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Determination of the casein content in bovine milk by 31P-NMR

Published online by Cambridge University Press:  02 October 2002

JOSEFINA BELLOQUE
Affiliation:
Instituto de Fermentaciones Industriales (C.S.I.C.), Juan De La Cierva 3, 28006 Madrid, Spain
MERCEDES RAMOS
Affiliation:
Instituto de Fermentaciones Industriales (C.S.I.C.), Juan De La Cierva 3, 28006 Madrid, Spain

Abstract

The relative proportion of caseins to total protein is a parameter that can be used to control the protein quality in standardised milk, an increasing tendency in dairy industries. 31P-NMR was used to analyse the casein content of milk, by the quantitation of the area under the resonances belonging to SerP, and using methylenediphosphonic acid as internal standard. This procedure yielded good results, as similar values of caseins were obtained from N Kjeldahl and NMR analysis for slightly heated milk samples. Heating at 95 °C for 15 min did not alter the casein content results. Casein content of raw, pasteurised and UHT milks (25·6±1·4, 26·4±1·8, 25·5±1·6 g casein/l milk, respectively), obtained by NMR, were not significantly different, giving an average of 25·8±1·6 g casein/l for bulk liquid milk. This work concluded that 31P-NMR could be used as an alternative method to determine casein in raw, pasteurised, dry and UHT milks.

Type
Original article
Copyright
Proprietors of Journal of Dairy Research 2002

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