Abstract
This study evaluated the performance of strips for colorimetric detection of alkaline phosphatase and peroxidase in milk, comparing them with a kit of reagents for alkaline phosphatase and the official methodology for peroxidase. The samples were analyzed at the Laboratory Inspection of Products of Animal Origin, State University of Londrina. For the comparison tests for the detection of alkaline phosphatase four treatments were made by adding different percentages of raw milk (1%, 2%, 5% and 10%) in the pasteurized milk, plus two control treatments. Thirty-eight samples triplicate for each treatment were analyzed. To compare the performance of tests for peroxidase 80 pasteurized milk samples were evaluated simultaneously by official methodology and by colorimetric strips. The performance of the alkaline phosphatase were different for the treatments with 1% and 2% of raw milk which had all the strips change color as the reagent kit showed the presence of phosphatase in just 2.63% and 5.26% the cases, respectively for each treatment. The colorimetric strips for alkaline phosphatase are more sensitive for the identification of small quantities compared to the reagent kit. The performance of tests for peroxidase showed no difference. The strips for the detection of peroxidase or alkaline phosphatase were effective and can replace traditional methods.
Highlights
A fosfatase alcalina (FA) e a peroxidase são enzimas naturalmente encontradas no leite cru e que, após a pasteurização, servem de indicadores para assegurar que o processo foi realizado adequadamente
Para avaliar a atividade da fosfatase alcalina no leite utilizaram-se quatro tratamentos adicionando-se diferentes porcentagens de leite cru (1%, 2%, 5% e 10%) ao leite pasteurizado
Tanto as leituras visuais do kit como a mensuração da absorbância mostraram que a sensibilidade do kit é menor do que a necessária para detectar as pequenas quantidades de fosfatase alcalina presentes no leite pasteurizado, ou seja, quando o mesmo possa se adicionado de pequenas quantidades de leite cru
Summary
Foram utilizadas amostras de leite pasteurizado integral de diferentes laticínios, destinadas ao consumo na região norte do Paraná. Todas as amostras analisadas apresentavam-se dentro do prazo de produção de 48 horas e foram encaminhadas acondicionadas em caixa de isopor com gelo industrial ao Laboratório de Inspeção de Produtos de Origem Animal (LIPOA) da Universidade Estadual de Londrina (UEL)
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