Desenvolvimento de metodologia analítica para determinação da concentração real de ácido lático em leite por cromatografia líquida de alto eficiência exclusão de íons

• Ano de defesa: 2008
• Autor(a) principal: Milagres, Maria Patrícia
• Orientador(a): Brandão, Sebastião César Cardoso
• Banca de defesa: Zacca, Jorge Jardim , Minim, Luis Antonio
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Mestrado em Ciência e Tecnologia de Alimentos
• Departamento: Ciência de Alimentos; Tecnologia de Alimentos; Engenharia de Alimentos
• País: BR
• Palavras-chave em Português: Fermentação; Ácido lático; Neutralizantes
• Palavras-chave em Inglês: Fermentation; Lactic Acid; Neutralization
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::CIENCIA E TECNOLOGIA DE ALIMENTOS::TECNOLOGIA DE ALIMENTOS
• Link de acesso: http://locus.ufv.br/handle/123456789/2838

According to Brazilian Federal Legislation, titratable acidity has been used as official method to determine acidity in milk quality analysis. The illegal neutralization of milk acidity by addition of products as NaOH can to mask the result of the titratable acidity analysis. Consequently milk of poor quality can be acceptable. The aim of this work was the development of a method to determine the real concentration of lactic acid in milk that can t be swindled by milk neutralizers. It was developed a laboratorial analysis method by High Performance Liquid Chromatography with ions exclusion HPLC-IE to determine the real concentration of lactic acid in milk. The chromatographic analysis were performed using an Aminex HPX-87 column, mobile phase of phosphoric acid 0,02 mol/L, pH 2,3, flow 0,5 mL x min-1, at 65º C, detection with UV at 210 nm. The acid lactic resolution was complete with relation to all the others components present in samples chromatograms. The retention time of the lactic acid was 14,2 minutes. Raw milk taken immediately after milking was incubated at 36º C up to 0,16, 0,17, 0,18, 0,19, 0,20% (w/v) titratable acidity, express in lactic acid. After reach acidity ones, the samples were prepared to determine the real concentration of lactic acid by HPLC. Fermented milks up to 0,16, 0,17, 0,18, 0,19, 0,20% (w/v) titratable acidity, was neutralized with NaOH 10 mol/L up to 0,15% (w/v) . After neutralization, the samples were prepared and injected to determine of real concentration of lactic acid by HPLC. Add to this, the method was tested for determination of citrate in milk. The analyses to determination of lactic acid by HPLC in fermented milk showed that there was significant increase of lactic acid concentration as increased as titratable acidity. The linear regression analyses to compare the acidity determined by titratable acidity and HPLC methods scored 0,9929% correlation. Titratable acidity of 0,18% lactic acid in milk, maximum limit allowed in Brazil, corresponded to 8 mM/L concentration of real lactic acid. Therefore these result suggest to 8 mM/L of lactic acid must be the maximum concentration of real lactic acid in raw, pasteurized, UHT and reconstituted milk. The addition of acidity neutralizers do not prevented the determination of real concentration of lactic acid by HPLC method developed in this work. Therefore the neutralization does not mask the product quality analyzed in this method.