Stela Meira - Academia.edu (original) (raw)

Papers by Stela Meira

Avanços e Desafios da Nutrição 3, 2019

The milking procedure are crucial to obtaining milk with good microbiological quality. The aim of... more The milking procedure are crucial to obtaining milk with good microbiological quality. The aim of this study was to evaluate the influence of hygienic milking on the quality of milk produced by three small farms of Bagé-RS. One sample was collected from each producer monthly. After three sample collections, a technical training was performed, showing to producers how conduct hygienic milking and a comparison was made with the results obtained from three sample collections after training. Samples of crude milk was submitted to mesophilic and psychrotrophic microrganisms counts and total and fecal coliforms evaluation. Also, physicochemical analyzes were performed in relation to alizarol, acidity, density and peroxidase. The results showed a reduction of bacterial counts and acidity, complying with the microbiological requirements of current legislation. PALAVRAS-CHAVE: leite, ordenha higiênica, qualidade físico-química, qualidade microbiológica. KEY-WORDS: milk, hygienic milking, phy...

New biotechnology, Jan 25, 2014

The antioxidant and antihypertensive activities of feather hydrolysates obtained with the bacteri... more The antioxidant and antihypertensive activities of feather hydrolysates obtained with the bacterium Chryseobacterium sp. kr6 were investigated. Keratin hydrolysates were produced with different concentrations of thermally denatured feathers (10-75 g l(-1)) and initial pH values (6.0-9.0). Soluble proteins accumulated in high amounts in media with 50 and 75 g l(-1) of feathers, reaching values of 18.5 and 22 mg ml(-1), respectively, after 48 hours of cultivation. In media with 50 g l(-1) of feathers, initial pH had minimal effect after 48 hours. Maximal protease production was observed after 24 hours of cultivation, and feather concentration and initial pH values showed no significant effect on enzyme yields at this time. Feather hydrolysates displayed in vitro antioxidant properties, and optimal antioxidant activities were observed in cultures with 50 g l(-1) feathers, at initial pH 8.0, after 48 hours growth at 30°C. Also, feather hydrolysates were demonstrated to inhibit the angio...

Yacon root is a functional food which contains antioxidants and prebiotics compounds. This study ... more Yacon root is a functional food which contains antioxidants and prebiotics compounds. This study aimed to evaluate the physical, chemical and prebiotic characteristics of a yacon extract powder obtained by ultrafiltration (UF) with membranes of 10 and 30 kDa and encapsulation of the resulting permeate by spray drying. Drying air temperatures of 140 and 160 oC and concentrations of gum arabic of 10 and 15% were tested. The samples had solubility values ​​greater than 90% while the hygroscopicity decreased with increasing gum concentration and drying temperature. Electron microscopy showed a strong tendency to agglomeration of smaller particles around the larger ones, mainly at a temperature of 140 oC. Regarding color, the parameter L* showed that drying at 160 oC produced darker samples and the parameters a* and b* indicated that all samples were greenish yellow. The concentration of inulin decreased during drying, whereas the levels of glucose and fructose increased due to the therm...

This work reports on the preparation, characterization and antibacterial activity of a nanocompos... more This work reports on the preparation, characterization and antibacterial activity of a nanocomposite formed from graphene oxide (GO) sheets decorated with silver nanoparticles (GO-Ag). The GO-Ag nanocomposite was prepared in the presence of AgNO3 and sodium citrate. The physicochemical characterization was performed by UV-vis spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), Raman spectroscopy and transmission electron microscopy (TEM). The average size of the silver nanoparticles anchored on the GO surface was 7.5 nm. Oxidation debris fragments (a byproduct adsorbed on the GO surface) were found to be crucial for the nucleation and growth of the silver nanoparticles. The antibacterial activity of the GO and GO-Ag nanocomposite against the microorganism Pseudomonas aeruginosa was investigated using the standard counting plate methodology. The GO dispersion showed no antibacterial activity against P. aeruginosa over the concentration range investigated. On the ...

Water soluble extracts (WSE) of ewe's cheeses produced in Uruguay and Brazil were evaluated f... more Water soluble extracts (WSE) of ewe's cheeses produced in Uruguay and Brazil were evaluated for their biological activities. Feta-type, Roquefort-type and Pecorino-type cheeses from Brazil, Pecorino Sardo-type and Cerrillano cheese samples from Uruguay, were analyzed. Antioxidant properties were evaluated using distinct methods. Scavenging of the cation radical of 2,2′-azino-bis-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS) ranged from 32 to 45% for Feta-type cheeses to 87% for Roquefort-type cheese. A similar trend was observed for the reducing power, where WSE from Roquefort-type cheese showed the highest activity among the evaluated cheese. Iron chelating activity was quite variable among the different WSE, being higher (50%) for a Pecorino-type cheese. Thiobarbituric acid reactive substance (TBARS) analysis presented similarity among most of the cheese samples, with inhibition values ranging from 25 to 51%. Scavenging of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical was obs...

Revista Thema

O objetivo deste trabalho foi analisar o conhecimento dos alunos do Instituto Federal Sul-rio-gra... more O objetivo deste trabalho foi analisar o conhecimento dos alunos do Instituto Federal Sul-rio-grandense (IFSul) Câmpus Bagé a respeito das informações contidas nos rótulos dos alimentos e na informação nutricional através da aplicação de um questionário. A informação mais procurada pelos 79 alunos entrevistados nos rótulos de alimentos foi a marca comercial do produto. Já 32,9% não tem o hábito de olhar a informação nutricional, apesar de afirmarem compreendê-la. A observação da presença de glúten ou lactose foi realizada apenas por pessoas consideradas intolerantes ou alérgicas. Sobre alimentos light e diet e aditivos alimentares, a maioria dos entrevistados afirma saber a diferença entre light e diet e desconhecer o que são aditivos alimentares. Em relação às melhorias para os rótulos de alimentos, 21,5% dos entrevistados não souberam opinar e 13% consideraram as informações já contidas no rótulo, suficientes. Apesar de os alunos entrevistados afirmarem ter conhecimento em relação...

Research, Society and Development

A vitivinicultura destaca-se na economia mundial por ser uma das indústrias de bebidas alcoólicas... more A vitivinicultura destaca-se na economia mundial por ser uma das indústrias de bebidas alcoólicas em maior expansão no mundo, estando em pleno crescimento no Brasil. Esse avanço também representa um aumento nos resíduos, visto que cerca de 30% do volume de uvas vinificadas gera bagaço. Além disso, se mal destinado, esse descarte pode se tornar um problema ambiental e econômico. O objetivo deste trabalho foi discutir a situação atual da vitivinicultura no Brasil, com enfoque em seus resíduos e nas medidas que estão sendo tomadas para aproveitamento desses como coproduto, alternativas de uso e indicações de opções para o futuro das indústrias do setor. O bagaço possui muitos nutrientes que permanecem após o processamento do fruto tais como fibras, minerais e compostos bioativos. Devido a isso, várias alternativas estão sendo propostas para aproveitar esse resíduo, desde uso em fertilizantes, em compostagem ou na alimentação animal, até como matéria prima no desenvolvimento de produtos...

Research, Society and Development

O objetivo deste estudo foi desenvolver e caracterizar doce cremoso a partir do bagaço de uvas Vi... more O objetivo deste estudo foi desenvolver e caracterizar doce cremoso a partir do bagaço de uvas Vitis vinifera vinificadas. O bagaço foi selecionado e caracterizado por análises físico-químicas, microbiológicas e de compostos bioativos. Após processamento, foram formulados dois doces cremosos, um com pectina industrial (Pectina) e outro com gomas ágar-ágar e carragena (Gomas). Os doces foram caracterizados por análises físico-químicas, microbiológicas, de compostos bioativos, reológica e teste sensorial. A contagem de bolores e leveduras foi maior (p<0,05) no bagaço (3,5x102 UFC.g-1) que nos doces (<102 UFC.g-1). Os teores de umidade e acidez foram menores (p<0,05) nos doces (Gomas: 34,75% e 0,48%; Pectina: 35,54% e 0,47%) que no bagaço (69,38% e 0,77%) (respectivamente). Já o teor de carboidratos e pH foram maiores (p<0,05) nos doces (Gomas: 50,39% e 3,56; Pectina: 48,05% e 3,53) que no bagaço (10,73% e 3,24) (respectivamente). As formulações apresentaram comportamento p...

Applied Clay Science

Abstract Halloysite and montmorillonite nanoclays have a wide range of industrial and medical app... more Abstract Halloysite and montmorillonite nanoclays have a wide range of industrial and medical applications, including food packaging. To ensure safe incorporation of these clays into nanocomposites, toxicological screening must be performed. In this study, the acute toxicity of three nanoclays, namely halloysite, bentonite and montmorillonite modified with octadecylamine (Mt-ODA), was evaluated using the free-living nematode Caenorhabditis elegans as in vivo model. Nanoclays were tested pure and adsorbed with nisin, an important antimicrobial peptide used as food preservative. Lethal concentration 50% (LC50), nematode development, reactive oxygen species (ROS) production, quantification of catalase (CAT) and superoxide dismutase (SOD) enzymes, and lipid peroxidation were the toxicological endpoints evaluated in C elegans. Halloysite and Mt-ODA had the lowest and highest LD50, respectively. The adsoption of nisin on halloysite and bentonite provoked an increase in surviving nematodes. All treatments altered the normal growth, in different degrees, being nematodes exposed to bentonite the most affected. ROS production increased in all treatments, especially Mt-ODA, where lipid peroxidation was enhanced, suggesting high oxidative stress.

Green Polymer Composites Technology, 2016

Ciência e Agrotecnologia, 2016

Yacon root is a functional food which contains antioxidants and prebiotics compounds. This study ... more Yacon root is a functional food which contains antioxidants and prebiotics compounds. This study aimed to evaluate the physical, chemical and prebiotic characteristics of a yacon extract powder obtained by ultrafiltration (UF) with membranes of 10 and 30 kDa and encapsulation of the resulting permeate by spray drying. Drying air temperatures of 140 and 160 ºC and concentrations of gum arabic of 10 and 15% were tested. The samples had solubility values greater than 90% while the hygroscopicity decreased with increasing gum concentration and drying temperature. Electron microscopy showed a strong tendency to agglomeration of smaller particles around the larger ones, mainly at a temperature of 140 ºC. Regarding color, the parameter L* showed that drying at 160 ºC produced darker samples and the parameters a* and b* indicated that all samples were greenish yellow. The concentration of inulin decreased during drying, whereas the levels of glucose and fructose increased due to the thermol...

LWT - Food Science and Technology, 2016

Journal of Applied Polymer Science, 2015

Food Chemistry, 2015

Three different nanoclays (bentonite, octadecylamine-modified montmorillonite and halloysite) wer... more Three different nanoclays (bentonite, octadecylamine-modified montmorillonite and halloysite) were studied as potential carriers for the antimicrobial peptides nisin and pediocin. Adsorption occurred from peptide solutions in contact with nanoclays at room temperature. Higher adsorption of nisin and pediocin was obtained on bentonite. The antimicrobial activity of the resultant bacteriocin-nanoclay systems was analyzed using skimmed milk agar as food simulant and the largest inhibition zones were observed against Gram-positive bacteria for halloysite samples. Bacteriocins were intercalated into the interlayer space of montmorillonites as deduced from the increase of the basal spacing measured by X-ray diffraction (XRD) assay. Infrared spectroscopy suggested non-electrostatic interactions, such as hydrogen bonding between siloxane groups from clays and peptide molecules. Transmission electron microscopy did not show any alteration in morphologies after adsorption of antimicrobial peptides on bentonite and halloysite. These results indicate that nanoclays, especially halloysite, are suitable nanocarriers for nisin and pediocin adsorption.

Avanços e Desafios da Nutrição 3, 2019

The milking procedure are crucial to obtaining milk with good microbiological quality. The aim of... more The milking procedure are crucial to obtaining milk with good microbiological quality. The aim of this study was to evaluate the influence of hygienic milking on the quality of milk produced by three small farms of Bagé-RS. One sample was collected from each producer monthly. After three sample collections, a technical training was performed, showing to producers how conduct hygienic milking and a comparison was made with the results obtained from three sample collections after training. Samples of crude milk was submitted to mesophilic and psychrotrophic microrganisms counts and total and fecal coliforms evaluation. Also, physicochemical analyzes were performed in relation to alizarol, acidity, density and peroxidase. The results showed a reduction of bacterial counts and acidity, complying with the microbiological requirements of current legislation. PALAVRAS-CHAVE: leite, ordenha higiênica, qualidade físico-química, qualidade microbiológica. KEY-WORDS: milk, hygienic milking, phy...

New biotechnology, Jan 25, 2014

The antioxidant and antihypertensive activities of feather hydrolysates obtained with the bacteri... more The antioxidant and antihypertensive activities of feather hydrolysates obtained with the bacterium Chryseobacterium sp. kr6 were investigated. Keratin hydrolysates were produced with different concentrations of thermally denatured feathers (10-75 g l(-1)) and initial pH values (6.0-9.0). Soluble proteins accumulated in high amounts in media with 50 and 75 g l(-1) of feathers, reaching values of 18.5 and 22 mg ml(-1), respectively, after 48 hours of cultivation. In media with 50 g l(-1) of feathers, initial pH had minimal effect after 48 hours. Maximal protease production was observed after 24 hours of cultivation, and feather concentration and initial pH values showed no significant effect on enzyme yields at this time. Feather hydrolysates displayed in vitro antioxidant properties, and optimal antioxidant activities were observed in cultures with 50 g l(-1) feathers, at initial pH 8.0, after 48 hours growth at 30°C. Also, feather hydrolysates were demonstrated to inhibit the angio...

Yacon root is a functional food which contains antioxidants and prebiotics compounds. This study ... more Yacon root is a functional food which contains antioxidants and prebiotics compounds. This study aimed to evaluate the physical, chemical and prebiotic characteristics of a yacon extract powder obtained by ultrafiltration (UF) with membranes of 10 and 30 kDa and encapsulation of the resulting permeate by spray drying. Drying air temperatures of 140 and 160 oC and concentrations of gum arabic of 10 and 15% were tested. The samples had solubility values ​​greater than 90% while the hygroscopicity decreased with increasing gum concentration and drying temperature. Electron microscopy showed a strong tendency to agglomeration of smaller particles around the larger ones, mainly at a temperature of 140 oC. Regarding color, the parameter L* showed that drying at 160 oC produced darker samples and the parameters a* and b* indicated that all samples were greenish yellow. The concentration of inulin decreased during drying, whereas the levels of glucose and fructose increased due to the therm...

This work reports on the preparation, characterization and antibacterial activity of a nanocompos... more This work reports on the preparation, characterization and antibacterial activity of a nanocomposite formed from graphene oxide (GO) sheets decorated with silver nanoparticles (GO-Ag). The GO-Ag nanocomposite was prepared in the presence of AgNO3 and sodium citrate. The physicochemical characterization was performed by UV-vis spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), Raman spectroscopy and transmission electron microscopy (TEM). The average size of the silver nanoparticles anchored on the GO surface was 7.5 nm. Oxidation debris fragments (a byproduct adsorbed on the GO surface) were found to be crucial for the nucleation and growth of the silver nanoparticles. The antibacterial activity of the GO and GO-Ag nanocomposite against the microorganism Pseudomonas aeruginosa was investigated using the standard counting plate methodology. The GO dispersion showed no antibacterial activity against P. aeruginosa over the concentration range investigated. On the ...

Water soluble extracts (WSE) of ewe's cheeses produced in Uruguay and Brazil were evaluated f... more Water soluble extracts (WSE) of ewe's cheeses produced in Uruguay and Brazil were evaluated for their biological activities. Feta-type, Roquefort-type and Pecorino-type cheeses from Brazil, Pecorino Sardo-type and Cerrillano cheese samples from Uruguay, were analyzed. Antioxidant properties were evaluated using distinct methods. Scavenging of the cation radical of 2,2′-azino-bis-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS) ranged from 32 to 45% for Feta-type cheeses to 87% for Roquefort-type cheese. A similar trend was observed for the reducing power, where WSE from Roquefort-type cheese showed the highest activity among the evaluated cheese. Iron chelating activity was quite variable among the different WSE, being higher (50%) for a Pecorino-type cheese. Thiobarbituric acid reactive substance (TBARS) analysis presented similarity among most of the cheese samples, with inhibition values ranging from 25 to 51%. Scavenging of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical was obs...

Revista Thema

O objetivo deste trabalho foi analisar o conhecimento dos alunos do Instituto Federal Sul-rio-gra... more O objetivo deste trabalho foi analisar o conhecimento dos alunos do Instituto Federal Sul-rio-grandense (IFSul) Câmpus Bagé a respeito das informações contidas nos rótulos dos alimentos e na informação nutricional através da aplicação de um questionário. A informação mais procurada pelos 79 alunos entrevistados nos rótulos de alimentos foi a marca comercial do produto. Já 32,9% não tem o hábito de olhar a informação nutricional, apesar de afirmarem compreendê-la. A observação da presença de glúten ou lactose foi realizada apenas por pessoas consideradas intolerantes ou alérgicas. Sobre alimentos light e diet e aditivos alimentares, a maioria dos entrevistados afirma saber a diferença entre light e diet e desconhecer o que são aditivos alimentares. Em relação às melhorias para os rótulos de alimentos, 21,5% dos entrevistados não souberam opinar e 13% consideraram as informações já contidas no rótulo, suficientes. Apesar de os alunos entrevistados afirmarem ter conhecimento em relação...

Research, Society and Development

A vitivinicultura destaca-se na economia mundial por ser uma das indústrias de bebidas alcoólicas... more A vitivinicultura destaca-se na economia mundial por ser uma das indústrias de bebidas alcoólicas em maior expansão no mundo, estando em pleno crescimento no Brasil. Esse avanço também representa um aumento nos resíduos, visto que cerca de 30% do volume de uvas vinificadas gera bagaço. Além disso, se mal destinado, esse descarte pode se tornar um problema ambiental e econômico. O objetivo deste trabalho foi discutir a situação atual da vitivinicultura no Brasil, com enfoque em seus resíduos e nas medidas que estão sendo tomadas para aproveitamento desses como coproduto, alternativas de uso e indicações de opções para o futuro das indústrias do setor. O bagaço possui muitos nutrientes que permanecem após o processamento do fruto tais como fibras, minerais e compostos bioativos. Devido a isso, várias alternativas estão sendo propostas para aproveitar esse resíduo, desde uso em fertilizantes, em compostagem ou na alimentação animal, até como matéria prima no desenvolvimento de produtos...

Research, Society and Development

O objetivo deste estudo foi desenvolver e caracterizar doce cremoso a partir do bagaço de uvas Vi... more O objetivo deste estudo foi desenvolver e caracterizar doce cremoso a partir do bagaço de uvas Vitis vinifera vinificadas. O bagaço foi selecionado e caracterizado por análises físico-químicas, microbiológicas e de compostos bioativos. Após processamento, foram formulados dois doces cremosos, um com pectina industrial (Pectina) e outro com gomas ágar-ágar e carragena (Gomas). Os doces foram caracterizados por análises físico-químicas, microbiológicas, de compostos bioativos, reológica e teste sensorial. A contagem de bolores e leveduras foi maior (p<0,05) no bagaço (3,5x102 UFC.g-1) que nos doces (<102 UFC.g-1). Os teores de umidade e acidez foram menores (p<0,05) nos doces (Gomas: 34,75% e 0,48%; Pectina: 35,54% e 0,47%) que no bagaço (69,38% e 0,77%) (respectivamente). Já o teor de carboidratos e pH foram maiores (p<0,05) nos doces (Gomas: 50,39% e 3,56; Pectina: 48,05% e 3,53) que no bagaço (10,73% e 3,24) (respectivamente). As formulações apresentaram comportamento p...

Applied Clay Science

Abstract Halloysite and montmorillonite nanoclays have a wide range of industrial and medical app... more Abstract Halloysite and montmorillonite nanoclays have a wide range of industrial and medical applications, including food packaging. To ensure safe incorporation of these clays into nanocomposites, toxicological screening must be performed. In this study, the acute toxicity of three nanoclays, namely halloysite, bentonite and montmorillonite modified with octadecylamine (Mt-ODA), was evaluated using the free-living nematode Caenorhabditis elegans as in vivo model. Nanoclays were tested pure and adsorbed with nisin, an important antimicrobial peptide used as food preservative. Lethal concentration 50% (LC50), nematode development, reactive oxygen species (ROS) production, quantification of catalase (CAT) and superoxide dismutase (SOD) enzymes, and lipid peroxidation were the toxicological endpoints evaluated in C elegans. Halloysite and Mt-ODA had the lowest and highest LD50, respectively. The adsoption of nisin on halloysite and bentonite provoked an increase in surviving nematodes. All treatments altered the normal growth, in different degrees, being nematodes exposed to bentonite the most affected. ROS production increased in all treatments, especially Mt-ODA, where lipid peroxidation was enhanced, suggesting high oxidative stress.

Green Polymer Composites Technology, 2016

Ciência e Agrotecnologia, 2016

Yacon root is a functional food which contains antioxidants and prebiotics compounds. This study ... more Yacon root is a functional food which contains antioxidants and prebiotics compounds. This study aimed to evaluate the physical, chemical and prebiotic characteristics of a yacon extract powder obtained by ultrafiltration (UF) with membranes of 10 and 30 kDa and encapsulation of the resulting permeate by spray drying. Drying air temperatures of 140 and 160 ºC and concentrations of gum arabic of 10 and 15% were tested. The samples had solubility values greater than 90% while the hygroscopicity decreased with increasing gum concentration and drying temperature. Electron microscopy showed a strong tendency to agglomeration of smaller particles around the larger ones, mainly at a temperature of 140 ºC. Regarding color, the parameter L* showed that drying at 160 ºC produced darker samples and the parameters a* and b* indicated that all samples were greenish yellow. The concentration of inulin decreased during drying, whereas the levels of glucose and fructose increased due to the thermol...

LWT - Food Science and Technology, 2016

Journal of Applied Polymer Science, 2015

Food Chemistry, 2015

Three different nanoclays (bentonite, octadecylamine-modified montmorillonite and halloysite) wer... more Three different nanoclays (bentonite, octadecylamine-modified montmorillonite and halloysite) were studied as potential carriers for the antimicrobial peptides nisin and pediocin. Adsorption occurred from peptide solutions in contact with nanoclays at room temperature. Higher adsorption of nisin and pediocin was obtained on bentonite. The antimicrobial activity of the resultant bacteriocin-nanoclay systems was analyzed using skimmed milk agar as food simulant and the largest inhibition zones were observed against Gram-positive bacteria for halloysite samples. Bacteriocins were intercalated into the interlayer space of montmorillonites as deduced from the increase of the basal spacing measured by X-ray diffraction (XRD) assay. Infrared spectroscopy suggested non-electrostatic interactions, such as hydrogen bonding between siloxane groups from clays and peptide molecules. Transmission electron microscopy did not show any alteration in morphologies after adsorption of antimicrobial peptides on bentonite and halloysite. These results indicate that nanoclays, especially halloysite, are suitable nanocarriers for nisin and pediocin adsorption.