Apparent viscosity, ηa, and first normal stress coefficient, ψ1, of six different concentrations ... more Apparent viscosity, ηa, and first normal stress coefficient, ψ1, of six different concentrations of cross-linked waxy maize (CWM), 3.5-5 % w/w, and tapioca, 2.8-4 % w/w, starch dispersions (SDs) showed power law relationships with shear rate, ̇γ , and increased with starch concentration. In both ηa and ψ1, volume fraction of the granules, ϕ, played a more important role than the amylose content of the continuous phase. Slope of ηa - ̇γ curves increased mildly with starch concentration, while slope of ψ1 - ̇γ curves was almost the same for CWM at all concentrations and 4 % tapioca SDs. Values of ηa and ψ1 predicted from dynamic rheological and apparent viscosity data based on the Goddard-Miller model were in reasonable agreement with experimental values.
In this study the operational extraction variables to obtain higher yields of inulin from Jerusal... more In this study the operational extraction variables to obtain higher yields of inulin from Jerusalem artichoke tubers (JAT), as well as the optimal conditions to obtain a stable and dispersible powdered product by either spray or freeze drying, were studied. With this purpose, the powder yield, moisture content, water activity and flowability or products obtained by different experimental conditions were analyzed. Inulin rich carbohydrates (IRC) extraction was performed from lyophilized and ground tubers employing distilled hot water as solvent. It was proved that the solid:solvent ratio (S:S) was the critical variable in the extraction process, followed by temperature. Thus, the IRC extraction was optimal without ultrasound assistance, at 76°C, employing a S:S of 1:16, during 90min. In addition, the powder obtained by freeze-drying of the IRC extract showed advantages respect to powders obtained by spray-drying regarding the yield and considering that maltodextrin was not necessary ...
The factors affecting the mechanical properties of biofilms formed by yeast species (Rhodotorula ... more The factors affecting the mechanical properties of biofilms formed by yeast species (Rhodotorula mucilaginosa, Candida krusei, C. kefyr and C. tropicalis) isolated from the juice processing industries have been investigated. Variables studied were: the food matrix (apple/pear juice), the sugar concentration (6/12 °Bx) and the hydrodynamic conditions (static/turbulent flow). A range of environmental cues were included as the mechanical properties of biofilms are complex. Yeast counts were significantly higher in turbulent flow compared with under static conditions. The thickness of the biofilm ranged from 38 to 148 μm, from static to turbulent flow. Yeast biofilms grown under turbulent flow conditions were viscoelastic with a predominant solid-like behavior and were structurally stronger than those grown under static conditions, indicating gel-type structures. Only the type of flow had a significant effect on [Formula: see text] and G*. Flow velocity and nutrient status modulated the...
Http Dx Doi Org 10 1080 08927014 2014 981165, Nov 1, 2014
The aim of the present work was to investigate the in situ rheological behavior of yeast biofilms... more The aim of the present work was to investigate the in situ rheological behavior of yeast biofilms growing on stainless steel under static and turbulent flow. The species used (Rhodototula mucilaginosa, Candida krusei, Candida kefyr and Candida tropicalis) were isolated from a clarified apple juice industry. The flow conditions impacted biofilm composition over time, with a predominance of C. krusei under static and turbulent flow. Likewise, structural variations occurred, with a tighter appearance under dynamic flow. Under turbulent flow there was an increase of 112 μm in biofilm thickness at 11 weeks (p < 0.001) and cell morphology was governed by hyphal structures and rounded cells. Using the in situ growth method introduced here, yeast biofilms were determined to be viscoelastic materials with a predominantly solid-like behavior, and neither this nor the G'0 values were significantly affected by the flow conditions or the growth time, and at large deformations their weak structure collapsed beyond a critical strain of about 1.5-5%. The present work could represent a starting point for developing in situ measurements of yeast rheology and contribute to a thin body of knowledge about fungal biofilm formation.
ABSTRACT The objective was to study and model the effect of the main formulation variables on the... more ABSTRACT The objective was to study and model the effect of the main formulation variables on the rheological and mechanical properties, colour and overall acceptability of apple jelly, and to optimize formulation variables in order to maximize overall acceptability. Formulation variables were juice proportion in the initial juice-sugar mix (J: 350–550 g/kg), product pH (2.8–3.6), concentration of added pectin (P: 0–10 g/kg), and final content of soluble solids (SS: 625–725 g/kg). Anova results showed that P was the main effect on all the rheological and mechanical properties. The strength of the pectin gel network increased at increasing values of P. Consequently, the jellies were more elastic and firm but more brittle, as well as more adhesive. Also, more work was required to disintegrate the jellies. Besides P, also J had a significant positive effect on storage modulus and adhesiveness, while SS had a significant positive effect on cohesiveness. Colour parameters were mainly affected by J. Overall acceptability was significantly affected by J > pH > SS, while P had no significant effect. The optimum was calculated to be at J = 500 g/kg, SS = 700 g/kg, pH = 3.4, and P = 5 g/kg.
The interactions between pilocarpine (PIL) and the anionic polyelectrolyte carbomer (CBR) were in... more The interactions between pilocarpine (PIL) and the anionic polyelectrolyte carbomer (CBR) were investigated. The effects of the chemical interactions on the chemical stability of the drug also were evaluated. The binary system was characterized by nuclear magnetic resonance techniques, Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction, scanning electron microscopy (SEM) and thermal analysis. The experiments showed that the complex, prepared by freeze-drying, is a solid amorphous form different from its precursors, thereby offering an interesting alternative for the preparation of extended release matrices. The solution stability of PIL was studied at pH 7 and 8, at 70 • C. The PIL solution stability was evaluated alone and in the presence of CBR. Results indicated that the drug in the presence of the polymer is 3.3 and 3.5 times more stable, at pH 7 and pH 8, respectively, than the drug without CBR. The activation energy and the frequency factor, according to Arrhenius plot, were estimated to be 13.9 ± 0.4 and 14.8 ± 0.5 kcal mol −1 , and 6.1 ± 0.3 and 7.6 ± 0.3, with and without the polymer, respectively.
ABSTRACT Dietary fibre enrichment of white bread with inulin-rich carbohydrate (IRC) powder extra... more ABSTRACT Dietary fibre enrichment of white bread with inulin-rich carbohydrate (IRC) powder extracted from Jerusalem artichoke tubers (IRC-J) was studied. Previously, it was shown that this IRC-J powder had higher prebiotic activity score than a commercial chicory inulin (IRC-C) powder, used for comparison. For bread making, 2.5 and 5.0 g of either IRC-J or IRC-C were added to 100 g of wheat flour, and the effects on dough viscoelastic properties and bread quality properties were analyzed, relative to a control sample (no IRC added). The lowest IRC concentration of both fibres had no significant effect on the elastic modulus (G’) of the dough, but the highest IRC level decreased G’, with a stronger effect of IRC-J. This was attributed to disruption of the starch-gluten matrix due to fibre replacement of flour. In turn, this was thought to impair gas retention (known as diluting effect), resulting in the observed decrease of bread specific volume and Cell/Total Area ratio, and the increase in crumb hardness and chewiness. IRC addition also had a significant effect on crumb and crust colour, and other crumb grain features. These effects were more significant at the highest IRC concentration of both fibres. Breads with 5.0 g of IRC-J were significantly darker, flatter, and more humid. All the sensory attributes of breads with 0 (control sample), 2.5 g IRC-J, and 2.5 g IRC-C were acceptable, and no significant differences were found between the three samples, in any of the attributes.
The aim of the present work was to investigate the in situ rheological behavior of yeast biofilms... more The aim of the present work was to investigate the in situ rheological behavior of yeast biofilms growing on stainless steel under static and turbulent flow. The species used (Rhodototula mucilaginosa, Candida krusei, Candida kefyr and Candida tropicalis) were isolated from a clarified apple juice industry. The flow conditions impacted biofilm composition over time, with a predominance of C. krusei under static and turbulent flow. Likewise, structural variations occurred, with a tighter appearance under dynamic flow. Under turbulent flow there was an increase of 112 μm in biofilm thickness at 11 weeks (p < 0.001) and cell morphology was governed by hyphal structures and rounded cells. Using the in situ growth method introduced here, yeast biofilms were determined to be viscoelastic materials with a predominantly solid-like behavior, and neither this nor the G'0 values were significantly affected by the flow conditions or the growth time, and at large deformations their weak structure collapsed beyond a critical strain of about 1.5-5%. The present work could represent a starting point for developing in situ measurements of yeast rheology and contribute to a thin body of knowledge about fungal biofilm formation.
Cloudy fruit juice is caused by colloidal suspension where the continuous medium is a solution of... more Cloudy fruit juice is caused by colloidal suspension where the continuous medium is a solution of pectin, sugars and organic acids, and the dispersed matter is mainly formed by cellular tissue comminuted during fruit processing. To obtain a clear juice, these suspended particles have to be removed. This process is known as clarification or fining, one of the most important
ABSTRACT In order to study the effect of fruit pulp on the structure of fruit jams, they were mod... more ABSTRACT In order to study the effect of fruit pulp on the structure of fruit jams, they were modeled as composites with a high-methoxyl pectin (HMP) gel matrix filled with apple particles. The effect of particle concentration (0, 1 and 2 wt%) and particle size (small: <125 µm, and large: 125–850 µm) on a pectin gel (0.5 wt% HMP, 65 wt% glucose, pH 3.0, 0.1 M citrate buffer) were studied. Rheological measurements showed that increasing concentration of small particles produced a significant increase in the elastic modulus of the composite gels. Penetration tests showed that 1 wt% small particles produced a significant decrease of gel strength, rupture strength, adhesiveness and brittleness. Increasing particle size produced a further decrease of these properties (only significant for gel strength). When concentration of small particles was raised to 2 wt%, these parameters (except brittleness) increased back to the control sample (0% particles) values.PRACTICAL APPLICATIONSKnowledge of the effect of fruit particles on the structure of pectin gels would allow controlling the rheological and mechanical properties of fruit jams in terms of the size and concentration of fruit pulp used in their formulation.
Particle size, shape, and volume fraction as well as soluble pectin content and electro-viscous e... more Particle size, shape, and volume fraction as well as soluble pectin content and electro-viscous effects on cloudy apple juice viscosity were investigated. Particle characteristics were micrographically determined by electron microscopy. More than 2300 particles were digitalized and statistically analyzed. Cloudy apple juice resulted in a suspension of irregular shape particles ranging from 0.25 to 5 m in size. A 10 °Brix juice had a particle volume fraction of 0 = 3.93 ∞ 10-3. Relative viscosity values were fitted to the generalized Sudduth equation. Intrinsic viscosity resulted 5.8 times greater than the theoretical value predicted by Einstein (␣ = 2.5). This was attributed to the first electro-viscous effect. Results also indicate that the effect of particle non-sphericity on cloudy apple juice viscosity can be neglected. Soluble pectin was found to increase juice viscosity significantly. Combined effects result in a strong linear increase of relative viscosity.
Apparent viscosity, ηa, and first normal stress coefficient, ψ1, of six different concentrations ... more Apparent viscosity, ηa, and first normal stress coefficient, ψ1, of six different concentrations of cross-linked waxy maize (CWM), 3.5-5 % w/w, and tapioca, 2.8-4 % w/w, starch dispersions (SDs) showed power law relationships with shear rate, ̇γ , and increased with starch concentration. In both ηa and ψ1, volume fraction of the granules, ϕ, played a more important role than the amylose content of the continuous phase. Slope of ηa - ̇γ curves increased mildly with starch concentration, while slope of ψ1 - ̇γ curves was almost the same for CWM at all concentrations and 4 % tapioca SDs. Values of ηa and ψ1 predicted from dynamic rheological and apparent viscosity data based on the Goddard-Miller model were in reasonable agreement with experimental values.
In this study the operational extraction variables to obtain higher yields of inulin from Jerusal... more In this study the operational extraction variables to obtain higher yields of inulin from Jerusalem artichoke tubers (JAT), as well as the optimal conditions to obtain a stable and dispersible powdered product by either spray or freeze drying, were studied. With this purpose, the powder yield, moisture content, water activity and flowability or products obtained by different experimental conditions were analyzed. Inulin rich carbohydrates (IRC) extraction was performed from lyophilized and ground tubers employing distilled hot water as solvent. It was proved that the solid:solvent ratio (S:S) was the critical variable in the extraction process, followed by temperature. Thus, the IRC extraction was optimal without ultrasound assistance, at 76°C, employing a S:S of 1:16, during 90min. In addition, the powder obtained by freeze-drying of the IRC extract showed advantages respect to powders obtained by spray-drying regarding the yield and considering that maltodextrin was not necessary ...
The factors affecting the mechanical properties of biofilms formed by yeast species (Rhodotorula ... more The factors affecting the mechanical properties of biofilms formed by yeast species (Rhodotorula mucilaginosa, Candida krusei, C. kefyr and C. tropicalis) isolated from the juice processing industries have been investigated. Variables studied were: the food matrix (apple/pear juice), the sugar concentration (6/12 °Bx) and the hydrodynamic conditions (static/turbulent flow). A range of environmental cues were included as the mechanical properties of biofilms are complex. Yeast counts were significantly higher in turbulent flow compared with under static conditions. The thickness of the biofilm ranged from 38 to 148 μm, from static to turbulent flow. Yeast biofilms grown under turbulent flow conditions were viscoelastic with a predominant solid-like behavior and were structurally stronger than those grown under static conditions, indicating gel-type structures. Only the type of flow had a significant effect on [Formula: see text] and G*. Flow velocity and nutrient status modulated the...
Http Dx Doi Org 10 1080 08927014 2014 981165, Nov 1, 2014
The aim of the present work was to investigate the in situ rheological behavior of yeast biofilms... more The aim of the present work was to investigate the in situ rheological behavior of yeast biofilms growing on stainless steel under static and turbulent flow. The species used (Rhodototula mucilaginosa, Candida krusei, Candida kefyr and Candida tropicalis) were isolated from a clarified apple juice industry. The flow conditions impacted biofilm composition over time, with a predominance of C. krusei under static and turbulent flow. Likewise, structural variations occurred, with a tighter appearance under dynamic flow. Under turbulent flow there was an increase of 112 μm in biofilm thickness at 11 weeks (p < 0.001) and cell morphology was governed by hyphal structures and rounded cells. Using the in situ growth method introduced here, yeast biofilms were determined to be viscoelastic materials with a predominantly solid-like behavior, and neither this nor the G'0 values were significantly affected by the flow conditions or the growth time, and at large deformations their weak structure collapsed beyond a critical strain of about 1.5-5%. The present work could represent a starting point for developing in situ measurements of yeast rheology and contribute to a thin body of knowledge about fungal biofilm formation.
ABSTRACT The objective was to study and model the effect of the main formulation variables on the... more ABSTRACT The objective was to study and model the effect of the main formulation variables on the rheological and mechanical properties, colour and overall acceptability of apple jelly, and to optimize formulation variables in order to maximize overall acceptability. Formulation variables were juice proportion in the initial juice-sugar mix (J: 350–550 g/kg), product pH (2.8–3.6), concentration of added pectin (P: 0–10 g/kg), and final content of soluble solids (SS: 625–725 g/kg). Anova results showed that P was the main effect on all the rheological and mechanical properties. The strength of the pectin gel network increased at increasing values of P. Consequently, the jellies were more elastic and firm but more brittle, as well as more adhesive. Also, more work was required to disintegrate the jellies. Besides P, also J had a significant positive effect on storage modulus and adhesiveness, while SS had a significant positive effect on cohesiveness. Colour parameters were mainly affected by J. Overall acceptability was significantly affected by J > pH > SS, while P had no significant effect. The optimum was calculated to be at J = 500 g/kg, SS = 700 g/kg, pH = 3.4, and P = 5 g/kg.
The interactions between pilocarpine (PIL) and the anionic polyelectrolyte carbomer (CBR) were in... more The interactions between pilocarpine (PIL) and the anionic polyelectrolyte carbomer (CBR) were investigated. The effects of the chemical interactions on the chemical stability of the drug also were evaluated. The binary system was characterized by nuclear magnetic resonance techniques, Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction, scanning electron microscopy (SEM) and thermal analysis. The experiments showed that the complex, prepared by freeze-drying, is a solid amorphous form different from its precursors, thereby offering an interesting alternative for the preparation of extended release matrices. The solution stability of PIL was studied at pH 7 and 8, at 70 • C. The PIL solution stability was evaluated alone and in the presence of CBR. Results indicated that the drug in the presence of the polymer is 3.3 and 3.5 times more stable, at pH 7 and pH 8, respectively, than the drug without CBR. The activation energy and the frequency factor, according to Arrhenius plot, were estimated to be 13.9 ± 0.4 and 14.8 ± 0.5 kcal mol −1 , and 6.1 ± 0.3 and 7.6 ± 0.3, with and without the polymer, respectively.
ABSTRACT Dietary fibre enrichment of white bread with inulin-rich carbohydrate (IRC) powder extra... more ABSTRACT Dietary fibre enrichment of white bread with inulin-rich carbohydrate (IRC) powder extracted from Jerusalem artichoke tubers (IRC-J) was studied. Previously, it was shown that this IRC-J powder had higher prebiotic activity score than a commercial chicory inulin (IRC-C) powder, used for comparison. For bread making, 2.5 and 5.0 g of either IRC-J or IRC-C were added to 100 g of wheat flour, and the effects on dough viscoelastic properties and bread quality properties were analyzed, relative to a control sample (no IRC added). The lowest IRC concentration of both fibres had no significant effect on the elastic modulus (G’) of the dough, but the highest IRC level decreased G’, with a stronger effect of IRC-J. This was attributed to disruption of the starch-gluten matrix due to fibre replacement of flour. In turn, this was thought to impair gas retention (known as diluting effect), resulting in the observed decrease of bread specific volume and Cell/Total Area ratio, and the increase in crumb hardness and chewiness. IRC addition also had a significant effect on crumb and crust colour, and other crumb grain features. These effects were more significant at the highest IRC concentration of both fibres. Breads with 5.0 g of IRC-J were significantly darker, flatter, and more humid. All the sensory attributes of breads with 0 (control sample), 2.5 g IRC-J, and 2.5 g IRC-C were acceptable, and no significant differences were found between the three samples, in any of the attributes.
The aim of the present work was to investigate the in situ rheological behavior of yeast biofilms... more The aim of the present work was to investigate the in situ rheological behavior of yeast biofilms growing on stainless steel under static and turbulent flow. The species used (Rhodototula mucilaginosa, Candida krusei, Candida kefyr and Candida tropicalis) were isolated from a clarified apple juice industry. The flow conditions impacted biofilm composition over time, with a predominance of C. krusei under static and turbulent flow. Likewise, structural variations occurred, with a tighter appearance under dynamic flow. Under turbulent flow there was an increase of 112 μm in biofilm thickness at 11 weeks (p < 0.001) and cell morphology was governed by hyphal structures and rounded cells. Using the in situ growth method introduced here, yeast biofilms were determined to be viscoelastic materials with a predominantly solid-like behavior, and neither this nor the G'0 values were significantly affected by the flow conditions or the growth time, and at large deformations their weak structure collapsed beyond a critical strain of about 1.5-5%. The present work could represent a starting point for developing in situ measurements of yeast rheology and contribute to a thin body of knowledge about fungal biofilm formation.
Cloudy fruit juice is caused by colloidal suspension where the continuous medium is a solution of... more Cloudy fruit juice is caused by colloidal suspension where the continuous medium is a solution of pectin, sugars and organic acids, and the dispersed matter is mainly formed by cellular tissue comminuted during fruit processing. To obtain a clear juice, these suspended particles have to be removed. This process is known as clarification or fining, one of the most important
ABSTRACT In order to study the effect of fruit pulp on the structure of fruit jams, they were mod... more ABSTRACT In order to study the effect of fruit pulp on the structure of fruit jams, they were modeled as composites with a high-methoxyl pectin (HMP) gel matrix filled with apple particles. The effect of particle concentration (0, 1 and 2 wt%) and particle size (small: <125 µm, and large: 125–850 µm) on a pectin gel (0.5 wt% HMP, 65 wt% glucose, pH 3.0, 0.1 M citrate buffer) were studied. Rheological measurements showed that increasing concentration of small particles produced a significant increase in the elastic modulus of the composite gels. Penetration tests showed that 1 wt% small particles produced a significant decrease of gel strength, rupture strength, adhesiveness and brittleness. Increasing particle size produced a further decrease of these properties (only significant for gel strength). When concentration of small particles was raised to 2 wt%, these parameters (except brittleness) increased back to the control sample (0% particles) values.PRACTICAL APPLICATIONSKnowledge of the effect of fruit particles on the structure of pectin gels would allow controlling the rheological and mechanical properties of fruit jams in terms of the size and concentration of fruit pulp used in their formulation.
Particle size, shape, and volume fraction as well as soluble pectin content and electro-viscous e... more Particle size, shape, and volume fraction as well as soluble pectin content and electro-viscous effects on cloudy apple juice viscosity were investigated. Particle characteristics were micrographically determined by electron microscopy. More than 2300 particles were digitalized and statistically analyzed. Cloudy apple juice resulted in a suspension of irregular shape particles ranging from 0.25 to 5 m in size. A 10 °Brix juice had a particle volume fraction of 0 = 3.93 ∞ 10-3. Relative viscosity values were fitted to the generalized Sudduth equation. Intrinsic viscosity resulted 5.8 times greater than the theoretical value predicted by Einstein (␣ = 2.5). This was attributed to the first electro-viscous effect. Results also indicate that the effect of particle non-sphericity on cloudy apple juice viscosity can be neglected. Soluble pectin was found to increase juice viscosity significantly. Combined effects result in a strong linear increase of relative viscosity.
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Papers by Diego Genovese