Original article Influence of pre-cure freezing of Iberian hams on lipolytic changes and lipid oxidation Trinidad Pe ´rez-Palacios, 1 * Jorge Ruiz, 1 Rau ´ l Grau, 2 Mo ´ nica Flores 3 & Teresa Antequera 1 1 Tecnologia de los Alimentos, Facultad de Veterinaria, Universidad de Extremadura, Avda. Universidad s ⁄ n, 10071, Ca´ceres, Spain 2 Instituto de Ingenierı´a de Alimentos para el Desarrollo, Departamento de Tecnologı´a de Alimentos, Universidad Polite´cnica, Valencia, Spain 3 Institituto de Agroquı´mica y Tecnologia de Alimentos (IATA, CSIC), Burjassot, Valencia, Spain (Received 23 March 2009; Accepted in revised form 14 August 2009) Summary The purpose of this work was to study the influence of pre-cure freezing of Iberian hams on lipolysis and lipid oxidation during the ripening of the product. At the green stage, the levels of fatty acids (FA) in the free fatty acids fraction were higher in pre-cure frozen (F) than in refrigerated (R) hams, whereas in the polar lipid fraction, FA and dimethyl acetals (DMA) values were higher in R than in F Iberian hams. These results point out the existence of lipolysis phenomena during the freezing storage. At the end of post-salting and at the final stage, both R and F hams showed similar FA and DMA profiles. The effect of pre-cure freezing of hams influenced lipolysis evolution throughout the processing. The development of lipid oxidation was similar in R and F hams, but Thiobarbituric acid-reactive substances (TBAR) values were significantly higher in F hams at the initial stage and at the end of post-salting and drying steps. Despite all these differences, at final stage the FA and DMA composition as well as TBAR levels were quite similar in R and F hams. Keywords Evolution, Iberian ham, lipolysis, oxidation, pre-freezing. Introduction Meat products from Iberian pigs are the most valuable in the market, both in Spain and several other countries, due to their exceptional sensory attributes (Garcı´a et al., 1996). These are a consequence, in part due to the lipolytic and oxidative phenomena that take place during the ripening process (Antequera et al., 1992; Andres et al., 2005). Lipolytic processes constitute the first step to free fatty acid (FFA) auto-oxidation, which in turn gives rise to numerous volatile compounds, which are responsible to a large extent for the Iberian dry-cured ham flavour features (Garcı´a et al., 1991; Ruiz et al., 1998; Andres et al., 2007). In addition, lipolysis also leads to changes in the fatty acid (FA) composition of the different lipid fractions, particularly polar lipids (PL) (Andres et al., 2005). Fatty acids released during the processing in Iberian ham come mainly from this fraction (Martin et al., 1999; Andres et al., 2005). The rate and extension of the lipolysis that takes place during the ripening of Iberian ham is related to the processing conditions and the features of the raw material (Martin et al., 1999; Andres et al., 2005). Freezing of raw thighs and frozen storage of the raw material before Iberian dry-cured ham processing is not a common strategy. Dry-cured ham producers believe that this procedure leads to lower quality dry-cured Iberian hams. The specific designation of origin that protects the production of dry-cured Iberian hams, specifically exclude freezing as a procedure for raw material storage. Nevertheless, there is not scientific evidence that pre-cure freezing has any effect on the quality of the derived Iberian dry-cured meat products. Such procedure could show several technological and economical advantages, such as the possibility of salting hams with more homogeneous weights or the processing of hams to avoid the fluctuations in seasonal availability and market price. Freezing could promote changes in physical (drip loss, texture modifications), chemical (lipolysis and FA oxi- dation, protein denaturation and aggregation, changes in colour), and sensory properties of meat, depending on the characteristics of the fresh meat, further processing of the meat, and frozen conditions (Carballo & Jime´nez, 2001). During frozen storage, the oxidation processes are slowed, but not completely hindered. Some lipid soluble radicals may even be more stable at the lower temperature and thereby propagate oxidation (Kanner, 1994). As far as lipolytic reactions are concerned, *Correspondent: Fax: +34 927 257110; e-mail: triny@unex.es International Journal of Food Science and Technology 2009, 44, 2287–2295 2287 doi:10.1111/j.1365-2621.2009.02071.x Ó 2009 The Authors. Journal compilation Ó 2009 Institute of Food Science and Technology