Protein and lipid oxidation in Parma ham during production

Evolution of lean meat tenderness stimulated by coordinated variation of water status, protein structure and tissue histology during cooking of braised pork

Tenderness of lean meat in braised pork is of great importance to the consumer palatability and acceptance. The influence of water status, protein structure and histological changes on lean meat tenderness during cooking was investigated. Results indicated that lean meat began to tenderize mainly after 20 min-cooking. In the early period of cooking, the decrease of total sulfhydryl content caused the protein oxidative cross-linking, leading to the gradual unfolding of the protein structure, thus resulting in a decrease of T₂₂ and an increase of centrifugal loss, which decreased the tenderness of lean meat. However, after cooking for 20 min, the β-sheet decreased and random coil increased, thus generating conversion between P₂₁ and P₂₂. The rupture of perimysium structure was observed. Changes in protein structure, water status, and tissue histology could facilitate the initiation and development of lean meat tenderness.

Elucidation of the Impact of Steaming on the Key Odorants of Jinhua Dry-Cured Ham Using the Sensomics Approach

Jinhua dry-cured ham (JDH) is a traditional fermented meat product favored by Chinese consumers. In this paper, the impact of steaming on the key odorants of JDH was investigated using the sensomics approach. Compounds with odor activity values (OAV) ≥1 were re-engineered in a triglyceride matrix to imitate the odor profiles of both raw and steamed JDHs. The aroma-active compounds were then confirmed by recombination and omission tests using triangle tests. The odor profiles of raw and steamed JDHs were obtained by quantitative descriptive analysis to compare the differences between the original and recombined models. The results showed that pentanal, hexanal, dimethyl trisulfide, (E,E)-2,4-decadienal, (E)-2-heptenal, furaneol, 3-methylbutanoic acid, 1-octen-3-one, and methional influenced the overall raw JDH odor significantly. Furaneol was first reported as a key compound that provides a caramel smell to the raw JDH. Apart from (E)-2-heptenal, dimethyl trisulfide, furaneol, 3-methylbutanoic acid, and methional, the remaining three compounds including 2-furfurylthiol, benzeneacetaldehyde, and phenylethyl alcohol showed a significant influence on the odor profile of steamed JDH. The statistical analysis of the odor profiles showed an 80.0% similarity between the recombination raw JDH and the real raw JDH, and a 76.3% similarity between the model and the real steamed JDH.

Effects of Partial Replacement of NaCl with KCl on Protein Properties and Quality Attributes of Lightly Salted Tilapias Fillets

The evolution of quality attributes and their association with the protein properties of lightly tilapias fillets salted with different replacement proportions of NaCl with KCl (0%, 10%, 30%, 50%, 70%, 100%) at the same ionic strength were investigated. KCl replacements using optimal substitution (50% of KCl) contributed to maintaining desired quality properties. Further, KCl replacement (about 50~70% of KCl) led to the insolubilization and weakened stability of myofibrillar proteins, represented by the unfolding of the myofibrillar protein, increased surface hydrophilic points, and strengthened internal protein-protein interaction, resulting in the structurally reinforced hardness and lower water-holding capacity. Excessive replacement (more than 70% of KCl) showed apparent deterioration in taste quality, coloration, and hardness received by sensory sensation caused by immoderate hydrolysis and aggravated oxidation of the myofibrillar protein. In this sense, insights into KCl replacements on protein properties might be a positive approach to improving quality attributes of lightly salted tilapias fillets.

Effects of antioxidants on physicochemical properties and odorants in heat processed beef flavor and their antioxidant activity under different storage conditions

Heat processed beef flavor (HPBF) is a common thermal process flavoring, whose flavor properties can be affected by lipid oxidation during storage. Addition of antioxidants is an option to avoid the changes of HPBF induced by lipid oxidation. In this study, the effects of three antioxidants, tert-butylhydroquinone (TBHQ), tea polyphenol (TP), and L-ascorbyl palmitate (L-AP), on volatile components, physicochemical properties, and antioxidant activities of HPBF were studied over 168 days at different temperatures (4, 20, and 50°C). Although all three antioxidants had little effect on browning, acidity, water activity, and secondary lipid oxidation products, L-AP and TBHQ showed greater capabilities to prevent the formation of primary lipid oxidation products than TP. According to the results of oxidation reduction potential and DPPH radical scavenging experiments, TBHQ had better antioxidant ability compared to L-AP and TP during the storage. Of note, TBHQ affected the flavor profiles of HPBF, mainly on volatile odorants produced by lipid degradation. TBHQ could mitigate the development of unfavorable odorants. This study indicated TBHQ would enhance lipid oxidation stability and maintain physicochemical properties and flavor profiles of HPBF during storage. It suggested that TBHQ could be applied as an alternative additive to improve the quality of HPBF related thermal process flavorings.

Tandem mass tag-based proteomics analysis of protein changes in the freezing and thawing cycles of Trachurus murphyi

We investigated the proteome variations in Trachurus murphyi with different cycles of freezing and thawing (FT) under frozen storage. A total of 2,482 proteins were assessed quantitatively, of which 269 proteins were recognized as differential abundance proteins during the second FT cycle until the eighth FT cycle. Bioinformatics analysis on gene ontology (GO) functional annotation and Kyoto Encyclopedia of Genes and Genomes pathway analyses of Differential Analysis of Proteins (DAPs) indicated multiple DAPs engaged with the protein structure, metabolic enzymes, and protein turnover. In addition, some of the observed proteins were probably the underlying markers of protein oxidation (PO). The analysis of PO sites revealed the sites of PO, such as amino adipic semialdehydes, γ-glutamic semialdehydes, and Schiff bases. Bioinformatics analyses demonstrated the involvement of differentially expressed proteins in the Hippo signaling pathway (Ko04390), indicating strong protein degradation with greater numbers of FT cycles under frozen storage. It provides an insight into quality stability from a proteomics quality perspective at the molecular level. The results obtained have deepened our current understandings of the mechanisms that reveal variations in proteomes and quality, as well as help promote quality control of T. murphyi across the cold transportation chain. PRACTICAL APPLICATION: Temperature fluctuation is one of the core issues during frozen food storage and distribution faced by the frozen food industry. Fluctuation may result in microstructural changes, ice recrystallization, and protein change in frozen food products. Tandem mass tag-based methods were adopted to study proteome variations in Trachurus murphyi muscles under different cycles of freezing and thawing under frozen storage conditions in this paper. The results obtained have deepened our current understandings of the mechanisms that reveal variations in proteomes and quality, as well as help promote quality control of T. murphyi across the cold transportation chain.

Evaluation of protein degradation and flavor compounds during the processing of Xuan'en ham

Protein degradation occurs during the processing of dry-cured ham, which has important influences on the flavor and quality of products. The aim of this work was to study the degradation kinetics of myofibrillar proteins (MPs) and sarcoplasmic proteins (SPs) extracted from the biceps femoris muscle during the processing of Xuan'en ham. A relationship between protein degradation and the flavor formation was found. During the processing of Xuan'en ham, MPs and SPs were mainly degraded in the salting stage and incipient fermentation. Accompanied by protein degradation, the content of carbonyl group in SPs increased gradually, but in MPs, it first increased and then decreased. Interconversion between sulfhydryl and disulfide bonds was investigated during this processing. Oxidation, degradation, and thermal effects significantly affected the surface hydrophobicity of proteins. More than one hundred volatile compounds have been identified at each stage of ham preparation. Among them, organic acids were the predominant group, followed by hydrocarbons, aldehydes, alcohols, ketones, and esters.

Volatile compounds in high-pressure-treated dry-cured ham: A review

The use of high pressure processing (HPP) for the treatment of dry-cured ham and other meat products has considerably increased worldwide. Its well-documented lethal effect on pathogenic and spoilage bacteria ensures the microbial safety of dry-cured ham and extends its shelf life. However, the effects of HPP on the volatile compounds, odor and aroma of dry-cured ham are less known. In the present review, the effects of HPP on the enzymes and microorganisms responsible for the generation of volatile compounds in dry-cured ham and the changes in the levels of the main groups of volatile compounds resulting from different HPP treatments are discussed. Particular attention is devoted to the fate of odor-active compounds after HPP treatments and throughout further commercial storage. The use of efficient sensory techniques yielding odor and aroma outputs closer to those perceived by consumers is encouraged. Needs for future research on the volatile compounds, odor and aroma of HPP-treated dry-cured ham are highlighted.

The effect of aging on beef taste, aroma and texture, and the role of microorganisms: a review

The present review summarizes the advantages and disadvantages of three different aging methods (traditional dry aging, wet aging in vacuum shrink pack and dry aging in a highly moisture-permeable bag), discusses the effects of aging on beef which focus on the formation of taste-active compounds and aroma-active compounds and texture changes, and speculates the role of microbes. All these three aging methods can improve the aroma, flavor and texture of beef to varying degrees. It is concluded that the improvement in the taste during aging may be attributed to the following three aspects: First, the release of reducing sugars from the transition of glycogen and ATP; Second, the formation of free amino acids (FAAs) and peptides through proteolysis; Third, IMP, GMP, inosine and hypoxanthine which are produced by the degradation of nucleotides. The improvement of aroma is related to the volatile aroma-active components, which are produced by the thermal oxidation/degradation of fatty acids and the Maillard reaction between amino acids and reducing sugars during aging. And the change of texture is mainly owing to the degradation of cytoskeletal myofibrin and collagen with intramural connective tissue in meat by the endogenous proteolysis system. The role of microorganism in aging will be the main direction of further research.

Influence of Muscle Type on Physicochemical Parameters, Lipolysis, Proteolysis, and Volatile Compounds throughout the Processing of Smoked Dry-Cured Ham

The influence of muscle type (biceps femoris, BF and semimembranosus, SM) on physicochemical parameters, volatile compounds, and the extent of proteolysis and lipolysis during the manufacturing of smoked dry-cured ham was investigated. A total of fifty smoked hams were sampled: raw ham, after salting, smoking, drying, and ripening. Almost all physicochemical parameters were affected by muscle type, manufacturing stage and their interactions. SM had lower water, ash, NaCl content, and water activity (aw), while fat and protein content were higher after ripening compared to BF. BF showed higher L*a*b* values compared to SM. The results of texture profile analysis showed that almost all analyzed parameters were influenced by muscle type and production stage. A total of 88 volatile compounds were identified, showing an increase in its number during processing: 31 volatile compounds were identified in raw ham and 72 after the ripening phase. Aldehydes and phenols were the predominant groups of compounds, followed by alcohols, ketones, aromatic hydrocarbons, aliphatic hydrocarbons, esters, and terpenes. Muscle type and production phase significantly affected lipid oxidation and the index of proteolysis: in SM, thiobarbituric acid reactive substances (TBARS) increased faster than in BF, while proteolysis had an opposite effect and was more pronounced in BF.

Proteolysis and protein oxidation throughout the smoked dry-cured ham process

During the five stages of smoked dry-cured ham processing, proteolysis and protein oxidation were simultaneously detected in the Biceps femoris (BF) and Semimembranosus (SM) muscles. Proteolysis was more advanced in BF than in SM throughout the process of production. The total FAA increased significantly (p < 0.05) throughout the processing, resulting in higher total FAA content in BF than in SM muscle. SDS-PAGE revealed progressive degradation of sarcoplasmic proteins of investigated muscles, with the pronounced changes for the 69.9-41.7 kDa region. SDS-PAGE of BF showed more intense degradation of myofibrillar proteins due to greater proteolysis in BF. Electrophoresis of myofibrillar proteins evidenced the marked degradation of 130 kDa, 96.7 kDa and 27-20.7 kDa bands in both muscles. A similar trend was observed for protein oxidation in BF and SM, with the final values of 26.36 and 23.7 nmol carbonyls/mg proteins, respectively. The Pearson correlation revealed a strong relationship between protein oxidation and proteolysis.

Quality Characteristics of Semi-Dried Restructured Jerky Processed Using Super-Heated Steam

Moisture content and water activity play important roles in extending the shelf life of dried meat products, such as jerky. However, the commonly used hot air drying process is time-consuming, costly, and adversely affects the quality of dried meat products, warranting the development of an advanced and economical drying method. This study investigated the effect of super-heated steam (SHS) drying on the quality characteristics of semi-dried restructured jerky as a measure to prevent the excessive quality deterioration of meat products during drying. The control sample was dried using hot air, and the treatment samples were dried using SHS at different temperatures (200, 250, and 300 °C) and for different durations (90, 105, and 120 min). With increasing SHS temperature and duration, the moisture content, water activity, and residual nitrite content of the jerky were reduced. The shear force values for treatments at 200 and 250 °C were lower than those for the control. With a non-significant difference in lipid oxidation compared with the control, the overall acceptability score was the highest for the treatment at 250 °C for 120 min. In conclusion, SHS (250 °C for 120 min) drying has a potential industrial value to replace the hot air drying method.

4-HNE Immunohistochemistry and Image Analysis for Detection of Lipid Peroxidation in Human Liver Samples Using Vitamin E Treatment in NAFLD as a Proof of Concept

Lipid peroxidation is a common feature of liver diseases, especially non-alcoholic fatty liver disease (NAFLD). There are limited validated tools to study intra-hepatic lipid peroxidation, especially for small specimen. We developed a semi-quantitative, fully automated immunohistochemistry assay for the detection of 4-hydroxynoneal (4-HNE) protein adducts, a marker of lipid peroxidation, for adaptation to clinical diagnostics and research. We used Hep G2 cells treated with 4-HNE to validate specificity, sensitivity, and dynamic range of the antibody. Staining and semi-quantitative automated readout were confirmed in human needle-biopsy liver samples from subjects with NAFLD and normal liver histology. The ability to detect changes in lipid peroxidation was tested in paired liver biopsies from NAFLD subjects, obtained before and after 4 weeks of treatment with the antioxidant vitamin E (ClinicalTrials.gov NCT01792115, n=21). The cellular calibrator was linear and NAFLD patients had significantly higher levels of 4-HNE adducts compared to controls (p=0.02). Vitamin E treatment significantly decreased 4-HNE (p=0.0002). Our findings demonstrate that 4-HNE quantification by immunohistochemistry and automated image analysis is feasible and able to detect changes in hepatic lipid peroxidation in clinical trials. This method can be applied to archival and fresh samples and should be considered for use in assessing NAFLD histology.

Commercial luncheon meat products and their in vitro gastrointestinal digests contain more protein carbonyl compounds but less lipid oxidation products compared to fresh pork

Because of the large diversity in processed meat products and the potential involvement of oxidation processes in the association between red and processed meat consumption and chronic diseases, the concentration of oxidation products after gastrointestinal digestion of commercial luncheon meat products was investigated. A broad spectrum of meat products (n = 24), displaying large variation in macro- and micronutrient composition and processing procedures, was digested in vitro by simulating digestion fluids of the human gastrointestinal tract. Lipid and protein oxidation was assessed in the meat products before digestion and in the corresponding digests by measurement of free malondialdehyde, 4-hydroxy-2-nonenal, hexanal and protein carbonyl compounds. Compared to an unprocessed cooked pork mince, that was included as a reference in the digestion experiment, levels of lipid oxidation products were low in the digests of most meat products. Only the digests of Parma ham had slightly higher or comparable levels as the reference pork. In contrast, protein carbonyl compounds were comparable or up to 6 times higher in the processed meat products compared to the reference pork. Particularly raw-cooked and precooked-cooked meat products and corresponding digests had higher protein carbonyl levels, but also lower protein contents and higher fat to protein ratios. In conclusion, most luncheon meat products and corresponding digests contained lower amounts of free lipid oxidation products, but more protein carbonyl compounds compared to the reference pork.

Effect of pulsed light treatment on Listeria inactivation, sensory quality and oxidation in two varieties of Spanish dry-cured ham

The efficacy of pulsed light (PL) for the surface decontamination of ready-to-eat dry-cured ham was studied in two Spanish varieties, Serrano and Iberian. Listeriainnocua was inoculated on the surface of ham slices that were vacuum-packaged and flashed with 2.1, 4.2 and 8.4 J/cm². Survivors were enumerated immediately after treatment. Peroxide values, sensory analysis and volatile profile were investigated during storage at 4 and 20 °C. Inactivation of Listeria was higher in Iberian (ca. 2 log cfu/cm²) than in Serrano ham (ca. 1 log cfu/cm²) with 8.4 J/cm². PL did not increase the peroxide values above the usual levels reported in dry-cured ham, and no rancid notes were observed in the sensory analysis. PL-treated samples showed an increase in the concentration of some volatile compounds, such as methional, dimethyl disulfide and 1-octen-3-one, which imparted slight sulfur and metallic notes, although they disappeared during storage.

Combined Application of High-Throughput Sequencing and Metabolomics Reveals Metabolically Active Microorganisms During Panxian Ham Processing

Panxian ham, a traditional Chinese dry-cured ham, is protected by national geographical indication. Similar to other fermented foods, the microbial population of dry-cured ham is pivotal to taste and flavor formation. This study aimed to establish the relationship between microorganisms and metabolites during the spontaneous fermentation of Panxian ham. Multivariate analysis based on metabolomics data revealed that continuous metabolic changes occurred during the entire fermentation process, with the most significant changes occurring in the initial stage of ripening. Thirty-one significantly different metabolites (SDMs) were identified as discriminant factor, and pathway analysis suggested that these metabolites were involved in 30 pathways, including alanine, aspartate, and glutamate metabolism; glycine, serine, and threonine metabolism; and arginine and proline metabolism. Microbial community analysis using the Illumina MiSeq platform indicated that the bacterial community was more complex than the fungal community, and their succession regulation differed during processing. At the genus level, 11 bacteria and five fungi were identified as core microbes, of which Staphylococcus was the dominant bacteria and Debaryomyces and Aspergillus were the dominant fungi. Further, statistical redundancy analysis (RDA) indicated that Staphylococcus, Debaryomyces, and Chromohalobacter promoted the production of amino and fatty acids; Cobetia and Aspergillus were associated with sugar metabolism, and Kushneria, Penicillium, and Yamadazyma were closely related with organic acids. These findings provide fundamental knowledge regarding the metabolically active microorganisms in Panxian ham, helping industrial processors to develop effective strategies for standardizing quality parameters.

Plant derived ingredients rich in nitrates or phenolics for protection of pork against protein oxidation

A pork model system containg phenolic extracts (citrus, rosemary, and acerola), traditional Spanish food ingredients (paprika, garlic, and oregano), or natural nitrate sources (beet, lettuce, arugula, spinach, chard, celery, and watercress) were oxidized by an hydrophilic (OX_Hydro, 2,2'-azobis(2-amidinopropane)-dihydrochloride; AAPH) or lipophilic (OX_Lip, 2,2'-azobis(2,4-dimethylvaleronitrile; AMVN) radical initiator. Citrus as well as lettuce and spinach protected almost fully against protein thiol loss and showed efficient radical scavenging activity as determined by ESR spectroscopy in both oxidizing systems. Rosemary was an efficient radical scavenger in both systems, but behaved as a prooxidant on thiols in the OX_Hydro system. Acerola was also found to be prooxidative as determined by increased radical signal intensity especially in the OX_Lip system, assigned to high concentration of ascorbate in the extract. Natural nitrate sources, especially lettuce and spinach, are accordingly potential substitutes for synthetic phenolic antioxidants protecting against protein thiol oxidation and radical formation in pork.

Light exposure accelerates oxidative protein polymerization in beef stored in high oxygen atmosphere

Protein oxidation of beef patties stored in high oxygen modified atmosphere packaging for 9 days was investigated. Meat was either stored in the dark, under light, or in the dark with addition of FeCl₂/H₂O₂/myoglobin (forced oxidation). SDS-PAGE analysis showed high degree of protein polymerization for meat exposed to light, compared to the other samples. Light exposure induced reducible (disulfide) and non-reducible cross-links, while mainly disulfides were formed in meat stored in the dark. Light exposure was responsible for 58% loss of free thiols (Cys residues). No significant loss of other amino acid residues was observed and none of the most common oxidation products of tryptophan, tyrosine, and phenylalanine were detected. Intrinsic fluorescence measurements of tryptophan showed 27% loss in samples exposed to light, which was ascribed to loss of protein solubility via protein polymerization rather than tryptophan oxidation. Protein carbonyls were mainly detected in forced oxidized samples at Day 0.

1H NMR and multivariate data analysis of the differences of metabolites in five types of dry-cured hams

In order to distinguish the taste styles of dry-cured hams (Jinhua, Xuanwei, Country, Parma and Bama), we established a ¹H nuclear magnetic resonance spectroscopy method to identify metabolites. Totally, 33 charged metabolites, including amino acids, organic acids, nucleic acids and their derivatives, sugars, alkaloids and others were identified. The abundant glutamate, lysine, alanine, leucine and lactate could be the major contributors of taste. Total variables were explained by PC1 (67.7%) and PC2 (16.0%) which showed that Parma and Xuanwei styles were close to each other (similar amino acids, peptide, organic acids and alkaloids contents). Bama style showed the highest PC1 and amino acids, organic acids and alkaloids contents. Country style was located on the left-most area of PC1 (the lowest amino acids, organic acids and peptide, but the highest sugars contents). Sensory evaluation revealed that Bama ham had the highest overall taste score, followed by Jinhua, Parma, Xuanwei and American Country ham. We concluded that the proportions and combinations of taste components explained the specific taste instead of any single component. These findings provided a better understanding of different metabolomics among hams.

Dose-Dependent Effects of Green Tea or Maté Extracts on Lipid and Protein Oxidation in Brine-Injected Retail-Packed Pork Chops

Background: Phenolic plant extracts are added as antioxidants in meat to prevent lipid oxidation, but depending on the concentration applied, may affect proteins either through covalent interactions or by serving as a prooxidant. Methods: Brine-injected pork chops prepared with green tea extract (25-160 ppm gallic acid equivalents (GAE)), or maté extract (25-160 ppm GAE) and stored (5 °C, 7 days) in high-oxygen atmosphere packaging (MAP: 80% O2 and 20% CO2) were analyzed for color changes, lipid oxidation by thiobarbituric acid reactive substances (TBARS), and protein oxidation evaluated by thiol loss and protein radical formation by electron spin resonance (ESR) spectroscopy, and compared to a control without antioxidant. Results: Extract of maté and green tea showed significant and comparable antioxidative effects against formation of TBARS in brine-injected pork chops for all concentrations applied compared to the control. Protein radical formation decreased significantly by addition of 25 ppm maté extract, but increased significantly by addition of 80-160 ppm green tea extract, when monitored as formation of protein radicals. Meanwhile, protein thiol groups disappeared when applying the extracts by reactions assigned to addition reactions of oxidized phenols from the extracts to protein thiols. Conclusion: Maté is accordingly a good source of antioxidants for protection of both lipids and proteins in brine-injected pork chops chill-stored in high-oxygen atmosphere, though the dose must be carefully selected.

Protein Oxidation and Sensory Quality of Brine-Injected Pork Loins Added Ascorbate or Extracts of Green Tea or Maté during Chill-Storage in High-Oxygen Modified Atmosphere

Background: Ascorbate is often applied to enhance stability and robustness of brine-injected pork chops sold for retail, but may affect protein oxidation, while plant extracts are potential substitutes. Methods: Brine-injected pork chops (weight-gain ~12%, NaCl ~0.9%) prepared with ascorbate (225 ppm), green tea extract (25 ppm gallic acid equivalents (GAE)), or maté extract (25 ppm GAE) stored (5 °C, seven days) in high-oxygen atmosphere packaging (MAP: 80% O₂ and 20% CO₂) were analyzed for color changes, sensory quality, and protein oxidation compared to a control without antioxidant. Results: No significant differences were observed for green tea and maté extracts as compared to ascorbate when evaluated based on lipid oxidation derived off-flavors, except for stale flavor, which maté significantly reduced. All treatments increased the level of the protein oxidation product, α-aminoadipic semialdehyde as compared to the control, and ascorbate was further found to increase thiol loss and protein cross-linking, with a concomitant decrease in the sensory perceived tenderness. Conclusions: Green tea and maté were found to equally protect against lipid oxidation derived off-flavors, and maté showed less prooxidative activity towards proteins as compared to ascorbate, resulting in more tender meat. Maté is a valuable substitute for ascorbate in brine-injected pork chops.

Physicochemical changes of semimembranosus muscle during the processing of dry-cured ham from Celta pig. Effect of crossbreeding with Duroc and Landrace genotypes

Physicochemical characteristics of dry-cured hams from three genetic types, Celta breed (C line), Celta × Duroc (C × D) and Celta × Landrace (C × L) were determined on the semimembranosus muscle during 551 days of aging. Hams were obtained from 60 pigs reared in extensive systems and finished with a commercial feeding. Physicochemical parameters (pH and water activity) and chemical composition, (moisture, intramuscular fat, ash, protein and total chlorides content), colour parameters (L*, a* and b*) and lipid oxidation (thiobarbituric acid reactive substances value) were studied during the whole process after salting, post-salting, drying and bodega stages. Hams from crosses were characterised by higher intramuscular fat (12.78% and 10.48% for C × D and C × L lines, respectively) and moisture (46.86% and 46.63% for C × D and C × L genotypes, respectively), contents respect to Celta pure line that showed values of 5.96% and 35.83% for intramuscular fat and water content, respectively. Concerning colour parameters, hams from Celta line had lower values for all colour traits. The influence of crossbreeding on most physicochemical parameters observed was mainly due to the differences in moisture and intramuscular fat between hams obtained from pure breed and crosses. As a general conclusion, the crossbreeding of Celta pig (especially with the Duroc line) allows to improve the quality of dry-cured hams.

Supplementing entire male pig diet with hydrolysable tannins: Effect on carcass traits, meat quality and oxidative stability

The purpose of the present study was to investigate the potential impact on carcass and meat quality of a sweet chestnut wood extract (SCWE)diet supplement for pigs, in particular on oxidative stability and fatty acid composition. Entire (non-castrated) male pigs (n=24) were assigned to treatment groups within litter and offered one of 4 finisher diets on an ad libitum basis: T0 (control), T1, T2 or T3, supplemented with 0, 1, 2 or 3% of commercially available SCWE, respectively. The highest SCWE supplementation reduced carcass fat deposition and water holding capacity of meat (higher thawing loss). In fresh meat, SCWE supplementation increased lipid (malondialdehyde) and protein oxidation (carbonyl groups in myofibril isolates). With regard to fat tissue, SCWE supplementation increased the proportion of polyunsaturated fatty acids.

Iron(II) Initiation of Lipid and Protein Oxidation in Pork: The Role of Oxymyoglobin

Iron(II), added as FeSO4·7H2O, was found to increase the rate of oxygen depletion as detected electrochemically in a pork homogenate from Longissimus dorsi through an initial increase in metmyoglobin formation from oxymyoglobin and followed by formation of primary and secondary lipid oxidation products and protein oxidation as detected as thiol depletion in myofibrillar proteins. Without added iron(II), under the same conditions at 37 °C, oxygen consumption corresponded solely to the slow oxymyoglobin autoxidation. Long-lived myofibrillar protein radicals as detected by ESR spectroscopy in the presence of iron(II) were formed subsequently to oxymyoglobin oxidation, and their level was increased by lipid oxidation when oxygen was completely depleted. Similarly, the time profile for formation of lipid peroxide indicated that oxymyoglobin oxidation initiates both protein oxidation and lipid oxidation.

Competitive kinetics as a tool to determine rate constants for reduction of ferrylmyoglobin by food components

Competitive kinetics were applied as a tool to determine apparent rate constants for the reduction of hypervalent haem pigment ferrylmyoglobin (MbFe(IV)O) by proteins and phenols in aqueous solution of pH 7.4 and I=1.0 at 25°C. Reduction of MbFe(IV)O by a myofibrillar protein isolate (MPI) from pork resulted in kMPI=2.2 ± 0.1 × 10(4)M(-1)s(-1). Blocking of the protein thiol groups on the MPI by N-ethylmaleimide (NEM) markedly reduced this rate constant to kMPI-NEM=1.3 ± 0.4 × 10(3)M(-1)s(-1) consistent with a key role for the Cys residues on MPI as targets for haem protein-mediated oxidation. This approach allows determination of apparent rate constants for the oxidation of proteins by haem proteins of relevance to food oxidation and should be applicable to other systems. A similar approach has provided approximate apparent rate constants for the reduction of MbFe(IV)O by catechin and green tea extracts, though possible confounding reactions need to be considered. These kinetic data suggest that small molar excesses of some plant extracts relative to the MPI thiol concentration should afford significant protection against MbFe(IV)O-mediated oxidation.

Controlled formation of emulsion gels stabilized by salted myofibrillar protein under malondialdehyde (MDA)-induced oxidative stress

This study presented the cold-set gelation of emulsions stabilized by salted myofibrillar protein (MP) under oxidative stress originated from malondialdehyde (MDA). Gel properties were compared over a range of MDA/NaCl concentrations including gel viscoelastic properties, strength, water-holding capacity (WHC), amount of protein entrapped, and microstructure. The oxidative stability of emulsion gels as indicated by lipid hydroperoxide was further determined and compared. Results indicated that emulsion stabilized by MP at swollen state under certain ionic strengths (0.2-0.6 M) was the premise of gel formation under MDA. In the presence of intermediate MDA concentrations (2.5-10 mM), the emulsion gels showed an improved elasticity, strength, WHC, and oxidative stability. This improvement should be mainly attributed to the enhanced protein-protein cross-linkings via MDA, which were homogeneously formed among absorbed and/or unabsorbed proteins, entrapping a greater amount and fractions of protein within network. Therefore, the oil droplets were better adherent to the gel matrix. Nevertheless, addition of high MDA concentrations (25-50 mM) led to the formation of excessive covalent bonds, which might break protein-protein bonds and trigger the desorption of protein from the interface. This ultimately caused "oil leak" phenomena as well as the collapse of gel structure and, thus, overall decreased gel properties and oxidative stability.

Competitive reduction of perferrylmyoglobin radicals by protein thiols and plant phenols

Radical transfer from perferrylmyoglobin to other target species (myofibrillar proteins, MPI) and bovine serum albumin (BSA), extracts from green tea (GTE), maté (ME), and rosemary (RE), and three phenolic compounds, catechin, caffeic acid, and carnosic acid) was investigated by electron paramagnetic resonance (EPR) spectroscopy to determine the concentrations of plant extracts required to protect against protein oxidation. Blocking of MPI thiol groups by N-ethylmaleimide was found to reduce the rate of reaction of MPI with perferrylmyoglobin radicals, signifying the importance of protein thiols as radical scavengers. GTE had the highest phenolic content of the three extracts and was most effective as a radical scavenger. IC50 values indicated that the molar ratio between phenols in plant extract and MPI thiols needs to be >15 in order to obtain efficient protection against protein-to-protein radical transfer in meat. Caffeic acid was found most effective among the plant phenols.

Dietary citrus pulp improves protein stability in lamb meat stored under aerobic conditions

The antioxidant effects of dried citrus pulp on proteins in lamb meat, when used as a replacement of concentrate in the feed, was studied using meat from 26 male Comisana lambs. The lambs of age 90 days had been grouped randomly to receive one of the three dietary treatments: (1) commercial concentrate with 60% barley (Control, n=8), (2) concentrate with 35% barley and 24% citrus pulp (Cp24, n=9), or (3) concentrate with 23% barley and 35% citrus pulp (Cp35, n=9). Slices from the longissimus thoracis et lomborum muscle were packed aerobically and stored for up to 6days at 4°C in the dark. The citrus pulp groups, Cp24 and Cp35, significantly decreased protein radicals and carbonyls, and preserved more thiols within six days of storage compared to the Control group. The citrus pulp groups significantly slowed down the rate of protein oxidation, indicating that dietary citrus pulp reduced oxidative changes in meat proteins.