Sensory and technological meat quality in carriers and non-carriers of the RN− allele in Hampshire crosses and in purebred Yorkshire pigs

Quantifying production, processing and post-slaughter effects on pork eating quality using random effects meta-regression

Random effects meta-regression techniques, analyzed using a restricted maximum likelihood (REML) approach, was used to determine the influence of various factors that may be experienced or imposed on pigs, carcases and pork on pork eating quality attributes and shear force of the M. longissimus dorsi (loin). This was done to inform the development of a pathway based eating quality system for pork. Estimated means of explanatory variables were obtained for those pathway factors where sufficient published studies met the criteria for inclusion in the analysis. Due to a lack of data for interactions between factors investigated, only single factors were included as fixed terms in the REML models. This analysis identified that moisture infusion (P < 0.001), ageing for more than 2 d post-slaughter (P = 0.006) and tenderstretching (P = 0.006) each resulted in significant improvements in tenderness. Cooking loins to an endpoint temperature of ≥ 80°C negatively impacted both tenderness (P = 0.022) and juiciness (P < 0.001) scores compared with 70 to 74°C. It was not possible to develop algorithms to reliably estimate the effects of multiple factors on pork eating quality attributes to a cuts-based level due to limited studies reporting data for treatment interactions.

Comparison and correlation analysis of different Swine breeds meat quality

This study was performed to determine the influence of pig breed and gender on the ultimate pH and physicochemical properties of pork. The correlations between pH and pork quality traits directly related to carcass grade, and consumer’s preference were also evaluated. The pH and meat grading scores for cold carcasses of 215 purebred pigs (Duroc, Landrace, and Yorkshire) from four different farms were obtained. Meat quality parameters of the pork loin were analyzed. Duroc and female animals were more affected compared to other breeds and male pigs. Duroc animals had the highest ultimate pH, carcass back fat thickness, marbling scores, yellowness, and fat content (p<0.05). Landrace pigs had the highest color lightness and cooking loss values (p<0.05). Among all trait parameters, marbling scores showed the highest significant differences when evaluating the impact of breed and gender on meat quality characteristics (p<0.001). Ultimate pH was positively correlated with carcass weight (0.20), back fat thickness (0.19), marbling score (0.17), and color score (0.16) while negatively correlated with cooking loss (−0.24) and shear force (−0.20). Therefore, pork samples with lower ultimate pH had lower cooking loss, higher lightness, and higher shear force values irrespective of breed.

Prediction of technological quality (cooking loss and Napole Yield) of pork based on fresh meat characteristics

In order to investigate if cooking loss and Napole Yield can be predicted from various fresh meat characteristics, pH (1, 15, 30, 60, 120 min and 24 h post mortem), temperature (1, 15, 30, 60, 120 min and 24 h post mortem), water-holding capacity (Honikel's drip loss method and centrifugation loss), and NMR T2 relaxation 24 h post mortem were measured in fresh porcine M. longissimus dorsi from 102 Hampshire crossbreeds of known RN(-) genotype. Subsequently, cooking loss and Napole Yield were determined on cooked and cured, cooked samples, respectively, and partial least squares regression (PLS) was carried out to investigate possible intercorrelations between the physico-chemical measurements performed on the fresh meat and cooking loss/Napole Yield. Significant correlations were found between NMR T2 relaxation measured in fresh pork 24 h post mortem and the cooking loss (R=0.64) and Napole Yield (R=0.58), whereas no correlations were found between traditionally applied methods such as pH measurements, Honikel's method and centrifugation, and the cooking loss/Napole Yield. Consequently, it is concluded that NMR T2 relaxation characteristics of fresh pork in contrast to traditional fresh meat characteristics contain information about factors of importance for cooking loss/Napole Yield from cooked uncured/cured pork. The result implies that low-field (LF) NMR data from fresh meat reflects information about water compartmentalisation and mobility that is partly decisive for subsequent heat-induced changes of importance for the distribution of water within the cooked meat. In addition, the obtained results show that LF NMR data measured on fresh meat also seems to contain information about the inherent water of importance for the technological characteristics of the meat even when the meat is cured before cooking.

Effects of breed and marination on the sensory attributes of pork from Large White and Hampshire-sired pigs

The effects of breed and marination were tested for their effects on meat pH, water holding (marinade uptake and losses) and eating quality (tenderness, juiciness and flavour). Loins were removed from one side of 20 Large White-sired and 20 Hampshire-sired pigs after slaughter, cut into four pieces and injected to 112% of their initial weight with water, a polyphosphate-containing marinade (pH 7.7) or a high pH marinade (pH 10.3). An uninjected piece of loin served as control. Samples were left overnight and then frozen before being thawed, cooked and assessed by a trained ten member sensory panel using 1-8 category scales. Hampshires had higher intramuscular fat (0.95%) than Large Whites (0.62%) but otherwise the effects of breed were small compared with marination. Both marinades significantly increased meat pH from 5.5 (control) by 0.2U, significantly reduced the cooking loss and increased the meat yield from about 80% to 90%. Water-injected samples lost large amounts of added water as drip after thawing and had a yield (76%) similar to the control. Marinaded samples retained more water post-cooking. Both marinades significantly increased tenderness (p<0.001) and juiciness (p<0.001) by about 1.0U compared with the control (4.4 for tenderness and 4.2 for juiciness). Pork flavour, however, was significantly reduced (p<0.001) and abnormal flavour was significantly increased (p<0.001) by marination. Tenderness was positively correlated with pH after injection (0.83) and yield (0.75); juiciness was also positively correlated with pH after injection (0.78) and yield (0.87). The absence of any significant difference in eating quality between control and water-injected samples, and the relatively large effects of marination, suggest that retained water (after cooking) is crucial in determining perceived tenderness and juiciness in pork.

Relationship between RN(-) genotype and drip loss in meat from Danish pigs

The presence of the RN(-)-gene determined in 72 halothane negative Danish pigs, either by a direct genotyping or the glycolytic potential of the meat, in relation to drip loss, was investigated. The drip loss in the M. longissimus dorsi from RN-carriers (n=26), as determined by genotyping was 9.9% compared to 8.6% in non-carriers (n=46) (P=0.07). When a glycolytic potential of >230 μmol lactate/g meat was used to differentiate between carriers and non carriers of the RN(-)-gene, the drip loss in carriers was 10.6% (n=17) compared to 8.7% in non-carriers (n=55) (P<0.01). These results suggest that the presence of the RN(-)-gene in Danish slaughter pigs only partially explains the large variation in drip loss observed in Danish pork.

Carcass and meat quality traits of four different pig crosses

The study compared properties of Finnish Landrace×Yorkshire crossbred sows mated with Finnish Landrace (FL), Norwegian Landrace (NL), Norwegian Duroc×Norwegian Landrace (NDL), or Swedish Hampshire (SH) boars. The focus was to study the cross-sectional area of loin, cross-sectional area and number of muscle fibres, loin colour and pH value as well as the ratio of water to protein in the loin. The four studied crosses were quite similar having only small differences in carcass and meat quality. The carcass lean content was the lowest in NDL. The loins of FL and NL were longer than the loins of NDL and of SH. The cross-sectional area of loin was the largest in SH. The loin of FL was lighter in colour and the loin of SH was redder than the loins of the other crosses studied. The protein content was lower and the ratio of water to protein higher in loin of SH than in the other crosses.

Joint analysis of quantitative trait loci and major-effect causative mutations affecting meat quality and carcass composition traits in pigs

Background

Detection of quantitative trait loci (QTLs) affecting meat quality traits in pigs is crucial for the design of efficient marker-assisted selection programs and to initiate efforts toward the identification of underlying polymorphisms. The RYR1 and PRKAG3 causative mutations, originally identified from major effects on meat characteristics, can be used both as controls for an overall QTL detection strategy for diversely affected traits and as a scale for detected QTL effects. We report on a microsatellite-based QTL detection scan including all autosomes for pig meat quality and carcass composition traits in an F2 population of 1,000 females and barrows resulting from an intercross between a Pietrain and a Large White-Hampshire-Duroc synthetic sire line. Our QTL detection design allowed side-by-side comparison of the RYR1 and PRKAG3 mutation effects seen as QTLs when segregating at low frequencies (0.03-0.08), with independent QTL effects detected from most of the same population, excluding any carrier of these mutations.

Results

Large QTL effects were detected in the absence of the RYR1 and PRKGA3 mutations, accounting for 12.7% of phenotypic variation in loin colour redness CIE-a* on SSC6 and 15% of phenotypic variation in glycolytic potential on SSC1. We detected 8 significant QTLs with effects on meat quality traits and 20 significant QTLs for carcass composition and growth traits under these conditions. In control analyses including mutation carriers, RYR1 and PRKAG3 mutations were detected as QTLs, from highly significant to suggestive, and explained 53% to 5% of the phenotypic variance according to the trait.

Conclusions

Our results suggest that part of muscle development and backfat thickness effects commonly attributed to the RYR1 mutation may be a consequence of linkage with independent QTLs affecting those traits. The proportion of variation explained by the most significant QTLs detected in this work is close to the influence of major-effect mutations on the least affected traits, but is one order of magnitude lower than effect on variance of traits primarily affected by these causative mutations. This suggests that uncovering physiological traits directly affected by genetic polymorphisms would be an appropriate approach for further characterization of QTLs.

Consequences of elimination of the Rendement Napole allele from Danish Hampshire

An elimination programme was carried out to remove the dominant Rendement Napole mutation (RN(-) ) from Danish Hampshire pigs. We reasoned that during and after the elimination of the RN(-) allele, genetic gain of production traits decreased while rate of inbreeding in the population increased compared to the period prior to elimination. The hypothesis was tested by estimating the genetic gain in seven production traits and measuring the rate of inbreeding in the population prior to and during the elimination period. Genetic gain was reduced for quantitative traits daily gain(30-100 kg) and feed conversion ratio, while gain for ultimate-pH, lean meat percentage and slaughter loss were increased slightly. There were no changes in genetic gain for daily gain(birth-30 kg) and conformation. RN polymorphism affected several of the quantitative traits. The RN(-) mutation had a dominant effect on the traits daily gain(birth-30 kg) , daily gain(30-100 kg) , slaughter loss, lean meat percentage and ultimate-pH. It exhibited overdominance for feed conversion ratio and additive effect for conformation. Rate of inbreeding decreased during the elimination of RN(-) . Our findings indicate that the consequences of the elimination programme were not as serious as were feared and that a carefully designed preselection strategy may avoid unacceptable loss of genetic gain and excessive loss of genetic variation.

NMR and the water-holding issue of pork

Consumers' awareness of food quality has never been more pronounced. Meat forms a substantial part of the food consumption, and accordingly techniques to control the quality of meat are needed. In addition, a better understanding of how basic biochemical and biophysical factors influence the final meat quality is also required for optimization of the quality. Water-holding capacity (WHC) is a major quality attribute of fresh meat. However, the exact mechanisms determining the WHC of meat are not fully understood. Especially, characteristics about proposed water populations in the meat and how they are interrelated with drip loss need to be studied further. Moreover, the distribution and mobility of water in muscle during its conversion to meat and how they are affected by intrinsic and extrinsic factors are poorly elucidated. Nuclear magnetic resonance (NMR) has during recent years gained increasing use within different areas of muscle physiology and meat science. NMR (1)H relaxation methodologies enable detection of the mobility of protons in heterogeneous materials and thereby provide possibilities for a characterization of the properties of water. The objective of this presentation is to give an overview of the use of NMR relaxation measurements to characterize the proposed water populations in meat and investigate how the distribution and mobility of the water changes postmortem. In addition, applications of NMR spectroscopy in metabolic studies will be considered.

Impact of RN genotype and ageing time on colour characteristics of the pork muscles longissimus dorsi and semimembranosus

The effect of RN genotype on pH decline, ultimate pH, pigment content, blooming and colour stability during 6 days of display at 5°C was studied in two pig muscles, M. longissimus dorsi (LD) and M. semimembranosus (SM), and furthermore the effect of anaerobic storage time (2 days vs. 9 days of ageing) on the same parameters was examined. The postmortem pH decline was faster and the ultimate pH lower in LD and SM of the RN(-) genotype compared with corresponding muscles from the rn(+) genotype. Pork of the RN(-) genotype was initially lighter and more red and yellow than pork of the rn(+) genotype due to a higher degree of blooming, which might be explained by the faster pH decline and/or lower ultimate pH. The level of oxymyoglobin (MbO(2)) was decisive for the redness of both muscles during display in air despite a higher presence of metmyoglobin (MetMb). Pork of the RN(-) genotype was thus redder than that of the rn(+) genotype throughout display in air despite higher oxidation to MetMb. Ageing for 9 days in chill improved the blooming potential in pork of both genotypes compared with 2 days of ageing, resulting in superior meat colour. However, only in pork from the RN(-) genotype, the colour was not negatively affected by ageing time upon display in air.

Effect of tumbling and RN genotype on sensory perception of cured-smoked pork loin

Effects of tumbling and RN genotype on sensory perception of cured-smoked loins were studied on loins from 32 crossbred female pigs containing Hampshire blood. Right-side loins were intermittently tumbled during 4 h, whereas left-side loins were left non-tumbled. Tumbled loins were more tender and uniform in cured colour as well as less acidulous in taste compared with non-tumbled loins. Further, the formation of undesirable pores was lower in tumbled loins. Final juiciness tended to be higher and meat taste intensity lower in tumbled loins, whereas initial juiciness did not differ. There were no significant interactions between tumbling and RN genotype for sensory attributes. RN(-) carriers (RN(-)/rn(+)) were more acidulous in taste, had more pronounced meat taste and were saltier than non-carriers (rn(+) /rn(+)). Moreover, they tended to have higher initial juiciness and more undesirable pores, and be less homogeneous in cured pink colour. No differences in consumer preference between the four treatments were detected in the ranking test, but most persons ranked non-tumbled loins highest regarding overall liking. Instrumental tenderness measurements agreed well with sensory tenderness scores.

Natural variations of precursors in pig meat affect the yield of heterocyclic amines--effects of RN genotype, feeding regime, and sex

Pig meat shows natural variations in the concentrations of precursors of heterocyclic amines (HCAs), which may affect formation of HCAs in cooked pig meat. To study this, 26 pigs with an inherent genetic variation (carriers and noncarriers of the RN(-) allele) were subjected to different feeding regimes (conventional feed compared with feed composed according to organic standards). In addition, the effect of sex (castrated males or females) was considered when assessing chemical and technological meat quality parameters. Concentrations of precursors of HCAs, i.e., creatine, residual glycogen, dipeptides, and free amino acids, were analyzed in the raw meat, and the levels of some HCAs (4,8-DiMeIQx, MeIQx, PhIP, harman, and norharman) were then determined in fried meat patties prepared from these pigs. The RN genotype most affected technological meat quality parameters and the level of precursors of HCAs, especially the level of residual glycogen, where carriers of the RN(-) allele showed levels four times as high as those of noncarriers (75.3 +/- 2.6 compared with 17.2 +/- 2.4 micromol/g meat, least-squares means +/- SE). The increased level of residual glycogen resulted in about 50% lower amounts of total mutagenic HCAs in cooked meat compared with cooked meat from normal pigs. Fried meat from carriers of the RN(-) allele obtained darker crust color than meat from noncarriers. Feeding regime and sex did not significantly affect the chemical composition of the meat or the formation of HCAs.