Contents and composition of individual phospholipid classes from biceps femoris related to the rearing system in Iberian pig.

During dry-cured ham processing, phospholipids (PL) are the main substrates of lipolysis and oxidation. However, the published data on individual PL classes in the pig muscle are inconsistent. This study determined the PL class contents and composition in biceps femoris of Iberian pigs according to the rearing system (Montanera vs Pienso). Phosphatidylcholine (PC), phosphatidylethanolamine (PE), cardiolipin (CL) and sphingomyelin contents were higher in the Montanera pigs than in the Pienso pigs. Total PL and PC, PE, phosphatidylinositol + phosphatidylserine and CL contained higher levels of oleic acid and slightly higher levels of n-3 polyunsaturated fatty acids (PUFA) but lower levels of n-6 PUFA in the Montanera pigs than in the Pienso pigs. The rearing system had no effect on the plasmalogen content but influenced aldehyde composition, mainly in PE and in total PL. These results can partially explain the differences in sensory properties of dry-cured ham between the Montanera and Pienso systems.

Identification of QTL with effects on intramuscular fat content and fatty acid composition in a Duroc x Large White cross.

BACKGROUND: Improving pork quality can be done by increasing intramuscular fat (IMF) content. This trait is influenced by quantitative trait loci (QTL) sought out in different pig populations. Considering the high IMF content observed in the Duroc pig, it was appealing to determine whether favourable alleles at a major gene or QTL could be found. The detection was performed in an experimental F2 Duroc x Large White population first by segregation analysis, then by QTL mapping using additional molecular information. RESULTS: Segregation analysis provided evidence for a major gene, with a recessive Duroc allele increasing IMF by 1.8% in Duroc homozygous pigs. However, results depended on whether data were normalised or not. After Box-Cox transformation, likelihood ratio was indeed 12 times lower and no longer significant. The QTL detection results were partly consistent with the segregation analysis. Three QTL significant at the chromosome wide level were evidenced. Two QTL, located on chromosomes 13 and 15, showed a high IMF Duroc recessive allele with an overall effect slightly lower than that expected from segregation analysis (+0.4 g/100 g muscle). The third QTL was located on chromosome 1, with a dominant Large White allele inducing high IMF content (+0.5 g/100 g muscle). Additional QTL were detected for muscular fatty acid composition. CONCLUSION: The study presented results from two complementary approaches, a segregation analysis and a QTL detection, to seek out genes involved in the higher IMF content observed in the Duroc population. Discrepancies between both methods might be partially explained by the existence of at least two QTL with similar characteristics located on two different chromosomes for which different boars were heterozygous. The favourable and dominant allele detected in the Large White population was unexpected. Obviously, in both populations, the favourable alleles inducing high IMF content were not fixed and improving IMF by fixing favourable alleles using markers can then be applied both in Duroc and LW populations. With QTL affecting fatty acid composition, combining an increase of IMF content enhancing monounsaturated fatty acid percentage would be of great interest.

Lipids in muscles and adipose tissues, changes during processing and sensory properties of meat products.

Dry-cured meat products represent a large part of the meat products on the European market. The technologies develop for these products lead to the production of a large scale of meat products with typical sensory traits. Numerous studies have been devoted to optimise the quality traits of these products which are considered as traditional products by the consumer and provide a high added value to the producer. Among the components of the raw material, lipids play a key role in the final quality of these products. Many sensory traits of dry-cured meat products depend on lipid traits of muscle and adipose tissues of fresh meat and on their degradation through a complex set of lipolytic and oxidative reactions during processing. Lipid traits of both muscle and adipose tissues of fresh meat are strongly related to pig rearing conditions, mainly genotype and feeding strategy. During processing, lipids undergo intense lipid hydrolysis controlled by both lipases and phospholipases, which remain active all along the process. Lipids are also subjected to oxidation, which generates numerous volatile compounds. These volatiles contribute to some typical aroma notes of dry-cured meat products such as rancid, aged ham and dry-cured odours. This paper reviews the recent knowledge on the influence of lipid traits of fresh meat, lipid hydrolysis and oxidation on the development of sensory traits of dry-cured meat products.

Activities of phospholipases A and lysophospholipases in glycolytic and oxidative skeletal muscles in the rabbit.

Oxidative muscles contain more free fatty acids than glycolytic muscles, which could explain in part their higher sensitivity to oxidation. These fatty acids are partly the result of phospholipid hydrolysis catalysed by phospholipases A and lysophospholipases. Up to now, very little is known on the activities of these enzymes in skeletal muscles. This study deals with the activities of phospholipases A and lysophospholipases in five rabbit muscles covering a large range of metabolic types (oxidative Soleus and Semimembranosus proprius muscles, glycolytic Psoas major and Longissimus lumborum muscles and intermediate Gastrocnemius laterale muscle). The results showed that (a) phospholipases A and lysophospholipases had maximal activity at pH 8-9; (b) phospholipases A and lysophospholipases retained more than 50% of their maximal activity at pH 5.5-6, the ultimate pH of muscles; (c) lysophospholipases exhibited a higher activity than phospholipases A (4-7-fold higher in the oxidative muscles, 11-fold higher in the intermediate muscle and 18-23-fold higher in the glycolytic muscles); and (d) phospholipase A and lysophospholipase activities were higher in oxidative muscles than in glycolytic muscles (10-25-fold higher for phospholipases A and 4-5-fold higher for lysophospholipases). Thus oxidative muscles have a higher potential activity for post-mortem hydrolysis of phospholipids. © 2000 Society of Chemical Industry.