Original research articleLipid characteristics of dry-cured “Tocino” during the manufacturing process. Effects of salting intensity and ripening temperature
Introduction
Subcutaneous fat is an important part of some dry-cured products such as dry-cured ham and bacon, and it is also used as an ingredient in other products such as pâté and sausages. Some traditional products also valorize the subcutaneous fat of pig. Dry-cured “Tocino” is a meat product made from the dorsolateral subcutaneous fat and is commonly consumed in the Iberian peninsula. The raw pieces used for its manufacture consist of subcutaneous fat, with or without skin, cut from the dorsal line and comprising the costal and ventral areas (Spanish Royal Decree no. 474, 2014). The pieces are first dry-salted and then dried and ripened for a variable period of time. The final product is consumed both raw and cooked in traditional dishes.
The quality of dry-cured Tocino depends on the composition and properties of raw fat and on the changes undergone during the manufacturing process. Due to the nature of this product, changes in the lipid fraction are responsible for the sensory characteristics of the final product. Lipolysis and oxidation are the main degradation processes that affect lipids during the processing of dry-cured pork products (Gandemer, 2002). Lipolysis plays an important role in the development of sensorial characteristics in processed meat products because of an increase in free fatty acid and diacylglycerol contents and a decrease in triacylglycerol content (Coutron-Gambotti and Gandemer, 1999, Motilva and Toldrá, 1993). These reactions are influenced by several factors such as the length of the different stages of the manufacturing processes, the level and the method of salting, and the ambient conditions during ripening (Buscailhon and Monin, 1994, Toldrá and Flores, 1998). This process occurs faster during the first months of processing and then slows down (Narváez-Rivas et al., 2007).
The oxidative changes that occur in lipids are complex processes that cause important modifications in meat and fat during processing and storage of meat products (Morrissey et al., 1998). During lipid oxidation, unsaturated fatty acids react with molecular oxygen, giving rise to primary and secondary products, most of which have an important effect on the overall flavour of dry cured meat products because of their typical aromas and their low odour threshold (Dirinck et al., 1997). These reactions occur during the processing and continue during storage (Motilva and Toldrá, 1993). Many factors are involved in lipid oxidation, including composition and characteristics of the fresh meat or fat (Ruiz and López-Bote, 2002) and the processing conditions (Buscailhon et al., 1993, Toldrá et al., 1997). During ripening, high temperatures, long drying times and high salt contents enhance lipid oxidation (Coutron-Gambotti and Gandemer, 1999, Toldrá and Flores, 1998). Besides its specific action, salt contains impurities such as metallic ions that favour its pro-oxidant effect (Ladikos and Lougovois, 1990).
The high presence of fat in the human diet in developed countries and the demonstrated effects of the fatty acid composition of the diet on cardiovascular disease and several other chronic diseases (WHO, 2003) have led to an increased interest in knowledge about the composition of fatty foods.
Despite the widespread acceptance and consumption of dry-cured Tocino, no scientific studies have been conducted on this meat product, and processing is still carried out using traditional procedures. Information on similar products (cured lard) is available (Paleari et al., 2004, Sirtori et al., 2005, Serra et al., 2007), but the studies are limited (only the main fatty acids were quantified in the total fat) and do not consider the effects of the manufacturing and ripening conditions. Consumers are increasingly demanding products of high quality, and it is therefore necessary to establish the scientific basis of the manufacture of products of high and constant quality. The aim of the present study was to characterize the lipid fractions and to study the lipolytic and oxidative changes that take place during the manufacture of dry-cured Tocino as well as the effect on these processes of some important processing parameters such as salting intensity and ripening temperature.
Section snippets
Samples and experimental design
Raw pieces of Tocino backfat were obtained from pigs of the pure Celta breed (an autochthonous breed in NW Spain) crossed with Duroc (C × D). Thirty pigs, castrated males and females, were used. The pigs were reared and fattened in an extensive outdoor system in a natural environment with huts, bushes and enough trees to provide shade. They were fed “ad libitum” with commercial feed (17% protein, 2.4% fat and 3250 kcal/kg metabolic energy) and had free access to water. Live weight at slaughtering
Proximate composition throughout the ripening process
Table 1 shows the total solid, fat and NaCl contents during ripening for the pieces submitted to the different manufacturing conditions. Being Tocino a fat piece, minimum moisture contents (around 4.8%) were observed in the fresh pieces which significantly (P < 0.01) decreased during ripening. During manufacture dehydration was not significantly affected by the temperature nor salting.
Fat expressed as percentage of the total solid content decreased from the beginning of the process due to the
Conclusions
The fatty acid profile of Tocino was generally consistent with previously reported profiles of cured lard and subcutaneous fat of dry-cured ham. A significant decrease (P < 0.001) in the total and some individual polyunsaturated fatty acids occurred during the ripening process, particularly in the polar lipid fraction. Increases in ripening temperature and salting time caused a significant decrease in the polyunsaturated fatty acids. Values of the nutritional and health indexes, calculated from
Acknowledgements
The authors wish to thank the Xunta de Galicia, Spain (the Regional Government) for its financial support under the consolidation and restructuring program of competitive research units: Strategic Research Partnerships (2009/060).
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