Heat-induced deamidation, dephosphorylation and breakdown of caseinate

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Abstract

The kinetics of deamidation, dephosphorylation and protein breakdown in heated caseinate solutions were studied. The extent of deamidation corresponded to the level of the amide present in asparagine. The order with respect to concentration was 1, the order with respect to time could not be established unequivocally. The temperature dependence was in accordance with a mechanism in which a succinimide intermediate was formed. The extent of protein breakdown, measured as formation of non-protein nitrogen (NPN), was also characterized by an order of 1 with respect to concentration. The temperature dependence was in accordance with peptide bond hydrolysis (the order with respect to time could not be established unequivocally). Formation of inorganic phosphate and dehydroalanine was determined in heated -casein solutions. More phosphate than dehydroalanine was formed, and based on literature results for lysinoalanine formation from dehydroalanine, it was concluded that hydrolysis of phosphoserine occurred more extensively than -elimination of phosphoserine. The order with respect to time for dephosphorylation seemed to increase with temperature, possibly due to a different temperature sensitivity of hydrolysis and -elimination.
Original languageEnglish
Pages (from-to)237-241
JournalInternational Dairy Journal
Volume9
DOIs
Publication statusPublished - 1999

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