HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Interpretive Summary __Erratum__ An erratum has been published Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Di Luccia, A. Articles by Addeo, F. Search for Related Content PubMed Articles by Di Luccia, A. Articles by Addeo, F.

Occurrence of β-casein fragments in cold-stored and curdled river buffalo (Bubalus bubalis L.) milk

A. Di Luccia^*,1, G. Picariello, A. Trani^*, G. Alviti^*, P. Loizzo^*, M. Faccia^* and F. Addeo^,

^* Dipartimento Progettazione e Gestione dei Sistemi Agro-Zootecnici e Forestali (PROGESA), Università di Bari, Via G. Amendola 165/A, 70126 Bari, Italy
Istituto di Scienze dell’Alimentazione (ISA) – Consiglio Nazionale delle Ricerche (CNR), Via Roma 52A/C, 83100 Avellino, Italy
Dipartimento di Scienza degli Alimenti, University of Naples "Federico II," Parco Gussone, Portici 80055, Italy

¹ Corresponding author: a.diluccia{at}agr.uniba.it

The safeguard of river buffalo Mozzarella cheese, a Protected Designation of Origin dairy product, has prompted an analytical study to trace the milk and curd used as raw material in cheesemaking. This is to prevent the illegal use of milk or curd from different geographical areas outside of those indicated in the official production protocol. For this purpose, we studied primary proteolysis occurring in fresh and frozen milk and curd to identify a molecular marker that could indicate the raw material used. Whole casein from frozen river buffalo milk was separated using cation-exchange chromatography and sodium dodecyl sulfate-PAGE, and a protein component with an estimated molecular weight of 15.3 kDa was detected. This protein component was revealed in fresh river buffalo milk as a faint electrophoresis band, which drastically increased in intensity in refrigerated and frozen milk as well as in curd and was found to be associated with β-CN through hydrophobic interaction. By using matrix-assisted laser desorption/ionization-time of flight peptide mass mapping, this component was identified as the C-terminal fragment f(69–209) of β-CN (expected molecular weight of 15,748.8 Da). β-Casein f(69–209), originating from the early hydrolysis of Lys₆₈-Ser₆₉ by plasmin, has no counterpart in bovine milk. The increased rate of hydrolysis by plasmin toward the cleavage site Lys₆₈-Ser₆₉ has to be ascribed to the elevated proline content of the peptide 61–73. The favored production of β-CN f(69–209) has also drawn attention to the complementary proteose peptone β-CN f(1–68) that is presumed to play a physiological role in inducing milk secretion similar to that of β-CN f(1–29). The higher in vivo and in vitro production rate, compared with ₁-CN formation, indicates that β-CN f(69–209) and its complementary fragment are candidate molecular markers to evaluate milk and curd freshness. We used indirect ELISA analysis based on the determination of remaining nonhydrolyzed β-CN to perform a quantitative evaluation of proteolysis.

Key Words: -casein • river buffalo milk • frozen milk • curd