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.     

Preference and juiciness of Iberian dry-cured loin as affected by intramuscular fat content, crossbreeding and rearing system

Preference ranking tests for juiciness and overall liking of dry cured loins from Iberian pigs with different genetic backgrounds (pure Iberian or crossbred Iberian×Duroc pigs), reared under different productive systems (outdoors on acorns and grass or indoors with mixed diets) and with different intramuscular fat (IMF) content, were conducted. IMF showed a positive influence on preference for juiciness and liking in subjects over 25 years of age, while younger consumers showed a similar trend for juiciness but not for preference. Loins from pure Iberian pigs showed significantly better ranking for juiciness and overall liking than those from crossbred pigs, even when the IMF content was similar. Dry cured loins from pigs reared outdoors and fed on acorns and pasture were ranked significantly better than those from animals fed indoors on concentrates, even though the mixed diets used were enriched in monounsaturated fatty acids and vitamin E in order to obtain meat with similar features to that of pigs reared outdoors, and despite very similar IMF contents. In conclusion, dry cured loins with high IMF content, from pure Iberian pigs and reared outdoors on acorns and grass attain the highest consumer preference.     

The crossbreeding of different Duroc lines with the Iberian pig affects colour and oxidative stability of meat during storage

Colour and oxidative stability of Longissimus dorsi (LD) and Biceps femoris (BF) muscles from 3 different Iberian × Duroc genotypes (GEN1: ♂ Iberian × ♀ Duroc1, GEN2: ♂ Duroc1 × ♀ Iberian; GEN3: ♂ Duroc2 × ♀ Iberian) were analysed during 10 days of refrigerated storage. GEN1 and GEN2 are reciprocal crosses, while the difference between GEN2 and GEN3 is the Duroc sire line. The genotype Duroc1 was selected for the manufacture of dry-cured-meat products while the genotype Duroc2 was selected for meat production. BF showed more intense colour and oxidative changes during storage than LD, which is in accordance with their different metabolic pattern, since BF is an intermediate oxidative muscle whereas LD is a glycolytic one. Important differences were found between crosses due to the genotype of the Duroc sire line; however, reciprocal crosses (GEN1 and GEN2) showed a similar pattern. The lowest post-mortem pH of GEN3 could be a deciding factor of the oxidative and colour stability during storage as GEN3 had higher drip and cook loss as well as higher susceptibility to iron-ascorbate-induced oxidation. In addition, chops from GEN3 were paler (lower L^∗) and showed a higher discolouration (higher decrease of a^∗) besides higher lipid (TBA-RS) and protein oxidation (carbonyl content) after the storage.     

基于改进自适应杂交粒子群优化算法和最小二乘支持向量机的空中目标威胁评估

评估空中目标威胁程度是防空指挥控制系统的核心环节,评估的准确程度将对防空作战产生重大影响。针对传统评估方法实时性差、工作量大、评估精度不足、无法同时进行多目标评估等缺陷,提出了一种基于自适应杂交粒子群优化（ACPSO）算法和最小二乘支持向量机（LSSVM）的空中目标威胁评估方法。首先,根据空中目标态势信息构建威胁评估系统框架;然后,采用ACPSO算法对LSSVM中的正则化参数和核函数参数进行寻优,针对传统杂交机制的不足提出改进的交叉杂交方式,并使杂交概率自适应调整;最后,对比分析了各系统的训练和评估效果,并用优化后的系统实现多目标实时动态威胁评估。仿真结果表明,所提方法评估精度高,所需时间短,可同时进行多目标评估,为空中目标威胁评估提供了一种有效的解决方法。     

基于动态参数的杂交粒子群优化算法

粒子群优化算法的局部搜索能力较差,搜索精度不够高,容易陷入局部极小解,且搜索性能对参数具有一定的依赖性。本文针对这些缺点,在借鉴遗传算法中杂交概念的基础上,进一步通过在速度进化方程中引进动态参数来提高算法的收敛速度和收敛率。经LevyNo. 5函数对改进算法的测试表明,相对杂交粒子群优化算法,该方法的收敛速度和平均收敛率均得到了不同程度的提高。     

Effect of Iberian×Duroc genotype on dry-cured loin quality

Dry-cured loins from three different pig genotypes were studied: GEN1: ♂ Iberian × ♀ Duroc1, GEN2: ♂ Duroc1 × ♀ Iberian; GEN3: ♂ Duroc2 × ♀ Iberian. GEN1 and GEN2 are reciprocal crosses, while the difference between GEN2 and GEN3 is the Duroc sire line. The genotype of pigs Duroc1 was selected for the manufacture of dry-cured meat products, while the genotype Duroc2 was selected for meat production. The chemical composition of the dry-cured loins was significantly different, especially the intramuscular fat (IMF) content which was highest in GEN2. Dry-cured loins from GEN3 showed lower CIE a^∗ and chroma values. IMF from GEN2 was more saturated whereas GEN3 had higher percentages of PUFA and MUFA. Loins from GEN3 had higher TBA-RS values (p > 0.05) and hexanal contents. Loins from GEN3 had higher Warner–Bratzler shear force (p > 0.05) and instrumental hardness than those from GEN2, being intermediate in GEN1. Panellists considered that loins from GEN2 were more marbled, more odorous, juicier, sweeter and less salty than loins from GEN3. Therefore, loins from GEN2 had the best quality, followed by GEN1, while GEN3 had the worst quality.     

Sensory characteristics of Iberian dry-cured loins: Influence of crossbreeding and rearing system

The sensory characteristics of Iberian dry-cured loins and the influence of crossbreeding (pure Iberian - IB, Iberian female×Duroc male - IB×D and Duroc female×Iberian male - D×IB) and rearing system (outdoors fed on acorns and pasture - MON, indoors fed on concentrates high in oleic acid sunflower oil and supplemented with 250mg/kg of α-tocopherol acetate -HOVE- and indoors fed on control concentrates - CON) on sensory attributes were studied. Dry-cured loins from IB-MON and IB-HOVE pigs, which showed the highest intramuscular fat (IMF) content (p<0.01), reached higher scores for brightness, marbling traits (intensity, size and shape) and juiciness, and lower for hardness, dryness and fibrousness than loins from crossbred pigs (IB×D-HOVE, IB×D-CON and D×IB-HOVE). In fact, IMF content was positively linked to juiciness and marbling attributes and negatively to dryness, hardness and fibrousness, which was also observed in the principal component analysis (PCA). Neither the crossbreeding nor the rearing system seemed to influence odour, flavour and taste features. The PCA evidenced that dry-cured loins from IB-MON and IB-HOVE batches gathered together and were placed near to marbling attributes, juiciness and IMF content.