Navegando por Autor "Carvalho, Antônio F. de"

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Effect of cleaning treatment on adhesion of Streptococcus agalactiae to milking machine surfaces
(Food and Bioprocess Technology, 2011-08-10) Pires, Ana Clarissa S.; Santos, Adbeel L.; Behaine, José Jorge S.; Araújo, Emiliane A.; Andrade, Nélio J. de; Carvalho, Antônio F. de
Streptococcus agalactiae is a common subclinical mastitis agent in dairy cattle. In this study, the influence of hygiene procedure time on the adhesion of S. agalactiae to rubber and silicone surfaces used in milking machines was evaluated. The effect of hygiene practices on the thermodynamic and microscopic features of both surfaces was also evaluated. The hydrophobicity of milking machines and bacterial surfaces was investigated by measuring the contact angle with a goniometer 0, 30, 90, and 180 days after a full hygiene procedure simulated using rubber and silicone coupons. As the time of cleaning procedures enhanced, there was a reduction in the adhesion of S. agalactiae to both surfaces. The rubber and silicone surfaces were hydrophobic in all treatments (ΔGTOTsws<0), while the bacterial surface presented hydrophilic behavior (ΔGTOTsws>0), which makes the adhesion process difficult. Photomicrographs showed rapid wear of both surfaces, pointing to damages caused by cleaning agents. However, the silicone was more resistant to cleaning and sanitizing treatments. Thus, this work shows that changes caused by hygiene procedures in the thermodynamic and in the morphology of milking surfaces have an enormous importance in the S. agalactiae adhesion and, consequently, in mastitis transmission between cattle herd.
Estudo da viscosidade de soluções proteicas através do analisador rápido de viscosidade (rva)
(Revista Instituto de Laticínios Cândido Tostes, 2014-02-14) Alves, Maura P.; Perrone, Ítalo T.; Souza, Alisson Borges de; Stephani, Rodrigo; Pinto, Cláudia Lúcia de Oliveira; Carvalho, Antônio F. de
Este trabalho objetivou determinar pelo analisador rápido de viscosidade (RVA) as curvas de viscosidade de soluções preparadas a partir de concentrados proteicos de soro (CPSs) e determinar o tempo ideal de tratamento térmico visando à obtenção da viscosidade máxima nesta etapa. Os CPSs, produzidos a partir de amostras de soro submetidas inicialmente a tratamentos térmicos e de microfiltração, apresentaram composição centesimal compatível com padrões internacionais com diferença significativa (p<0,05) entre as amostras apenas para o teor de gordura. Pela análise dos perfis viscográficos observou-se que os CPSs produzidos a partir de soro microfiltrado apresentaram valores de viscosidade mais altos que aqueles submetidos ao tratamento térmico para todos os dados coletados. Além disso, o tempo ideal de tratamento térmico das soluções de CPSs visando maximizar a viscosidade durante o aquecimento foi de, aproximadamente, 10 minutos. Os resultados possibilitam a aplicação dos CPSs pelas indústrias alimentícias considerando a característica desejada no produto final, sendo que o RVA mostrou-se uma ferramenta apropriada para estudo de funcionalidade desses concentrados.
Stability of casein micelles cross-linked with genipin: A physicochemical study as a function of pH
(International Dairy Journal, 2017-05) Casanova, Federico; Silva, Naaman F. Nogueira; Gaucheron, Frédéric; Nogueira, Márcio H.; Teixeira, Alvaro V. N. C.; Perrone, Italo Tuler; Alves, Maura Pinhero; Fidelis, Priscila Cardoso; Carvalho, Antônio F. de
Chemical or enzymatic cross-linking of casein micelles (CMs) increases their stability against dissociating agents. In this paper, a comparative study of stability between native CMs and CMs cross-linked with genipin (CMs-GP) as a function of pH is described. Stability to temperature and ethanol were investigated in the pH range 2.0e7.0. The size and the charge ( z -potential) of the particles were determined by dynamic light scattering. Native CMs precipitated below pH 5.5; CMs-GP precipitated from pH 3.5 to 4.5, whereas no precipitation was observed at pH 2.0e3.0 or pH 4.5e7.0. The isoelectric point of CMs-GP was determined to be pH 3.7. Highest stability against heat and ethanol was observed for CMs-GP at pH 2, where visible coagulation was determined only after 800 s at 140 C or 87.5% (v/v) of ethanol. These results confirmed the hypothesis that cross-linking by GP increased the stability of CMs.