Pork belly quality variation and its association with fatness level.

Belly is a very popular pork cut composed of different layers of fat and muscle tissue. This work aims to investigate the effect of belly fatness on the morphological, mechanical (firmness) and compositional characteristics of fresh pork bellies and the distribution of the fat within the belly slice. A total of 182 bellies, selected to ensure variability of fatness, sexes and genotypes, were scanned by computed tomography (CT) to determine the fat content which, together with the genotype, led to the formation of 5 classes: F1 class below 26%, F2 class from 26% to 33.9%, and F3 class above 33.9% of fat content from common commercial crossbred pigs; F4 class with an average fatness of 47.3% from pure Duroc pigs; and last, F5 class with 62.6% average fat content from Iberian×Duroc pigs. The distribution of the fat in the central belly slice obtained by CT revealed important differences by region although the fat content was proportional to the overall fatness of the belly. Both belly weight and belly firmness increased with higher fatness. In bellies from common commercial pigs, an increase of SFA and MUFA and a decrease of PUFA as fatness increased was observed. This study highlights variations in belly characteristics among different fat classes, indicating considerable differences in the quality of bellies currently available in the market. This may influence producers and consumers acceptability such that fat content could be considered as a quality criterion to pre-classify bellies and better match the raw product with its final destination.

Five genomic regions have a major impact on fat composition in Iberian pigs.

The adipogenic nature of the Iberian pig defines many quality attributes of its fresh meat and dry-cured products. The distinct varieties of Iberian pig exhibit great variability in the genetic parameters for fat deposition and composition in muscle. The aim of this work is to identify common and distinct genomic regions related to fatty acid composition in Retinto, Torbiscal, and Entrepelado Iberian varieties and their reciprocal crosses through a diallelic experiment. In this study, we performed GWAS using a high density SNP array on 382 pigs with the multimarker regression Bayes B method implemented in GenSel. A number of genomic regions showed strong associations with the percentage of saturated and unsaturated fatty acid in intramuscular fat. In particular, five regions with Bayes Factor >100 (SSC2 and SSC7) or >50 (SSC2 and SSC12) explained an important fraction of the genetic variance for miristic, palmitoleic, monounsaturated (>14%), oleic (>10%) and polyunsaturated (>5%) fatty acids. Six genes (RXRB, PSMB8, CHGA, ACACA, PLIN4, PLIN5) located in these regions have been investigated in relation to intramuscular composition variability in Iberian pigs, with two SNPs at the RXRB gene giving the most consistent results on oleic and monounsaturated fatty acid content.

Genetic parameters and crossbreeding effects of fat deposition and fatty acid profiles in Iberian pig lines.

The aim of this study was to estimate the genetic and environmental parameters and crossbreeding effects on fatty acid and fat traits in the Iberian pig. Our final goal is to explore target selection traits and define crossbreeding strategies. The phenotypes were obtained under intensive management from 470 animals in a diallelic experiment involving Retinto, Torbiscal, and Entrepelado lines. The data set was composed of backfat thickness at the fourth rib (BFT), intramuscular fat (IMF) in the longissimus thoracis (LT), and the fatty acid profile for IMF and subcutaneous fat (SCF) traits. Data were analyzed through a Bayesian bivariate animal model by using a reparameterization of Dickerson's model. The results obtained showed an important genetic determinism for all traits analyzed with heritability ranging from 0.09 to 0.67. The common environment litter effect also had an important effect on IMF (0.34) and its fatty acid composition (0.06-0.53) at slaughter. The additive genetic correlation between BFT and IMF (additive genetic correlation [] = 0.31) suggested that it would be possible to improve lean growth independent of the IMF with an appropriate selection index. Furthermore, the high additive genetic correlation ( = 0.68) found between MUFA tissues would seem to indicate that either the LT or SCF could be used as the reference tissue for MUFA selection. The relevance of the crossbreeding parameters varied according to the traits analyzed. Backfat thickness at the fourth rib and the fatty acid profile of the IMF showed relevant differences between crosses, mostly due to line additive genetic effects associated with the Retinto line. On the contrary, those for IMF crosses were probably mainly attributable to heterosis effects. Particularly, heterosis effects were relevant for the Retinto and Entrepelado crosses (approximately 16% of the trait), which could be valuable for a crossbreeding system involving these lines.

Chemical composition and oxidative status of tissues from Iberian pigs as affected by diets: extensive feeding v. oleic acid- and tocopherol-enriched mixed diets.

The present work was intended to analyse the chemical composition and oxidative stability of the muscle biceps femoris and adipose tissues from Iberian pigs fed different finishing diets: free-range feeding on grass and acorns in a 'Montanera' traditional system (MON), fed in confinement with a mixed diet containing high-oleic sunflower oil (115 g/kg of diet) and supplemented with 250 mg/kg α-tocopherol (HOVE), and fed in confinement with a tocopherol-non-supplemented control mixed diet (CON). Muscles from MON pigs contained significantly (P < 0.05) higher amounts of intramuscular fat than those from HOVE and CON pigs. Muscles from MON and HOVE pigs had significantly higher levels of α-tocopherol than muscles from CON pigs whereas free-range feeding provided significantly higher levels of γ-tocopherol to muscles from MON pigs than the experimental diets did to CON and HOVE pigs. Adipose tissues from MON and HOVE pigs contained significantly lower proportions of saturated fatty acids and significantly higher levels of oleic acid and monounsaturated fatty acids than those from CON pigs. Tissues from MON pigs contained significantly smaller levels of polyunsaturated fatty acids than those from CON and HOVE pigs. To a higher extent, feeding background affected the fatty acid composition of polar lipids from the muscle biceps femoris than that of neutral lipids. Tissues from MON pigs contained significantly smaller ω-6/ω-3 values than those from pigs fed mixed diets. Compared to tissues from CON pigs, those from MON and HOVE pigs exhibited a higher oxidative stability as a likely result of a most favourable fatty acid composition and the presence of higher tocopherol levels.

Effects of dietary incorporation of different antioxidant extracts and free-range rearing on fatty acid composition and lipid oxidation of Iberian pig meat.

This investigation was designed to evaluate the effects of feeding either free range or in confinement using concentrated diets with the same ingredients and oil source (5.5% of olive oleins) but with different antioxidant supplementation [control diet with a basal level of α-tocopheryl acetate (control); 200 mg/kg synthetic all-rac-α-tocopheryl acetate (Eall-rac); 200 mg/kg natural RRR-α-tocopheryl-acetate (ERRR-); flavonoid extract-enriched diet (AFlav); and phenolic compound-enriched extract (APhen)] on the fatty acid composition and lipid oxidation of Iberian pig muscle longissimus dorsi. The α-tocopherol concentration was significantly higher in muscles from free-range and ERRR- pigs than in muscles from Eall-rac pigs, and γ-tocopherol was only detected in muscles from free-range pigs. Longissimus dorsi muscles from free-range pigs had a significantly lower content of saturated fatty acids and higher content of polyunsaturated fatty acids than muscles from the other five groups of pigs fed in confinement; however, no significant effect on monounsaturated fatty acids was observed. No effect of dietary antioxidant supplementation (synthetic or natural α-tocopherol, flavonoid extract, or phenol extract) on the fatty acid composition of muscles was observed. A significant influence of dietary treatment on lipid oxidation was observed after 3 (P < 0.01), and 7 and 10 (P < 0.001) days of refrigerated storage, respectively. The lowest thiobarbituric acid-reactive substances (TBARS) values were found in pork chops from the free-range and ERRR- groups, intermediate values from the Eall-rac group, followed by AFlav and APhen, while the highest TBARS values corresponded to muscles from pigs fed the control concentrate. The source of α-tocopherol had a significant effect on lipid oxidation (P < 0.05), whereas the AFlav and APhen groups had similar TBARS values.

Study of the branched hydrocarbon fraction of intramuscular lipids from Iberian dry-cured ham.

Branched hydrocarbons from the unsaponifiable lipid fraction of intramuscular fat from Iberian dry-cured hams were analyzed. Thirty-four hams were distributed into four groups according to the feed system of the pigs (extensive system "Montanera" and intensive system "Pienso") and genotype (Iberian and Iberian×Duroc). A total of 35 different hydrocarbons were identified in this study. Some differences were found in the levels of branched, cyclical and unsaturated hydrocarbons as a function of the diet of the pigs (3-hexyl-1,1-dimethyl cyclopentane, p<0.05; 3-octadecene, p<0.01; neophytadiene, p<0.001; 1-ethylundecyl benzene, p<0.01; cyclohexadecane, p<0.001; cyclotriacontane, p<0.05). However, the genotype had a limited effect in the level of branched hydrocarbons found. The study of branched hydrocarbons in intramuscular fat from dry-cured Iberian ham allows differentiation between the pigs management systems.

Linear hydrocarbons content of intramuscular lipids of dry-cured Iberian ham.

This study has been carried out to determine the linear hydrocarbons content (n-alkane and n-alkene) in intramuscular lipids (biceps femoris muscle) of dry-cured Iberian ham considering "feeding system" (Montanera: fed on acorns and pasture and concentrate feed) and "genotype" (hams from Iberian pure pigs and hams from Iberian crossbreed with Duroc in a 50%). The linear hydrocarbons from n-C(14) to n-C(32) range were present in the four studied groups. n-Alkenes fraction (60-76 mg/kg of intramuscular fat) was higher than n-alkanes fraction (34-38 mg/kg). The most abundant n-alkane and n-alkene were the shortest chain ones. Feeding and genotype did not influence linear hydrocarbons content (neither n-alkanes nor n-alkenes).

Lipid traits of muscles as related to genotype and fattening diet in Iberian pigs: total intramuscular lipids and triacylglycerols.

Thirty pigs were allotted into four groups according to the fattening diet ("Montanera", diet= acorns and pasture; and "Pienso", diet=concentrated diet) and genotype (Iberian and Iberian×Duroc pigs). Lipid, fatty acid and triacylglycerol compositions,were measured in Biceps femoris muscle. Fattening diet largely affected muscle lipid composition. Total intramuscular lipid and triacylglycerol contents were higher in Montanera pigs than in Pienso pigs (8.0-8.1% vs 6.0-6.8% and 7.4-7.3% vs 6.2-5.4%, respectively). In Montanera pigs, triacylglycerols contained more oleic acid (54.7-56.8% vs 53.5-53.8% and less stearic and palmitic acids (8.8-8.4% vs 9.4-10.2% and 22.2-23.3 vs 23.7-24.4% respectively) and accordingly less PSO and more POL, POO and OOO(†) triacylglycerols compared to Pienso pigs (13.1-13.6% vs 16.2-19.2%, 4.4-3.5% vs 3.0-2.7%, 53.1% vs 51.3-51.9% and 10.1-12.3% vs 8.3-8.6%, respectively). Genotype had no effect on lipid and triacylglycerol contents of muscles and showed only a slight effect on fatty acid and triacylglycerol compositions.

n-Alkane content of intramuscular lipids of Iberian fresh ham from different feeding systems and crossbreeding.

n-Alkane content of intramuscular lipids (Biceps femoris muscle) of the Iberian pig have been determined. Thirty-four pigs, divided into four groups, based in the feeding system (Montanera, fed on acorns and pasture; and Pienso, fed on a concentrate feed) and in the genotype (Iberian pure pigs; and Iberian crossbred with Duroc 50%) were studied. n-Alkane content of intramuscular lipids has not been affected by neither crossbreeding nor feeding, although the analysis of feeds administered to the pigs showed greater n-alkane values in pasture (consumed by animals in montanera), than in acorns and concentrate feed.

Study of the branched hydrocarbon fraction of intramuscular lipids from Iberian fresh ham.

Branched hydrocarbons from the unsaponifiable lipid fraction of the Biceps femoris muscle of Iberian pigs were analyzed. Fifty-five Iberian pigs were distributed to seven groups according to management system (short Montanera and long Montanera, i.e. fed on acorn and pasture for 55 and 75 days prior to slaughter, respectively, and Pienso, fed on a concentrate diet), and genetic type. A branched hydrocarbon, neophytadiene, was identified only in samples from the pigs fed on the extensive system, with higher levels being found in pigs from the long Montanera group, than in those from the short Montanera group; this compound was not found in the Pienso group. Genotype did not affect the level of branched hydrocarbons found.

Oxidative stability and fatty acid composition of pig muscles as affected by rearing system, crossbreeding and metabolic type of muscle fibre.

Muscle fibre type, fatty acid composition of phospholipids (PLs) and triacylglycerols (TGs) and susceptibility of muscle to lipid oxidation were studied in Biceps femoris (BF) and Tibialis cranialis (TC) muscles from Iberian and Iberian×Duroc pigs reared indoors and outdoors. Fatty acid composition of TGs was not affected by muscle fibre type and crossbreeding, but was strongly influenced by rearing system. In PLs crossbreeding slightly affected monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA) content in BF muscle, whereas rearing system showed a great influence on fatty acid composition of PLs. Oxidative fibres showed a positive relationship with saturated fatty acid (SFA) and MUFA contents and a negative one with PUFA content of PLs. Susceptibility of muscle to lipid oxidation was strongly influenced by diet, animals reared indoors and fed on concentrates showing higher levels of 2-thiobarbituric acid reactive substances (TBARS). Iberian×Duroc pigs tended to show slightly higher values of lipid oxidation than pure Iberian pigs. With regards to muscle fibre type, BF had lower TBARS values than TC, although within muscle no relationship was found between muscle fibre type and lipid oxidation.

In situ transesterification of fatty acids from Iberian pig subcutaneous adipose tissue.

The purpose of this study was to optimize a rapid method for fatty acid analysis in Iberian pig subcutaneous adipose tissue. An in situ transesterification method was used to avoid the lengthy lipid extraction step. Samples were in situ transesterified with 5% HCl/methanol at 70°C, and toluene was used to help dissolve lipids. The method had advantages over other in situ methods since only 45 min were required to completely transesterify the fatty acids, and 10 min to obtain the fatty acid profile. A sample size of 25 mg of adipose tissue was suitable. The in situ transesterification gave higher fatty acid concentrations than conventional lipid extraction and transesterification, the differences being significant for all the fatty acids. Relative fatty acid contents were similar to those found by the conventional method.