Browsing by Author "Ferreira, Isabel M.P.L.V.O."
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- Casein breakdown in terrincho ovine cheese: comparison with bovine cheese and with bovine/ovine cheesesPublication . Ferreira, Isabel M.P.L.V.O.; Veiros, C.; Pinho, Olívia; Veloso, Ana C.A.; Peres, António M.; Mendonça, ÁlvaroTerrincho cheese is an uncooked, pressed cheese made from raw whole ovine milk from the “Churra da Terra Quente” breed. It requires a minimum ripening time of 30 d. A detailed evaluation of the effect of ripening time on the breakdown of the casein fractions, along with the formation of major breakdown products of casein hydrolysis, was monitored by HPLC to contribute to a more complete characterization of this product. In 30-d-old cheeses, only 20% of αS1-casein remained intact; the β-casein fraction was more resistant to hydrolysis. The ripening time of Terrincho cheese can be predicted using 2 variables of normalized peak areas of αS1-casein and αS1-I peptide, and a constant; the estimation error is 2.5 d. The pH 4.3-insoluble fraction of Terrincho and cheeses manufactured with bovine milk and with ovine milk combined with 2 levels of bovine milk (10 and 20%) revealed different chromatographic and electrophoretic profiles, especially the αS1-casein fraction. Similar proteolysis progress was observed, particularly in the percentage of casein fraction degradation. However, using both analytical methods, the detection of 10% bovine milk at 30 d of ripening was no longer possible as result of αS1-casein hydrolysis. The discriminate analysis applied to HPLC data indicated that at 30 d of ripening, differences between the casein fractions of Terrincho cheese and mixture cheeses were mainly from β1-casein content. The function thus obtained was able to correctly classify all the samples according to cheese type. Using the descriptive sensory profile, Terrincho cheese at 30 d of ripening could be distinguished from bovine and mixture cheeses owing to its higher fracturability and adhesiveness and lower elasticity and hardness, which correlated with its lower total casein content.
- Detecção de adulterações em produtos alimentares contendo leite e/ou proteínas lácteasPublication . Veloso, Ana C.A.; Teixeira, Natércia; Ferreira, Isabel M.P.L.V.O.; Ferreira, Margarida A.A critical review of the most relevant analytical methodologies for quality and authenticity control of dairy products and foods containing milk proteins is presented. Chromatographic, electrophoretic and immunological methods are used for: detection of cow's milk in ewe and goat milks, detection of whey added to milk, detection of caseins and/or whey proteins in non-lactic foods and study compounds resulting from milk proteins degradation. Techniques based on polimerase chain reaction are also suitable for detection of cow's milk on cheeses of ewe and goat milks.
- Evaluation of cheese authenticity and proteolysis by HPLC and urea-polyacrylamide gel electrophoresisPublication . Veloso, Ana C.A.; Peres, António M.; Mendonça, Álvaro; Teixeira, Natércia; Ferreira, Isabel M.P.L.V.O.Chromatographic and electrophoretic methods have been established as useful tools in characterising cheese ripening and in the detection of milk adulteration. The purpose of this work was to evaluate casein proteolysis of cheeses made from bovine, ovine or mixtures of bovine and ovine milks, as well as ovine cheese authenticity, for 30 days of ripening by HPLC and urea–polyacrylamide gel electrophoresis. Complementary information was obtained by both techniques when applied to the study of casein proteolysis during 30 days of ripening of ovine milk cheeses, ovine milk cheeses with 10% and 20% of bovine milk and bovine milk cheeses, manufactured according to the traditional Terrincho technology. For ovine cheeses, a-casein was the fraction that showed the higher degradation during cheese ripening. A similar behaviour was observed for ovine milk cheese with 10% of bovine milk. The profile for ovine milk cheese with 20% of bovine milk was more similar to that obtained for bovine cheese. Concerning bovine milk cheeses, electrophoresis was the most sensitive technique for the evaluation of proteolysis in these cheeses. Ten and 20% of bovine milk could be detected in ovine milk cheeses by urea–polyacrylamide gel electrophoresis and HPLC, respectively, even after 30 days of ripening.