suspensions on account of their rheological behaviour.

Food Hydrocolloids, 2000

Venezuela, a tropical country, has many species, widely disseminated, that are able to produce gu... more Venezuela, a tropical country, has many species, widely disseminated, that are able to produce gum in good yield. We have been working on gums from species belonging to many families. It has been demonstrated that 29 species located in different counties of Zulia State, Venezuela, South America, produce gum easily. The gum produced from the studied species was collected a week after the injury was made at trunk level. Most of these gums are very soluble in water and are produced in high yield. The analytical data of gums from Mimosaceae species were determined. The properties of the gums from Acacia macracantha, A. tortuosa, A. glomerosa, Enterolobium cyclocarpum and Samanea saman are very interesting. The gums from A. macracantha and A. tortuosa have high solubility, comparable to that reported for A. senegal. This behavior contrasts with that of A. glomerosa which forms a gel easily. The viscosity of E. cyclocarpum (100 ml/g), comparable to some Combretum gums, is higher than that reported for the Acacia gums studied so far. 13C NMR spectra of the polysaccharides isolated from these gums showed interesting structural features. The properties of these Mimosaceae gums may have potential economical interest. The proven presence of native species, adapted to the precise ecological conditions, capable of yielding good quality gum offers an opportunity for attention to be given to increasing agroforestry development within Venezuela based on those species. The climatological conditions of hot arid areas are suitable for commercial gum production in high yield.

Carbohydrate Polymers, 2008

Acacia macracantha, a Venezuelan Gummiferae species, exudes a soluble gum which has a very high p... more Acacia macracantha, a Venezuelan Gummiferae species, exudes a soluble gum which has a very high polydispersity index (Mw/Mn = 3.75). It consists of carbohydrate predominantly and a proteinaceous material as a minor component. The relatively high nitrogen content (4.98%) led to study the latter material. Fractionation of the gum by atmospheric pressure size exclusion chromatography (APSEC) was monitored by determination of total protein and carbohydrate contents. High pressure exclusion chromatography (HPSEC), coupling on-line with multi-angle light scattering (MALLS) and differential refractive index (DRI) detectors were also used. The elution profiles of the original gum and those of the gum after basic and enzymatic hydrolyses showed a heterogeneous system. Studies of the highest molecular weight fraction, that contain carbohydrate and protein, revealed the presence of hydroxyproline, serine, and lysine. On the other hand, sequential acid hydrolysis study of this fraction demonstrated the presence of rhamnose and arabinose as terminal and internal residues, respectively. The findings suggest that the gum from A. macracantha contains probably AG and AGP.

Food Hydrocolloids, 2000

The polysaccharides isolated from Spondias purpurea var. lutea and Spondias cytherea contain gala... more The polysaccharides isolated from Spondias purpurea var. lutea and Spondias cytherea contain galactose, as main component, arabinose, mannose, xylose and rhamnose residues. On the other hand, glucuronic acid and its 4-0-methyl derivative are present in those polysaccharides in contrast to the presence of galacturonic acid reported for other Spondias gums. S. cytherea gum has the highest intrinsic viscosity (63 ml/g). The values of nitrogen are comparable to those observed for some Acacia included in series Vulgares. Comparison of the specific optical rotation values and the 13C-NMR spectra of the polysaccharides from S. purpurea var. lutea and S. purpurea, may be very useful to distinguish those two close botanical species. The high solubility of the Spondias gums studied and the absence of tannin may have potential industrial application therefore, it is necessary to do toxicological studies of those Spondias gums.

Carbohydrate Polymers, 2007

Steady shear flow properties of Acacia tortuosa gum aqueous dispersions at different concentratio... more Steady shear flow properties of Acacia tortuosa gum aqueous dispersions at different concentrations (15–40% w/v) were studied at 20 °C using a controlled shear rate Couette rheometer and Mooney–Ewart sensor systems. Flow curves showed shear thinning non-Newtonian behaviour with a tendency to a Newtonian plateau at high-shear rate. The results obtained fitted the Sisko model very well. The influence of temperature (5–40 °C) on the flow curves was studied at given gum concentration (40% w/v). The infinite-shear rate Newtonian viscosity derived from the Sisko model fitted an Arrhenius-type equation. A controlled stress rheometer was used to conduct small amplitude oscillatory shear tests with the double cone geometry on A. tortuosa gum dispersion (40% w/v). It was clearly observed that the gum dispersion exhibited viscoelastic properties in a given temperature range (5–25 °C). The elastic component was always higher than the viscous one. The frequency dependence of the dynamic moduli and the failure of the Cox–Merz rule supported the existence of a soft gel-like structure which weakened with temperature. The surface tension of A. tortuosa aqueous solutions was measured in a concentration range (0.01–1.5% w/v). The equilibrium value reached at (0.5% w/v) was (42.6 mN/m), which is significantly lower than the corresponding to A. senegal gum (46.9 mN/m). The rheological behaviour and surface tension of A. tortuosa gum suggest that it may compete with arabic gum in some industrial applications.

Carbohydrate Polymers, 2000

The polysaccharide, isolated from Spondias mombin gum exudate, was subjected to acid hydrolysis a... more The polysaccharide, isolated from Spondias mombin gum exudate, was subjected to acid hydrolysis and Smith degradation processes in order to investigate its relevant structural features. Chemical and spectral evidence suggested the existence of small blocks of (1→3)-linked β-d-galactosyl residues, interspersed with 6-O substituted d-galactosyl residues, in the backbone of the investigated structure; these residues are also in the side-chains. In addition, there was arabinose, up to three units long, predominantly in the form of furanosyl residues (terminal, 2-O- and 3-O-linked). Arabinopyranosyl residues (terminal and 2-O-linked) as well as rhamnose and mannose are also present in minor amounts. Uronic acids, β-d-glucuronic acid and its 4-O-methyl analogue, are attached at the C-6 and C-4 positions of the galactose moieties in the backbone. These sugar acid residues were difficult to remove from the core. 13C-NMR spectroscopy confirmed the results obtained by chemical methods, and showed the presence of reducing terminal sugar residues and internal acetyl groups.

Food Hydrocolloids, 2009

Rheological studies of Cedrela odorata gum aqueous dispersions demonstrated viscoelastic properti... more Rheological studies of Cedrela odorata gum aqueous dispersions demonstrated viscoelastic properties. Mechanical spectra derived from small amplitude oscillatory shear (SAOS) results support the onset of gel-like structure at given conditions (10% w/v, 20 C). The increase in the storage and loss moduli, along with the drop in their frequency dependence, observed at higher gum concentrations, indicates a slower relaxation mechanism, which may be related to the increasing number and structural complexity of transient junction zones among macromolecules. The transition from gel-like to sol-like structure, at higher temperature, was detected from SAOS results. The flow behaviour of the aqueous gum dispersions under steady shear is highly non-Newtonian and can be modelled by the Sisko equation. The Cox-Merz rule was found to fail at critical gum concentration for the onset of gel-like behaviour and also at a temperature slightly above the gel-sol transition. C. odorata gum aqueous dispersions may have interesting applications as stabilisers of emulsions and suspensions on account of their rheological behaviour.

Food Hydrocolloids, 2014

Under the geological conditions of wells and during the drilling operation, some of the water-bas... more Under the geological conditions of wells and during the drilling operation, some of the water-based mud compositions are sometimes not effective for the drilling success of the oil wells (case of the oil wells in the south Algeria). For this, the aim of this study is to examine the influence of polymer types [carboxymethylcellulose (CMC) and polyanionic cellulose (PAC)] on the physicochemical and rheological properties of water-based drilling muds. A mud samples were prepared with a polymers (PAC or CMC) according to mud formulations currently used in the wells drilling. The properties are controlled at such values that the mud provides optimum performance. For this purpose, the physico-chemical (pH, Pb: mud alkalinity) and rheological (apparent viscosity, yield point, and behavior rheological) were measured out on the studied muds. According to the obtained results, the rheological characteristics of studied muds (yield point and plastic viscosity) were clearly improved in the polymers presence. However, it should be noted that the PAC has given the better results compared to the CMC at a concentration of 8 g/l. By against in the temperature presence (hot rolling), the CMC is a good controller agent of mud filtrate compared to those containing the PAC for the same concentration.

Carbohydrate Polymers, 2007

Steady shear flow properties of Acacia tortuosa gum aqueous dispersions at different concentratio... more Steady shear flow properties of Acacia tortuosa gum aqueous dispersions at different concentrations (15-40% w/v) were studied at 20°C using a controlled shear rate Couette rheometer and Mooney-Ewart sensor systems. Flow curves showed shear thinning non-Newtonian behaviour with a tendency to a Newtonian plateau at high-shear rate. The results obtained fitted the Sisko model very well. The influence of temperature (5-40°C) on the flow curves was studied at given gum concentration (40% w/v). The infinite-shear rate Newtonian viscosity derived from the Sisko model fitted an Arrhenius-type equation. A controlled stress rheometer was used to conduct small amplitude oscillatory shear tests with the double cone geometry on A. tortuosa gum dispersion (40% w/v). It was clearly observed that the gum dispersion exhibited viscoelastic properties in a given temperature range (5-25°C). The elastic component was always higher than the viscous one. The frequency dependence of the dynamic moduli and the failure of the Cox-Merz rule supported the existence of a soft gel-like structure which weakened with temperature. The surface tension of A. tortuosa aqueous solutions was measured in a concentration range (0.01-1.5% w/v). The equilibrium value reached at (0.5% w/v) was (42.6 mN/m), which is significantly lower than the corresponding to A. senegal gum (46.9 mN/m). The rheological behaviour and surface tension of A. tortuosa gum suggest that it may compete with arabic gum in some industrial applications.

Carbohydrate Polymers, 2008

Acacia macracantha, a Venezuelan Gummiferae species, exudes a soluble gum which has a very high p... more Acacia macracantha, a Venezuelan Gummiferae species, exudes a soluble gum which has a very high polydispersity index (Mw/ Mn = 3.75). It consists of carbohydrate predominantly and a proteinaceous material as a minor component. The relatively high nitrogen content (4.98%) led to study the latter material. Fractionation of the gum by atmospheric pressure size exclusion chromatography (APSEC) was monitored by determination of total protein and carbohydrate contents. High pressure exclusion chromatography (HPSEC), coupling on-line with multi-angle light scattering (MALLS) and differential refractive index (DRI) detectors were also used. The elution profiles of the original gum and those of the gum after basic and enzymatic hydrolyses showed a heterogeneous system. Studies of the highest molecular weight fraction, that contain carbohydrate and protein, revealed the presence of hydroxyproline, serine, and lysine. On the other hand, sequential acid hydrolysis study of this fraction demonstrated the presence of rhamnose and arabinose as terminal and internal residues, respectively. The findings suggest that the gum from A. macracantha contains probably AG and AGP.

Food Hydrocolloids, 2009

Rheological studies of Cedrela odorata gum aqueous dispersions demonstrated viscoelastic properti... more Rheological studies of Cedrela odorata gum aqueous dispersions demonstrated viscoelastic properties. Mechanical spectra derived from small amplitude oscillatory shear (SAOS) results support the onset of gel-like structure at given conditions (10% w/v, 20 °C). The increase in the storage and loss moduli, along with the drop in their frequency dependence, observed at higher gum concentrations, indicates a slower relaxation mechanism, which may be related to the increasing number and structural complexity of transient junction zones among macromolecules. The transition from gel-like to sol-like structure, at higher temperature, was detected from SAOS results. The flow behaviour of the aqueous gum dispersions under steady shear is highly non-Newtonian and can be modelled by the Sisko equation. The Cox–Merz rule was found to fail at critical gum concentration for the onset of gel-like behaviour and also at a temperature slightly above the gel–sol transition. C. odorata gum aqueous dispersions may have interesting applications as stabilisers of emulsions and suspensions on account of their rheological behaviour.

Food Hydrocolloids, 2000

Venezuela, a tropical country, has many species, widely disseminated, that are able to produce gu... more Venezuela, a tropical country, has many species, widely disseminated, that are able to produce gum in good yield. We have been working on gums from species belonging to many families. It has been demonstrated that 29 species located in different counties of Zulia State, Venezuela, South America, produce gum easily. The gum produced from the studied species was collected a week after the injury was made at trunk level. Most of these gums are very soluble in water and are produced in high yield. The analytical data of gums from Mimosaceae species were determined. The properties of the gums from Acacia macracantha, A. tortuosa, A. glomerosa, Enterolobium cyclocarpum and Samanea saman are very interesting. The gums from A. macracantha and A. tortuosa have high solubility, comparable to that reported for A. senegal. This behavior contrasts with that of A. glomerosa which forms a gel easily. The viscosity of E. cyclocarpum (100 ml/g), comparable to some Combretum gums, is higher than that reported for the Acacia gums studied so far. 13C NMR spectra of the polysaccharides isolated from these gums showed interesting structural features. The properties of these Mimosaceae gums may have potential economical interest. The proven presence of native species, adapted to the precise ecological conditions, capable of yielding good quality gum offers an opportunity for attention to be given to increasing agroforestry development within Venezuela based on those species. The climatological conditions of hot arid areas are suitable for commercial gum production in high yield.

Carbohydrate Polymers, 2008

Acacia macracantha, a Venezuelan Gummiferae species, exudes a soluble gum which has a very high p... more Acacia macracantha, a Venezuelan Gummiferae species, exudes a soluble gum which has a very high polydispersity index (Mw/Mn = 3.75). It consists of carbohydrate predominantly and a proteinaceous material as a minor component. The relatively high nitrogen content (4.98%) led to study the latter material. Fractionation of the gum by atmospheric pressure size exclusion chromatography (APSEC) was monitored by determination of total protein and carbohydrate contents. High pressure exclusion chromatography (HPSEC), coupling on-line with multi-angle light scattering (MALLS) and differential refractive index (DRI) detectors were also used. The elution profiles of the original gum and those of the gum after basic and enzymatic hydrolyses showed a heterogeneous system. Studies of the highest molecular weight fraction, that contain carbohydrate and protein, revealed the presence of hydroxyproline, serine, and lysine. On the other hand, sequential acid hydrolysis study of this fraction demonstrated the presence of rhamnose and arabinose as terminal and internal residues, respectively. The findings suggest that the gum from A. macracantha contains probably AG and AGP.

Food Hydrocolloids, 2000

The polysaccharides isolated from Spondias purpurea var. lutea and Spondias cytherea contain gala... more The polysaccharides isolated from Spondias purpurea var. lutea and Spondias cytherea contain galactose, as main component, arabinose, mannose, xylose and rhamnose residues. On the other hand, glucuronic acid and its 4-0-methyl derivative are present in those polysaccharides in contrast to the presence of galacturonic acid reported for other Spondias gums. S. cytherea gum has the highest intrinsic viscosity (63 ml/g). The values of nitrogen are comparable to those observed for some Acacia included in series Vulgares. Comparison of the specific optical rotation values and the 13 C-NMR spectra of the polysaccharides from S. purpurea var. lutea and S. purpurea, may be very useful to distinguish those two close botanical species. The high solubility of the Spondias gums studied and the absence of tannin may have potential industrial application therefore, it is necessary to do toxicological studies of those Spondias gums. ᭧

Carbohydrate Polymers, 2007

Steady shear flow properties of Acacia tortuosa gum aqueous dispersions at different concentratio... more Steady shear flow properties of Acacia tortuosa gum aqueous dispersions at different concentrations (15–40% w/v) were studied at 20 °C using a controlled shear rate Couette rheometer and Mooney–Ewart sensor systems. Flow curves showed shear thinning non-Newtonian behaviour with a tendency to a Newtonian plateau at high-shear rate. The results obtained fitted the Sisko model very well. The influence of temperature (5–40 °C) on the flow curves was studied at given gum concentration (40% w/v). The infinite-shear rate Newtonian viscosity derived from the Sisko model fitted an Arrhenius-type equation. A controlled stress rheometer was used to conduct small amplitude oscillatory shear tests with the double cone geometry on A. tortuosa gum dispersion (40% w/v). It was clearly observed that the gum dispersion exhibited viscoelastic properties in a given temperature range (5–25 °C). The elastic component was always higher than the viscous one. The frequency dependence of the dynamic moduli and the failure of the Cox–Merz rule supported the existence of a soft gel-like structure which weakened with temperature. The surface tension of A. tortuosa aqueous solutions was measured in a concentration range (0.01–1.5% w/v). The equilibrium value reached at (0.5% w/v) was (42.6 mN/m), which is significantly lower than the corresponding to A. senegal gum (46.9 mN/m). The rheological behaviour and surface tension of A. tortuosa gum suggest that it may compete with arabic gum in some industrial applications.

Carbohydrate Polymers, 2000

The polysaccharide, isolated from Spondias mombin gum exudate, was subjected to acid hydrolysis a... more The polysaccharide, isolated from Spondias mombin gum exudate, was subjected to acid hydrolysis and Smith degradation processes in order to investigate its relevant structural features. Chemical and spectral evidence suggested the existence of small blocks of (1→3)-linked β-d-galactosyl residues, interspersed with 6-O substituted d-galactosyl residues, in the backbone of the investigated structure; these residues are also in the side-chains. In addition, there was arabinose, up to three units long, predominantly in the form of furanosyl residues (terminal, 2-O- and 3-O-linked). Arabinopyranosyl residues (terminal and 2-O-linked) as well as rhamnose and mannose are also present in minor amounts. Uronic acids, β-d-glucuronic acid and its 4-O-methyl analogue, are attached at the C-6 and C-4 positions of the galactose moieties in the backbone. These sugar acid residues were difficult to remove from the core. 13C-NMR spectroscopy confirmed the results obtained by chemical methods, and showed the presence of reducing terminal sugar residues and internal acetyl groups.

Food Hydrocolloids, 2009

Rheological studies of Cedrela odorata gum aqueous dispersions demonstrated viscoelastic properti... more Rheological studies of Cedrela odorata gum aqueous dispersions demonstrated viscoelastic properties. Mechanical spectra derived from small amplitude oscillatory shear (SAOS) results support the onset of gel-like structure at given conditions (10% w/v, 20 C). The increase in the storage and loss moduli, along with the drop in their frequency dependence, observed at higher gum concentrations, indicates a slower relaxation mechanism, which may be related to the increasing number and structural complexity of transient junction zones among macromolecules. The transition from gel-like to sol-like structure, at higher temperature, was detected from SAOS results. The flow behaviour of the aqueous gum dispersions under steady shear is highly non-Newtonian and can be modelled by the Sisko equation. The Cox-Merz rule was found to fail at critical gum concentration for the onset of gel-like behaviour and also at a temperature slightly above the gel-sol transition. C. odorata gum aqueous dispersions may have interesting applications as stabilisers of emulsions and suspensions on account of their rheological behaviour.

Food Hydrocolloids, 2014

Under the geological conditions of wells and during the drilling operation, some of the water-bas... more Under the geological conditions of wells and during the drilling operation, some of the water-based mud compositions are sometimes not effective for the drilling success of the oil wells (case of the oil wells in the south Algeria). For this, the aim of this study is to examine the influence of polymer types [carboxymethylcellulose (CMC) and polyanionic cellulose (PAC)] on the physicochemical and rheological properties of water-based drilling muds. A mud samples were prepared with a polymers (PAC or CMC) according to mud formulations currently used in the wells drilling. The properties are controlled at such values that the mud provides optimum performance. For this purpose, the physico-chemical (pH, Pb: mud alkalinity) and rheological (apparent viscosity, yield point, and behavior rheological) were measured out on the studied muds. According to the obtained results, the rheological characteristics of studied muds (yield point and plastic viscosity) were clearly improved in the polymers presence. However, it should be noted that the PAC has given the better results compared to the CMC at a concentration of 8 g/l. By against in the temperature presence (hot rolling), the CMC is a good controller agent of mud filtrate compared to those containing the PAC for the same concentration.

Carbohydrate Polymers, 2007

Steady shear flow properties of Acacia tortuosa gum aqueous dispersions at different concentratio... more Steady shear flow properties of Acacia tortuosa gum aqueous dispersions at different concentrations (15-40% w/v) were studied at 20°C using a controlled shear rate Couette rheometer and Mooney-Ewart sensor systems. Flow curves showed shear thinning non-Newtonian behaviour with a tendency to a Newtonian plateau at high-shear rate. The results obtained fitted the Sisko model very well. The influence of temperature (5-40°C) on the flow curves was studied at given gum concentration (40% w/v). The infinite-shear rate Newtonian viscosity derived from the Sisko model fitted an Arrhenius-type equation. A controlled stress rheometer was used to conduct small amplitude oscillatory shear tests with the double cone geometry on A. tortuosa gum dispersion (40% w/v). It was clearly observed that the gum dispersion exhibited viscoelastic properties in a given temperature range (5-25°C). The elastic component was always higher than the viscous one. The frequency dependence of the dynamic moduli and the failure of the Cox-Merz rule supported the existence of a soft gel-like structure which weakened with temperature. The surface tension of A. tortuosa aqueous solutions was measured in a concentration range (0.01-1.5% w/v). The equilibrium value reached at (0.5% w/v) was (42.6 mN/m), which is significantly lower than the corresponding to A. senegal gum (46.9 mN/m). The rheological behaviour and surface tension of A. tortuosa gum suggest that it may compete with arabic gum in some industrial applications.

Carbohydrate Polymers, 2008

Acacia macracantha, a Venezuelan Gummiferae species, exudes a soluble gum which has a very high p... more Acacia macracantha, a Venezuelan Gummiferae species, exudes a soluble gum which has a very high polydispersity index (Mw/ Mn = 3.75). It consists of carbohydrate predominantly and a proteinaceous material as a minor component. The relatively high nitrogen content (4.98%) led to study the latter material. Fractionation of the gum by atmospheric pressure size exclusion chromatography (APSEC) was monitored by determination of total protein and carbohydrate contents. High pressure exclusion chromatography (HPSEC), coupling on-line with multi-angle light scattering (MALLS) and differential refractive index (DRI) detectors were also used. The elution profiles of the original gum and those of the gum after basic and enzymatic hydrolyses showed a heterogeneous system. Studies of the highest molecular weight fraction, that contain carbohydrate and protein, revealed the presence of hydroxyproline, serine, and lysine. On the other hand, sequential acid hydrolysis study of this fraction demonstrated the presence of rhamnose and arabinose as terminal and internal residues, respectively. The findings suggest that the gum from A. macracantha contains probably AG and AGP.

Food Hydrocolloids, 2009

Rheological studies of Cedrela odorata gum aqueous dispersions demonstrated viscoelastic properti... more Rheological studies of Cedrela odorata gum aqueous dispersions demonstrated viscoelastic properties. Mechanical spectra derived from small amplitude oscillatory shear (SAOS) results support the onset of gel-like structure at given conditions (10% w/v, 20 °C). The increase in the storage and loss moduli, along with the drop in their frequency dependence, observed at higher gum concentrations, indicates a slower relaxation mechanism, which may be related to the increasing number and structural complexity of transient junction zones among macromolecules. The transition from gel-like to sol-like structure, at higher temperature, was detected from SAOS results. The flow behaviour of the aqueous gum dispersions under steady shear is highly non-Newtonian and can be modelled by the Sisko equation. The Cox–Merz rule was found to fail at critical gum concentration for the onset of gel-like behaviour and also at a temperature slightly above the gel–sol transition. C. odorata gum aqueous dispersions may have interesting applications as stabilisers of emulsions and suspensions on account of their rheological behaviour.

Food Hydrocolloids, 2000

Venezuela, a tropical country, has many species, widely disseminated, that are able to produce gu... more Venezuela, a tropical country, has many species, widely disseminated, that are able to produce gum in good yield. We have been working on gums from species belonging to many families. It has been demonstrated that 29 species located in different counties of Zulia State, Venezuela, South America, produce gum easily. The gum produced from the studied species was collected a week after the injury was made at trunk level. Most of these gums are very soluble in water and are produced in high yield. The analytical data of gums from Mimosaceae species were determined. The properties of the gums from Acacia macracantha, A. tortuosa, A. glomerosa, Enterolobium cyclocarpum and Samanea saman are very interesting. The gums from A. macracantha and A. tortuosa have high solubility, comparable to that reported for A. senegal. This behavior contrasts with that of A. glomerosa which forms a gel easily. The viscosity of E. cyclocarpum (100 ml/g), comparable to some Combretum gums, is higher than that reported for the Acacia gums studied so far. 13C NMR spectra of the polysaccharides isolated from these gums showed interesting structural features. The properties of these Mimosaceae gums may have potential economical interest. The proven presence of native species, adapted to the precise ecological conditions, capable of yielding good quality gum offers an opportunity for attention to be given to increasing agroforestry development within Venezuela based on those species. The climatological conditions of hot arid areas are suitable for commercial gum production in high yield.

Carbohydrate Polymers, 2008

Acacia macracantha, a Venezuelan Gummiferae species, exudes a soluble gum which has a very high p... more Acacia macracantha, a Venezuelan Gummiferae species, exudes a soluble gum which has a very high polydispersity index (Mw/Mn = 3.75). It consists of carbohydrate predominantly and a proteinaceous material as a minor component. The relatively high nitrogen content (4.98%) led to study the latter material. Fractionation of the gum by atmospheric pressure size exclusion chromatography (APSEC) was monitored by determination of total protein and carbohydrate contents. High pressure exclusion chromatography (HPSEC), coupling on-line with multi-angle light scattering (MALLS) and differential refractive index (DRI) detectors were also used. The elution profiles of the original gum and those of the gum after basic and enzymatic hydrolyses showed a heterogeneous system. Studies of the highest molecular weight fraction, that contain carbohydrate and protein, revealed the presence of hydroxyproline, serine, and lysine. On the other hand, sequential acid hydrolysis study of this fraction demonstrated the presence of rhamnose and arabinose as terminal and internal residues, respectively. The findings suggest that the gum from A. macracantha contains probably AG and AGP.

Food Hydrocolloids, 2000

The polysaccharides isolated from Spondias purpurea var. lutea and Spondias cytherea contain gala... more The polysaccharides isolated from Spondias purpurea var. lutea and Spondias cytherea contain galactose, as main component, arabinose, mannose, xylose and rhamnose residues. On the other hand, glucuronic acid and its 4-0-methyl derivative are present in those polysaccharides in contrast to the presence of galacturonic acid reported for other Spondias gums. S. cytherea gum has the highest intrinsic viscosity (63 ml/g). The values of nitrogen are comparable to those observed for some Acacia included in series Vulgares. Comparison of the specific optical rotation values and the 13C-NMR spectra of the polysaccharides from S. purpurea var. lutea and S. purpurea, may be very useful to distinguish those two close botanical species. The high solubility of the Spondias gums studied and the absence of tannin may have potential industrial application therefore, it is necessary to do toxicological studies of those Spondias gums.

Carbohydrate Polymers, 2007

Steady shear flow properties of Acacia tortuosa gum aqueous dispersions at different concentratio... more Steady shear flow properties of Acacia tortuosa gum aqueous dispersions at different concentrations (15–40% w/v) were studied at 20 °C using a controlled shear rate Couette rheometer and Mooney–Ewart sensor systems. Flow curves showed shear thinning non-Newtonian behaviour with a tendency to a Newtonian plateau at high-shear rate. The results obtained fitted the Sisko model very well. The influence of temperature (5–40 °C) on the flow curves was studied at given gum concentration (40% w/v). The infinite-shear rate Newtonian viscosity derived from the Sisko model fitted an Arrhenius-type equation. A controlled stress rheometer was used to conduct small amplitude oscillatory shear tests with the double cone geometry on A. tortuosa gum dispersion (40% w/v). It was clearly observed that the gum dispersion exhibited viscoelastic properties in a given temperature range (5–25 °C). The elastic component was always higher than the viscous one. The frequency dependence of the dynamic moduli and the failure of the Cox–Merz rule supported the existence of a soft gel-like structure which weakened with temperature. The surface tension of A. tortuosa aqueous solutions was measured in a concentration range (0.01–1.5% w/v). The equilibrium value reached at (0.5% w/v) was (42.6 mN/m), which is significantly lower than the corresponding to A. senegal gum (46.9 mN/m). The rheological behaviour and surface tension of A. tortuosa gum suggest that it may compete with arabic gum in some industrial applications.

Carbohydrate Polymers, 2000

The polysaccharide, isolated from Spondias mombin gum exudate, was subjected to acid hydrolysis a... more The polysaccharide, isolated from Spondias mombin gum exudate, was subjected to acid hydrolysis and Smith degradation processes in order to investigate its relevant structural features. Chemical and spectral evidence suggested the existence of small blocks of (1→3)-linked β-d-galactosyl residues, interspersed with 6-O substituted d-galactosyl residues, in the backbone of the investigated structure; these residues are also in the side-chains. In addition, there was arabinose, up to three units long, predominantly in the form of furanosyl residues (terminal, 2-O- and 3-O-linked). Arabinopyranosyl residues (terminal and 2-O-linked) as well as rhamnose and mannose are also present in minor amounts. Uronic acids, β-d-glucuronic acid and its 4-O-methyl analogue, are attached at the C-6 and C-4 positions of the galactose moieties in the backbone. These sugar acid residues were difficult to remove from the core. 13C-NMR spectroscopy confirmed the results obtained by chemical methods, and showed the presence of reducing terminal sugar residues and internal acetyl groups.

Food Hydrocolloids, 2009

Rheological studies of Cedrela odorata gum aqueous dispersions demonstrated viscoelastic properti... more Rheological studies of Cedrela odorata gum aqueous dispersions demonstrated viscoelastic properties. Mechanical spectra derived from small amplitude oscillatory shear (SAOS) results support the onset of gel-like structure at given conditions (10% w/v, 20 C). The increase in the storage and loss moduli, along with the drop in their frequency dependence, observed at higher gum concentrations, indicates a slower relaxation mechanism, which may be related to the increasing number and structural complexity of transient junction zones among macromolecules. The transition from gel-like to sol-like structure, at higher temperature, was detected from SAOS results. The flow behaviour of the aqueous gum dispersions under steady shear is highly non-Newtonian and can be modelled by the Sisko equation. The Cox-Merz rule was found to fail at critical gum concentration for the onset of gel-like behaviour and also at a temperature slightly above the gel-sol transition. C. odorata gum aqueous dispersions may have interesting applications as stabilisers of emulsions and suspensions on account of their rheological behaviour.

Food Hydrocolloids, 2014

Under the geological conditions of wells and during the drilling operation, some of the water-bas... more Under the geological conditions of wells and during the drilling operation, some of the water-based mud compositions are sometimes not effective for the drilling success of the oil wells (case of the oil wells in the south Algeria). For this, the aim of this study is to examine the influence of polymer types [carboxymethylcellulose (CMC) and polyanionic cellulose (PAC)] on the physicochemical and rheological properties of water-based drilling muds. A mud samples were prepared with a polymers (PAC or CMC) according to mud formulations currently used in the wells drilling. The properties are controlled at such values that the mud provides optimum performance. For this purpose, the physico-chemical (pH, Pb: mud alkalinity) and rheological (apparent viscosity, yield point, and behavior rheological) were measured out on the studied muds. According to the obtained results, the rheological characteristics of studied muds (yield point and plastic viscosity) were clearly improved in the polymers presence. However, it should be noted that the PAC has given the better results compared to the CMC at a concentration of 8 g/l. By against in the temperature presence (hot rolling), the CMC is a good controller agent of mud filtrate compared to those containing the PAC for the same concentration.

Carbohydrate Polymers, 2007

Steady shear flow properties of Acacia tortuosa gum aqueous dispersions at different concentratio... more Steady shear flow properties of Acacia tortuosa gum aqueous dispersions at different concentrations (15-40% w/v) were studied at 20°C using a controlled shear rate Couette rheometer and Mooney-Ewart sensor systems. Flow curves showed shear thinning non-Newtonian behaviour with a tendency to a Newtonian plateau at high-shear rate. The results obtained fitted the Sisko model very well. The influence of temperature (5-40°C) on the flow curves was studied at given gum concentration (40% w/v). The infinite-shear rate Newtonian viscosity derived from the Sisko model fitted an Arrhenius-type equation. A controlled stress rheometer was used to conduct small amplitude oscillatory shear tests with the double cone geometry on A. tortuosa gum dispersion (40% w/v). It was clearly observed that the gum dispersion exhibited viscoelastic properties in a given temperature range (5-25°C). The elastic component was always higher than the viscous one. The frequency dependence of the dynamic moduli and the failure of the Cox-Merz rule supported the existence of a soft gel-like structure which weakened with temperature. The surface tension of A. tortuosa aqueous solutions was measured in a concentration range (0.01-1.5% w/v). The equilibrium value reached at (0.5% w/v) was (42.6 mN/m), which is significantly lower than the corresponding to A. senegal gum (46.9 mN/m). The rheological behaviour and surface tension of A. tortuosa gum suggest that it may compete with arabic gum in some industrial applications.

Carbohydrate Polymers, 2008

Acacia macracantha, a Venezuelan Gummiferae species, exudes a soluble gum which has a very high p... more Acacia macracantha, a Venezuelan Gummiferae species, exudes a soluble gum which has a very high polydispersity index (Mw/ Mn = 3.75). It consists of carbohydrate predominantly and a proteinaceous material as a minor component. The relatively high nitrogen content (4.98%) led to study the latter material. Fractionation of the gum by atmospheric pressure size exclusion chromatography (APSEC) was monitored by determination of total protein and carbohydrate contents. High pressure exclusion chromatography (HPSEC), coupling on-line with multi-angle light scattering (MALLS) and differential refractive index (DRI) detectors were also used. The elution profiles of the original gum and those of the gum after basic and enzymatic hydrolyses showed a heterogeneous system. Studies of the highest molecular weight fraction, that contain carbohydrate and protein, revealed the presence of hydroxyproline, serine, and lysine. On the other hand, sequential acid hydrolysis study of this fraction demonstrated the presence of rhamnose and arabinose as terminal and internal residues, respectively. The findings suggest that the gum from A. macracantha contains probably AG and AGP.