Determination of cow's milk and ripening time in nonbovine cheese by capillary electrophoresis of the ethanol-water protein fraction

José Manuel Herrero-Martinez, Ernesto F. Simó-Alfonso, Guillermo Ramis-Ramos, Cecilia Gelfi, Pier Giorgio Righetti

Research output: Contribution to journalArticle

Abstract

A novel method is reported for analyzing adulteration of goat and ewe cheeses with cow's milk: capillary zone electrophoresis (CZE) in isoelectric, acidic buffers (50 mM imino diacetic acid, IDA, pH = p/ 2.3). The cheese samples were extracted with a 20:80 v/v ethanol-water mixture in presence of 3 M urea and 1% β-mercaptoethanol for 1 h. After centrifugation and lipid extraction, the samples were dissolved in 50 mu IDA, 6 M urea and 0.5% hydroxyethyl cellulose and analyzed by CZE at 700 V/cm. A total of 18 characteristic peaks were resolved among the three types of cheeses and 18 variables were defined as their respective areas. There was excellent similarity among the electrophoretic patterns obtained with cheeses of a given type of milk, while cheeses made with different types of milk were easily distinguishable. Most peaks were common to all cheeses, but the profile differed depending on the type of milk used. Principal component analysis, linear discriminant analysis, and partial least squares regression (PLS) were used for statistical analysis of the data obtained by CZE. In particular, by using PLS multivariate regression, the contents of cow's milk in presumably pure goat and ewe cheeses, as well as in binary and ternary mixtures, could be predicted with relative standard deviations of ca. 6-7%. In addition, the ripening time in goat and ewe cheeses could also be predicted.

Original languageEnglish
Pages (from-to)633-640
Number of pages8
JournalElectrophoresis
Volume21
Issue number3
DOIs
Publication statusPublished - 2000

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Keywords

  • Capillary zone electrophoresis
  • Cheese
  • Isoelectric buffers
  • Proteins

ASJC Scopus subject areas

  • Clinical Biochemistry

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