Production systems and influence on eating quality of pork

The present paper reviews the available information on the eating quality of pork from the perspective of production systems considered at farm level. Among the specifications differentiating systems having a claim on eating quality, breed, feeding strategy, rearing conditions and slaughter age/weight of the pigs may influence pork eating quality. Specific genetic X environment interactions such as the use of slow growing-fat local breeds reared in extensive conditions, as encountered in local Mediterranean systems, lead to high eating quality of pork and pork products Organic production per se has little influence on the eating quality of pork. Welfare-oriented specifications such as enriched living environment, outdoor access or free-range rearing have limited consequences on pork quality. Because boar taint negatively impacts the consumer acceptability of pork, a total ban on castration to improve animal welfare would be a real challenge for the management of pork quality in those countries where entire male pig production is not currently common.     

Effects of muscle cortisol concentration on muscle fiber characteristics, pork quality, and sensory quality of cooked pork

The effect of muscle cortisol concentration on muscle fiber characteristics and technological and sensory quality of pork was investigated. With the exception of the percentage of type IIA fibers, muscle fiber characteristics were not associated to cortisol levels. However, muscle cortisol concentration was positively associated with muscle pH(24h) (r = 0.23, P<0.05) and negatively associated with drip loss (r = -0.49, P<0.001), lightness (r = -0.24, P<0.05), shear force (r = -0.25, P<0.05), and texture profile analysis-hardness (r = -0.35, P<0.01). Additionally, the water-holding capacity of meat samples was affected by cortisol levels, with lower cortisol concentrations associated with less tender samples. These results indicate that the concentration of cortisol in the muscle is related with meat quality as well as the sensory quality of cooked pork.     

The relation of blood glucose level to muscle fiber characteristics and pork quality traits

The purpose of this study was to examine the relationships between blood glucose level, muscle fiber characteristics, and pork quality. Muscle samples were classified into three groups based on blood glucose level measured at slaughter. Pigs with higher area percentages of fiber type IIB showed higher blood glucose levels compared to pigs with lower area percentages of fiber type IIB. The high blood glucose level group presented lower pH values at 45 min and 24 h postmortem, and also had higher L^∗ values and reduced water holding capacity. In addition, blood glucose level had a negative relationship with pH_45 min and the solubility of sarcoplasmic and myofibrillar proteins, whereas it had a positive relationship with drip loss and filter-paper fluid uptake. In conclusion, blood glucose level was related to muscle fiber area composition and could partially indicate ultimate pork quality.     

Comparing the histochemical characteristics and meat quality traits of different pig breeds

The purpose of this study was to compare the muscle histochemical characteristics and meat quality traits between Berkshire, Landrace, Yorkshire, and crossbred pigs. A total of 594 pigs were evaluated. A clear difference between histochemical properties was observed from the results for fiber type composition. In Berkshire pigs, the area percentage of type I fibers was higher (P < 0.001) and that of type IIb fibers was lower (P < 0.05) than those of other breeds. The muscle pH_45min and pH_24h were significantly higher in Berkshire pigs. Drip loss and color parameters were significantly different between the breeds (P < 0.001). The Berkshire pigs, which showed the highest muscle pH and lowest drip loss and L^* values, contained a significantly higher percentage of type I fibers than the other breeds. By comparing the fiber type compositions of the different breeds, the results imply that the longissimus dorsi muscle of Berkshire pigs is more oxidative than that of other breeds. A high pH value in Berkshire pigs is due to a high percentage of type I fibers and a low percentage of type IIb fibers. Based on these results, we conclude that muscle fiber composition can explain in parts the variation of meat quality across and within breeds.     

Surface-enhanced laser desorption/ionisation time-of-flight mass spectrometry: A tool to predict pork quality

Expression of water soluble proteins of fresh pork Longissimus thoracis from 4 pure breed pigs (Duroc, Large White, Landrace, and Piétrain) was studied to identify candidate protein markers for meat quality. Surface-enhanced laser desorption/ionisation time-of-flight mass spectrometry (SELDI-TOF-MS) was used to obtain the soluble protein profiles of Longissimus thoracis muscles. The pure breeds showed differences among the studied meat quality traits (pH_u, drip loss, androstenone, marbling, intramuscular fat, texture, and moisture), but no significant differences were detected in sensory analysis. Associations between protein peaks obtained with SELDI-TOF-MS and meat quality traits, mainly water holding capacity, texture and skatole were observed. Of these peaks, a total of 10 peaks from CM10 array and 6 peaks from Q10 array were candidate soluble protein markers for pork loin quality. The developed models explained a limited proportion of the variability, however they point out interesting relationships between protein expression and meat quality.     

The influence of breed on the carcass and eating quality of pork.

Twelve gilts from four breeds were reared from 30 to 65 kg liveweight and assessed for carcass, muscle and eating quality. The breeds were Large White (LW), Gloucester Old Spot (GOS) Crossbreed 1 (C1) and Crossbreed 2 (C2). The latter two were commercial products from breeding companies. There were small differences in quality between the breeds. C1 had about 2% more lean than the others. GOS had shorter carcasses, a higher proportion of total lean in the fore limb and thicker backfat but were not fatter overall. C1 and C2 had lower pH₁ measurements than LW or GOS but similar colour and drip loss measurements in M. longissimus lumborum. There were positive but weak relationships between pH₁ and percentage fat (r= +0.1 to +0.3). C1 had the more tender meat. When all breeds were pooled, about 9 % of the variation in toughness was accounted for by variation in percentage lean or fat. There was no suggestion that the pure breeds or fatter pigs had meat of better eating quality.     

Relationships between biochemical characteristics and meat quality of Longissimus thoracis and Semimembranosus muscles in five porcine lines

Five porcine genetic lines which represent a high proportion of European pig production were fully characterized for meat quality parameters and muscle biochemical characteristics (Longissimus thoracis, LT, and Semimembranosus, SM). The line characterisation was based on 100 animals each representing Large White, Landrace, Duroc, Piétrain (Halothane negative) and Meishan (a Meishan/Large White crossbred line) prevalent genetic backgrounds. Different meat quality parameters (pH 45min, pH ultimate, electrical conductivity, and colour measurements), as well as muscle water holding capacity, muscle metabolic and contractile traits, fibre type, size and frequencies were measured and their relationships studied. The main differences in the LT were found between the Meishan and Piétrain genetic lines, in relation to the muscle fibre size (larger in Piétrain). The Duroc line was characterized by the muscle oxidative traits and the Landrace by the high percentage of fast glycolytic fibres. In SM, Duroc and Piétrain were distinguished from Landrace and Meishan according to the metabolic and contractile characteristics of this muscle. Large White tended to lie between the other breeds for many of the traits. The measured muscle characteristics were related to differences in drip loss and marbling values and could thereby influence the eating quality of pork. Overall the results show differences between the genetic lines for a number of muscle traits which could have impact on consumer appeal and eating quality. The present findings should serve to emphasise the importance of including eating quality as a trait in breed selection.     

Factors affecting the eating quality of pork

In the last decade studies with the specific objective of improving the sensory quality of pork have come to the forefront of meat research, likely a result of consumer complaints of blandness levelled against modern lean meat and the frequent reference to the more strongly flavored meat that was available years ago. Regardless of the lack of scientific evidence to substantiate or refute these claims, the consumer perception of deteriorated quality is real and presents a challenge for the pork industry. Hence, this review has been undertaken with the aim of providing insight into potential sources of amelioration of the eating quality of fresh pork. Existing works are collated, encompassing animal effects, such as, species, breed, muscle type, fat, and ultimate pH, as well as environmental influences, including pre-slaughter conditions of and housing and exercise, and post-slaughter parameters, such as, electrical stimulation, chilling, and cooking.     

The influence of carcass backfat and intramuscular fat level on pork eating quality

To evaluate the contribution of fatness level towards pork eating quality, carcass and meat eating quality data were analysed from 721 pigs of three genotypes (with 0, 0.25 and 0.50 Duroc inclusion level). Animals (entire male and female) were reared from 30 to 90 kg liveweight on one of seven feeding regimens which involved combinations of diet formulation and feeding level, so as to produce carcasses of widely differing fatness levels. This experimental design produced coefficients of variation for classification P₂ backfat thickness of 21.11 (mean 11.59 mm, SE 0.093) and intramuscular fat (IMF) of 63.60 (mean 13.4 g kg⁻¹, SE 0.33). The treatments also produced considerable variation for eating quality as assessed by trained sensory panel (1–8 scale) and objectively (shear force) as shown by the following coefficients of variation: shear force 22.01% (mean 334 N, SE 2.77), juiciness 16.12% (mean 4.95, SE 0.297), tenderness 19.65% (mean 5.06, SE 0.370), pork flavour 13.22% (mean 4.56, SE 0.225), abnormal flavour 34.46% (mean 2.02, SE 0.259) and overall acceptability 18.42% (mean 4.78, SE 0.328). Correlation coefficients between carcass fatness measurements and eating quality characteristics were calculated. Although shear force was significantly correlated with both classification P₂(r = −0.213) and IMF (r = − 0.189), taste panel tenderness was not significantly correlated to fatness level. Of the taste panel parameters evaluated, only juiciness showed a significant correlation (P < 0.05) with classification P₂(r = − 0.086). None of the eating quality characteristics as evaluated by taste panel correlated significantly with IMF. These results do not support the belief that fatness level per se has a major influence on pork eating quality. © 2000 Society of Chemical Industry     

Effect of Duroc content, sex and ageing period on meat and eating quality attributes of pork loin

This study was conducted to determine the effect of percentage Duroc content of entire male and female pigs and ageing period on meat and eating quality attributes of pork loin (M. longissimus thoracis et lumborum). A total of 84 pigs [entire males (n=42) and female (n=42)] of 0% Duroc (100% Large White), 50% Duroc (Duroc×Large White) or 100% Duroc (n=14 pigs per sex×genotype combination) were slaughtered at a liveweight of 100 kg. Steaks from the M. longissimus lumborum of female pigs were aged for either 2 or 7 days post-slaughter and evaluated using a consumer taste panel. Eating quality attributes of tenderness, flavour and overall liking of pork loin steaks from female pigs were not (P>0.05) influenced by Duroc content. Pork from 100% Duroc pigs was juicier (P=0.05) and had a higher (1.84%, P=0.05) intramuscular fat content than pork from 0 and 50% Duroc pigs (1.40 and 1.25%, respectively). Pork from entire male pigs had a lower (P<0.001) intramuscular fat content, was darker (P<0.01) in colour and recorded higher (P<0.01) Warner Bratzler shear force values compared with pork from female carcasses. Ageing pork loin steaks in vacuum bags for 7 days improved tenderness (P<0.01), flavour (P<0.05) and overall liking (P<0.05) compared with steaks aged for 2 days post-slaughter. Ageing of pork steaks for 7 days post-slaughter improved eating quality attributes far more effectively than increasing percentage Duroc content of pigs, which only influenced consumer scores for juiciness.     

A survey of pork quality in relation to pre-slaughter conditions, slaughterhouse facilities, and quality assurance

A survey at five pigs' slaughterhouses was performed to investigate the effect of a quality assurance system, pre-slaughter conditions and slaughterhouse facilities on pork quality. Totally, 2246 pigs were included over four transports per slaughterhouse, i.e. two transports were produced according to a quality assurance system and the other two were conventional pigs. Meat quality was measured on 446 pigs. The pH in the longissimus dorsi muscle and the electrical conductivity in the semimembranosus muscle were measured 30min post-mortem. Twenty-four hours later pH and electrical conductivity in both the longissimus dorsi and the semimembranosus muscle were measured. Pigs managed according to a chain quality protocol showed an overall higher potential for improved meat quality. Differences in meat quality between the different slaughterhouses were also found, however they were dependent on muscle type and time of measuring. Influencing factors on pork quality seemed to be stocking density during transport, the handling during offloading the pigs from the truck, stocking density, and air temperature during lairage.     

The effect of genotype, sex and management strategy on the eating quality of pork

Two hundred and sixteen (Large White×Landrace×Duroc) crossbred pigs were used to determine the influence of genotype, sex, and management strategies on pork quality. The experiment was a 2×3×3 factorial design with the main treatments being genotype (A?- 50% and B?- <25% Duroc bloodline), sex (females, surgical barrows and immunological barrows) and management strategy (control?- C, dietary conjugated linoleic acid supplementation?- CLA, and porcine somatotropin administration?- pST). Genotype A pigs had less backfat (P2 site), higher intramuscular fat percentage, higher muscle ultimate pH (pH(u)) and surface exudate, and the pork was tougher and less acceptable compared with Genotype B pigs. Female pigs had lower muscle pH(u), higher surface exudate and tougher pork compared with both surgical and immunological barrows. Pigs fed the control diet had lower muscle pH(u) and higher surface exudate compared with pigs fed the CLA supplemented diet or administered pST. Pigs fed the control diet had higher consumer likeness scores for flavour, tenderness, juiciness and overall acceptability compared with pigs fed the CLA supplemented diet or administered pST. The results from this experiment indicate that pork eating quality is reliant on a complex interaction between genotype and sex. The results also indicate that management strategies such as pST administration and CLA supplementation, while being effective in reducing backfat, have the potential to have a negative impact on pork quality.     

Association of blood glucose,blood lactate,serum cortisol levels,muscle metabolites,muscle fiber type composition,and pork quality traits

The objective of this study was to investigate the relationship of blood glucose levels with blood lactate, serum cortisol levels, postmortem muscle glycogen and lactate content, muscle fiber type composition, and pork quality traits. Compared to pigs with lower blood glucose levels, pigs with higher blood glucose levels showed higher blood lactate and serum cortisol levels at exsanguination, and they had lower residual glycogen and higher lactate content in the muscle at 45 min postmortem. In addition, pigs with higher blood glucose levels had higher type IIB and lower type I area composition and finally exhibited lower muscle pH, paler color, and excessive loss of fluid on surface. These results imply that measuring blood glucose levels at exsanguination can be useful to indicate early glycolytic rates during postmortem and thus may be of value in the identification of pork with undesirable quality traits.     

Influence of dietary fat on pork eating quality

This study compared the influence of dietary fat sources on meat quality, fatty acid composition and sensory attributes in pork. The experiment was conducted with 43 entire male pigs (Pietrain×(Landrace×Large White)) which were fed a basal diet without added fat (control diet) or supplemented with different sources of fat: animal fat (1%, AF1; 3%, AF3), soyabean oil (1%, SBO1) and calcium soaps of palm oil (1%, CaSPO1). Dietary fat supplementation did not significantly affect ultimate pH, colour, Warner-Bratzler shear force values, sensory attributes or SFA. Pigs fed SBO1 had the lowest proportion of MUFA and the highest of PUFA. In conclusion, these dietary fat sources could be recommended for inclusion in diets, at these levels, with no detrimental effect on eating quality. Despite finding no significant differences, the PCA afforded a comprehensive view of the predominating attributes of pork from animals fed the different fats.     

Meat quality: Influence of fatness of pigs on the eating quality of pork

The eating qualities of pork from the longissimus dorsi muscles of pigs showing a wide variation in fatness (10-40 mm, back fat thickness) were assessed by taste panel after either the excised muscle had been grilled or a complete loin joint had been roasted. The average panel scores for texture and juiciness covered a wide range but were not consistently related to fatness. Although meat from fatter pigs tended to be judged more tender in direct comparisons, overall the results did not support the contention that fatness in the carcass is associated with tenderness in the lean meat.     

市售生鲜猪肉品质特征差异研究

通过对市场上生鲜猪肉的新鲜度、系水力、肉色、嫩度等肉质指标的测定,从包装方式、认证方式、猪品种方面分析市售生鲜猪肉品质差异状况,为指导合理消费及制定相应的标准提供参考.结果表明:分割包装肉样的新鲜度较未经分割包装的差,但是在水分含量、系水力、嫩度方面品质较好;未经认证猪肉与绿色猪肉、有机猪肉相比,存在系水力较差、嫩度较差、水分含量合格率较低的问题;本地猪肉与杂交猪肉相比,具有系水力好、肉色鲜红、质地细嫩等优良品质特点     

Influence of heat on protein degradation, ultrastructure and eating quality indicators of pork

BACKGROUND: Heating temperature is an important factor affecting meat palatability. This study aimed to evaluate the influence of heating temperature on some eating quality indicators, protein degradation and ultrastructure of pork muscle fibres and their correlations. RESULTS: Cooking loss (CL) increased gradually (P < 0.05) with increasing temperature. Warner–Bratzler shear force (WBSF) increased in two separate phases from 25 to 50 °C and again from 60 to 100 °C (P < 0.05), with a steady phase from 50 to 60 °C (P > 0.05); conversely, a significant increase in pH (P < 0.05) occurred between 50 and 60 °C. Strong correlations (P < 0.01) among pH, CL, WBSF and colour parameters L* and b* were observed following the heating process. Increasing temperature induced gradual degradation of many muscle proteins, but myosin was not significantly degraded until 80 °C and actin showed no visible degradation throughout the whole heating process. Meanwhile, the structure of muscle fibres also changed significantly on heating, with sarcomeres contracting transversely and longitudinally and becoming condensed, but there was no occurrence of breakage within fibres. CONCLUSION: Heating temperature has a great effect on eating quality indicators, protein degradation and ultrastructure of pork muscle fibres. Copyright © 2010 Society of Chemical Industry     

Correlations of trained panel sensory values of cooked pork with fatty acid composition,muscle fiber type,and pork quality characteristics in Berkshire pigs

The objective was to examine the relationship of trained panel sensory scores of cooked pork with fatty acid composition, muscle fiber type, and meat quality characteristics from Berkshire pigs. No or few associations were found between the panel sensory scores of cooked meat, especially tenderness attributes, and fatty acid composition; however, intramuscular fat content positively correlated with off-flavor score (r = 0.31). On the other hand, the morphological characteristics of muscle fibers were correlated with panel sensory values. Muscles with smaller cross-sectional area and higher density of fibers were more closely associated with softer, more tender panel scores and a lower number of chews than muscles with larger fiber area and lower density of fibers. The water holding capacity test of filter-paper fluid uptake was moderately correlated with panel scores of softness (r = 0.33), initial tenderness (r = 0.38), chewiness (r = 0.40), juiciness (r = − 0.27), flavor intensity (r = − 0.23), and off-flavor (r = 0.30). Panel sensory values of Berkshire pig meat was moderately related to postmortem meat quality, especially water holding capacity. A more thorough understanding of the relationships between fatty acid composition and muscle fiber type with palatability is needed.     

Short-term feeding strategies and pork quality

Two experiments were done to determine whether short-term supplementation (5 days pre-slaughter) with magnesium acetate, or a combination of magnesium acetate, tryptophan, vitamin E and vitamin C would improve pork quality. In the first experiment the pigs (Pietrain×Yorkshire, n=96) were fed a standard feed or a magnesium supplemented feed for 5 days prior to slaughter. As a possible stress factor half of the animals were slaughtered upon arrival at the slaughterplant whereas the remaining animals were allowed two hours of rest in lairage before slaughter. Magnesium supplementation did not result in an increase in plasma magnesium concentration at slaughter. Omission of lairage resulted in higher plasma glucose concentrations, but plasma lactate concentrations were not affected. Drip loss and ultimate pH were not affected by diet or omission of lairage. Omission of lairage resulted in poorer color characteristics. This effect was prevented by supplementation with magnesium. In the second experiment the pigs (Pietrain×Yorkshire, n=92) were fed a standard feed or this standard feed supplemented with magnesium acetate, tryptophan, vitamin E and vitamin C for 5 days prior to slaughter. Supplementation with vitamin E did not increase muscle vitamin E concentration. Inclusion of supplements in the diet failed to improve water-holding capacity or color characteristics. These results indicate that short-term supplementation with magnesium acetate, tryptophan, vitamin E and vitamin C is of little value in improving pork quality when pigs are not stressed beyond levels associated with routine slaughter procedures.