Contribution of muscle aminopeptidases to ¯avor development in dry-cured ham Fidel Toldra *, M-ConcepcioÂn Aristoy, MoÂnica Flores Instituto de AgroquõÂmica y TecnologõÂa de Alimentos (CSIC), Apt. 73, 46100 Burjassot, Valencia, Spain Abstract The activity of muscle aminopeptidases (alanyl, arginyl, leucyl and pyroglutamyl aminopeptidases) have been assayed along the processing of dry-cured ham. The generation of free amino acids resulting from aminopeptidase action on N-terminal of proteins and peptides has been also analyzed. The assayed aminopeptidases, except pyroglutamyl aminopeptidase, showed good stability. Alanyl and arginyl aminopeptidases have optimal neutral pH near the pH in ham and, in addition, their spectrum of activity against terminal amino acids is in coincidence with the observed release of free amino acids in ham. So, both aminopeptidases appear to be the main contributors to the generation of free amino acids during the processing of dry-cured ham. # 2000 Elsevier Science Ltd. All rights reserved. Keywords: Ham; Flavor; Aminopeptidases; Amino acids 1. Introduction Dry-cured hams constitute a typical food product from the Mediterranean area, some of the most impor- tant and well-known being Iberian, Serrano, Parma and Bayonne hams. The quality of dry-cured hams depends on many factors although the raw materials (Armero, Baselga, Aristoy & ToldraÂ, 1999) and the ripening/drying conditions (Toldra , 1998; Toldra , Flores & Sanz, 1997) are the most important. The gen- eration of the ®nal characteristic aroma of dry-cured ham is reached after several months of process as a result of previous enzymatic reactions such as proteo- lysis and lipolysis (Toldra & Flores, 1998). The volatile compounds found in the headspace of Spanish Serrano dry-cured ham, derived from oxidative decomposition of lipids, are aliphatic hydrocarbons, aliphatic alcohols and aldehydes, esters, ketones and furans (Flores, Grimm, Toldra & Spanier, 1997). However, there are other volatile compounds derived from the degradation or reaction of amino acids that also contribute to the aroma of dry-cured ham (Flores, Spanier & ToldraÂ, 1998). This is the case of methyl branched alcohols and aldehydes, sulphur compounds are important contributors to meat ¯avour because of their low ¯avour thresholds, pyrazines that contribute to roasted aromas and furans (Toldra & Flores). The objective of this study is to elucidate the role of muscle aminopeptidases in the generation of free amino acids and thus understand its contribution to the ¯avor of dry-cured ham 2. Materials and methods 2.1. Dry-cured hams Thirty hams from 6-month-old pigs (LandraceLarge White) were submitted to the dry-curing process which consisted of the traditional stages of salting (14 days), post-salting (40 days) and ripening-drying until the 12th month of ®nal processing time. Six hams were taken at each sampling time (0, 40, 100, 240 and 365 days). The muscle Biceps femoris was excised and used for the assay of aminopeptidases activity and analysis of free amino acids as described below. 2.2. Measurement of enzyme activity The enzyme crude extracts were prepared as described by Lauart and Mantle (1988) with slight modi®cations: 10 g of muscle Biceps femoris, with no visible fat or connective tissue, was homogenized in 50 ml of 50 mM phosphate buer containing 5 mM ethylene glycol 0963-9969/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S0963-9969(00)00032-6 Food Research International 33 (2000) 181±185 www.elsevier.com/locate/foodres * Corresponding author. Tel.: +34-96-390-0022; fax: +34-96-363- 6301. E-mail address: ftoldra@iata.csic.es (F. ToldraÂ).