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Volume 84, Number 3, May-June 2004
Page(s) 285 - 296
Lait 84 (2004) 285-296
DOI: 10.1051/lait:2004006

Casein fraction of ovine milk from indigenous Greek breeds

Golfo Moatsoua, Maria Samoladab, Alexandra Katsabekia and Emmanuel Anifantakisa

a  Laboratory of Dairy Technology, Department of Food Science and Technology, Agricultural University of Athens, Iera Odos 75, 118 55 Athens, Greece
b  Laboratory of Dairy Technology, Department of Agricultural Science, Aristotle University of Thessaloniki, 54006 Thessaloniki, Greece

(Received 22 July 2003 - Accepted 21 November 2003 - Published online 26 March 2004)

Abstract - Whole casein fractions isoelectrically prepared from bulk milks from four different indigenous Greek ovine breeds were analysed by urea-PAGE and reversed-phase HPLC. Individual caseins prepared by fractionation on a cation-exchange column were used to locate the peaks on the chromatograms. Apart from heterogeneity that was depicted in the peak shape of caseins, there was also quantitative variability regarding the $\alpha$s- and $\beta$-casein contents. According to the RP-HPLC results, the relative percentages of individual caseins ranged as follows: $\kappa$-casein from 9.1% to 10.8%, $\alpha$s2-casein from 12.0% to 16.4%, $\alpha$s1-casein from 33.9% to 39.9% and $\beta$-casein from 37.0% to 42.3%. According to the results obtained by both methods, the composition of the casein fraction from the Karagouniko breed was the most different, since it had the greatest $\beta$-casein content and the lowest $\alpha$s-casein to $\beta$-casein ratio. The relative percentages of the individual caseins in two of the four breeds (Frisarta and Chios) were similar. The quantification results of urea-PAGE and RP-HPLC analyses were in general similar with respect to the means. However, the relative standard deviations of the chromatographic method were better and this was also true for the resolution of the components of the whole casein fraction.

Résumé - Fractions caséiques des laits de mélange provenant de troupeaux de brebis indigènes grecques. Les fractions caséiques des laits de mélange de quatre troupeaux de brebis indigènes grecques ont été analysées par électrophorèse en gel de polyacrylamide à pH alcalin en présence d'urée (urée-PAGE) et par chromatographie liquide haute performance en phase inversée (RP-HPLC). L'identification des caséines a été effectuée par l'analyse des caséines individuelles préparées par chromatographie d'échange de cations. Les résultats des analyses par RP-HPLC ont démontré que le contenu en caséines principales variait dans les proportions suivantes: caséine $\kappa$, de 9,1 à 10,8 %, caséine $\alpha$s2, de 12,0 à 16,4 %, caséine $\alpha$s1, de 33,9 à 39,9 % et caséine $\beta$, de 37,0 à 42,3 %. Les résultats obtenus par les deux méthodes ont démontré que la fraction caséique du troupeau Karagouniko était la plus différente parmi les laits analysés ; elle a présent la plus haute teneur en caséine $\beta$ et le plus faible rapport caséine $\alpha$s1 sur caséine $\beta$. Les pourcentages relatifs des caséines individuelles de deux des quatre troupeaux étudiés étaient en général similaires. La résolution et les écarts types relatifs estimés par la chromatographie, étaient meilleurs que ceux estimés par urée-PAGE.

Key words: Ovine casein / indigenous ovine breeds / chromatography / RP-HPLC / electrophoresis

Mots clés : Caséine de brebis / troupeaux de brebis indigènes / chromatographie / électrophorèse

Corresponding author: Golfo Moatsou

© INRA, EDP Sciences 2004

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