Food Chemistry 52 (1995) 63-69 Copyright 0 1994 Elsevier Science Limited -2&s& ELSEVIER Printed in Great Britain. All rights reserved 0308-8146/95/~9.50 Physical and chemical changes in different zones of normal and PSE dry cured ham during processing Jacint Amau, Luis Guerrero, Gloria Casademont & Pere Gou Centre de Tecnologia de la Carn, Institut de Recerca i Tecnologia Agroalimentciries (IRTA), Granja Camps i Armet, 17121 Monells (Girona), Spain (Received 13 December 1993; revised version received and accepted 25 March 1994) Dry cured ham is a nonhomogeneous product that undergoes a salting and dehvdration orocess that determines the dynamics of the migration of the water, NaCl, nitrate’ and nitrite. INTRODUCTION The main hurdles for microbiological stability of dry cured ham are pH, temperature and water activity (Leistner, 1985). Tarr (1941) offered the first proof that nitrite was the agent responsible for the cured flavour and also that it had an antimicrobial function. A pH below 6.0 at 24 h post mortem is one of the re- quirements for optimal curing of hams. The pH does not further diminish during the process, and remains around 6.0 in Spanish ham (Flores et al., 1985; Carrascosa et al., 1988), Parma ham (Raczynski et al., 1978; Bellatti et al., 1983) and country style ham (Melo et al., 1974). There- fore, it is not an important parameter in the monitor- ing of microbial growth during the aging process. Meat of a pale, soft and exudative nature (PSE) is a serious problem in the meat industry. The weight losses of Parma hams classified as PSE were 4% higher than in normal hams and no difference was found in NaCl concentration (Maggi & Oddi, 1988). Increased weight loss and a small increase in salt absorption were ob- served in cured PSE country style hams (Kemp et al., 1974). There are very few studies on the effect of PSE on the physicochemical characteristics of dry cured ham, using Spanish technology (Arnau, 1991). The aim of the present study is to analyse the changes of moisture, pH, NaCl, nitrate and nitrite in different zones of normal and PSE hams during the dry curing procedure. A decrease in water activity is the main factor responsible for the preservation of the product. This is achieved essentially by the penetration of salt and removal of water from the meat. Several studies have been carried out on NaCl distribution during the pro- cess (Frbystein et al., 1989; Palmia et al., 1992) and on changes in physical and chemical characteristics during the process (Baldini et al., 1977; Flores et al., 1985), but none of them have included anatomical dissection. MATERIAL AND METHODS Ham selection Fifteen normal and 15 PSE gilt hams weighing between 9 and 10 kg were selected according to their electrical conductivity and pH. Potassium nitrate is used for meat curing, but must be reduced to nitrite in order to give the meat the char- acteristic colour of cured meat products. Huerta (1986) studied the evolution of nitrate and nitrite at three lev- els in the central part of the ham during the process. Measurements of electrical conductivity were taken with a Quality meter (Tecpro) at 24 h post mortem. The pH was measured at 45 min (pH,,) and 24 h post mortem (pH& using a portable pH meter (Crison). Both pH and conductivity were measured in the Semimembranosus muscle. Hams with a pHd5 c 6.0 and The changes of moisture, pH, NaCl, nitrate and nitrite in different zones of the ham during the process were evaluated in 15 normal and 15 PSE hams. No diff- erence in pH was found between PSE and normal hams. When all the sampling times were analysed together, the PSE hams were found to contain more moisture and NaCl than normal hams in certain muscles. In most zones, pH increased during the process. The external zones showed a higher salt concentration at the beginning, but this trend reversed during aging owing to salt penetration from the drier external zones to the more humid inner zones. The total NaCl in the lean tissue of the hams increased after salting and remained constant after the resting phase. Nitrate diminished quickly during the resting period, especially in the external zones, whereas nitrite increased after the salting period and did not exceed 10 ppm at the end of the process. 63