A rapid increase in the economy, population, industrialization, and urbanization of Asian countries has driven the fast development of their meat industries over recent decades. This consistent increase in meat production and consumption in Asia has been the major cause for the development of the global meat industry. Meat production methods and consumption are very diverse across different regions and countries in Asia, and thus, it is impossible to cover the technological demands of all Asian countries in this review. Here, we have mainly highlighted the differences in meat production methods and consumption in Asia during recent decades and the meat technology demands of three east Asian countries, namely China, Korea, and Japan, and one south Asian country, India. A brief introduction of the meat industry, in particular the production and consumption trend in these countries, is provided in this article. The technology demands for fresh and processed meat products are then reviewed.

•High-pressure homogenization (HPH) modified myofibrillar protein powder (MP-P).•HPH induced protein dissociation, unfolding and rearrangement in MP-P.•HPH produced amorphous protein structure with high thermal stability in MP-P.•15,000 psi HPH increased protein flexibility for enhanced functionalities in water.•MP-P can be used as protein supplements in formulated food at low ionic strength.To expand utilization of meat in various products, the structural, physicochemical and functional changes of water soluble myofibrillar protein powder (WSMP-P) were investigated as affected by high-pressure homogenization (HPH) intensities (0–20,000 psi). HPH modified the structure of WSMP-P by random dissociation (myofibril and myosin polymer dissociation), partial unfolding and rearrangement (actin trimer formation), producing an amorphous protein structure with high thermal stability. α-Helix and β-turn conversion to β-sheet structures occurred at pressures above 15,000 psi, suggesting an increase in myosin conformation flexibility with minor aggregation. Moreover, HPH was able to improve the water solubility and emulsifying properties of WSMP-P. This might be resulted from its unfolded flexible structure with submicron size and high surface net charge in aqueous suspensions induced by HPH. The findings regarding the improved functionality evidence potential of applying WSMP-P as protein supplements in formulated food or beverage at low ionic conditions.Download high-res image (167KB)Download full-size image

•Generation of bioactive peptides by endogenous enzymes was investigated.•Post-mortem aging led to increased peptides content in duck meat.•The samples after 3 days post-mortem aging possessed strongest antioxidant activity.•Purified fraction C displayed highest antioxidant activity.•The peptide sequences were identified by nano LC–MS/MS.The objective of this study was to investigate the endogenous release of bioactive peptides in duck meat during 7 days of post-mortem aging. The degradation of muscle proteins led to release of small peptides (<5 kDa). The peptides formed in the samples after 3 days post-mortem exhibited highest DPPH radical scavenging, oxygen radical scavenging (ORAC) and ferric reducing antioxidant power (FRAP). By using size-exclusion chromatography, the initial extract was purified into three fractions (A–C) in which fraction C exhibited the highest antioxidant activity. In total 18 peptides were sequenced and identified in the fractions by nano LC–MS/MS. Among these peptides, the peptides of fraction C possessed the lowest molecular weight and consisted of the highest amount of hydrophobic amino acid, which might be responsible for the antioxidant property of aged duck meat. The present findings provide an insight into the release of bioactive peptides in duck meat during post-mortem aging.

•Heating for 0–30 min caused the setting of protein gel in meat emulsions.•LF-NMR distinguished fat and water proton mobility in meat emulsion systems.•Raman spectroscopy quantified the changes in secondary protein structures.•PCA determined the critical time for gel setting in heated meat emulsions.Emulsion-type sausages were produced, at 80 °C for either 0, 10, 20 or 30 min, using homogeneous Taihu pork batters. Low-field nuclear magnetic resonance (LF-NMR), with or without deuterium oxide (D2O) substitution, evaluated the proton mobility states related to both water and fat molecules, or fat molecules only, respectively, in the sausage samples, during heat-induced gelation. The decreasing trend in the area proportion of main peak T21, reflected a tighter gel structure in emulsion-type sausages. Raman spectra (400–3600 cm–1) revealed decreased α-helix, but increased β-sheet, β-turns and random coil contents, during the gelling process. Moreover, principal component analysis (PCA) showed significant correlations between secondary protein structures with distribution of water and fat in the gel matrix. Furthermore, this study established the relationship of water and fat protons mobility with changes in secondary protein structures, and described the critical time of gel formation in emulsion-type pork sausages.

It has been reported that isolated dietary soy and meat proteins have distinct effects on physiology and liver gene expression, but the impact on protein expression responses are unknown. Because these may differ from gene expression responses, we investigated dietary protein-induced changes in liver proteome. Rats were fed for 1 week semisynthetic diets that differed only regarding protein source; casein (reference) was fully replaced by isolated soy, chicken, fish, or pork protein. Changes in liver proteome were measured by iTRAQ labeling and LC–ESI–MS/MS. A robust set totaling 1437 unique proteins was identified and subjected to differential protein analysis and biological interpretation. Compared with casein, all other protein sources reduced the abundance of proteins involved in fatty acid metabolism and Pparα signaling pathway. All dietary proteins, except chicken, increased oxidoreductive transformation reactions but reduced energy and essential amino acid metabolic pathways. Only soy protein increased the metabolism of sulfur-containing and nonessential amino acids. Soy and fish proteins increased translation and mRNA processing, whereas only chicken protein increased TCA cycle but reduced immune responses. These findings were partially in line with previously reported transcriptome results. This study further shows the distinct effects of soy and meat proteins on liver metabolism in rats.

Triple TOF MS/MS was used to identify adducts between rosmarinic acid (RosA)-derived quinones and meat proteins in a gel model under oxidative stress. Seventy-five RosA-modified peptides responded to 67 proteins with adduction of RosA. RosA conjugated with different amino acids in proteins, and His, Arg, and Lys adducts with RosA were identified for the first time in meat. A total of 8 peptides containing Cys, 14 peptides containing His, 48 peptides containing Arg, 64 peptides containing Lys, and 5 peptides containing N-termini that which participated in adduction reaction with RosA were identified, respectively. Seventy-seven adduction sites were subdivided into all adducted proteins including 2 N-terminal adduction sites, 3 Cys adduction sites, 4 His adduction sites, 29 Arg adduction sites, and 39 Lys adduction sites. Site occupancy analyses showed that approximately 80.597% of the proteins carried a single RosA-modified site, 14.925% retained two sites, 1.492% contained three sites, and the rest 2.985% had four or more sites. Large-scale triple TOF MS/MS mapping of RosA-adducted sites reveals the adduction regulations of quinone and different amino acids as well as the adduction ratios, which clarify phenol–protein adductions and pave the way for industrial meat processing and preservation.Keywords: adducts; rosmarinic acid; total meat proteins; triple TOF MS/MS;

•The high power ultrasound made caspase-3 and calpain activations significantly higher.•Degradation of calpastatin reduced by ultrasound revealed the ability of caspase-3 to cleave calpastatin.•Ultrasound enhanced the accumulation of the 30 kDa troponin-T degradation product.•TEM images of myofibrils showed ultrasound resulted in the enlargement of I-bands and the shrinkage in the length of A-bands.In this investigation, ultrasonic treatments at a frequency of 40 kHz and power of 1500 W made caspase-3 and calpain activities significantly higher in chicken muscle after slaughter during 5 d storage (p < 0.01). Additionally Western blotting analysis of α-spectrin showed that ultrasonic treatments caused the production of α-spectrin degradation products of 120 and 150 kDa more dense than the control (p < 0.01). Degradation of calpastatin during chicken meat ageing was induced by ultrasound treatments (p < 0.01), which suggested the ability of caspase-3 to cleave calpastatin. SDS–PAGE showed that all treatments enhanced accumulation of the 30 kDa troponin-T degradation product (p < 0.01), and transmission electron microscopy images of myofibrils displayed that damage of ultrasound treatment for 60 min was more extensive than at 30 min. The findings proved the low-frequency and high power ultrasonic treatments improved disruption of myofibrillar structures and increased proteolysis of chicken meat faster by triggering an apoptosis cascade.

•Freez-thaw cycles increase lipid and protein oxidation, reduce colour stability and pH of chicken breast meat.•SDS–PAGE and DSC profile shows that multiple freez-thaw cause structural changes in muscle protein.•Nuclear magnetic resonance (NMR) relaxometery profile indicate the reduce myowater in chicken breast meat.The objective of this study was to determine the effects of repeated freeze–thaw cycles (0–6) on any physico-chemical changes and lipid and protein oxidation in chicken breast. The results showed that meat colour, a∗ (redness) and b∗ (yellowness) values decreased while L∗ values (lightness) increased with increasing cycle numbers. Increasing freeze–thaw cycles resulted in a greater degree of lipid and protein oxidation, as evidenced by higher contents of malondialdehyde and carbonyl compounds, and lower contents of sulfhydryl groups. Differential scanning calorimetry profiles and SDS–PAGE banding patterns of myofibrillar proteins indicated slight denaturation of myosin and actin with repeated freeze–thaw cycles. The structural changes occurring in proteins caused by oxidation directly affected the ability of muscles to retain water, as confirmed by the nuclear magnetic resonance relaxometery profile. In conclusion, multiple freeze–thaw cycles increased lipid and protein oxidation and decreased water holding capacity and colour stability of broiler chicken breast.

LTQ Orbitrap MS/MS was used to identify the adducts between quinones derived from rosmarinic acid (RosA) and thiol compounds, including cysteine (Cys), glutathione (GSH), and peptides digested from myosin. Two adducts of quinone–RosA/Cys and quinone–RosA/2Cys, one quinone–RosA/GSH adduct, and three quinone–RosA/peptide adducts were identified by extracted ion and MS2 fragment ion chromatograms. By using MALDI-TOF/TOF MS, the adduction reaction between RosA and myosin in myofibrillar protein isolates was determined, demonstrating that the accurate reaction site was at Cys949 of myosin. The effect of reaction conditions, including stirring time, temperature, and oxidative stress, on the formation of adducts was further investigated. The formation of quinone–RosA/Cys and quinone–RosA/GSH increased with stirring time. Both adducts increased with temperature, whereas the reactivity of the addition reaction of GSH was higher than that of Cys. With increasing oxidation stress, the formation of quinone–RosA/GSH adduct increased and that of quinone–RosA/Cys adduct decreased.

LuxS-mediated quorum-sensing mechanism, which was based on the production of universal signal molecule called autoinducer-2 (AI-2), regulates important physiological traits and a variety of adaptive processes in different bacteria. But little was known about AI-2/LuxS of lactobacillus bacteria from fermented meat. Bacterial strains of the species Lactobacillus sakei; Lactobacillus sp. and Lactobacillus plantarum, all isolated from Chinese fermented meat, were found to possess AI-2 activity and LuxS every 3 h during 36 h. In contrast, all the strains were found to have AI-2 activity and the full-length cDNA sequences of LuxS gene were obtained. The qRT-PCR analysis indicated that all LuxS gene showed strongly up-regulated after high nitrate concentration shock. The changes of LuxS during 36 h were shown in wavy curve rather than parabolic curve different from the lasted reports. The fact that AI-2 activity and LuxS gene are produced by bacterial strains found in the Chinese fermented meat. And also increased by meat-relevant stress conditions, indicated that AI-2/LuxS signaling might be important in regulation of microbial succession during ripened of Chinese fermented meat.

•We examine the role of caspase and calpain in degrading calpastatin in beef muscle.•Calpain and caspase-3 inhibitors inhibited postmortem degradation of calpastatin.•μ-Calpain, in vitro, reproduced the degradation patterns of calpastatin.•Caspase-3, in vitro, only reproduced 100 kDa fragment.•Calpastatin plays a role in bridging the gap between caspase and calpain systems.The objective of this study was to investigate the contribution of caspase and calpain, on the proteolysis of calpastatin in postmortem beef muscle, by examining the influences of calpain inhibitor MDL-28170 and caspase-3 inhibitor DEVD-CHO on calpastatin degradation and the in vitro proteolysis of calpastatin by caspase-3, -6 and μ-calpain. In this study, both calpain- and caspase-3-inhibitors suppressed postmortem degradation of calpastatin. In vitro treatment of calpastatin with μ-calpain resulted in degradation products similar in size to those occurring naturally in aged beef muscle. With addition of caspase-3, only the 100 kDa degradation fragment was present during the early phase of ageing, and subsequently, was likely to have been inactivated by calpain or other factors. Therefore, calpain was the major contributor to the proteolysis of calpastatin in postmortem beef muscle. While caspase-3 was involved in calpastatin degradation during the early postmortem period, calpastatin maybe plays an important role in bridging the gap between caspase and calpain systems.

To find a promising molecular method for meat traceability, three methods of single nucleotide polymorphism (SNP) detection: RFLP-PCR analysis, high-resolution melting (HRM) analysis, and TaqMan probe analysis, have been compared in terms of accuracy, ease of use, throughput capability, and cost. We genotyped ten pork DNA samples across three SNPs. The results showed that the HRM genotyping method was the most accurate and easiest to use with the lowest cost, while TaqMan probe analysis provided similar results, but its cost was much higher.

The antioxidant activities of the peptides extracted from Jinhua ham were evaluated on the basis of hydroxyl radical scavenging activity, DPPH radical scavenging activity, and Fe2+ chelating ability. The peptide extracts exhibited great hydroxyl radical scavenging activity and DPPH radical scavenging activity as well as Fe2+ chelating ability at the concentration of 1 mg/mL, which suggested the presence of peptides with antioxidant activity. The peptides were separated using size exclusion chromatography and reversed-phase HPLC. The fraction with highest DPPH radical scavenging activity was further purified and identified using liquid chromatography tandem matrix-assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry (HPLC-MALDI-TOF/TOF-MS). The sequence of the antioxidant peptide was identified as Gly-Lys-Phe-Asn-Val. The assessment of fractions indicated that the hydrophobic fractions contributed more to free radical scavenging activities than the hydrophilic peptides. It was concluded that natural peptides extracted and isolated from the Jinhua ham by several chromatographic techniques have antioxidant activities.

Calpain has been considered to be the most important protease involved in tenderization during the conversion of muscle into meat. However, recent evidence suggests the possible involvement of the key apoptosis protease, caspase, on post-mortem tenderization. This study used inhibitors of calpain and caspase-3 to treat chicken muscle immediately after slaughter and followed the changes in caspase-3 and calpain activities together with their expression during 5 days of aging. Addition of calpain inhibitors to the system resulted in significantly higher caspase-3 activities (p < 0.01) during storage. Western blot analysis of pro-caspase-3 and α-spectrin cleavage of the 120 kDa peptide (SBDP 120) showed that the addition of calpain inhibitors resulted in the formation of higher amounts of the active form of caspase-3 compared with the control (p < 0.01). Inclusion of inhibitors of caspase-3 led to lower calpain activities (p < 0.01) and dramatically reduced the expression of calpain-1 and calpain-2 (p < 0.01). Concomitantly, this inhibition resulted in greater calpastatin expression compared with the control (p < 0.01). The findings of this investigation show that calpain prevented the activation of caspase-3, whereas caspase-3 appeared to enhance the calpain activity during post-mortem aging through inhibition of calpastatin. It is therefore suggested that there is a relationship between caspase-3 and calpain which contributes to the tenderizing process during the conversion of muscle tissue into meat.

The objective of this study was to investigate the potential contribution of caspase-3 to meat postmortem tenderisation by examining the role of caspase-3 in the degradation of myofibrillar proteins and disruption of myofibril structure in vitro. Myofibrillar protein prepared from chicken muscle was incubated with EDTA or EDTA plus caspase-3 at 25 °C for 16 h and used for detecting muscle protein degradation and ultrastructure of myofibril. Results revealed that caspase-3 reproduced the degradation patterns of titin, nebulin and α-actinin during postmortem storage of meat, but caused little proteolysis of desmin and no appearance of 28–30 kDa peptides. Meanwhile, caspase-3 also induced the weakening in the I band adjacent to Z-lines, which occurred during meat postmortem ageing. Therefore, caspase-3 could account only for a part of the myofibrillar protein degradation observed in naturally aged meat and is likely involved in postmortem tenderisation of meat together with other endogenous proteases.Research highlights► We examine if caspase-3 could reproduce the degradation patterns of protein during ageing in vitro. ► Caspase-3 could reproduce the degradation patterns of titin, nebulin and α-actinin. ► Caspase-3 caused little proteolysis of desmin and no appearance of 28–30 kDa peptides. ► Caspase-3 also induced the weakening in I band adjacent to Z-lines. ► Caspase-3 is likely involved in tenderisation together with other proteases.

The objective of the study was to investigate in vitro degradation of myofibrils by caspase-3 or -6. Myofibrillar proteins prepared from beef skeletal muscle were incubated with caspase-3 or -6 at 30 °C for 2 or 12 h, and subsequently, protein degradation was detected. Results showed that caspase-3 and -6 reproduced the degradation patterns of titin and nebulin observed during normal postmortem (PM) aging; however, they only reproduced the 28 kDa fragment derived from troponin-T. Caspase-3 induced only minor degradation of desmin. However, caspase-6 caused increasing degradation of desmin with extended incubation time and produced three degradation fragments (45, 29, and 27 kDa) of which only the 45 kDa fragment has been reported in aged beef. Therefore, caspase-3 or -6 could only reproduce a part of myofibrillar protein degradation or degradation fragments observed in naturally aged meat and may be involved in PM proteolysis of muscle proteins together with other endogenous proteases.

Changes of meat shear force and its characteristics during cooking have been extensively studied, but great variability existed due to the cooking method among different studies. This study was designed to focus on the dynamic changes of beef intramuscular connective tissue (IMCT) and muscle fiber during water-bath heating and their effects on beef shear force. At 4 d postmortem, beef semitendinosus muscles were divided into 11 steaks and then cooked respectively to an internal temperature of 40, 50, 55, 60, 65, 70, 75, 80, 85, and 90°C (the remainder was not cooked as control). Collagen content and its solubility, transition temperature of perimysia and endomysia, fiber diameter, and Warner–Bratzler shear force values (WBSF) were determined. The results showed that fiber diameter decreased gradually during cooking, concomitant with the increases in filtering residue and WBSF. The maximum transition temperature (Tmax) of endomysial components was lower than that of perimysial components (50.2 vs. 65.2°C). Muscle fiber and IMCT (especially perimysia) shrank during cooking, resulting in the increase of WBSF when the internal temperature was lower than 75°C, but further cooking led to the disintegration of perimysial structure, lowing up the increase of WBSF between 75 and 90°C. For beef semitendinosus muscle, the internal temperature of 65°C is a critical cooking point where meat gets tougher.

The objective of this study was to investigate the potential contribution of apoptosis related downstream executioner caspase3 to post mortem skeletal muscle proteolysis by use of caspase3 selective inhibitor DEVD–CHO (N-acetyl–Asp–Glu–Val–Asp–CHO). After slaughter, four chicken breast muscles were removed and cut into small pieces, then marinated in treatment solution containing DEVD–CHO, or in control solution, and stored at 4 °C for 1, 3 or 7 d. Meat samples were obtained and used for detecting muscle protein degradation or calpain activity. Results showed that DEVD–CHO had inhibited the degradation of muscle skeletal proteins (titin, nebulin, desmin and troponin-T) significantly, whereas the activity of calpains had not been influenced. Therefore, the degradation of muscle proteins should not been exclusively attributed to the calpain system, and the effector caspase3 may be a new protease involved in meat post mortem tenderization.

The structure and oxidation properties of cooked cured meat pigment (CCMP) were investigated by comparing the change in spectra of CCMP before and after oxidisation. CCMP was extracted using petroleum ether/acetone/ethyl acetate step by step from precooked cured beef. The extracted sample was oxidised by being exposed to air with normal lighting or adding 1.5 ppm H2O2, respectively. The structure of CCMP was identified as a pentacoordinate mononitrosylheme complex by electron paramagnetic resonance (EPR), HPLC/ESI-HR-MS, Raman and FT–IR spectra. The changed EPR spectra of CCMP in acetone oxidised under different conditions suggested a new proposal that the NO− group might not detach itself from iron porphyrin during oxidation in air with normal lighting, but changed in conjugated structure, and the structure tended to axial symmetry by analysis of the changes in g factor. This hypothesis was further supported by the results of the HPLC/ESI-HR-MS and Raman spectrum.

In this study, changes of intramuscular phospholipids and free fatty acids were tracked during the processing of Nanjing dry-cured duck. Phospholipids were identified and quantified by high performance liquid chromatography combined with UV and evaporative light scattering detectors. The types and quantities of free fatty acids and fatty acids derived from phospholipids were analyzed by capillary gas chromatography. The results showed that raw duck meat had high quantities of phosphatidylethanolamine, and phosphatidylcholine (37.95% and 54.07% of total phospholipids, respectively), which contained high percentages of polysaturated fatty acids. The percentages of total phospholipids, phosphatidylethanolamine, and phosphatidylcholine decreased during processing, with a concomitant increase in quantities of free fatty acids. The lipolysis of phospholipids, especially phosphatidylethanolamine is the main contributor to the increase of free fatty acids.

Nanjing cooked duck is one of the few low temperature cooked meat products in traditional Chinese featured meat products. It is famous for its delicate processing, savoury, and tender flavour. Taste compounds of Nanjing cooked duck during processing, namely free amino acids, peptides and nucleotides, were analyzed. During boiling, both free amino acids and flavour nucleotides decreased significantly. Most peptides decreased during processing and the changes of total peptides were consistent with the nucleotides. Results showed that the special processes before boiling, especially brining, produced an increased of effect on the taste compounds, which could be the reason for the savoury taste of Nanjing cooked duck.

Fresh meat is a highly perishable product due to its biological composition. Many interrelated factors influence the shelf life and freshness of meat such as holding temperature, atmospheric oxygen (O2), endogenous enzymes, moisture, light and most importantly, micro-organisms. With the increased demand for high quality, convenience, safety, fresh appearance and an extended shelf life in fresh meat products, alternative non-thermal preservation technologies such as high hydrostatic pressure, superchilling, natural biopreservatives and active packaging have been proposed and investigated. Whilst some of these technologies are efficient at inactivating the micro-organisms most commonly related to food-borne diseases, they are not effective against spores. To increase their efficacy against vegetative cells, a combination of several preservation technologies under the so-called hurdle concept has also been investigated. The objective of this review is to describe current methods and developing technologies for preserving fresh meat. The benefits of some new technologies and their industrial limitations is presented and discussed.

This study investigated the effect of early post-mortem temperature on broiler protein characteristics and meat quality. Muscles were kept at different temperatures (0, 20 and 40 °C) until 4 h post-mortem and then stored at 4 °C. Rapid degradation of ATP and glycogen, thus inducing a high rate of lactate formation and pH drop, were found in the 40 °C group during incubation. When extracting proteins, a lower protein content of the sarcoplasmic fraction and a higher protein content of the myofibrillar fraction were found in the 40 °C group at 24 h post-mortem; SDS-PAGE and western-blotting results revealed that phosphorylase was associated with the myofibrillar fraction. Furthermore, the 40 °C group had paler surfaces, higher drip loss and lower processing properties. These data suggest that elevated temperature during early post-mortem period, resulting in rapid glycolysis, induced phosphorylase denaturation and association with myofibrillar proteins thus generating pale and exudative characteristics.

•200 MPa HPP may contribute to the development of protein networks in the gel, thus improving the rheological properties of meat batters•200 MPa HPP at 10°C for 2 min reduced cook loss of sausages with reduced-fat and reduced-salt content•200 MPa HPP improved textural properties of sausages with reduced-fat and reduced-salt contentThis study investigated the role of high-pressure processing (HPP) for improving the functional properties of meat batters and the textural properties of reduced-fat sausages. Application of 200 MPa pressure at 10 °C for 2 min to pork batters containing various fat contents (0–30%) affected their rheological properties, cooking losses, color, textual properties and their protein imaging. The results revealed that both application of 200 MPa and increasing fat content decreased cooking loss, as well as improved the textural and rheological properties. Cooking losses, texture and sensory evaluation of 200 MPa treated sausages having 20% fat were similar to those of the 0.1 MPa treated sausages having 30% fat. Principal component analysis revealed that certain quality attributes were affected differently by the levels of fat addition and by HPP. These findings indicated the potential of HPP for improving yield and texture of emulsion-type sausages having reduced fat contents.

Heterocyclic aromatic amines (HAAs), potent mutagens/carcinogens, are pyrolysis formed during the cooking of meat and fish. In the present study, the effects of various cooking methods, pan-frying, deep-frying, charcoal grilling and roasting on the formation of HAAs in chicken breast and duck breast were studied. The various HAAs formed during cooking were isolated by solid-phase extraction and analyzed by high-performance liquid chromatography (HPLC). Results showed that chicken breast cooked by charcoal grilling contained the highest content of total HAAs, as high as 112 ng/g, followed by pan-fried duck breast (53.3 ng/g), charcoal grilled duck breast (32 ng/g), pan-fried chicken breast (27.4 ng/g), deep-fried chicken breast (21.3 ng/g), deep-fried duck breast (14 ng/g), roasted duck breast (7 ng/g) and roasted chicken breast (4 ng/g). For individual HAA, the most abundant HAA was 9H-pyrido-[4,3-b]indole (Norharman), which was detected in charcoal grilled chicken breast at content as high as 32.2 ng/g, followed by 1-methyl-9H-pyrido[4,3-b] indole (Harman) and 2-amino-1-methyl-6-phenylimidazo[4,5-f]pyridine(PhIP) at 32 and 31.1 ng/g in charcoal grilled chicken breast, respectively. The content of PhIP in pan-fried duck and chicken breast were 22 and 18.3 ng/g, respectively. Generally, the type and content of HAAs in cooked poultry meat varies with cooking method and cooking conditions.

The objective was to determine the effect of three different protease inhibitors, caspase-6 specific inhibitor VEID-CHO (N-Acetyl-Val-Glu-Ile-Asp-al), calpain inhibitor leupeptin or calpain inhibitor EGTA on protein degradation, ultrastructure of myofibrils and calpain activity during postmortem (PM) aging of chicken muscle. Results showed that proteolysis of nebulin, troponin-T and desmin during 14-days postmortem storage were inhibited significantly by leupeptin. Inhibitive effects of VEID-CHO and EGTA on these protein degradations were significant only during 1-day postmortem storage. The activities of calpains were inhibited noticeably by leupeptin and EGTA, but not by VEID-CHO. Samples treated with VEID-CHO, leupeptin and EGTA retarded structural disruption of chicken muscle fibers. These results demonstrate that calpain is a major contributor to PM tenderization; while caspase-6 plays, if any, a minimal role in the conversion of chicken muscle to meat.Highlights► We investigate the role of caspase-6 in chicken muscle by use of VEID-CHO. ► Caspase-6 caused minimal proteolysis of myofibrillar proteins. ► Calpain is a major contributor to the PM tenderization. ► Caspase-6 plays minimal role in the conversion of chicken muscle to meat.

Recently, a novel consideration has focused on the potential relationship of apoptosis and the protease caspases and the underlying mechanism for meat postmortem tenderization. In this study, apoptosis inducers, camptothecin and etoposide as well as Ca2+ were used to treat chicken muscle immediately after slaughter and follow the changes in caspase-3 activities and changes in the myofibrillar structures during 7 days of ageing. All three treatments resulted in significantly higher caspase-3 activities during storage (p < 0.05), with the natural substrates, whereas Western blotting analysis of the α-spectrin cleavage product, 120 kDa peptide (SBDP 120), showed that Ca2+ was more effective than either camptothecin or etopside, and all were most active up to day 3 (p < 0.01). According to SDS-PAGE, each treatment enhanced the accumulation of the 30 kD Troponin-T degradation product, especially during the first 3 days (p < 0.05), and this was supported by the degradation of myofibrils observed by electron microscopy (TEM). TEM images showed the treatments resulted in enlargement of the I-bands and shrinkage of A-bands; however Z-lines were only slightly affected, even at day 7. The findings revealed that the three apoptosis inducers could increase myofibrillar dissociation and proteolysis during the first 3 days of chicken meat ageing. Because of the high activity of caspase-3 during the early postmortem period, it is possible that caspase-3 contributes to the conversion of muscle into meat.

Structural changes, textural properties and their relationships in pork myofibrillar proteins (PMP) were studied by Raman spectroscopy, texture profile analysis (TPA) and principal component analysis (PCA). Raman spectroscopy analysis revealed the occurrence of secondary structural changes in myofibrillar proteins. Modifications in the amide I (1600–1700 cm−1) and amide III (1200–1300 cm−1) regions indicated a significant (p < 0.05) decrease in α-helix content, accompanied by a significant (p < 0.05) increase in β-sheets, β-turns and random coil content. Texture property changes were also determined by TPA. All these features contributed to the formation of strong, irreversible heat-induced gels. The application of a dimensionality reducing technique such as PCA proved to be useful to determine the most influential properties of heat-induced gel. Significant (p < 0.05) correlations were found between these structural changes and the textural characteristic (hardness) in the pork myofibrillar proteins system by PCA.

In order to reveal the relationship between phospholipase A2 and antioxidant enzymes and drip loss in pork, the study was designed to examine the effects of phospholipase A2 and antioxidant enzymes on the water-holding capacity of pork during postmortem chilling. Six PSE and RFN samples (longissimus muscle) were used to determine the activities of phospholipase A2 (tPLA2, cPLA2 + sPLA2 and iPLA2), superoxide dismutase (SOD) and GSH-Px, and acid phospholipase. The results showed that pH1 h and pH24 h from PSE pork were lower (p < 0.01) than for normal pork (RFN), but the L* value at 1 h and 24 h postmortem, TBARS content, drip loss at 48 h and 96 h, cooking loss, tPLA2 activity and iPLA2 were higher (p < 0.01) than of normal pork. Correlation analysis indicated that drip loss at 48 h was negatively related to pH1 h (p < 0.01) and pH24 h (p < 0.01) but positively to T1 h (p < 0.01) and the activities of total phospholipase A2 (p < 0.05) and calcium-independent phospholipases A2 (p < 0.01). The tPLA2 and GSH-Px play important roles in drip loss.

In this study, PCR-denaturing gradient gel electrophoresis (DGGE) was used to investigate the bacterial communities of vacuum-packaged pork during chilled storage. Eight kinds of lactic acid bacteria (LAB) were identified from the strains isolated from MRS plates by PCR–DGGE of the V3 region, and Lactobacillus sakei was the representative isolate at the end of the monitoring. By means of the direct meat analysis of PCR–DGGE, LAB increased gradually and Carnobacterium sp./Car. divergens, Lactobacillus sakei and Lactococcus sp./Lc. piscium, became the predominant bacteria at the end of the storage. The results of Lactobacillus-specific PCR and DGGE showed that different Lactobacillus populations were present at different storage periods and Lb. sakei became the predominant bacteria in the end. In conclusion, the PCR–DGGE technique as a culture-independent method is applicable to monitoring bacterial population dynamics in vacuum-packaged pork.

Pale, soft, exudative-like (PSE-like) broiler muscle is a growing problem for meat industry all over the world. However, limited studies have been made to assess broiler meat quality in China. The aim of this study was to investigate the characteristics and incidence of PSE-like broiler muscle commercially produced in China. A total of 1 274 Pectoralis muscles of Arbor Acre broiler were randomly obtained from the processing line to determine the commercial incidence of PSE-like muscle based on color. Furthermore, broiler Pectoralis muscles selected from the 1 274 muscle samples were classified as PSE-like muscle (L*>53, n=33) and normal muscle (L*>48 and L*=53, n=33) to assess meat quality. It was determined that PSE-like muscle had lower muscle pH values, lower water-holding capacity (WHC), lower sarcoplasmic protein solubility, and lower total protein solubility than the normal muscle did. SDS-PAGE profile also showed that bands of approximate 96 and 24 kDa in sarcoplasmic protein and myofibrillar protein varied between these two groups, suggesting partial denaturation of sarcoplasmic proteins and precipitation on myofillarments. Correlation analysis showed that L* values have significant correlation with WHC and protein solubility. Furthermore, the distribution of L* values exhibited a normal curve with range varying from 42.70 to 58.37. It was considered that approximately 23.39% of the population was PSE-like muscle. These results suggest that PSE-like meat can represent a significant portion of commercially processed broiler breast meat in China and that the L* value measurement could be used to sort broiler meat quality using a cut-off point.