Mechanisms controlling pork quality development: The biochemistry controlling postmortem energy metabolism

Influence of post-mortem muscle glycogen content on the quality of beef during aging

Introduction: Glycolic changes which occur post-mortem have an impact on the physical and sensory features of beef, which in turn determine the successive processes and influence such beef quality traits as colour, tenderness, and cooling loss. The aim of this study was evaluation of the post-mortem changes in bovine meat during aging, quantitative analysis of glycogen and lactic acid, as well as examination of their impact on technological and sensory quality of selected muscles from Holstein-Friesian × Limousin breed carcasses.

Material and Methods: The study included three muscles of different metabolic qualities and sarcomere length: m. semitendinosus, m. longissimus dorsi, and m. psoas major, collected from nine bull carcasses aged 24 ±2 months.

Results: Significant correlations were found between the volume of cooling loss on individual days of aging and the pH value of muscle tissue, lactic acid and glycogen content, as well as beef lightness. However, no significant dependency between the volume of glycogen and the intensity of red and yellow colours was detected.

Conclusion: The colorimetric analysis of glycogen and lactic acid can be an effective tool in predicting the quality of beef.

Integrative Analysis of Metabolomic, Proteomic and Genomic Data to Reveal Functional Pathways and Candidate Genes for Drip Loss in Pigs

The aim of this study was to integrate multi omics data to characterize underlying functional pathways and candidate genes for drip loss in pigs. The consideration of different omics levels allows elucidating the black box of phenotype expression. Metabolite and protein profiling was applied in Musculus longissimus dorsi samples of 97 Duroc × Pietrain pigs. In total, 126 and 35 annotated metabolites and proteins were quantified, respectively. In addition, all animals were genotyped with the porcine 60 k Illumina beadchip. An enrichment analysis resulted in 10 pathways, amongst others, sphingolipid metabolism and glycolysis/gluconeogenesis, with significant influence on drip loss. Drip loss and 22 metabolic components were analyzed as intermediate phenotypes within a genome-wide association study (GWAS). We detected significantly associated genetic markers and candidate genes for drip loss and for most of the metabolic components. On chromosome 18, a region with promising candidate genes was identified based on SNPs associated with drip loss, the protein "phosphoglycerate mutase 2" and the metabolite glycine. We hypothesize that association studies based on intermediate phenotypes are able to provide comprehensive insights in the genetic variation of genes directly involved in the metabolism of performance traits. In this way, the analyses contribute to identify reliable candidate genes.

Application of near infrared reflectance (NIR) spectroscopy to identify potential PSE meat

BACKGROUND

Pale, soft and exudative (PSE) meat is a quality problem that causes a large economic loss to the pork industry. In the present work, near infrared (NIR) quantification and identification methods were used to investigate the feasibility of differentiating potential PSE meat from normal meat.

RESULTS

NIR quantification models were developed to estimate meat pH and colour attributes (L*, a*, b*). Promising results were reported for prediction of muscle pH (R(2) CV  = 70.10%, RPDCV = 1.83) and L* (R(2) CV  = 77.18%, RPDCV = 1.91), but it is still hard to promote to practical application at this level. The Factorisation Method applied to NIR spectra could differentiate potential PSE meat from normal meat at 3 h post-mortem. Correlation analysis showed significant relationship between NIR data and LF-NMR T2 components that were indicative of water distribution and mobility in muscle. PSE meat had unconventionally faster energy metabolism than normal meat, which caused greater water mobility.

CONCLUSION

NIR spectra coupled with the Factorisation Method could be a promising technology to identify potential PSE meat. The difference in the intensity of H2 O absorbance peaks between PSE and normal meat might be the basis of this identification method. © 2015 Society of Chemical Industry.

Changes in expression of monocarboxylate transporters, heat shock proteins and meat quality of Large White Yorkshire and Ghungroo pigs during hot summer period

OBJECTIVE

Present study explores the effect of hot summer period on the glycolytic rate of early post-mortem meat quality of Ghungroo and Large White Yorkshire (LWY) pig and comparative adaptability to high temperature between above breeds by shifting the expression of stress related genes like mono-carboxylate transporters (MCTs) and heat shock proteins (HSPs).

METHODS

Healthy pigs of two different breeds, viz., LYW and Ghungroo (20 from each) were maintained during hot summer period (May to June) with a mean temperature of about 38°C. The pigs were slaughtered and meat samples from the longissimus dorsi (LD) muscles were analyzed for pH, glycogen and lactate content and mRNA expression. Following 24 h of chilling, LD muscle was also taken from the carcasses to evaluate protein solubility and different meat quality measurements.

RESULTS

LWY exhibited significantly (p<0.01) higher plasma cortisol and lactate dehydrogenase concentration than Ghungroo indicating their higher sensitivity to high temperature. LD muscle from LWY pigs revealed lower initial and ultimate pH values and higher drip loss compared to Ghungroo, indicating a faster rate of pH fall. LD muscle of Ghungroo had significantly lower lactate content at 45 min postmortem indicating normal postmortem glycolysis and much slower glycolytic rate at early postmortem. LD muscle of LWY showed rapid postmortem glycolysis, higher drip loss and higher degrees of protein denaturation. Ghungroo exhibited slightly better water holding capacity, lower cooking loss and higher protein solubility. All HSPs (HSP27, HSP70, and HSP90) and MCTs (MCT1, MCT2, and MCT4) in the LD muscle of pigs inclined to increase more in Ghungroo than LWY when exposed to high temperature.

CONCLUSION

Effect of high temperature on the variation of HSPs and MCTs may play a crucial role in thermal tolerance and adaptation to different climatic conditions, pH regulation, muscle acidification, drip loss, protein denaturation and also in postmortem meat quality development.

Different Statistical Approaches to Investigate Porcine Muscle Metabolome Profiles to Highlight New Biomarkers for Pork Quality Assessment

The aim of this study was to elucidate the underlying biochemical processes to identify potential key molecules of meat quality traits drip loss, pH of meat 1 h post-mortem (pH1), pH in meat 24 h post-mortem (pH24) and meat color. An untargeted metabolomics approach detected the profiles of 393 annotated and 1,600 unknown metabolites in 97 Duroc × Pietrain pigs. Despite obvious differences regarding the statistical approaches, the four applied methods, namely correlation analysis, principal component analysis, weighted network analysis (WNA) and random forest regression (RFR), revealed mainly concordant results. Our findings lead to the conclusion that meat quality traits pH1, pH24 and color are strongly influenced by processes of post-mortem energy metabolism like glycolysis and pentose phosphate pathway, whereas drip loss is significantly associated with metabolites of lipid metabolism. In case of drip loss, RFR was the most suitable method to identify reliable biomarkers and to predict the phenotype based on metabolites. On the other hand, WNA provides the best parameters to investigate the metabolite interactions and to clarify the complex molecular background of meat quality traits. In summary, it was possible to attain findings on the interaction of meat quality traits and their underlying biochemical processes. The detected key metabolites might be better indicators of meat quality especially of drip loss than the measured phenotype itself and potentially might be used as bio indicators.

iTRAQ-based quantitative proteomic analysis reveals the distinct early embryo myofiber type characteristics involved in landrace and miniature pig

Background

Pig (Sus scrofa) is a major source of dietary proteins for human consumption and is becoming a valuable model in agricultural and biomedical research. The recently developed isobaric tag for relative and absolute quantitation (iTRAQ) method allows sensitive and accurate protein quantification. Here, we performed the first iTRAQ-based quantitative proteomic analyses of Landrace (LR) and Wuzhishan (WZS) pig longissimus dorsi muscle tissues during early embryonic development.

Results

The iTRAQ-based early embryonic longissimus dorsi muscle study of LR and WZS ranging from 21 to 42 days post coitus (dpc) identified a total of 4431 proteins from17,214 peptides, which were matched with 36,4025 spectra at a false discovery rate of 5 %. In both WZS and LR, the largest amount of differentially expressed proteins (DEPs) were found between 28 and 35 dpc. 252 breed-DEPs were selected by GO analysis, including 8 myofibrillar proteins. Only MYHCI/IIA mRNA were detected due to early embryonic stages, and significantly higher expression of them were found in WZS during these 4 stages. MYHCI was first found in WZS at 28 dpc and expressed in both breeds at later stages, while MYHCII protein was not detected until 35 dpc in both breeds. Thus, 33 myogenic breed-DEPs selected from last two stages were analyzed by STRING, which showed that some myofibrillar proteins (MYH1, TPM4, MYH10, etc.) and functional proteins (CSRP2, CASQ2, OTC, etc.), together with candidate myogenic proteins (H3F3A, HDGFRP2, etc.), probably participate in the regulatory network of myofiber formation.

Conclusion

Our iTRAQ-based early embryonic longissimus dorsi muscle study of LR and WZS provides new data on the in vivo muscle development distinctions during early embryonic development, which contributes to the improved understanding in the regulation mechanism of early myogenesis in agricultural animals.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2464-1) contains supplementary material, which is available to authorized users.

Effect of creatine monohydrate supplementation on carcass traits, meat quality and postmortem energy metabolism of finishing pigs

The objective of this study was to evaluate the effects of creatine monohydrate (CMH) supplementation on meat quality and postmortem energy metabolism of finishing pigs. In total, 48 healthy Duroc–Large White cross castrated male pigs were randomly allocated into two treatments, and fed either a CHM-free basal diet or a basal diet with CMH supplementation (0.8%) for 14 days. At the end of the experiment, six pigs from each treatment were weighed individually and slaughtered. The muscle from longissimus dorsi was collected to evaluate the meat quality and energy metabolism-related parameters. The results showed that CMH supplementation did not affect the loin eye area, back fat depth or dressing percentage (P > 0.05). The muscle pH45 min was higher, whereas drip loss and cooking loss were lower in the CMH supplementation group (P < 0.05). CMH supplementation increased the concentrations of creatine (P < 0.05), adenosine triphosphate (P < 0.05), adenosine diphosphate (P < 0.01) and creatine kinase activity (P < 0.05), and decreased the concentration of lactic acid (P < 0.05), and the activities of lactate dehydrogenase (P < 0.05) and pyruvate kinase (P < 0.05) in muscle postmortem. However, no differences were observed between groups for chemical composition, textural characteristics and glycolytic potential of longissimus dorsi muscle (P > 0.05). These findings suggest that dietary supplementation with CMH during the finishing period in pigs could delay early pH decline and decrease the rate of glycolysis in postmortem longissimus dorsi muscle resulting in a decreased drip loss.

Effects of water-misting sprays with forced ventilation on post mortem glycolysis, AMP-activated protein kinase and meat quality of broilers after transport during summer

Effects of water-misting sprays with forced ventilation on post mortem glycolysis, adenosine monophosphate-activated protein kinase (AMPK) and meat quality of broilers after transport during summer were investigated in the present paper. A total of 105 mixed-sex Arbor Acres broilers were divided into three treatment groups: (i) 45 min transport without rest (T); (ii) 45 min transport with 1 h rest (TR); and (iii) 45 min transport with 15 min water-misting sprays with forced ventilation and 45 min rest (TWFR). Each treatment consisted of five replicates with seven birds each. The results indicated that the water-misting sprays with forced ventilation could mitigate the stress caused by transport under high temperature conditions during summer, which reduced the energy depletion in post mortem Pectoralis major (PM) muscle. This resulted in a higher energy status compared to the T group, which would decrease the expression of phosphorylation of AMPK (p-AMPK). Furthermore, decreased the expression of p-AMPK then slowed down the rate of glycolysis in post mortem PM muscle during the early post mortem period, which in turn lessened the negative effects caused by transport on meat quality. In conclusion, water-misting sprays with forced ventilation may be a better method to control the incidence of the pale, soft and exudative meat in broilers.

Are fish fed with cyanobacteria safe, nutritious and delicious? A laboratory study

Toxic cyanobacterial blooms, which produce cyclic heptapeptide toxins known as microcystins, are worldwide environmental problems. On the other hand, the cyanobacteria protein (30–50%) has been recommended as substitute protein for aquaculture. The present laboratory study verified the feasibility of cyanobacteria protein substitution and risk assessment. Goldfish were fed diets supplemented lyophilised cyanobacteria powder for 16 weeks with the various doses: 0% (control), 10%, 20%, 30% and 40%. Low doses (10% and 20%) promoted growth whereas high doses (30% and 40%) inhibited growth. In cyanobacteria treated fish, the proximate composition of ash, crude fat content and crude protein content decreased in 16 weeks; the saturated fatty acid (SFA) content significantly increased; the n-3 polyunsaturated fatty acid content, collagen content and muscle pH significantly decreased; cooking loss percents increased significantly. Muscle fiber diameter and myofibril length were negatively correlation. Additionally, flavour compounds (e.g., amino acids, nucleotides, organic acids and carnosine) changed significantly in the treated fish, and odour compounds geosmin and 2-methylisoborneol increased significantly. The estimated daily intake (EDI) of microcystins in muscle was close to or exceeded the World Health Organization (WHO) tolerable daily intake (TDI), representing a great health risk. Cyanobacterie is not feasible for protein sources use in aquaculture.

Estimation of pork quality traits using exsanguination blood and postmortem muscle metabolites

The current study was designed to estimate the pork quality traits using metabolites from exsanguination blood and postmortem muscle simultaneously under the Korean standard pre- and post-slaughter conditions. A total of 111 Yorkshire (pure breed and castrated male) pigs were evaluated under the Korean standard conditions. Measurements were taken of the levels of blood glucose and lactate at exsanguination, and muscle glycogen and lactate content at 45 min and 24 h postmortem. Certain pork quality traits were also evaluated. Correlation analysis and multiple regression analysis including stepwise regression were performed. Exsanguination blood glucose and lactate levels were positively correlated with each other, negatively related to postmortem muscle glycogen content and positively associated with postmortem muscle lactate content. A rapid and extended postmortem glycolysis was associated with high levels of blood glucose and lactate, with high muscle lactate content, and with low muscle glycogen content during postmortem. In addition, these were also correlated with paler meat color and reduced water holding capacity. The results of multiple regression analyses also showed that metabolites in exsanguination blood and postmortem muscle explained variations in pork quality traits. Especially, levels of blood glucose and lactate and content of muscle glycogen at early postmortem were significantly associated with an elevated early glycolytic rate. Furthermore, muscle lactate content at 24 h postmortem alone accounted for a considerable portion of the variation in pork quality traits. Based on these results, the current study confirmed that the main factor influencing pork quality traits is the ultimate lactate content in muscle via postmortem glycolysis, and that levels of blood glucose and lactate at exsanguination and contents of muscle glycogen and lactate at postmortem can explain a large portion of the variation in pork quality even under the standard slaughter conditions.

Pre-slaughter rectal temperature as an indicator of pork meat quality

This study investigates whether rectal temperature of pigs, prior to slaughter, can give an indication of the risk of developing pork with PSE characteristics. A total of 1203 pigs were examined, measuring the rectal temperature just before stunning, of which 794 rectal temperatures were measured immediately after stunning. pH30LT (M. Longissimus thoracis) and temperature of the ham (Temp30Ham) were collected from about 530 carcasses, 30 min after sticking. The results present a significant positive linear correlation between rectal temperature just before and after slaughter, and Temp30Ham. Moreover, pH30LT is negatively correlated with rectal temperature and Temp30Ham. Finally, a linear mixed model for pH30LT was established with the rectal temperature of the pigs just before stunning and the lairage time. This model defines that measuring rectal temperature of pigs just before slaughter allows discovery of pork with PSE traits, taking into account pre-slaughter conditions.

Selective removal of ATP degradation products from food matrices II: Rapid screening of hypoxanthine and inosine by molecularly imprinted matrix solid-phase dispersion for evaluation of fish freshness

A water compatible molecularly imprinted polymer (MIP), synthesized using theophylline (TPH) as dummy-template and acrylamide (AM) as functional monomer, has been employed as supporting material in matrix solid-phase dispersion combined with ultra performance liquid chromatography-photodiode array detection (MSPD-UPLC-PDA) for selective determination of adenosine triphosphate (ATP) derivatives in fish samples. ATP degradation products are used as freshness index for assessment of fish quality. The solid sample was directly blended with MIP in MSPD procedure resulting in sample disruption and subsequent adsorption of the compounds on the MIP. By using n-hexane and ammonium hydroxide aqueous solution at pH 9 as the washing and elution solvent, respectively, satisfactory recoveries and clean chromatograms have been obtained. Good linearity for hypoxanthine (HYP) and inosine (INO) has been observed with correlation coefficients (R(2)) of 0.9987 and 0.9986, respectively. The recoveries of the two ATP derivatives at three different spiked levels ranged from 106.5% to 113.4% for HYP and from 103.1% to 111.2% for INO, with average relative standard deviations lower than 4.2% in both cases. This new method, which is rapid, simple and sensitive, can be used as an alternative tool to conventional tedious methods.

Correlations among various blood parameters at exsanguination and their relationships to pork quality traits

The objectives of this study were to investigate the correlations between various blood parameters compared with cortisol and lactate levels under the standard pre-slaughter procedure and handling conditions and to assess their potential as indicators of pork quality traits. Despite there being no additional pre-slaughter stress treatment, there is considerable variation in blood parameters at exsanguination. Serum cortisol and blood lactate levels, widely used indicators of stress, were positively correlated with blood glucose and electrolytes, such as calcium, potassium and sodium. Moreover, these parameters were significantly correlated with a rapid rate of early postmortem glycolysis and reduced water-holding capacity. In particular, blood lactate and glucose levels significantly differed between porcine quality classes. However, other blood parameters including electrolytes did not significantly differ between quality classes though they significantly correlated with pork quality traits. Therefore, serum cortisol, blood lactate and glucose have potential as indicators of the rate and extent of postmortem metabolism and ultimate pork quality under the standard procedure and handling conditions of pre-slaughter.

Comparison of the meat quality, post-mortem muscle energy metabolism, and the expression of glycogen synthesis-related genes in three pig crossbreeds

Post-mortem muscle energy metabolism plays an important role in pork quality. To analyse the differences of meat quality and energy metabolism, three commercial pig crossbreeds frequently used in China were studied, they were DT (Duroc × Taihu; n = 16), PIC (five-way crossbreed from Pig Improvement Co., UK; n = 29) and DLY (Duroc × (Landrace × Yorkshire); n = 19) pigs. The results showed that DT pigs had a higher post-mortem pH45 min and pH24 h, lower shear force and drip loss, higher muscle free-glucose and glycogen contents, and lower lactic acid content than did PIC and DLY pigs. Post-mortem muscle free-glucose content of these three pig crossbreeds changed little, from 45 min to 96 h post-mortem. The expression levels of PRKAG3 (encoding a regulatory subunit of the AMP-activated protein kinase) and GYS1 (encoding muscle glycogen synthase) genes of DT pigs were significantly lower than those of PIC and DLY pigs. DT pigs had a higher expression level of glycogenin-1-like (encoding glycogenin) gene than did PIC and DLY pigs. In conclusion, DT pigs had better meat quality than did the other two pig crossbreeds. We deduced that the post-mortem muscle energy status and metabolism of DT pigs might be an important reason for their good meat quality, and future research should focus on the molecular and physiological mechanism of post-mortem muscle energy metabolism to find ways to improve meat quality.

Glycolytic potential and activity of adenosine monophosphate kinase (AMPK), glycogen phosphorylase (GP) and glycogen debranching enzyme (GDE) in steer carcasses with normal (<5.8) or high (>5.9) 24h pH determined in M. longissimus dorsi

Muscle glycogen concentration (MGC) and lactate (LA), activity of glycogen debranching enzyme (GDE), glycogen phosphorylase (GP) and adenosine monophosphate kinase (AMPK) were determined at 0.5h (T0) and 24h (T24) post-mortem in Longissimus dorsi samples from 38 steers that produced high pH (>5.9) and normal pH (<5.8) carcasses at 24h postmortem. MGC, LA and glycolytic potential were higher (P<0.05) in normal pH carcasses. GDE activity was similar (P>0.05) in both pH categories. GP activity increased between T0 and T24 only in normal pH carcasses. AMPK activity was four times higher in normal pH v/s high pH carcasses, without changing its activity over time. Results reinforce the idea that differences in postmortem glycogenolytic/glycolytic flow in L. dorsi of steers showing normal v/s high muscle pH at 24h, could be explained not only by the higher initial MGC in normal pH carcasses, but also by a high and sustained activity of AMPK and an increased GP activity at 24h postmortem.

The effect of transportation of broilers during summer on the expression of heat shock protein 70, postmortem metabolism and meat quality

The objective of this study was to determine the effects of different transport times on broilers during summer on stress, meat quality, and early postmortem muscle metabolites. Arbor Acres broiler chickens (n = 105) were randomly categorized into 5 treatments: unstressed control, 0.5 h, 1 h, 2 h, and 4 h transport. Each treatment consisted of 3 replicates with 7 birds each. All birds (except the control group) were transported according to a designed protocol. With the extension of transport time, the activities of plasma creatine kinase (CK) and lactate dehydrogenase (LDH) gradually increased. The content of heat shock protein 70 (Hsp70) did not change significantly during 0.5 h transport compared to the control group, but was significantly higher (P < 0.05) at 1 h or more of transport time. Also, transport times of 2 h or more resulted in a death rate of 20%-33% of broilers. We found that the breast meat in the 0.5 h transport group had significantly (P < 0.05) higher L* values, drip loss, cooking loss, AMP/ATP ratio, and phosphorylation of AMP-activated protein kinase (p-AMPK). In addition, pH24h was lower compared to the control group, increasing the likelihood of pale, soft, and exudative (PSE)-like meat. However, no significant variations were found in meat color, drip loss, or cooking loss in other transport groups compared to the control group under the condition of this study. Muscle glycogen content decreased with time of transportation. There were significant correlations among p-AMPK and meat quality (P < 0.05). These results indicate that preslaughter transport during summer may cause severe physiological and biochemical changes of broilers. Further investigations studying the deeper relationship between biological indicators and meat quality according to the similar transport conditions would provide a better understanding of the effect of transport duration on meat quality.

CE-TOF MS-based metabolomic profiling revealed characteristic metabolic pathways in postmortem porcine fast and slow type muscles

To determine key compounds and metabolic pathways associated with meat quality, we profiled metabolites in postmortem porcine longissimus lumborum (LL) and vastus intermedius (VI) muscles with different aging times by global metabolomics using capillary electrophoresis-time of flight mass spectrometry. Loading analyses of the principal component analysis showed that hydrophilic amino acids and β-alanine-related compounds contributed to the muscle type positively and negatively, respectively, whereas glycolytic and ATP degradation products contributed to aging time. At 168h postmortem, LL samples were characterized by abundance of combinations of amino acids, dipeptides, and glycolytic products, whereas the VI samples were characterized by abundance of both sulfur-containing compounds and amino acids. The AMP and inosine contents in the VI were approx. 10 times higher than those in the LL at 4h postmortem, suggesting different rates of inosine 5'-monophosphate (IMP) accumulation by adenylate kinase 7 and 5'-nucleotidase, and subsequent different production levels of IMP and hypoxanthine between these two porcine muscles.

Comparison of energy metabolism and meat quality among three pig breeds

The objective of this study was to evaluate the effects of muscle-fibre types and hormones on glycolytic potential and meat quality traits and their association with glycolytic-related gene expression in three different altitude pig breeds. The pig breeds studied were the Tibetan pig (TP, high altitude), the Liang-Shan pig (LSP, middle altitude) and the Duroc×(Landrace×Yorkshire) cross (DLY, flatland). The results indicated that TP and LSP had better meat quality than DLY (P<0.01). The glycolytic potential (GP) increased in the order of TP Collapse

Key Words

• glycolytic potential
• hormone
• meat quality
• muscle-fiber type
• pig

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MESH Headings

• Animals
• Breeding
• Carrier Proteins/genetics
• Carrier Proteins/physiology
• Energy Metabolism/genetics
• Epinephrine/analysis
• Food Quality
• Gene Expression
• Genotype
• Glucagon/analysis
• Glycolysis/genetics
• Meat/analysis
• Membrane Proteins/genetics
• Membrane Proteins/physiology
• Muscle Fibers, Skeletal
• Myosin Heavy Chains
• Swine/genetics
• Thyroid Hormones/genetics
• Thyroid Hormones/physiology
• Thyroid Hormone-Binding Proteins

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Grants Collapse

Affiliation(s)

Linyuan Shen College of Animal Science and Technology, Sichuan Agricultural University, Ya'an, Sichuan, China
Huaigang Lei
Shunhua Zhang
Xuewei Li
Mingzhou Li
Xiaobing Jiang
Kangping Zhu
Li Zhu

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Nutritional and physiological responses of finishing pigs exposed to a permanent heat exposure during three weeks

The aim of the current study was to investigate the effect of a permanent heat exposure during 21 days on pig performance, nutrient digestibility, physiological response and key enzyme of skeletal muscle energy metabolism. Twenty-four male finishing pigs (crossbreed castrates, 79.0 ± 1.50 kg body weight) were allocated to three groups (n = 8): (1) Control (ambient temperature (AT) 22°C, ad libitum feeding), (2) Group HE (AT 30°C, ad libitum feeding) and (3) Group PF (AT 22°C, pair-fed to Group HE). The permanent heat exposure decreased feed intake (p < 0.01), daily body weight gain (p < 0.05) and the digestibility of gross energy, dry matter, crude protein and ash (p < 0.05); rectal temperature and respiration rate were significantly increased (p < 0.01). The levels of plasma cortisol, creatine kinase and lactate dehydrogenase were also significantly increased in Group HE (p < 0.05). Furthermore, the heat exposure changed intracellular energy metabolism, where the AMP-activated protein kinase was activated (p = 0.02). This was combined with changes in parameters of glycolysis such as an accumulation of lactic acid (p = 0.02) and a drop of pH24 h (p = 0.02), an increase of hexokinase and pyruvate kinase activity (p < 0.01) and, finally, the maturation process of post mortem muscle was influenced. Due to pair-feeding it was possible to evaluate the effects of heat exposure, which were not dependent on reduced feed intake. Such effects were, e.g., reduced nutrient digestibility and changed activities of several enzymes in muscle and blood serum.

Quantitative phosphoproteomic analysis of porcine muscle within 24 h postmortem

Protein phosphorylation can regulate most of the important processes in muscle, such as metabolism and contraction. The postmortem (PM) metabolism and rigor mortis have essential effects on meat quality. In order to identify and characterize the protein phosphorylation events involved in meat quality development, a quantitative mass spectrometry-based phosphoproteomic study was performed to analyze the porcine muscle within 24h PM using dimethyl labeling combined with the TiSH phosphopeptide enrichment strategy. In total 305 unique proteins were identified, including 160 phosphoproteins with 784 phosphorylation sites. Among these, 184 phosphorylation sites on 93 proteins had their phosphorylation levels significantly changed. The proteins involved in glucose metabolism and muscle contraction were the two largest clusters of phosphoproteins with significantly changed phosphorylation levels in muscle within 24 h PM. The high phosphorylation level of heat shock proteins (HSPs) in early PM may be an adaptive response to slaughter stress and protect muscle cell from apoptosis, as observed in the serine 84 of HSP27. This work indicated that PM muscle proteins underwent significant changes at the phosphorylation level but were relatively stable at the total protein level, suggesting that protein phosphorylation may have important roles in meat quality development through the regulation of proteins involved in glucose metabolism and muscle contraction, thereby affecting glycolysis and rigor mortis development in PM muscle.

BIOLOGICAL SIGNIFICANCE

The manuscript describes the characterization of postmortem (PM) porcine muscle within 24 h postmortem from the perspective of protein phosphorylation using advanced phosphoproteomic techniques. In the study, the authors employed the dimethyl labeling combined with the TiSH phosphopeptide enrichment and LC-MS/MS strategy. This was the first high-throughput quantitative phosphoproteomic study in PM muscle of farm animals. In the work, both the proteome and phosphoproteome were analyzed, and the large number of identified peptides, phosphopeptides and phosphorylation sites can greatly enrich the current farm animal protein database. The proteins involved in glycometabolism, muscle contraction and heat shock proteins (HSPs) showed significantly changed phosphorylation levels during PM meat development. This work indicated that PM muscle proteins underwent significant changes at phosphorylation level but were relatively stable at the total protein level, suggesting that protein phosphorylation may have important roles in meat development through the regulation of proteins involved in metabolism and muscle contraction, thereby affecting glycolysis and rigor mortis development in PM muscle. The work can promote the understanding of PM muscle metabolism and meat quality development, and be helpful for future meat quality control.

Monitoring of color and pH in muscles of pork leg (m. adductor and m. semimembranosus)

In order to identify PSE pork meat, pH and color testing was performed directly in a cutting plant (72 hours post mortem) in this research. Specifically pork leg muscles musculi adductor (AD) and semimembranosus (SM) from five selected suppliers (A, B, C, D, E) were examined. Twenty samples of meat for each muscle were examined from each supplier. The measured pH values ranged from 5.43 to 5.63, and the L* values from 46.13 to 57.18. No statistically significant differences in pH values and color were detected among the various suppliers with the exception of the a* and b* parameters for two suppliers, namely A and B (p<0.01). On the contrary, a statistically significant difference (p<0.5) was recorded between individual muscles (AD/SM) across all the suppliers (A, B, C, D, E) with the exception of a* parameter from suppliers B, C, D, E, and pH values for the E supplier. Our results revealed that individual muscles differ in values of pH and color. In comparison with literature, pH and lightness L* values in musculus adductor point to PSE (pale, soft and exudative) meat, while the values of musculus semimebranosus to RFN (red, firm and non-exudative). Use of PSE meat in production of meat products can cause several problems. In particular, it causes light color, low water-holding capacity, poor fat emulsifying ability, lower yield, granular or crumbly texture and poor consistency of the finished product. Therefore classification of the meat directly cutting plant may be possible solution for this problem. The finished product pruduces from muscles of musculi semimembranosus can obtain better quality than the finished product from musculi adductor.

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 45min 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.

Regulation of post-mortem glycolysis in ruminant muscle

As a tissue, muscle has the unique ability to switch its metabolic source of ATP, the energy currency underpinning muscle function. During oxygen debt, such as that occurring immediately following the death of animals, anaerobic metabolism is initiated in an attempt to restore homeostasis within the muscle. The cascade of biochemical events that are initiated is paramount in the context of meat quality. This review revisits this reasonably well-known subject but takes a new perspective by drawing on the understanding outside the traditional discipline of meat science. Our understanding of the intrinsic regulators of glycolytic flux has improved but knowledge gaps remain. Further efforts to understand how the glycolytic enzyme kinetics are influenced by both pre- and post-slaughter factors will be beneficial in the ongoing quest to maximise fresh meat quality.

Influence of modified atmosphere packaging on meat quality parameters of turkey breast muscles

Poultry meat is often stored in modified atmosphere packaging (MAP) or vacuum packaging to improve consumer acceptance and shelf life. The aim of this study was to determine how different packaging conditions influence meat quality. Therefore, in three independent experiments, turkey breast muscle cutlets were packaged either in vacuum or in different modified atmosphere mixtures (80% O2, 20% CO2 [MAP 1]; 80% N2, 20% CO2 [MAP 2]; and 20% O2, 20% CO2, 60% N2 [MAP 3]) and stored for 12 days at 3°C. Color, pH, electrical conductivity, total viable counts, and Pseudomonas species were determined on days 1, 4, 8, and 12 of storage. On the same days, samples were collected for analysis of thiobarbituric acid-reactive substance and total volatile basic nitrogen concentrations. Sensory parameters and liquid loss were determined on days 4, 8, and 12. Vacuum-packaged meat had the highest liquid loss and lowest sensory results. MAP 1-packaged meat showed the highest sensory, redness, and thiobarbituric acid-reactive substance values. MAP 2-packaged meat had lower sensory values. MAP 3-packaged meat had lower redness and sensory values, especially at the end of storage. The study showed an impact of the packaging condition on different quality parameters, with a small advantage for storage of turkey cutlets in high-oxygen packages.

Genome-wide association study of meat quality traits in a White Duroc×Erhualian F2 intercross and Chinese Sutai pigs

Thousands of QTLs for meat quality traits have been identified by linkage mapping studies, but most of them lack precise position or replication between populations, which hinder their application in pig breeding programs. To localize QTLs for meat quality traits to precise genomic regions, we performed a genome-wide association (GWA) study using the Illumina PorcineSNP60K Beadchip in two swine populations: 434 Sutai pigs and 933 F2 pigs from a White Duroc×Erhualian intercross. Meat quality traits, including pH, color, drip loss, moisture content, protein content and intramuscular fat content (IMF), marbling and firmness scores in the M. longissimus (LM) and M. semimembranosus (SM) muscles, were recorded on the two populations. In total, 127 chromosome-wide significant SNPs for these traits were identified. Among them, 11 SNPs reached genome-wise significance level, including 1 on SSC3 for pH, 1 on SSC3 and 3 on SSC15 for drip loss, 3 (unmapped) for color a*, and 2 for IMF each on SSC9 and SSCX. Except for 11 unmapped SNPs, 116 significant SNPs fell into 28 genomic regions of approximately 10 Mb or less. Most of these regions corresponded to previously reported QTL regions and spanned smaller intervals than before. The loci on SSC3 and SSC7 appeared to have pleiotropic effects on several related traits. Besides them, a few QTL signals were replicated between the two populations. Further, we identified thirteen new candidate genes for IMF, marbling and firmness, on the basis of their positions, functional annotations and reported expression patterns. The findings will contribute to further identification of the causal mutation underlying these QTLs and future marker-assisted selection in pigs.

Effect of temperature and pH on postmortem color development of porcine M. longissimus dorsi and M. semimembranosus

BACKGROUND

Purchasing pork that is boned within 1 h postmortem and not aged is customary in China, and final pork color would not be fully realized. The relationship between early postmortem, pre-rigor meat color and 24 h postmortem, post-rigor pork color was investigated and related to the rate of pH and temperature decline within the longissimus dorsi (LD) and the semimembranosus (SM) muscles of pork carcasses. Muscle color, pH and temperature were measured at 45 min and at 3, 9, 15 and 24 h postmortem in carcasses of F₂ White Duroc and Chinese Erhualian pigs.

RESULTS

Pork color at 45 min postmortem was not indicative of that at 24 h postmortem in LD and SM, although muscle pH values and temperature at 45 min postmortem were significantly correlated with the LD and SM ultimate color. High muscle pH was associated with decreased L*, whereas high muscle temperature increased L*. Muscle pH and temperature had little effect on a* and b* in LD and color evolution in SM.

CONCLUSIONS

Results indicated that meat color inspected shortly after slaughter does not reflect post-rigor meat quality.

Properties of raw meat and meat curry from spent goat in relation with post-mortem handling conditions

The properties of raw meat and meat curry from spent goat meat in relation with post-mortem handling conditions were evaluated. The conditions evaluated were: cooking of meat within 1-2 h post-slaughter (condition 1); deboning meat storage at 25 ± 2 °C for 5-6 h and cooking (condition 2); post-slaughter storage of carcass at room temperature for 5-6 h, then deboning followed by storage of meat at refrigeration temperature for 5-6 h and cooking (condition 3); deboning and storage of meat at 25 ± 2 °C for 10-12 h and cooking (condition 4). Significant difference was observed in pH values in condition 1 (p < 0.01) and moisture content (p < 0.05) of raw meat as compared to the conditions 2, 3 and 4. However, the moisture content of cooked meat was significantly higher (p < 0.05) for conditions 1 and 2 as compared to the conditions 3 and 4. Significant differences were also observed in muscle fiber diameter values of different conditions, that is, the mean values were significantly higher (p < 0.05) for conditions 2 and 4 and significantly lower for condition 1. The mean water holding capacity and cooking yield values were highest in condition 1, followed by conditions 2, 3 and 4. The significant differences was also observed in shear force value of cooked meat chunks, that is, the mean value was significantly higher (p < 0.01) for condition 2 and significantly lower for condition 1. Sensory scores were significantly higher in condition 1 and significantly lower in condition 2. However, sensory scores for condition 4 were almost similar to the condition 1.

Progress and recent advances in fabrication and utilization of hypoxanthine biosensors for meat and fish quality assessment: a review

This review provides an update on the research conducted on the fabrication and utilization of hypoxanthine (Hx) biosensors published over the past four decades. In particular, the review focuses on progress made in the development and use of Hx biosensors for the assessment of fish and meat quality which has dominated research in this area. The various fish and meat freshness indexes that have been proposed over this period are highlighted. Furthermore, recent developments and future advances in the use of screen-printed electrodes and nanomaterials for achieving improved performances for the reliable determination of Hx in fish and meat are discussed.

Consequences of divergent selection for residual feed intake in pigs on muscle energy metabolism and meat quality

Selection to decrease Residual Feed Intake (RFI) is a relevant way to improve feed efficiency in growing pigs. However, RFI criterion is correlated with body composition and muscle characteristics. Present study evaluated adaptive responses to divergent selection on RFI on muscle metabolism and homeostasis through AMP-activated protein kinase pathway. Consequences on technological and sensory meat quality were also analyzed in two lines of Large White pigs after six generations of divergent selection on RFI. RFI(-) pigs (n=60) exhibited similar growth rate but lower feed intake and conversion ratio, and were leaner than RFI(+) pigs (n=57). Despite higher glycogen content, metabolic enzyme capacities involved in glycolytic, fatty acid oxidation pathway and energy balance were reduced in the Longissimus muscle of the RFI(-) pigs. Reduced muscle homeostasis in the RFI(-) line influenced post-mortem metabolism and impaired technological quality traits of loin and ham but had only slight effects on meat eating quality.