Carmen Müller - Academia.edu (original) (raw)
Papers by Carmen Müller
Química Nova, 2015
The objectives of this work were to investigate the microstructure, crystallinity and thermal sta... more The objectives of this work were to investigate the microstructure, crystallinity and thermal stability of nanofibrillated cellulose obtained from oat hulls using bleaching and acid hydrolysis at a mild temperature (45 ºC) followed by ultrasonication. The oat hulls were bleached with peracetic acid, and after bleaching, the compact structure around the cellulosic fibers was removed, and the bundles became individualized. The extraction time (30 or 60 min) did not affect the properties of the nanofibrillated cellulose, which presented a higher crystallinity index and thermal stability than the raw material (oat hulls). The nanocellulose formed interconnected webs of tiny fibers with diameters of 70-100 nm and lengths of several micrometers, producing nanofibers with a relatively high aspect ratio, thus indicating that these materials are suitable for polymer reinforcement.
Journal of Polymers and the Environment, 2012
The objectives of this work were to develop biodegradable trays from cassava starch, sugarcane fi... more The objectives of this work were to develop biodegradable trays from cassava starch, sugarcane fibers and Na-montmorillonite (Na-MMT) using a baking process and to study the effects of these components on the physical properties, photo-and bio-degradation of the trays. The sample F20 (produced with 20 g fiber/100 g formulation) showed the maximum yield production (100 %). All formulations resulted in well-shaped trays with densities between 0.1941 and 0.2966 g/cm 3. The addition of fibers and Na-MMT resulted in less dense and less rigid trays compared to control samples (only starch). The studied processing conditions resulted in good nanoclay dispersion, leading to the formation of an exfoliated structure. The evaluation of the photo-degradation stability of the trays under UV exposure for 336 h showed that a sample produced with a specific combination of fiber and nanoclay (20 g fiber and 5 g nanoclay/100 g formulation) had the highest loss in stress at break (91 %). Biodegradation assays showed that Control trays (starch) and F20 (20 g fiber/100 g formulation) lost a greater percentage of their weight after 90 days of incubation in soil, with losses of up to 85.50 and 82.70 %, respectively.
Carbohydrate Polymers, 2013
Biodegradable films were produced from blends contained a high amount of thermoplastic starch (TP... more Biodegradable films were produced from blends contained a high amount of thermoplastic starch (TPS) and poly(lactic acid) (PLA) plasticized with different adipate or citrate esters. It was not possible to obtain pellets for the production of films using only glycerol as a plasticizer. The plasticization of the PLA with the esters and mixture stages added through extrusion was critical to achieve a blend capable of producing films by blow extrusion. Adipate esters were the most effective plasticizers because they interacted best with the PLA and yielded films with appropriate mechanical properties.
Polímeros, 2015
The demand for renewably sourced biodegradable materials has increased the need to produce materi... more The demand for renewably sourced biodegradable materials has increased the need to produce materials that combine appropriate functional properties at competitive costs. Thermoplastic starch and polyester blends are an interesting alternative to current materials due to the low cost of starch and the functional properties and processability of the resulting blends. Producing thermoplastic starch (TPS) requires using a plasticiser at concentrations between 20 and 30%wt (in relation to starch). Glycerol is the most common plasticiser due to its high plasticising capacity and thermal stability at processing temperatures. The objective of this study was to evaluate glycerol waste from the biodiesel industry, with different degrees of purification, as plasticisers for TPS / poly (butylene adipate-co-terephthalate) (PBAT) blends. Different purities of glycerol produced films with similar mechanical, optical and barrier properties to those made with purified glycerol (99.7%). Therefore, crude glycerol is a renewable alternative plasticiser that reduces the cost of plasticisation by 6-fold.
Información tecnológica, 2007
Información tecnológica, 2008
Se estudiaron procesos de pre-tratamiento para la eliminación de grasas y sales minerales del sue... more Se estudiaron procesos de pre-tratamiento para la eliminación de grasas y sales minerales del suero de queso tipo ácido, para el aprovechamiento del contenido de proteínas y lactosa. Se analizaron procesos de separación tales como centrifugación y precipitación termo-cálcica seguidos de una etapa de micro-filtración. El proceso de centrifugación combinado con micro-filtración se mostró más eficiente en lo que se refiere a la eliminación de grasa, obteniéndose un promedio de 90% de recuperación de proteínas y de lactosa.
Journal of Food Engineering, 2015
Polímeros, 2012
Biodegradable films of thermoplastic starch and poly (butylene adipate co-terephthalate) (PBAT) c... more Biodegradable films of thermoplastic starch and poly (butylene adipate co-terephthalate) (PBAT) containing fatty acids were characterized thermally and with infrared and Raman spectroscopies. The symmetrical character of the benzene ring in PBAT provided a means to illustrate the difference between these spectroscopic techniques, because a band appeared in the Raman spectrum but not in the infrared. The thermal analysis showed three degradation stages related to fatty acids, starch and PBAT. The incorporation of saturated fatty acids with different molecular mass (caproic, lauric and stearic) did not change the nature of the chemical bonds among the components in the blends of starch, PBAT and glycerol, according to the thermal analysis, infrared and Raman spectroscopies.
Journal of Polymers and the Environment, 2014
Poly(lactic acid) (PLA) and thermoplastic starch (TPS) sheets plasticized with different adipate ... more Poly(lactic acid) (PLA) and thermoplastic starch (TPS) sheets plasticized with different adipate and citrate esters were produced by a calendering-extrusion process. The incorporation of plasticizers significantly reduced the glass transition temperature and increased the PLA chain mobility thus improving the mechanical properties. Among the plasticizers employed, diethyl adipate significantly increased the elongation of the sheets and slightly increased the water vapor permeability. Micrographs revealed the incompatibility between starch and PLA, and there was no plasticizer phase separation, suggesting that the plasticizer concentration was adequate. The incorporation of adipate or citrate esters improves the mechanical properties and processability of PLA/TPS sheets produced by calendering extrusion at a pilot scale.
International Journal of Dairy Technology, 2010
Minas Frescal cheeses produced with the addition of the probiotic culture Bifidobacterium Bb-12 a... more Minas Frescal cheeses produced with the addition of the probiotic culture Bifidobacterium Bb-12 and without (C1) or with (C2) lactic acid were evaluated in relation to the microbiological, physicochemical and sensory properties. After 28 days of storage, the cheeses without lactic acid showed lower moisture and pH, in addition to higher acidity and syneresis. This behaviour influenced the texture profile of the cheeses, making them harder and chewier. The colour attributes L* and b* diminished during the storage. The majority of the consumers classified the cheeses as having good acceptability and they would buy this type of functional food.
Materials Science and Engineering: C, 2013
Biodegradable films were produced using the blown extrusion method from blends that contained cas... more Biodegradable films were produced using the blown extrusion method from blends that contained cassava thermoplastic starch (TPS), poly(butylene adipate-co-terephthalate) (PBAT) and poly(lactic acid) (PLA) with two different extrusion processes. The choice of extrusion process did not have a significant effect on the mechanical properties, water vapor permeability (WVP) or viscoelasticity of the films, but the addition of PLA decreased the elongation, blow-up ratio (BUR) and opacity and increased the elastic modulus, tensile strength and viscoelastic parameters of the films. The films with 20% PLA exhibited a lower WVP due to the hydrophobic nature of this polymer. Morphological analyses revealed the incompatibility between the polymers used.
Journal of Polymers and the Environment, 2012
ABSTRACT Biodegradable films were produced by extrusion from blends of starch, glycerol and poly(... more ABSTRACT Biodegradable films were produced by extrusion from blends of starch, glycerol and poly(butylene adipate co-terephthalate), a biodegradable polyester, with the addition of 1.5 % (wt/wt) saturated fatty acids (caproic, lauric or stearic). Films containing fatty acids had higher crystallinity than control films and the longer the carbon chain of the acid was, the more crystalline the film. Fatty acids with up to 12 carbon atoms did not alter the viscoelastic characteristic of the films. Further, the incorporation of fatty acids did not decrease the hydrophilicity of the films in comparison with the control film without a fatty acid.
Journal of Food Engineering, 2010
The effects of a probiotic bacterium (Bifidobacterium Bb-12) and lactic acid on the microbiologic... more The effects of a probiotic bacterium (Bifidobacterium Bb-12) and lactic acid on the microbiological, physicochemical, rheological and microstructural proprieties of Minas Frescal cheese were evaluated after 1 day and after 28 days of storage (5 ± 1°C). The cheese was produced with four different treatments: with no lactic acid (C1 and C2), with lactic acid (C3 and C4) and with bifidobacteria (C2 and C3). The cheese formulations containing bifidobacteria were classified as probiotic. The addition of bifidobacteria to the cheese did not influence its yield, protein or lipid levels one day after production. Moreover, after 28 days of storage, the cheese samples with no lactic acid showed lower moisture levels compared to the samples containing lactic acid (P < 0.05). The absence of lactic acid had an influence on the rheological and microstructural behavior, making them more elastic, firm and compact, however all the cheese samples evaluated showed a higher tendency to viscosity than to elasticity. The Minas Frescal cheese with Bifidobacterium Bb-12 and lactic acid showed great potential as a functional food, with possible industrial and commercial application.
International Journal of Food Science & Technology, 2013
Blends of starch with polyesters have commonly been used in the production of biodegradable films... more Blends of starch with polyesters have commonly been used in the production of biodegradable films. However, the components in the blend are not always miscible; therefore, the use of compatibilisers is recommended. The objective of the present work was to study the compatibilisation effect of adipic acid (0.5%; 1.0%; 1.5% (w/w)) on films consisting of starch/glycerol/poly (butylene adipate-co-terephthalate) (PBAT) produced by reactive extrusion. Films compatibilised with adipic acid exhibited statistically significant increase in tensile strength (from 7.28 to 8.45-9.13 MPa), elongation (in this case only with 0.5% of adipic acid) (516.51-679.10%), Young's modulus (21.72-28.75 MPa) and reduction in water vapour permeability (9.76-8.32 9 10 À11 g per s.m.Pa) compared with the control film, which lacked the compatibiliser. Films produced using the compatibiliser also presented a microstructure with fewer cracks. There were no differences in the thermal degradation and crystallinity profile of the films.
Carbohydrate Polymers, 2013
Tartaric acid (TA), a dicarboxylic acid, can act as a compatibiliser in starch/polyester blends. ... more Tartaric acid (TA), a dicarboxylic acid, can act as a compatibiliser in starch/polyester blends. A mixture design was proposed to evaluate the effect of TA on the properties of starch/poly (butylene adipate co-terephthalate) (PBAT) blown films plasticised with glycerol. The interaction between the starch/PBAT and the TA has a positive effect on the tensile strength and puncture force. Additionally, greater proportions of TA increased Young's modulus. The starch+PBAT/TA and Gly/TA interactions contributed to a reduction in the water vapour permeability of the films. The inclusion of TA did not change the crystallinity of the samples. Formulations with intermediate proportions of TA (0.8 g/100 g) were shown to produce the best compatibilising effect. This was observed by DMA analysis as a consequence of the perfect equilibrium between the contributions of TA as a compatibiliser and in the acidolysis of starch, resulting in films with a tensile strength of 5.93 MPa, a possible alternative to non-biodegradable packaging.
Polymer Testing, 2014
The influence of the processing conditions (cooling rate) and coating on the physicochemical prop... more The influence of the processing conditions (cooling rate) and coating on the physicochemical properties of thermoplastic starch/poly(lactic acid) blend sheets was studied. Two cooling rates were used: fast and slow, and in the latter case the sheets were both non-coated and coated with cross-linked chitosan. The physicochemical properties investigated were crystallinity, morphology, water affinity (moisture sorption isotherm, water vapor permeability, water solubility and contact angle) and mechanical properties. In general, the sheets cooled at the slow rate were more crystalline, less permeable and less soluble in water than those cooled at the fast rate. They also produced a more homogeneous morphology. The coated sheets were less soluble in water and mechanically stronger than uncoated sheets cooled at the slow rate. The concentration of plasticizer in the TPS affected only the sorption isotherm and contact angle since a higher plasticizer content caused a greater affinity for water.
Food Research International, 2013
Effect of the application of Bifidobacterium BB-12 microencapsulated by spray drying with prebiot... more Effect of the application of Bifidobacterium BB-12 microencapsulated by spray drying with prebiotics on the properties of ricotta cream
Química Nova, 2015
The objectives of this work were to investigate the microstructure, crystallinity and thermal sta... more The objectives of this work were to investigate the microstructure, crystallinity and thermal stability of nanofibrillated cellulose obtained from oat hulls using bleaching and acid hydrolysis at a mild temperature (45 ºC) followed by ultrasonication. The oat hulls were bleached with peracetic acid, and after bleaching, the compact structure around the cellulosic fibers was removed, and the bundles became individualized. The extraction time (30 or 60 min) did not affect the properties of the nanofibrillated cellulose, which presented a higher crystallinity index and thermal stability than the raw material (oat hulls). The nanocellulose formed interconnected webs of tiny fibers with diameters of 70-100 nm and lengths of several micrometers, producing nanofibers with a relatively high aspect ratio, thus indicating that these materials are suitable for polymer reinforcement.
Journal of Polymers and the Environment, 2012
The objectives of this work were to develop biodegradable trays from cassava starch, sugarcane fi... more The objectives of this work were to develop biodegradable trays from cassava starch, sugarcane fibers and Na-montmorillonite (Na-MMT) using a baking process and to study the effects of these components on the physical properties, photo-and bio-degradation of the trays. The sample F20 (produced with 20 g fiber/100 g formulation) showed the maximum yield production (100 %). All formulations resulted in well-shaped trays with densities between 0.1941 and 0.2966 g/cm 3. The addition of fibers and Na-MMT resulted in less dense and less rigid trays compared to control samples (only starch). The studied processing conditions resulted in good nanoclay dispersion, leading to the formation of an exfoliated structure. The evaluation of the photo-degradation stability of the trays under UV exposure for 336 h showed that a sample produced with a specific combination of fiber and nanoclay (20 g fiber and 5 g nanoclay/100 g formulation) had the highest loss in stress at break (91 %). Biodegradation assays showed that Control trays (starch) and F20 (20 g fiber/100 g formulation) lost a greater percentage of their weight after 90 days of incubation in soil, with losses of up to 85.50 and 82.70 %, respectively.
Carbohydrate Polymers, 2013
Biodegradable films were produced from blends contained a high amount of thermoplastic starch (TP... more Biodegradable films were produced from blends contained a high amount of thermoplastic starch (TPS) and poly(lactic acid) (PLA) plasticized with different adipate or citrate esters. It was not possible to obtain pellets for the production of films using only glycerol as a plasticizer. The plasticization of the PLA with the esters and mixture stages added through extrusion was critical to achieve a blend capable of producing films by blow extrusion. Adipate esters were the most effective plasticizers because they interacted best with the PLA and yielded films with appropriate mechanical properties.
Polímeros, 2015
The demand for renewably sourced biodegradable materials has increased the need to produce materi... more The demand for renewably sourced biodegradable materials has increased the need to produce materials that combine appropriate functional properties at competitive costs. Thermoplastic starch and polyester blends are an interesting alternative to current materials due to the low cost of starch and the functional properties and processability of the resulting blends. Producing thermoplastic starch (TPS) requires using a plasticiser at concentrations between 20 and 30%wt (in relation to starch). Glycerol is the most common plasticiser due to its high plasticising capacity and thermal stability at processing temperatures. The objective of this study was to evaluate glycerol waste from the biodiesel industry, with different degrees of purification, as plasticisers for TPS / poly (butylene adipate-co-terephthalate) (PBAT) blends. Different purities of glycerol produced films with similar mechanical, optical and barrier properties to those made with purified glycerol (99.7%). Therefore, crude glycerol is a renewable alternative plasticiser that reduces the cost of plasticisation by 6-fold.
Información tecnológica, 2007
Información tecnológica, 2008
Se estudiaron procesos de pre-tratamiento para la eliminación de grasas y sales minerales del sue... more Se estudiaron procesos de pre-tratamiento para la eliminación de grasas y sales minerales del suero de queso tipo ácido, para el aprovechamiento del contenido de proteínas y lactosa. Se analizaron procesos de separación tales como centrifugación y precipitación termo-cálcica seguidos de una etapa de micro-filtración. El proceso de centrifugación combinado con micro-filtración se mostró más eficiente en lo que se refiere a la eliminación de grasa, obteniéndose un promedio de 90% de recuperación de proteínas y de lactosa.
Journal of Food Engineering, 2015
Polímeros, 2012
Biodegradable films of thermoplastic starch and poly (butylene adipate co-terephthalate) (PBAT) c... more Biodegradable films of thermoplastic starch and poly (butylene adipate co-terephthalate) (PBAT) containing fatty acids were characterized thermally and with infrared and Raman spectroscopies. The symmetrical character of the benzene ring in PBAT provided a means to illustrate the difference between these spectroscopic techniques, because a band appeared in the Raman spectrum but not in the infrared. The thermal analysis showed three degradation stages related to fatty acids, starch and PBAT. The incorporation of saturated fatty acids with different molecular mass (caproic, lauric and stearic) did not change the nature of the chemical bonds among the components in the blends of starch, PBAT and glycerol, according to the thermal analysis, infrared and Raman spectroscopies.
Journal of Polymers and the Environment, 2014
Poly(lactic acid) (PLA) and thermoplastic starch (TPS) sheets plasticized with different adipate ... more Poly(lactic acid) (PLA) and thermoplastic starch (TPS) sheets plasticized with different adipate and citrate esters were produced by a calendering-extrusion process. The incorporation of plasticizers significantly reduced the glass transition temperature and increased the PLA chain mobility thus improving the mechanical properties. Among the plasticizers employed, diethyl adipate significantly increased the elongation of the sheets and slightly increased the water vapor permeability. Micrographs revealed the incompatibility between starch and PLA, and there was no plasticizer phase separation, suggesting that the plasticizer concentration was adequate. The incorporation of adipate or citrate esters improves the mechanical properties and processability of PLA/TPS sheets produced by calendering extrusion at a pilot scale.
International Journal of Dairy Technology, 2010
Minas Frescal cheeses produced with the addition of the probiotic culture Bifidobacterium Bb-12 a... more Minas Frescal cheeses produced with the addition of the probiotic culture Bifidobacterium Bb-12 and without (C1) or with (C2) lactic acid were evaluated in relation to the microbiological, physicochemical and sensory properties. After 28 days of storage, the cheeses without lactic acid showed lower moisture and pH, in addition to higher acidity and syneresis. This behaviour influenced the texture profile of the cheeses, making them harder and chewier. The colour attributes L* and b* diminished during the storage. The majority of the consumers classified the cheeses as having good acceptability and they would buy this type of functional food.
Materials Science and Engineering: C, 2013
Biodegradable films were produced using the blown extrusion method from blends that contained cas... more Biodegradable films were produced using the blown extrusion method from blends that contained cassava thermoplastic starch (TPS), poly(butylene adipate-co-terephthalate) (PBAT) and poly(lactic acid) (PLA) with two different extrusion processes. The choice of extrusion process did not have a significant effect on the mechanical properties, water vapor permeability (WVP) or viscoelasticity of the films, but the addition of PLA decreased the elongation, blow-up ratio (BUR) and opacity and increased the elastic modulus, tensile strength and viscoelastic parameters of the films. The films with 20% PLA exhibited a lower WVP due to the hydrophobic nature of this polymer. Morphological analyses revealed the incompatibility between the polymers used.
Journal of Polymers and the Environment, 2012
ABSTRACT Biodegradable films were produced by extrusion from blends of starch, glycerol and poly(... more ABSTRACT Biodegradable films were produced by extrusion from blends of starch, glycerol and poly(butylene adipate co-terephthalate), a biodegradable polyester, with the addition of 1.5 % (wt/wt) saturated fatty acids (caproic, lauric or stearic). Films containing fatty acids had higher crystallinity than control films and the longer the carbon chain of the acid was, the more crystalline the film. Fatty acids with up to 12 carbon atoms did not alter the viscoelastic characteristic of the films. Further, the incorporation of fatty acids did not decrease the hydrophilicity of the films in comparison with the control film without a fatty acid.
Journal of Food Engineering, 2010
The effects of a probiotic bacterium (Bifidobacterium Bb-12) and lactic acid on the microbiologic... more The effects of a probiotic bacterium (Bifidobacterium Bb-12) and lactic acid on the microbiological, physicochemical, rheological and microstructural proprieties of Minas Frescal cheese were evaluated after 1 day and after 28 days of storage (5 ± 1°C). The cheese was produced with four different treatments: with no lactic acid (C1 and C2), with lactic acid (C3 and C4) and with bifidobacteria (C2 and C3). The cheese formulations containing bifidobacteria were classified as probiotic. The addition of bifidobacteria to the cheese did not influence its yield, protein or lipid levels one day after production. Moreover, after 28 days of storage, the cheese samples with no lactic acid showed lower moisture levels compared to the samples containing lactic acid (P < 0.05). The absence of lactic acid had an influence on the rheological and microstructural behavior, making them more elastic, firm and compact, however all the cheese samples evaluated showed a higher tendency to viscosity than to elasticity. The Minas Frescal cheese with Bifidobacterium Bb-12 and lactic acid showed great potential as a functional food, with possible industrial and commercial application.
International Journal of Food Science & Technology, 2013
Blends of starch with polyesters have commonly been used in the production of biodegradable films... more Blends of starch with polyesters have commonly been used in the production of biodegradable films. However, the components in the blend are not always miscible; therefore, the use of compatibilisers is recommended. The objective of the present work was to study the compatibilisation effect of adipic acid (0.5%; 1.0%; 1.5% (w/w)) on films consisting of starch/glycerol/poly (butylene adipate-co-terephthalate) (PBAT) produced by reactive extrusion. Films compatibilised with adipic acid exhibited statistically significant increase in tensile strength (from 7.28 to 8.45-9.13 MPa), elongation (in this case only with 0.5% of adipic acid) (516.51-679.10%), Young's modulus (21.72-28.75 MPa) and reduction in water vapour permeability (9.76-8.32 9 10 À11 g per s.m.Pa) compared with the control film, which lacked the compatibiliser. Films produced using the compatibiliser also presented a microstructure with fewer cracks. There were no differences in the thermal degradation and crystallinity profile of the films.
Carbohydrate Polymers, 2013
Tartaric acid (TA), a dicarboxylic acid, can act as a compatibiliser in starch/polyester blends. ... more Tartaric acid (TA), a dicarboxylic acid, can act as a compatibiliser in starch/polyester blends. A mixture design was proposed to evaluate the effect of TA on the properties of starch/poly (butylene adipate co-terephthalate) (PBAT) blown films plasticised with glycerol. The interaction between the starch/PBAT and the TA has a positive effect on the tensile strength and puncture force. Additionally, greater proportions of TA increased Young's modulus. The starch+PBAT/TA and Gly/TA interactions contributed to a reduction in the water vapour permeability of the films. The inclusion of TA did not change the crystallinity of the samples. Formulations with intermediate proportions of TA (0.8 g/100 g) were shown to produce the best compatibilising effect. This was observed by DMA analysis as a consequence of the perfect equilibrium between the contributions of TA as a compatibiliser and in the acidolysis of starch, resulting in films with a tensile strength of 5.93 MPa, a possible alternative to non-biodegradable packaging.
Polymer Testing, 2014
The influence of the processing conditions (cooling rate) and coating on the physicochemical prop... more The influence of the processing conditions (cooling rate) and coating on the physicochemical properties of thermoplastic starch/poly(lactic acid) blend sheets was studied. Two cooling rates were used: fast and slow, and in the latter case the sheets were both non-coated and coated with cross-linked chitosan. The physicochemical properties investigated were crystallinity, morphology, water affinity (moisture sorption isotherm, water vapor permeability, water solubility and contact angle) and mechanical properties. In general, the sheets cooled at the slow rate were more crystalline, less permeable and less soluble in water than those cooled at the fast rate. They also produced a more homogeneous morphology. The coated sheets were less soluble in water and mechanically stronger than uncoated sheets cooled at the slow rate. The concentration of plasticizer in the TPS affected only the sorption isotherm and contact angle since a higher plasticizer content caused a greater affinity for water.
Food Research International, 2013
Effect of the application of Bifidobacterium BB-12 microencapsulated by spray drying with prebiot... more Effect of the application of Bifidobacterium BB-12 microencapsulated by spray drying with prebiotics on the properties of ricotta cream