International Dairy Journal 15 (2005) 663–668 Migration of water-soluble nitrogenous compounds of Feta cheese from the cheese blocks into the brine A.-M. Michaelidou, E. Alichanidis, A. Polychroniadou à , G. Zerfiridis Laboratory of Dairy Technology, School of Agriculture, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece Received 15 April 2004; accepted 1 September 2004 Abstract Themigrationofwater-solublenitrogenouscompoundsofFetacheesefromthecheeseintobrinewasmonitoredovera5-month period, and the nature of the compounds diffusing into the brine was investigated. Reversed-phase high-performance liquid chromatography analysis of the water extract of Feta cheese and of the brine showed that both contained serum proteins and variouspeptides;thechromatographicprofileschangedwiththeageofthecheese.Also,differencesbetweenchromatogramsofthe waterextractofthecheeseandthebrineatthesameagewereobserved.Itseemslikelythattheparametersdrivingthesolubilityof peptidesin120gL 1 trichloroaceticacid(sizeandhydrophobicity)alsodeterminetheirpotentialfordiffusionintothebrine.Amino acids also migrate into the brine, with the hydrophobicity and shape of the side chain governing their diffusing ability. r 2005 Elsevier Ltd. All rights reserved. Keywords: Feta cheese; Brine; Serum proteins; Peptides; Amino acids 1. Introduction Fetaisasoft,whitecheesethatismaturedandstored inbrineuntilitsconsumption.ThewatercontentinFeta cheeseis550–560gkg 1 ,andthecheesetobrineratiois about 7–8:1. Proteolysis in Feta cheese is more intense during the first15days,whenthecheeseiskeptatarelativelyhigh temperature (about 16 1C). All soluble nitrogenous fractionsshowanimportantincreaseduringthisperiod. When the cheese is transferred into a refrigerator, the rate of casein and peptide degradation decreases (Michaelidou-Koniordou, 1997). The breakdown of a s1 -casein starts early; 40–50% is hydrolysed in 15–20 days and important amounts of small peptides and free amino acids are produced during this period. The hydrolysis of b-casein starts later and is less pro- nounced. Most of the identified peptides originate from the N-terminal region of a s1 -casein. The main proteoly- tic agent is rennet, followed by the proteases and peptidases of the starter culture and the non-starter lactic acid bacteria (Polychroniadou, 2004). During ripening and storage, some nitrogenous compounds migrate from the cheese blocks to the brine of the container. Polychroniadou, Michaelidou, and Paschaloudis (1999) showed that the extraction of water-soluble nitrogenous compounds from Feta cheese was significantly (Po0:05) affected by the cheese to waterratiobutnotbytheNaClcontent,becauseofthe lowpHofthecheese(4.6). The objective of this study was to monitor the migration of the nitrogenous compounds from blocks of Feta cheese into the surrounding brine over a 5- month period and to investigate the nature of the compounds diffusing into the brine. 2. Materials and methods 2.1. Samples Batches of commercial Feta cheese were prepared fromovinemilkinthreedifferentcheeseplantsusingthe ARTICLE IN PRESS www.elsevier.com/locate/idairyj 0958-6946/$-see front matter r 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.idairyj.2004.09.013 à Corresponding author. Fax: +302310998789. E-mail address: annapoly@agro.auth.gr (A. Polychroniadou).