Proteomic profile of dry-cured ham relative to PRKAG3 or CAST genotype, level of salt and pastiness

1H NMR Reveals the Mechanism of Potassium Lactate on Proteolysis and Taste Metabolites of Rugao Ham

To deepen the understanding of the effect of potassium lactate on the taste of Rugao ham, proteolysis index, enzyme activities and protein degradation of Rugao ham salted with potassium lactate (0%, 0.5%, 1%, 2%) were investigated. Metabolites of Rugao ham were identified by 1H nuclear magnetic resonance (NMR) spectroscopy and the metabolic pathways of the key metabolites were enriched by the Kyoto Encyclopedia of Genes and Genomes (KEGG); the relationship between taste and metabolites was assessed by partial least square discriminant analysis (PLS-DA). The hams with 2% potassium lactate showed lower cathepsin B and L activities, and higher aminopeptidase activities than that of the control group. The contents of free amino acids and organic acids significantly increased from the control to the treatment of 2% potassium lactate. PLS-DA further demonstrated that aspartate, glutamate, alanine, serine, threonine, acetate, lactate, succinate, carnosine, β-glucose and glycerol were the key metabolites to improve the taste of Rugao ham in the treatment of 2% potassium lactate. Metabolic pathways analysis further demonstrated that amino acids metabolism was the main pathway for the taste development of Rugao ham.

LC-MS/MS-based metabolomics and sensory evaluation characterize metabolites and texture of normal and spoiled dry-cured hams

The spoiled dry-cured ham commonly shows unpleasant taste and odour. To deepen the understanding in the formation mechanism of unpleasant taste in spoiled ham, sensory attributes, texture parameters, protein degradation, metabolites were investigated between normal and spoiled hams; the relationship between the sensory quality and metabolites of dry-cured ham was further evaluated by partial least square discriminant analysis (PLS-DA). The scores of richness and overall acceptance were significantly lower in spoiled ham, and more than 12.5-fold values in adhesiveness were found in spoiled ham than normal ham. Myofibrillar proteins including actin, troponin-T and myosin light chain showed excessive degradation in spoiled ham. Forty-two kinds of metabolites mainly derived from protein degradation were identified by LC-MS/MS, and amino acid derivatives and oligopeptides were the key components to distinguish spoiled and normal hams demonstrated by PLS-DA. Purine metabolism, pyrimidine metabolism and protein degradation were the main metabolism pathways in spoiled ham.

The Influence of the Type of Dry-Cured Italian PDO Ham on Cathepsin B Activity Trend during Processing

Cathepsin B activity was measured during processing in hams originating from the main Italian prosciutto PDOs: Parma, San Daniele and Toscano. Sixty-five heavy pig thighs, from sixty-five Italian large white x Italian Landrace pigs bred and slaughtered in the same conditions were considered. Five thighs represented the post-mortem control time. The other 60 were distributed one plant per PDO, following a balanced plan. The thighs were sampled at the biceps femoris in groups of four per plant in the following ripening phases: salting, resting, drying, greasing, end of curing. The activity of the Cathepsin B (U/g protein) was determined by means of fluorescence measurements. The Cathepsin B ripening trend of the various PDOs was significantly different, particularly during the initial and mid-curing stage. This activity correlates with the proteolysis index through a PDO dependent pattern, indicating that different processing conditions can influence the quality of prosciutto, since they determine its biochemical development.

A comprehensive review on molecular mechanism of defective dry-cured ham with excessive pastiness, adhesiveness, and bitterness by proteomics insights

Excessive bitterness, pastiness, and adhesiveness are the main organoleptic and textural defects of dry-cured ham, which often cause a lot of financial losses to manufacturers and seriously damage the quality of the product. These sensory and textural defects are related to the protein degradation of dry-cured ham. Proteomics shows great potential to improve our understanding of the molecular mechanism of sensory and textural defects and identify biomarkers for monitoring their quality traits. This review presents some of the major achievements and considerations in organoleptic and textural defects of dry-cured ham by proteomics analysis in the recent decades and gives an overview about how to correct sensory and textural defects of dry-cured ham. Proteomics reveals that muscle proteins derived from myofibril and cytoskeleton and involved in metabolic enzymes and oxygen transport have been identified as potential biomarkers in defective dry-cured ham. Relatively high residual activities of cathepsin B and L are responsible for the excessive degradation of these protein biomarkers in defective dry-cured ham. Ultrasound-assisted mild thermal or high-pressure treatment shows a good correction for the organoleptic and textural defects of dry-cured ham by changing microstructure and conformation of muscle proteins by accelerating degradation of proteins and polypeptides into free amino acids.

Proteomic Profiles of the Longissimus Muscles of Entire Male and Castrated Pigs as Related to Meat Quality

There are indications of reduced meat quality in entire male pigs (EMs) in comparison to surgically castrated pigs (SCs); however, the differences are not strongly confirmed, and the etiology is not clarified. In the present study, samples of the longissimus dorsi, pars lumborum muscle (LL) from EMs (n = 12) and SCs (n = 12) of the same age and weight were evaluated at the physico-chemical and proteomic level. EMs exhibited lower intramuscular fat content, higher collagen content with higher solubility, a higher level of protein carbonyl groups (indicating higher protein oxidation), lower water holding capacity, and tougher meat than SCs. Proteomic analysis revealed differences in heat shock proteins expression, while a greater abundance of several other identified proteins (malate dehydrogenase, Na/K-transporting adenosintriphosphatase (ATP-ase) subunit alpha-1, and blood plasma proteins) indicates that EMs have a more oxidative metabolic profile than that of SCs. More abundant protein fragments (mainly actin and myosin heavy chain) suggest a higher degree of proteolysis in EMs, which was not followed by lower meat toughness.

Proteomic footprint of ultrasound intensification on sliced dry-cured ham subjected to mild thermal conditions

Ultrasound can intensify the heating process used to correct texture defects in dry-cured hams. The effect of ultrasound-assisted heating on the proteome of sliced dry-cured ham was evaluated. Dry-cured hams with high proteolysis index (PI > 36) were sliced, vacuum packed and subjected to conventional (CV) and ultrasound-assisted (US) thermal treatments. Comparative proteome profiling between sample groups was assessed by two-dimensional electrophoresis (2-DE) coupled to tandem mass spectrometry. It was found that protein fragmentation increased markedly after US thermal treatment. Specifically, fragments of the major myofibrillar protein, actin, were abundantly over-represented following US heating. In addition, five unfragmented sarcoplasmic proteins (i.e. fatty acid-binding protein, peroxiredoxin-6, superoxide dismutase, carbonyl reductase and aminoacylase) showed increased abundance in the US sample group. These results suggest candidate biomarkers to monitor proteolysis intensity and proteolysis-independent effects linked to cured ham quality by ultrasound application. SIGNIFICANCE: The present proteome profiling study of treated dry-cured ham demonstrates the impact of ultrasound action on proteins. Moreover, negative organoleptic effects can be appearing with ultrasound treatment due to proteolysis increase. Therefore, the proteolysis monitoring could help to control these effects. In this regards, our results suggest that actin can be a candidate biomarker to monitor proteolysis intensity.

Application of temperature and ultrasound as corrective measures to decrease the adhesiveness in dry-cured ham. Influence on free amino acid and volatile compound profile

The impact of low temperature treatment and its combination with ultrasound has been evaluated in order to correct texture defects in dry-cured hams. A total of 26 dry-cured hams, classified as high proteolysis index (PI>36%), were used. From these hams, ten slices from each ham sample were cut, vacuum packed and submitted to three different treatments: control (without treatment), conventional thermal treatments (CV) and thermal treatment assisted by power ultrasound (US). The impact of these treatments on instrumental adhesiveness, free amino acid and volatile compounds profile were assessed. Statistical analysis showed that both US and CV treatments, significantly (P < .001) decreased the instrumental adhesiveness of dry-cured hams from 85.27 g for CO to 40.59 and 38.68 g for US and CV groups, respectively. The total free amino acid content was significantly (P < .001) affected by both treatments, presenting higher values the samples from the US group (6691.5 vs. 6067.5 vs. 5278.2 mg/100 g dry matter for US, CV and CO groups, respectively). No significant differences were observed between US and CV treatments. All the individual free amino acids were influenced by ultrasound and temperature treatments, showing the highest content in sliced dry-cured ham submitted to ultrasounds at 50 °C, except for isoleucine which presented the highest level in samples from CV group. Similarly, significant differences (P < .05) were also detected in the total volatile compound content between CO and US groups, with a higher concentration in the CO batch (56,662.84 AU × 10³/g of dry-cured ham) than in the US treatment (45,848.47 AU × 10³/g of dry-cured ham), being the values in the CV treatment intermediate (48,497.25 AU × 10³/g of dry-cured ham). Aldehydes, ethers and esters, carboxylic acids and sulphur compounds were more abundant in the CO group, while CV group showed higher concentrations of ketones, alcohols and nitrogen compounds.

Effects of ultrasound on the beef structure and water distribution during curing through protein degradation and modification

The objective of this study was to explore the mechanisms of power ultrasound (PUS, 150 and 300W) and treatment time (30 and 120min) on the water-holding capacity (WHC) and tenderness of beef during curing. Beef muscle at 48h post mortem was subjected to PUS treatment at a frequency of 20kHz. Analysis of compression loss and shear force showed that PUS-assisted curing significantly increased the WHC and the tenderness of beef compared to static brining (p<0.05). According to the analysis of LF-NMR, PUS treatment could increase the P₂₁ values which indicated an improvement in water-binding ability of beef muscle. SDS-PAGE and LC-ESI-MS/MS analysis suggested that PUS induced moderate oxidation of myosin causing polymerization, which may contribute to increased water retention. On the other hand, an increased tenderness of beef is suggested by the increased MFI values and proteolysis of desmin and troponin-T. Transmission electron microscopy (TEM) further supported the effects of PUS on WHC and tenderness changes due to the swelling and disruption of myofibrils. Thus, these results provide knowledge about the mechanism for improving WHC and tenderness of beef by PUS curing, which could be employed as an emerging technology for various meat curing processes.

Proteomics of Parma Dry-Cured Ham: Analysis of Salting Exudates

The production of Parma dry-cured ham involves the steps of salting, drying, and ripening. Although sea salt is the only preserving agent, there are strategies being developed with the goal of reducing salt content in order to decrease its negative impact on consumer health. A 24 h pressure treatment was applied before salting to reduce thickness and inequalities in shape. To evaluate the potential impact of the pressure step on the process outcome, differential proteomic analyses by complementary 2D-PAGE and LC-MS/MS were carried out on exudates collected at day 1, 5, and 18 of the salting phase for hams treated or untreated with pressure. Specific proteins were found differentially abundant in exudates from pressed vs unpressed hams and as a function of time. These changes include glycolytic enzymes and several myofibrillar proteins. These findings indicate that pressure causes a faster loosening of the myofibrillar structure with the release of specific groups of proteins.

Animal board invited review: advances in proteomics for animal and food sciences

Animal production and health (APH) is an important sector in the world economy, representing a large proportion of the budget of all member states in the European Union and in other continents. APH is a highly competitive sector with a strong emphasis on innovation and, albeit with country to country variations, on scientific research. Proteomics (the study of all proteins present in a given tissue or fluid - i.e. the proteome) has an enormous potential when applied to APH. Nevertheless, for a variety of reasons and in contrast to disciplines such as plant sciences or human biomedicine, such potential is only now being tapped. To counter such limited usage, 6 years ago we created a consortium dedicated to the applications of Proteomics to APH, specifically in the form of a Cooperation in Science and Technology (COST) Action, termed FA1002--Proteomics in Farm Animals: www.cost-faproteomics.org. In 4 years, the consortium quickly enlarged to a total of 31 countries in Europe, as well as Israel, Argentina, Australia and New Zealand. This article has a triple purpose. First, we aim to provide clear examples on the applications and benefits of the use of proteomics in all aspects related to APH. Second, we provide insights and possibilities on the new trends and objectives for APH proteomics applications and technologies for the years to come. Finally, we provide an overview and balance of the major activities and accomplishments of the COST Action on Farm Animal Proteomics. These include activities such as the organization of seminars, workshops and major scientific conferences, organization of summer schools, financing Short-Term Scientific Missions (STSMs) and the generation of scientific literature. Overall, the Action has attained all of the proposed objectives and has made considerable difference by putting proteomics on the global map for animal and veterinary researchers in general and by contributing significantly to reduce the East-West and North-South gaps existing in the European farm animal research. Future activities of significance in the field of scientific research, involving members of the action, as well as others, will likely be established in the future.

Application to proteomics to understand and modify meat quality

The use of proteomics in the field of meat science has gained in robustness and accuracy. This is consistent with the genomic and bioinformatic tools. Its application to sensorial and technological meat quality traits is discussed as well as the emergence of sanitary and nutritional issue which will grow in a next future.

Analysis of raw hams using SELDI-TOF-MS to predict the final quality of dry-cured hams

The relationship between protein profiles of Gluteus medius (GM) muscles of raw hams obtained from 4 pure breed pigs (Duroc, Large White, Landrace, and Piétrain) with the final quality of the Semimembranosus and Biceps femoris muscles of dry-cured hams was investigated. As expected, Duroc hams showed higher levels of marbling and intramuscular fat content than the other breeds. Piétrain hams were the leanest and most conformed, and presented the lowest salt content in dry-cured hams. Even if differences in the quality traits (colour, water activity, texture, composition, intramuscular fat, and marbling) of dry-cured hams were observed among the studied breeds, only small differences in the sensory attributes were detected. Surface-enhanced laser desorption/ionisation time-of-flight mass spectrometry (SELDI-TOF-MS) was used to obtain the soluble protein profiles of GM muscles. Some associations between protein peaks obtained with SELDI-TOF-MS and quality traits, mainly colour (b*) and texture (F(0), Y(2), Y(90)) were observed. Candidate protein markers for the quality of processed dry-cured hams were identified.

SNP variation in the promoter of the PRKAG3 gene and association with meat quality traits in pig

Background

The PRKAG3 gene encodes the γ3 subunit of adenosine monophosphate activated protein kinase (AMPK), a protein that plays a key role in energy metabolism in skeletal muscle. Non-synonymous single nucleotide polymorphisms (SNPs) in this gene such as I199V are associated with important pork quality traits. The objective of this study was to investigate the relationship between gene expression of the PRKAG3 gene, SNP variation in the PRKAG3 promoter and meat quality phenotypes in pork.

Results

PRKAG3 gene expression was found to correlate with a number of traits relating to glycolytic potential (GP) and intramuscular fat (IMF) in three phenotypically diverse F1 crosses comprising of 31 Large White, 23 Duroc and 32 Pietrain sire breeds. The majority of associations were observed in the Large White cross. There was a significant association between genotype at the g.-311A>G locus and PRKAG3 gene expression in the Large White cross. In the same population, ten novel SNPs were identified within a 1.3 kb region spanning the promoter and from this three major haplotypes were inferred. Two tagging SNPs (g.-995A>G and g.-311A>G) characterised the haplotypes within the promoter region being studied. These two SNPs were subsequently genotyped in larger populations consisting of Large White (n = 98), Duroc (n = 99) and Pietrain (n = 98) purebreds. Four major haplotypes including promoter SNP’s g.-995A>G and g.-311A>G and I199V were inferred. In the Large White breed, HAP1 was associated with IMF% in the M. longissmus thoracis et lumborum (LTL) and driploss%. HAP2 was associated with IMFL% GP-influenced traits pH at 24 hr in LTL (pHULT), pH at 45 min in LTL (pH₄₅LT) and pH at 45 min in the M. semimembranosus muscle (pH₄₅SM). HAP3 was associated with driploss%, pHULT pH₄₅LT and b* Minolta. In the Duroc breed, associations were observed between HAP1 and driploss% and pHUSM. No associations were observed with the remaining haplotypes (HAP2, HAP3 and HAP4) in the Duroc breed. The Pietrain breed was monomorphic in the promoter region. The I199V locus was associated with several GP-influenced traits across all three breeds and IMF% in the Large White and Pietrain breed. No significant difference in promoter function was observed for the three main promoter haplotypes when tested in vitro.

Conclusion

Gene expression levels of the porcine PRKAG3 are associated with meat quality phenotypes relating to glycolytic potential and IMF% in the Large White breed, while SNP variation in the promoter region of the gene is associated with PRKAG3 gene expression and meat quality phenotypes.