PRKAG3 and CAST genetic polymorphisms and quality traits of dry-cured hams—III. Associations in Slovenian dry-cured ham Kraški pršut and their dependence on processing

Effects of Animal Diet and Processing Methods on the Quality Traits of Dry-Cured Ham Produced from Turopolje Pigs

The Turopolje pig (TP) is a local Croatian pig breed that almost became extinct in the second half of the 20th century. Today, the TP is still endangered, and a new conservation strategy based on products with higher added value is needed to preserve the breed. There is little information on the quality of TP meat products such as smoked and dry-cured ham, including the impact of natural feeds or processing innovations such as smoke reduction. This study, therefore, investigated the effects of the animal's diet (either conventionally fed or acorn-supplemented) and the processing method (standard or lightly smoked) on the quality traits of dry-cured TP ham. Twenty hams, evenly distributed among the treatments, were processed for 15 months and then analysed for physicochemical and textural traits, volatiles and sensory profile. The hams from acorn-supplemented pigs lost less weight during processing (p ≤ 0.05). Otherwise, the diet had no significant effect on most examined ham traits. The exceptions were protein content and the texture parameter hardness, which decreased (p ≤ 0.05), and the degree of proteolysis and colour parameters, which increased (p ≤ 0.05) as a result of acorn supplementation. However, these effects were generally small and varied between the inner (m. biceps femoris) and outer (m. semimembranosus) muscles. Furthermore, acorn supplementation was associated with less typical ham odour and lower sensory scores for sweetness and colour uniformity (p ≤ 0.05). The smoke reduction had no effect on the physicochemical and colour properties but resulted in a significant reduction (p ≤ 0.05) in the volatile phenolic compounds and an improved texture to the hams. This was reflected both in reduced (p ≤ 0.05) hardness, identified in the instrumental analysis, and in an increased (p ≤ 0.05) softness, solubility and moistness, identified in the sensory evaluation. To summarize, the quality of the TP ham under the conditions studied was only slightly affected by acorn supplementation, whereas reduced smoking had a more significant effect, which was mainly reflected in an improved texture.

Finishing season and feeding resources influence the quality of products from extensive-system Gascon pigs. Part 1: Carcass traits and quality of fresh loin

Consumers perceive pork products from local breeds reared in extensive systems positively because of their specific quality properties and regional identity. The sensory, nutritional and technological qualities of these products depend, among other things, on pig production, especially its climatic conditions and the availability of feed resources, which can influence traits of muscle and fat tissue. The present study (part 1) was part of a larger project that assessed the influence of the finishing season and feeding resources on carcass and tissue traits and the quality of meat and dry-cured ham from Gascon pigs in an extensive system. Following the specifications of the Protected Designation of Origin "Noir de Bigorre", castrated Gascon males were reared on rangelands (grassland and forest areas) and received a supplementary diet from 5 to 6 months of age until slaughter at a minimum of 12 months of age and ca. 170 kg live weight. Three finishing seasons were considered as follows: Winter (n = 18), Spring (n = 22) and Autumn (n = 23). To estimate specific effects of season on productive and quality traits and avoid bias due to effects of genes known to influence these traits, polymorphisms in the RYR1, PRKAG3, MC4R and LEPR genes were included in the analysis models. The finishing season did not influence growth rate. Compared to Winter pigs, Spring and Autumn pigs had slightly lower carcass fatness (P < 0.05), higher ultimate pH and redder and darker color of the Longissimus muscle (LM) (P < 0.01). Loin drip loss was low overall, but was higher for Spring pigs, whereas cooking loss and shear force were similar among seasons. Spring pigs tended to have the lowest LM lipid content, whereas LM myoglobin content remained unaffected. Autumn pigs had lower potential of lipid oxidation in LM than Winter and Spring pigs (P < 0.01), but muscle metabolic traits assessed via glycolytic and oxidative enzyme activities did not differ among seasons. The finishing season modified the backfat fatty acid (FA) profile, with a lower polyunsaturated FA percentage in Autumn pigs than Winter or Spring pigs (P < 0.001), even though the saturated and monounsaturated FA percentages did not differ. In particular, Spring pigs had the lowest n-6:n-3 and C18:2:C18:3 ratios (P < 0.001), as a result of grazing. Overall, Spring and Autumn finishing seasons seem more favorable to technological and sensory pork attributes, with an additional positive effect of Spring finishing on pork nutritional value.

Genetic parameter estimation and gene association analyses for meat quality traits in open-air free-range Iberian pigs

Meat quality of Iberian pigs is defined by the combination of their genetic characteristics and the particular production system. To carry out a genetic analysis of the main meat quality traits, we estimated their heritabilities, genetic correlations and the association effects of 32 selected SNPs of 12 candidate genes. A total of ten traits were measured in longissimus dorsi samples from 1,199 Iberian pigs fattened in the traditional free-range system: water holding capacity (thawing, cooking and centrifuge force water losses), instrumental colour (lightness L*, redness a* and yellowness b*), myoglobin content, shear force on cooked meat, and shear force and maximum compression force on dry-cured loin. Estimated heritability values were low to moderate (0.01 to 0.43) being the lowest for L* and the highest for cooking loss. Strong genetic correlations between water holding capacity traits (0.93 to 0.96) and between myoglobin content and a* (0.94) were observed. The association analyses revealed 19 SNPs significantly associated with different traits. Consistent and strong effects were observed between PRKAG3 SNPs (rs319678464G > C and rs330427832C > T), MYH3_rs81437544T > C, CASP3_rs319658214G > T and CTSL_rs332171512A > G and water losses. Also for CAPN1_rs81358667G > A and CASP3_rs319658214G > T and shear force. The SNPs mapping on PRKAG3 showed the highest effects on Minolta colour traits. Genotyping of these SNPs could be useful for the selection of Iberian young boars with similar estimated breeding values for productive traits.

Quality of Dry-Cured Ham from Entire, Surgically and Immunocastrated Males: Case Study on Kraški Pršut

Alternative solutions to the surgical castration of piglets need to be assessed because this is a particularly sensitive issue for the processing of traditional pork products. Currently, the available information about the advantages and drawbacks of castration for dry-cured products is limited; thus, the objective of this study was to evaluate the quality of Slovenian dry-cured ham (Kraški pršut) from entire males (EM), immunocastrates (IC) and surgical castrates (SC). Hams (12 per sex group) were processed for one year and physical-chemical, rheological and sensory analysis of the dry-cured hams was performed. With regard to processing aptitude, the main difference was in the subcutaneous fat thickness, which influenced the level of dehydration and salt intake. This was further reflected in the physical-chemical traits and the texture, which were measured instrumentally or assessed by panelists. Regarding the aforementioned traits, EM and IC were generally similar and different from SC. On the contrary, sensory profiling of odor, taste and flavor demonstrated that EM had the lowest overall sensory quality, different from both IC and SC, and presented odors and flavors described as sweat, manure, sharp and persistent. We confirmed that dry-curing did not eliminate the perception of boar taint in the product from EM. The IC were similar in many aspects to EM except for the odor, taste and flavor of dry-cured hams, in which case they were more similar to SC.

The effect of salting time and sex on chemical and textural properties of dry cured ham

Effect of reduced salting and pig sex on the quality of Slovenian dry-cured ham Kraški pršut was studied. A total of 48 hams from 24 crossbred pigs (12 gilts, 12 castrates) were submitted to two different salting regimes; standard salting for 18 days (HS hams, n = 24) and shortened salting (LS hams, n = 24) for 10 days. Reduced salting time effectively reduced salt content but resulted also in higher extent of proteolysis of LS hams which was associated with differences in texture and colour of biceps femoris muscle. Lower fat oxidative stability was observed in HS hams. With regard to sex effect, the hams originating from gilts were more proteolysed which was associated with differences in texture and colour. Lipid oxidation was similar in gilts and castrates.

Polymorphism distribution of RYR1, PRKAG3, HFABP, MYF-5 and MC4R genes in crossbred pigs

This study was designed to screen the crossbred pigs for SNPs in five candidate genes, associated with pork quality traits and to differentiate their genotypes by PCR-RFLP. The results indicated that genotypes of crossbred pigs were NN (90%) and Nn (10%) for RYR1; RR (83%) and QR (17%) for PRKAG3; HH (98%), Hh (1%) and hh (1%) for HFABP; DD (99%) and CD (1%) for MYF-5; and AG (57%), GG (26%) and AA (17%) for MC4R SNPs, respectively. Allelic frequencies for five SNPs {RYR1 (1843C>T), PRKAG3 (c.599G>A), HFABP (c.1322C>T), MYF-5 (c.1205A>C) and MC4R (c.1426A>G)} were 0.95 and 0.05 (N/n), 0.08 and 0.92 (Q/R), 0.99 and 0.01 (H/h), 0.00 and 1.00 (C/D) and 0.45 and 0.55 (A/G), respectively. The effect of RYR1 (1843C>T) SNP was significant on pH₄₅ (P < 0.05), pH₂₄ (P < 0.05) and protein % (P < 0.05). The PRKAG3 (c.599G>A) and MC4R (c.1426A>G) SNP had significant association with dressing percentages. The results revealed that RYR1, PRKAG3 and MC4R SNPs may be used in marker associated selection for pork quality traits in crossbred pigs.

Comparison of microbial communities from different Jinhua ham factories

Microbes in different aged workshops play important roles in the flavor formation of Jinhua ham. However, microbial diversity, community structure and age related changes in workshops are poorly understood. The microbial community structure and diversity in Jinhua ham produced in factories that have 5, 15, and 30 years of history in processing hams were compared using the pyrosequencing technique. Results showed that 571,703 high-quality sequences were obtained and located in 242 genera belonging to 18 phyla. Bacterial diversity and microbial community structure were significantly different with the years of workshops. Three-phase model to characterize the changes of ham microbial communities was proposed. Gas chromatography–mass spectrometry assays indicated that the hams produced in different aged workshops have great differences in number and relative contents of volatiles compounds. These results suggest that different aged factories could form special and well-balanced microbial diversity, which may contribute to the unique flavor characteristics in Jinhua ham.

Effects of single nucleotide polymorphisms and haplotypes of the protein kinase AMP-activated non-catalytic subunit gamma 3 (PRKAG3) gene on production, meat quality and carcass traits in Italian Large White pigs

PRKAG3 is a major gene for meat quality and production in pigs. In this study, we investigated two single nucleotide polymorphisms (SNPs) of the PRKAG3 promoter region (g.-995A>G and g.-311A>G) in 381 pigs of different breeds. Association between these SNPs and three major haplotypes, constructed including other three substitutions (c.89C>A, c.154A>G and c.595G>A) and different traits (meat quality parameters: pH_2h, pH_u, glycogen and lactate content, glycolytic potential and cathepsin B activity of Semimembranosus muscle; estimated breeding values and random residuals for growth performances and carcass traits) were analysed in 271 Italian Large White performance tested pigs. A significant effect (P=0.043) of the g.-995A>G SNP on cathepsin B activity and a suggestive effect (P=0.067) of the g.-311A>G SNP on pH_u were found. The haplotype [g.-995G:g.-311G:c.89A:c.154G:c.595G] was associated with pH_u (P=0.024), glycolytic potential (P=0.040) and cathepsin B activity (P=0.086). This study on haplotypes, including promoter region SNPs, contribute to explain the effect of this gene on meat quality traits in pigs.

Genome-wide association study for ham weight loss at first salting in Italian Large White pigs: towards the genetic dissection of a key trait for dry-cured ham production

Protected designation of origin dry-cured hams are the most important productions of the Italian heavy pig industry. Hams capable of minimal seasoning losses produce better quality dry-cured hams. Ham weight loss during the first 7 days in brine (first salting) is highly correlated with the total loss of weight up to the end of seasoning, and it has quite high heritability (0.30-0.61). For these reasons, ham weight loss at first salting has been included as a meat quality trait in the Italian heavy pig selection program. In this work, we carried out a genome-wide association study for this parameter in the Italian Large White pig breed by genotyping 1365 animals with the Illumina BeadChip PorcineSNP60 chip. A total of 44 single nucleotide polymorphisms (SNPs) had a P_{nominal value} below 5.0E-04, five of which were below 5.0E-05 and one of them (ALGA0057985 on chromosome 10) was associated with this trait at a P_Bonferroni threshold of 0.10. These SNPs identified a total of at least 29 putative QTLs that were located on most porcine autosomal chromosomes. This study provides genomic information that could be useful in dissecting this complex trait by identifying potential candidate genes whose function could contribute to understanding the biological mechanisms affecting meat quality for seasoning aptitude.

Application of quantitative magnetization transfer magnetic resonance imaging for characterization of dry-cured hams

Quantitative magnetization transfer magnetic resonance imaging (qMT-MRI) was employed to characterize dry-cured ham tissues differing in anatomical positions and processing protocols. Experimentally obtained MR images of dry-cured ham sections were analyzed by the well-established binary-spin-bath (BSB) model. The model enabled an efficient discrimination between a free-water proton pool and a restricted-macromolecular proton pool. Significant differences in restricted pool sizes were found among different ham sections. Values of the restricted pool size obtained by the model were in a good agreement with chemically determined protein content. The study confirmed the feasibility of the applied qMT-MRI as a nondestructive tool for characterization of dry-cured ham tissues.

Genome Wide Association Studies (GWAS) Identify QTL on SSC2 and SSC17 Affecting Loin Peak Shear Force in Crossbred Commercial Pigs

Of all the meat quality traits, tenderness is considered the most important with regard to eating quality and market value. In this study we have utilised genome wide association studies (GWAS) for peak shear force (PSF) of loin muscle as a measure of tenderness for 1,976 crossbred commercial pigs, genotyped for 42,721 informative SNPs using the Illumina PorcineSNP60 Beadchip. Four 1 Mb genomic regions, three on SSC2 (at 4 Mb, 5 Mb and 109 Mb) and one on SSC17 (at 20 Mb), were detected which collectively explained about 15.30% and 3.07% of the total genetic and phenotypic variance for PSF respectively. Markers ASGA0008566, ASGA0008695, DRGA0003285 and ASGA0075615 in the four regions were strongly associated with the effects. Analysis of the reference genome sequence in the region with the most important SNPs for SSC2_5 identified FRMD8, SLC25A45 and LTBP3 as potential candidate genes for meat tenderness on the basis of functional annotation of these genes. The region SSC2_109 was close to a previously reported candidate gene CAST; however, the very weak LD between DRGA0003285 (the best marker representing region SSC2_109) and CAST indicated the potential for additional genes which are distinct from, or interact with, CAST to affect meat tenderness. Limited information of known genes in regions SSC2_109 and SSC17_20 restricts further analysis. Re-sequencing of these regions for informative animals may help to resolve the molecular architecture and identify new candidate genes and causative mutations affecting this trait. These findings contribute significantly to our knowledge of the genomic regions affecting pork shear force and will potentially lead to new insights into the molecular mechanisms regulating meat tenderness.

Use of multiparametric magnetic resonance microscopy for discrimination among different processing protocols and anatomical positions of Slovenian dry-cured hams

A novel multiparametric magnetic resonance microscopy (MRM) approach was applied to the Slovenian Kraški pršut dry-cured ham samples in order to evaluate its potential for discrimination among biceps femoris and semimembranosus muscle from two hams, differing in processing (salting duration) and thus in water and salt content. The approach is based on apparent diffusion coefficient (ADC) mapping as well as on longitudinal (T1) and transversal (T2) nuclear magnetic resonance relaxation time mapping. Three-dimensional maps were acquired and analyzed by one dimensional (1D) ADC, T1, and T2 distributions as well as by paired two-dimensional ADC-T1, ADC-T2 and T1-T2 distributions. The discriminating potential of the applied MRM approach was confirmed by differences among both 1D and 2D distributions of different ham samples. In addition, distribution peak positions highly correlated with the conventionally determined moisture content.

The relationship between the polymorphism of the porcine CAST gene and productive traits in pigs

Urbański, P., Pierzchała, M., Terman, A., Kamyczek, M., Różycki, M., Roszczyk, A. and Czarnik, U. 2015. The relationship between the polymorphism of the porcine CAST gene and productive traits in pigs. Can. J. Anim. Sci. 95: 361–367. The aim of the study was to characterize the polymorphism of the calpastatin gene identified with ApaLI, Hpy188I and PvuII restriction enzymes in two pig breeds and one line bred in Poland, and to evaluate the relationship between the CAST genotype and carcass traits. The analysis covered a total of 617 pigs of two breeds, Polish Landrace (185) and Polish Large White (216), and synthetic line L990 (216). All animals studied appeared to be monomorphic at two loci: CAST/ApaLI and CAST/Hpy188I, while three genotypes were observed at CAST/PvuII locus. Statistical analysis was carried out for each breed separately using the least square methods of the GLM procedure. The model included the effect of the CAST genotype, fixed effect of the RYR1 genotype and the effect of the sire. Because the RYR1 genotype could significantly modify the effect of other genes, the effect of the RYR1 genotype was included in the statistical model. The relationship between the polymorphism and several productive traits was identified in each of the study groups of pigs. Animals carrying the heterozygous genotype at this locus showed most extreme values for some of the traits tested. Our results suggest that the CAST /PvuII genotype might be utilized in the selection of valuable pig carcass traits, particularly weight and size of the loin.