Myofibrillar protein from different muscle fiber types: implications of biochemical and functional properties in meat processing

Impact of Flammulina velutipes polysaccharide on properties and structural changes of pork myofibrillar protein during the gel process in the absence or presence of oxidation

The present study aimed to investigate the impact of Flammulina velutipes polysaccharide (FVSP) on the rheological properties and structural alterations of myofibrillar protein (MP) and oxidized MP (OMP), utilizing techniques such as rhehometer, fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). In the unoxidized system, the addition of 5.00% FVSP significantly improved (p < 0.05) the storage and loss moduli of the composite gel and promoted the α-helix to β-sheet transformation. These effects enhanced the protein's gel strength and water-holding capacity (WHC). In the oxidation system, 5.00% FVSP had significant effects (p < 0.05) on repair and improvement of the oxidized MP. These effects inhibited the cross-linking aggregation and degradation of the protein. In addition, the addition of FVSP significantly improved the gel properties of MPs after oxidation (p < 0.05), hindered fracture of the protein gel network structure. In summary, polysaccharides have a substantial effect on the functional characteristics of MP, and FVSP could potentially be applied in meat products.

The impacts of freeze-drying-induced stresses on the quality of meat and aquatic products: Mechanisms and potential solutions to acquire high-quality products

Freeze-drying is a preservation method known for its effectiveness in dehydrating food products while minimizing their deterioration. However, protein denaturation and oxidation during freezing and drying can degrade the quality of meat and aquatic products. Therefore, finding the strategies to ensure the dried products' sensory, functional, and nutritional attributes is crucial. This study aimed to summarize protein denaturation mechanisms and overall quality changes in meat and aquatic products during freezing and drying, while also exploring methods for quality control. Different freeze-drying conditions result in varying levels of oxidation and functionality in meat and aquatic products, leading to changes in quality, such as altered fatty and amino acid compositions, protein digestibility, and sensory attributes. To obtain high-quality dried products by freeze-drying, several parameters should be considered, including sample type, freezing and drying temperatures, moisture content, pulverization effects, and storage conditions.

Impact of cooking temperature on pork longissimus, and muscle fibre type, on quality traits and protein denaturation of four pork muscles

Variations in pork quality impact consumer acceptance, and fibre type differences between muscles contribute to this variation. The aim was to investigate the influence of variations in muscle fibre types and protein denaturation peaks across four pork muscles and the influence of ageing and cooking temperature on longissimus quality traits. The longissimus, masseter, cutaneous trunci, and psoas major from 13 carcases were removed 1-day postmortem and subjected to 0- or 14-days ageing (d0, d14). Quality traits, protein denaturation peak temperature (DSC), fibre diameter and fibre type proportions were measured. Cook loss for longissimus was similar on d0 and d14, but was higher on d14 for masseter, cutaneous trunci, and psoas major. Warner-Bratzler shear force was highest, and ultimate pH was lowest, for longissimus, and similar among cutaneous trunci, masseter, and psoas major. Masseter had lowest L* and highest a* and longissimus and cutaneous trunci had highest L* and lowest a*. The DSC temperature peaks for longissimus occurred at lower temperatures relative to the other muscles. Fibre diameter was largest for type-IIb fibres relative to type-IIa and type-I. Longissimus and cutaneous trunci had predominantly type-IIb glycolytic (71%, 51% respectively), masseter had predominantly type-IIa intermediate (50%) and psoas major had predominantly type-I oxidative (48%) fibres. The glycolytic longissimus had the lowest DSC temperature peaks and the lowest quality meat. Masseter had the highest proportion of type-I fibres but was generally similar in quality traits to psoas major, and also similar to cutaneous trunci which had more glycolytic fibres than masseter.

A review on the relation between grinding process and quality of ground meat

This review is providing an overview of the actual and past research in the field of ground meat. The forces that are acting in the meat grinder are well understood. The higher the forces that are acting on the meat while grinding, the stronger the disintegration of the meat cells after the process. These forces can be calculated as energy transfer in meat grinders using specific mechanical energy (SME). The amount of non-intact cells (ANIC) can be used to describe the extent of disintegrated cells. Different methods are available to rate the quality of ground meat, which is mainly influenced by the raw material and processing. Over the past decades of industrialization, the landscape of ground meat production has changed. However, the effects of the process adjustments on the quality of ground meat are not yet sufficiently described in the literature.

Effect of sodium salt on meat products and reduction sodium strategies - A review

Sodium salt is one of the important additives in food processing. However, excessive intake of sodium salt may cause a series of cardiovascular diseases. Nowadays, sodium intake in most countries is higher than the World Health Organization recommends maximum consumption (5 g/d). 20% of the sodium intake in diets comes from meat products. Therefore, reducing the content of sodium salt in meat products and developing sodium salt-reduction meat products have attracted more and more attention for consumers. In this paper, the roles of sodium salt in meat product processing were reviewed. At the same time, sodium salt reduction strategies and existing problems were summarized and discussed. Multiple factors need to be considered to improve the salt-reduction meat product's quality. Relying on a single technology has a narrow application area, and it is difficult to achieve salt reduction. Therefore, a combination of multiple strategies could obtain a more ideal effect.

Influence of sodium chloride on muscle UV autofluorescence characteristics

Salted and tumbled pork teres major muscle samples, with varying sodium chloride content (1.1 % to 1.9 %), were examined by UV fluorescence spectroscopy. Results indicated that muscle fluorescence varies with salt level as a consequence of the protein denaturation state. The 1.5 % NaCl level was the threshold beyond which the fluorescence properties no longer changed markedly. Changes in muscle fluorescence do not appear to be linearly related to salt levels. Hence, we explored whether the change in fluorescence relies on other factors relating to the variability of carcass characteristics and on muscle physicochemical changes that are partly dependent on stress response and on postmortem metabolism evolution.

Glycosylation modification: A promising strategy for regulating the functionalities of myofibrillar proteins

Myofibrillar proteins (MPs), the most important proteins in muscle, play a vital role in the texture, flavor, sensory and consumer acceptance of final muscle-based food products. Over the past several decades, conjugation of carbohydrates to MPs via glycosylation is of particular interest due to the substantial enhancement in MPs characteristics. Studying the covalent interactions between carbohydrates and MPs under various processing conditions and molecular mechanisms by which carbohydrates affect the functionalities of MPs can introduce new perspectives for design and production of muscle-based foods. However, there is no insightful and comprehensive summary of the structural, physicochemical and functional characteristics changes of MPs induced by glycosylation modification and how these changes can be adopted to potentially promote the science-based development of tailor-made muscle foods. Based on this, the functionalities of MPs as well as their practical limiting issues are initially highlighted. A comprehensive overview of fabrication strategies is then introduced. Additionally, changes in the structural and functional properties of MPs regulated by glycosylation have also been carefully summarized. On this basis, the research limitations to be solved and our perspectives for the future development of muscle-based foods are put forward.

Effects of heating rates on the self-assembly behavior and gelling properties of beef myosin

BACKGROUND

Myosin is the most important component of myofibrillar protein, with excellent gelling properties. To date, heating treatment remains the mainstream method for forming gel in meat products, and it has the most extensive application in the field of meat industry. However, at present, there are few reports on the effects of heating rates on myosin self-assembly and aggregation behavior during heating treatment.

RESULTS

The present study aimed to investigate the effects of different heating rates (1, 2, 3 and 5 °C min^-1 ) on the self-assembly behavior, physicochemical, structural and gelling properties of myosin. At the lowest heating rate of 1 °C min^-1 , the myosin gel had a dense microstructure, the highest elastic modulus (G') and water holding capacity compared to higher heating rates (2, 3 and 5 °C min^-1 ). At higher temperatures (40, 45 °C), the surface hydrophobicity, turbidity, particle size distribution and self-assembly behavior of myosin in pre-gelling solutions showed that myosin had sufficient time to denature, underwent full structure unfolding before aggregation at the heating rate of 1°C min^-1 , and formed regular and homogeneous spherical aggregates. Therefore, the myosin gel also had a better three-dimensional network.

CONCLUSION

The heating rates had an important effect on the quality of myosin gels, and had theoretical implications for improving the quality of meat gel products. © 2023 Society of Chemical Industry.

Higher Protein Digestibility of Chicken Thigh than Breast Muscle in an In Vitro Elderly Digestion Model

This study investigated the protein digestibility of chicken breast and thigh in an in vitro digestion model to determine the better protein sources for the elderly in terms of bioavailability. For this purpose, the biochemical traits of raw muscles and the structural properties of myofibrillar proteins were monitored. The thigh had higher pH, 10% trichloroacetic acid-soluble α-amino groups, and protein carbonyl content than the breast (p<0.05). In the proximate composition, the thigh had higher crude fat and lower crude protein content than the breast (p<0.05). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of myofibrillar proteins showed noticeable differences in the band intensities of tropomyosin α-chain and myosin light chain-3 between the thigh and breast. The intrinsic tryptophan fluorescence intensity of myosin was lower in the thigh than in the breast (p<0.05). Moreover, circular dichroism spectroscopy of myosin revealed that the thigh had higher α-helical and lower β-sheet structures than the breast (p<0.05). The cooked muscles were then chopped and digested in the elderly digestion model. The thigh had more α-amino groups than the breast after both gastric and gastrointestinal digestion (p<0.05). SDS-PAGE analysis of the gastric digesta showed that more bands remained in the digesta of the breast than that of the thigh. The content of proteins less than 3 kDa in the gastrointestinal digesta was also higher in the thigh than in the breast (p<0.05). These results reveal that chicken thigh with higher in vitro protein digestibility is a more appropriate protein source for the elderly than chicken breast.

Enhanced Gel Properties of Duck Myofibrillar Protein by Plasma-Activated Water: Through Mild Structure Modifications

This study assessed the gel properties and conformational changes of duck myofibrillar protein (DMP) affected by plasma-activated water (PAW) generated at various discharge times (0 s, 10 s, 20 s, 30 s, and 40 s). With the treatment of PAW-20 s, the gel strength and water-holding capacity (WHC) of DMP gels were significantly increased when compared to the control group. Throughout the heating process, dynamic rheology revealed that the PAW-treated DMP had a higher storage modulus than the control. The hydrophobic interactions between protein molecules were significantly improved by PAW, resulting in a more ordered and homogeneous gel microstructure. The increased sulfhydryl and carbonyl content in DMP indicated a higher degree of protein oxidation with PAW treatment. Additionally, the circular dichroism spectroscopy demonstrated that PAW induced α-helix and β-turn transformed to β-sheet in DMP. Surface hydrophobicity, fluorescence spectroscopy, and UV absorption spectroscopy suggested that PAW altered DMP's tertiary structure, although the electrophoretic pattern indicated that the primary structure of DMP was mostly unaffected. These results suggest that PAW can improve the gel properties of DMP through mild alteration in its conformation.

Effects of partial replacement of unwashed Antarctic krill surimi by Litopenaeus vannamei surimi on the heat-induced gelling and three-dimensional-printing properties

There is an emerging consumption of the Antarctic krill (AK) muscle-based food due to its excellent nutritional value and enormous biomass storage capacity. However, the coarse texture of the muscle and the weak gelling properties of AK protein impede its expansion in surimi-based products. This investigation successfully prepared heat-induced gels of AK surimi with desirable textural properties by including Litopenaeus vannamei in varying proportions. Higher concentrations of L. vannamei resulted in improved three-dimensional printability, greater water-holding capacity (WHC), larger viscoelastic modulus, and a well-formed microstructural matrix of AK surimi, due to an increased level of myofibrillar protein. Compared with AK, L. vannamei muscle had double the salt-soluble protein content, which was corroborated by increased intensity of bands of actin, paramyosin, tropomyosin, and myosin light chains on reducing SDS-PAGE. DSC results indicated that a high ratio of L. vannamei elevated the denaturation temperature and enthalpy of myosin, sarcoplasmic protein, and actin, suggesting a high degree of cross-linking. It was also found that when hydroxypropyl cassava starch was added at 0.5% (w/w), WHC and gel strength were further improved with a more compact gel matrix. The successful preparation of unwashed mixed surimi with AK meat fully exploited in this study provides an option for AK surimi-based product industrialization.

Naringenin Promotes Myotube Formation and Maturation for Cultured Meat Production

Cultured meat is an emerging technology for manufacturing meat through cell culture rather than animal rearing. Under most existing culture systems, the content and maturity of in vitro generated myotubes are insufficient, limiting the application and public acceptance of cultured meat. Here we demonstrated that a natural compound, naringenin (NAR), promoted myogenic differentiation of porcine satellite cells (PSCs) in vitro and increased the content and maturity of generated myotubes, especially for PSCs that had undergone extensive expansion. Mechanistically, NAR upregulated the IGF-1/AKT/mTOR anabolic pathway during the myogenesis of PSCs by activating the estrogen receptor β. Moreover, PSCs were mixed with hydrogels and cultured in a mold with parallel micro-channels to manufacture cultured pork samples. More mature myosin was detected, and obvious sarcomere was observed when the differentiation medium was supplemented with NAR. Taken together, these findings suggested that NAR induced the differentiation of PSCs and generation of mature myotubes through upregulation of the IGF-1 signaling, contributing to the development of efficient and innovative cultured meat production systems.

Application of Machine Learning Using Color and Texture Analysis to Recognize Microwave Vacuum Puffed Pork Snacks

The objective of the study was to create artificial neural networks (ANN) capable of highly efficient recognition of modified and unmodified puffed pork snacks for the purposes of obtaining an optimal final product. The study involved meat snacks produced from unmodified and papain modified raw pork (Psoas major) by means of microwave-vacuum puffing (MVP) under specified conditions. The snacks were then analyzed using various instruments in order to determine their basic chemical composition, color and texture. As a result of the MVP process, the moisture-to-protein ratio (MPR) was reduced to 0.11. A darker color and reduction in hardness of approx. 25% was observed in the enzymatically modified products. Multi-layer perceptron networks (MLPN) were then developed using color and texture descriptor training sets (machine learning), which is undoubtedly an innovative solution in this area.

Qualitative Attributes of Commercial Pig Meat from an Italian Native Breed: The Nero d’Abruzzo

The main objective of this study was to characterize the main qualitative properties of commercial meat obtained from the Nero d’Abruzzo pig, a native breed of Central Italy. In order to valorize this animal production, a direct comparison was made with commercial meat products obtained from hybrid pigs. Over a period of 30 days, 76 steaks for each breed were purchased from the market, and samples were analyzed for total lipid content, fatty acids profile, Coenzyme Q10 content, resistance of meat to oxidative processes, volatile profile of cooked meat and electrophoretic profile of myofibrillar and sarcoplasmic proteins. Results showed the Nero d’Abruzzo to be richer in fat, which, however, is characterized by a higher concentration of α-linolenic acid, to which are attributed important health benefits. The native breed was also richer in Coenzyme Q10, a compound credited with antioxidant potential, whose presence could explain the better oxidative stability of meat samples that were cooked and stored for up to 7 days at +4 °C. In support of this last data, our finding of the characterization of the volatile profile of cooked meat, at the end of the storage period, showed in Nero d’Abruzzo a reduction in the accumulation of hexanal, notoriously associated with oxidative events and the development of unpleasant aromatic notes. In conclusion, aspects that can justify the nutritional superiority of this niche production compared to meat coming from cosmopolitan breeds have been identified.

Effects of different frozen temperatures of pork meat batter on quality characteristics of reduced-sodium pork sausages using pre-rigor muscle

Objective

The objective of this study was to evaluate quality characteristics of reduced-salt pork sausage (PS) using pre-rigor muscle compared to those of regular-salt PS. In addition, effects of freezing on sausage batter with different temperatures (−30°C vs −70°C) on quality characteristics of both sausage batter and cooked sausages during frozen storage were observed.

Methods

Pre-rigor and post-rigor pork hams were used to manufacture low-fat sausages. Sausages using post-rigor (Post) muscle were manufactured at a salt level of 1.5%, whereas those with pre-rigor (Pre) muscle were processed at salt level of 1.0%. After these muscles were made at two salt levels (1.5% salt, Post-rigor; 1.0% salt, Pre-rigor), Sausage batters were stored at two frozen temperatures (−30°C vs −70°C). During storage for 12 wks, they were measured for physicochemical and textural properties every 4 wks up to 12 wks.

Results

pH values and temperatures of sausage batter of pre-rigor muscle were higher than those of post-rigor muscle regardless of the frozen temperature. The lightness and yellowness values of batter at the initial storage were the highest during storage. For PS, there were no differences in most parameters measured among all treatments. However, expressible moisture values (%) of Pre-30 and Pre-70 were lower than those of Post-30 (p<0.05).

Conclusion

Regardless of frozen temperature during storage, quality characteristics of pre-rigor PS with salt level of 1.0% salt were similar to those of post-rigor PS with salt level of 1.5%. By using the pre-rigor muscle, salt content could be reduced by one third of the regular-salt level (1.5%) of post-rigor muscle.

The science of plant-based foods: Constructing next-generation meat, fish, milk, and egg analogs

Consumers are increasingly demanding foods that are more ethical, sustainable and nutritious to improve the health of themselves and the planet. The food industry is currently undergoing a revolution, as both small and large companies pivot toward the creation of a new generation of plant-based products to meet this consumer demand. In particular, there is an emphasis on the production of plant-based foods that mimic those that omnivores are familiar with, such as meat, fish, egg, milk, and their products. The main challenge in this area is to simulate the desirable appearance, texture, flavor, mouthfeel, and functionality of these products using ingredients that are isolated entirely from botanical sources, such as proteins, carbohydrates, and lipids. The molecular, chemical, and physical properties of plant-derived ingredients are usually very different from those of animal-derived ones. It is therefore critical to understand the fundamental properties of plant-derived ingredients and how they can be assembled into structures resembling those found in animal products. This review article provides an overview of the current status of the scientific understanding of plant-based foods and highlights areas where further research is required. In particular, it focuses on the chemical, physical, and functional properties of plant-derived ingredients; the processing operations that can be used to convert these ingredients into food products; and, the science behind the formulation of vegan meat, fish, eggs, and milk alternatives.

Non-thermal processing has an impact on the digestibility of the muscle proteins

Muscle proteins undergo several processes before being ready in a final consumable form. All these processes affect the digestibility of muscle proteins and subsequent release of amino acids and peptides during digestion in the human gut. The present review examines the effects of different processing techniques, such as curing, drying, ripening, comminution, aging, and marination on the digestibility of muscle proteins. The review also examines how the source of muscle proteins alters the gastrointestinal protein digestion. Processing techniques affect the structural and functional properties of muscle proteins and can affect their digestibility negatively or positively depending on the processing conditions. Some of these techniques, such as aging and mincing, can induce favorable changes in muscle proteins, such as partial unfolding or exposure of cleavage sites, and increase susceptibility to hydrolysis by digestive enzymes whereas others, such as drying and marination, can induce unfavorable changes, such as severe cross-linking, protein aggregation, oxidation induced changes or increased disulfide (S-S) bond content, thereby decreasing proteolysis. The underlying mechanisms have been discussed in detail and the conclusions drawn in the light of existing knowledge provide information with potential industrial importance.

Effect of chickpea (Cicer arietinum L.) protein isolate on the heat-induced gelation properties of pork myofibrillar protein

BACKGROUND

Heat-induced composite gels were prepared with 30 mg mL^-1 pork myofibrillar protein (MP) and chickpea protein isolate (CPI) (0, 3, 6, 9, 12, and 15 g kg^-1 ) in 0.6 mol L^-1 NaCl, at pH 7.0. The gel strength, water-holding capacity, rheological properties, and microstructure of MP-CPI composite gels were investigated.

RESULTS

Chickpea protein isolate improved (P < 0.05) gel strength and water-holding capacity of the MP composite gels. The rheological properties of MP-CPI composite gels were improved significantly by the addition of CPI. Meanwhile, the effects of CPI on the storage modulus of composite gels were positively correlated with the increased addition of CPI. Furthermore, according to low-field nuclear magnetic resonance (LF-NMR) results, the addition of CPI reduced the relaxation time of the composite gels and the relaxation peak area of free water, indicating that CPI could improve the water-holding capacity of MP-CPI composite gels. The microstructure of MP-CPI composite gels presented smaller and more uniform pores, which means that more water could be retained.

CONCLUSION

The addition of chickpea protein isolate improved the gel strength, water-holding capacity, rheological properties, and microstructure of MP gels, indicating that CPI could be a potential protein additive to improve the microstructure, texture, and functional quality of meat products. © 2020 Society of Chemical Industry.

Myoprotein-phytophenol interaction: Implications for muscle food structure-forming properties

Phenolic compounds are commonly incorporated into muscle foods to inhibit lipid oxidation and modify product flavor. Those that are present in or extracted from plant sources (seeds, leaves, and stems) known as "phytophenols" are of particular importance in the current meat industry due to natural origins, diversity, and safety record. Apart from these primary roles as antioxidants and flavorings, phytophenols are now recognized to be chemically reactive with a variety of food constituents, including proteins. In processed muscle foods, where the structure-forming ability is critical to a product's texture-related quality attributes and palatability, the functional properties of proteins, especially gelation and emulsification, play an essential role. A vast amount of recent studies has been devoted to protein-phenol interactions to investigate the impact on meat product texture and flavor. Considerable efforts have been made to elucidate the specific roles of phytophenol interaction with "myoproteins" (i.e., muscle-derived proteins) probing the structure-forming process in cooked meat products. The present review provides an insight into the actions of phytophenols in modifying and interacting with muscle proteins with an emphasis on the reaction mechanisms, detection methods, protein functionality, and implications for structural characteristics and textural properties of muscle foods.

Genome-wide transcriptome profiling reveals the mechanisms underlying muscle group-specific phenotypic changes under different raising systems in ducks

Although a number of nongenetic factors have been reported to be able to modulate skeletal muscle phenotypes in meat-type birds, neither the underlying mechanisms nor the muscle group–specific phenotypic and molecular responses have been fully understood. In the present study, a total of 240 broiler ducks were used to compare the effects of floor raising system (FRS) and net raising system (NRS) on the physicochemical properties and global gene expression profiles of both breast and thigh muscles at the posthatching week 4 (W4), W8, and W13. Our results showed that compared with FRS, NRS generally induced higher pH, lower lightness (L∗) and yellowness (b∗), lower drip loss and cooking loss, and lower shear force in either breast or thigh muscles during early posthatching stages but subsequently showed less pronounced or even reverse effects. Meanwhile, it was observed that the raising system differently changed the myofiber characteristics depending on the muscle group and the developmental stage. Genome-wide transcriptome analysis showed that compared with FRS, NRS induced the most extensive gene expression changes in breast muscle (BM) at W4 but in thigh muscle (TM) at W13, suggesting the asynchronous molecular responses of BM and TM to the raising system and period. Most of differentially expressed genes in either BM or TM between NRS and FRS were enriched in the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes terms associated with regulation of muscle cellular functions, metabolic and contractile activities, and tissue remodeling, indicating similar molecular mechanisms principally responsible for the raising system-caused phenotypic changes in both muscle groups. Nevertheless, several crucial pathways (e.g., adipocytokine signaling, AGE-RAGE signaling, and apoptosis) and genes (e.g., ANO6, ACER2, UCP3, DTL, and TMEM120A) were tightly related to the muscle group–specific adaptive remodeling on different raising systems. These data could not only contribute to a better understanding of the molecular mechanisms behind meat quality but also provide novel insights into the molecular causes of the muscle group–specific adaptive remodeling in response to environmental stimuli.

Effect of low-temperature vacuum heating on physicochemical properties of sturgeon (Acipenser gueldenstaedti) fillets

BACKGROUND

Sturgeon is popular for its nutritious value and its taste. However, sturgeon fillets are traditionally heated in 100 °C boiling water, resulting in unfavorable taste and with a negative effect on the quality. This study considered the effect of combinations of vacuum and low-temperature treatments (LTVH groups) on sturgeon fillets compared with the traditional heat treatment (TC groups).

RESULTS

The results show that the LTVH groups had lower cooking-loss rates. All LTVH fillets were changed to a white color, and appeared 'done', as did the TC fillets. The LTVH and TC methods gave rise to significant differences in texture: the springiness of the LTVH groups decreased with heating time, and decreased rapidly in the TC groups (P < 0.05); hardness and chewiness increased with time and temperature in the LTVH groups, but decreased in the TC groups. More compact and denser gaps were observed in LTVH70 groups and TC groups. Less protein and lipid oxidation was evident in LTVH groups, including more myofibril protein solubility; there was less protein aggregation, fewer thiobarbituric acid reactive substance, and Schiff base.

CONCLUSION

Vacuum and low-temperature treated sturgeon fillets can be served as a good alternative. This treatment caused slight tissue damage and less proteolysis and lipid oxidation, which is beneficial for the quality of aquatic products.

Muscle tissue engineering in fibrous gelatin: implications for meat analogs

Bioprocessing applications that derive meat products from animal cell cultures require food-safe culture substrates that support volumetric expansion and maturation of adherent muscle cells. Here we demonstrate scalable production of microfibrous gelatin that supports cultured adherent muscle cells derived from cow and rabbit. As gelatin is a natural component of meat, resulting from collagen denaturation during processing and cooking, our extruded gelatin microfibers recapitulated structural and biochemical features of natural muscle tissues. Using immersion rotary jet spinning, a dry-jet wet-spinning process, we produced gelatin fibers at high rates (~ 100 g/h, dry weight) and, depending on process conditions, we tuned fiber diameters between ~ 1.3 ± 0.1 μm (mean ± SEM) and 8.7 ± 1.4 μm (mean ± SEM), which are comparable to natural collagen fibers. To inhibit fiber degradation during cell culture, we crosslinked them either chemically or by co-spinning gelatin with a microbial crosslinking enzyme. To produce meat analogs, we cultured bovine aortic smooth muscle cells and rabbit skeletal muscle myoblasts in gelatin fiber scaffolds, then used immunohistochemical staining to verify that both cell types attached to gelatin fibers and proliferated in scaffold volumes. Short-length gelatin fibers promoted cell aggregation, whereas long fibers promoted aligned muscle tissue formation. Histology, scanning electron microscopy, and mechanical testing demonstrated that cultured muscle lacked the mature contractile architecture observed in natural muscle but recapitulated some of the structural and mechanical features measured in meat products.

Effects of High Pressure Modification on Conformation and Digestibility Properties of Oyster Protein

To expand the utilization of oyster protein (OP), the effects of high pressure (100 to 500 MPa) on chemical forces, structure, microstructure, and digestibility properties were investigated. High pressure (HP) treatment enhanced the electrostatic repulsion (from -13.3Control to -27.8HP200 mV) between protein molecules and avoided or retarded the formation of protein aggregates. In addition, the HP treated samples showed uniform distribution and small particle size. The changes in electrostatic interaction and particle size contributed to the improvement of solubility (from 10.53%Control to 19.92%HP500 at pH 7). The stretching and unfolding of protein were modified by HP treatment, and some internal hydrophobic groups and -SH groups were exposed. HP treatment modified the secondary structure of OP. The treated samples contained less α-helix and β-sheet structures, whereas the proportions of β-sheet and random coil structures were increased. The treated samples have high digestibility in the stomach (from 26.3%Control to 39.5%HP500) and in the total digestive process (from 62.1%Control to 83.7%HP500). In addition, the total digestive production showed higher percentages of small peptides (<1 kDa) after HP treatment. The protein solubility and digestibility were increased after HP treatment, and high solubility and high digestibility might increase the chance that OP become a kind of protein supplement.

Effect of immunocastration and caponization on fatty acid composition of male chicken meat

Recently, immunocastration with Improvac (ImmC). has been tested in broilers and a considerable reduction in serum testosterone concentration (reduced by 79% compared to roosters) was observed. The aim of this study was to evaluate the effect of immunocastration on meat fatty acid (FA) composition and its comparison with caponized and intact males (roosters). The study was conducted with 3 experimental groups: control group (roosters), the group of birds submitted to surgical caponization (SurgC), and the group of birds submitted to immunocastration with Improvac. The comparison of breast meat partial FA sums of castrated (SurgC and ImmC) with control birds (roosters) revealed that castrated birds showed significantly higher content of n-3 polyunsaturated fatty acids (n-3 PUFA) than control birds (1.76 vs. 1.46 g/100 g of total FA; superiority of 20.2%), which has contributed to the occurrence of significant differences on both the n-6/n-3 ratio and the atherogenicity index (AI). In contrast, on leg meat portion, castrated birds displayed higher contents of both total saturated and monounsaturated fatty acids (SFA and MUFA, with 2.2 and 4.1% more, respectively) and lower total n-6 PUFA content (8.3% less) than was observed in control birds, which contributed to significant differences in the AI index. On the other hand, the comparison of breast meat portion from SurgC with ImmC showed that immunocastration contributed to lower total SFA and higher total n-6 PUFA, which have contributed to significant differences on both Polyunsaturated/Saturated (P/S) and n-6/n-3 ratios. Whereas, on leg meat portion no significant differences were observed on partial sums and a single difference was observed on the thrombogenicity index. Immunocastration of broilers has contributed to minor changes in the FA profile, but has improved the overall lipid quality indexes in both breast and leg meat portions. Therefore, immunocastration could be applied as an alternative method to caponization without negative consequences in meat FA profile.

Glycolysis and pH Decline Terminate Prematurely in Oxidative Muscles despite the Presence of Excess Glycogen

Meat from oxidative skeletal muscle has a higher postmortem ultimate pH, which was originally thought to be a result from decreased antemortem glycogen stores. Therefore, we hypothesized that excess glycogen may not resolve the high ultimate pH of meat from oxidative muscles in ruminants and poultry. To test this hypothesis, an in vitro muscle glycolytic buffer system containing excess glycogen was used to compare glycolysis and pH decline of glycolytic and oxidative muscle from beef, lamb, chicken, and turkey. Glycogen concentration of both glycolytic and oxidative muscle homogenates was similar at 0 min and decreased significantly with time in all species tested. All homogenates contained residual glycogen at 1440 min, indicating glycogen was provided in excess. The ultimate pH of the oxidative muscle homogenates was significantly increased compared to the glycolytic muscle. The oxidative muscle also contained decreased lactate and decreased glucose 6-phosphate in all the species tested at 1440 min. Combined these data suggest that glycolysis and pH decline of oxidative muscles terminate prematurely at higher ultimate pH even in the presence of excess glycogen across livestock species. Additionally, the data indicated that the in vitro glycolytic buffer system can be used to study species specific meat quality problems in beef, lamb, chicken, and turkey.

Comparison of physicochemical traits of dry-cured ham from purebred Berkshire and crossbred Landrace × Yorkshire × Duroc (LYD) pigs

This study was conducted to compare the physicochemical traits of dry-cured hams made from two different pig breeds: Berkshire and Landrace × Yorkshire × Duroc (LYD). Pigs were slaughtered at a live weight of approximately 110 kg and cooled at 0°C for 24 h in a chilling room. Then, the ham portion of the carcasses were cut and processed by dry-curing for physicochemical analyses. The dry-cured hams from Berkshire contain higher crude protein, fat, and ash level than those from LYD, whereas the hams from LYD had higher moisture contents than those from Berkshire(p < 0.05). The pH values of the hams from Berkshire were lower than those from LYD (p < 0.05). The hams from Berkshire had lower L* and b* values than those from LYD (p < 0.05). Palmitoleic acid (C16:1), oleic acid (C18:1), elaidic acid (C18:1t), monounsaturated fatty acids, and ratio of n-6 and n-3 fatty acids (n-6/n-3) in the ham from Berkshire were higher than LYD (p < 0.05). Free amino acids such as aspartic acid, threonine, serine, asparagine, glutamic acid, and lysine in hams from Berkshire were higher than those from LYD (p < 0.05). The microbial population had no significant difference between Berkshire and LYD dry-cured ham. The cross sections of dry cured ham showed difference from different breeds using scanning electron microscope and indicates some differences in texture. Considering the meat quality parameters of ham, hams from Berkshire could provide variety of ham for consumer who are seeking various different qualities and stories.

Effect of gellan gum on functional properties of low-fat chicken meat batters

The effects of substituting pork back-fat with addition of gellan gum and water on gel characteristics, rheological property, water mobility, and distribution of chicken meat batters were studied. The addition of gellan gum significantly affected the cooking yield, color, texture, and rheological property of chicken meat batters (p < .05). The cooking yield and textural properties were not significantly different (p > .05) when gellan gum was added with 0, 0.2, and 0.4%. When the level of gellan gum reached 0.6%, the cooked chicken meat batters had significantly lower L* value, cooking yield, hardness, springiness, cohesiveness, and chewiness values (p < .05). The initial storage modulus (G') of chicken batters was significantly decreased (p < .05) with increasing gellan gum. During the heating, an increase in denaturation temperature of the myosin head and tail were observed in chicken batters with added gellan gum. The G' of chicken batters with 0, 0.2, and 0.4% gellan gum were not significant difference (p > .05) at 80C, but the G' of chicken batters with 0.6% gellan gum was significantly decreased (p < .05). LF-NMR revealed that T₂₁ and T₂₂ were significantly increased (p < .05) with increasing the water and gellan gum content while P₂₁ and P₂₂ were not significantly different (p > .05) in the chicken batters with 0, 0.2, and 0.4% gellan gum. A significant decrease was observed (p < .05) in the chicken batter with 0.6% gellan gum. Overall, added 0.2 and 0.4% gellan gum to chicken meat batters could reduce pork back-fat. PRACTICAL APPLICATIONS: Emulsion-type meat products contain a high level of fat, saturated fatty acids, and cholesterol, which have a potential negative effect on consumers health. However, animal fat plays an important role in the textural properties and water-holding capacity of meat products. One of great challenges in meat processing is how to find a fat substitute to produce low-fat meat products which have overall acceptable quality. This study showed that the addition of gellan gum influenced the textural properties of chicken batters and changed the dynamic rheological behavior. The addition of 0.2 and 0.4% gellan gum kept a stable cooking yield and textural properties of cooked chicken batters and also reduced the pork back-fat. LF-NMR could reflect the cooking yield and gel properties of the chicken batters. Gellan gum may be used to replace pork back-fat to produce low-fat chicken meat batters having overall acceptability in meat industry for meeting consumer demand.

Age-related changes in the carcass composition and meat quality of fallow deer (DAMA DAMA L.)

The present study investigated the possible differences in carcass composition as well as texture, structure and percentage of different muscle types of the most valuable muscles (BF - biceps femoris, SM - semimembranosus, and L - longissimus) from fallow deer (Dama dama L.) bucks shot in the forest farm in north-western Poland at four different ages: 18, 30, 42 and 54 months. It was found that carcasses of young fallow deer (18-30 months), compared to older animals, were characterised by a higher dressing proportion, a higher percentage of the most valuable commercial cuts (the saddle, haunch and shoulder), high meat yield with the lowest percentage of bones and a lower percentage of skin and head. Their muscles, compared with older animals, were characterised by a lower percentage of red fibres, lower muscle fibre area, thinner perimysium and endomysium, lower amount of intramuscular fat and as a consequence lower hardness, springiness, cohesiveness, as well as a higher pH and lower thermal drip.

Effect of Meat Type, Animal Fatty Acid Composition, and Isothermal Temperature on the Viscoelastic Properties of Meat Batters

The aim of this research was to simultaneously study the effect of meat type (chicken breast and leg meat), animal fatty acid composition (selected pork backfats having a low and high degree of saturation, respectively), and isothermal temperature (50, 60, 70, and 80 °C) on the viscoelastic properties of meat batters during and after application of different time-temperature profiles. Gelation of meat proteins contributed most to the viscoelastic properties of meat batters during heating, whereas crystallization of the lipids especially contributed to the viscoelastic properties during the cooling phase. Although the meat type had little effect on the final viscoelastic properties of the meat product, the fatty acid composition had a clear impact on the melting peak area (and therefore solid fat content) of lard, and subsequently on the final viscoelastic properties of meat batters prepared with different types of fats, with higher G' (elastic modulus) values for the most saturated animal fat. The crystallization of the fat clearly transcended the effect of the meat type with regard to G' at the end of the process. With increasing (isothermal) temperature, G' of meat batters increased. Therefore, it could be concluded that the structural properties of heated meat batters mainly depend on the heating temperature and the fatty acid composition, rather than the meat type.

PRACTICAL APPLICATION

Quality characteristics of cooked sausages depend on multiple factors such as the meat and fat type, non-meat ingredients and processing conditions. From this study it could be concluded that the structural properties of cooked sausage batters mainly depend on the heating temperature and the fatty acid composition, rather than the meat type. Because the fatty acid composition of different animal fats differs widely, these results may be a concern for all manufactures of cooked sausages products with regard to the product structure and final texture, keeping in mind that rendered fat was used in this study, which is not common in sausage making.

Carcass and meat characteristics from farm-raised and wild fallow deer (Dama dama) and red deer (Cervus elaphus): A review

Deer species are utilised for food, hunting and other products throughout the world. Consumers are typically exposed to venison derived predominantly from both farm-raised or wild fallow (Dama dama) and red deer (Cervus elaphus). The production of venison under farm conditions, compared to the meat of deer hunted in the wild, allows for a regular supply of a consistently good meat. It is lean, tasty, and rich in proteins and minerals, with a low content of fat and cholesterol. Overall, the worldwide demand for meat is still growing, and both the potential of farming deer species and their use as meat producers have led to an increased interest in venison. The current knowledge about various factors (e.g. nutrition, age, sex, condition, season) affecting venison and game meat has significantly increased during past decades but information regarding the interaction between production system or pre- and post-slaughter handling and ultimate deer meat quality are still very limited.

Rheology and microstructure of myofibrillar protein-olive oil composite gels: effect of different non-meat protein as emulsifier

BACKGROUND

Heat-induced composite gels were prepared with 20 g kg^-1 (2%) myofibrillar protein (MP) sol and 100 g kg^-1 (10%) olive oil pre-emulsified by MP or non-meat protein in 0.6 mol L^-1 NaCl, at pH 6.2. The effect of different non-meat protein (soy protein isolate, egg-white protein isolate and sodium caseinate) pre-emulsions on the rheological properties and microstructure of MP gel was evaluated.

RESULTS

Adding emulsion enhanced the gel strength of MP gel except for the soy protein isolate (SPI) as emulsifier group, but all emulsion group markedly improved (P < 0.05) the water-holding capacity and the storage modulus (G') of MP gels. SDS-PAGE show that some non-meat protein bands partially participated in the formation of MP composite gels with different kinds of emulsion added. Micrographs revealed that these emulsions made the gels become denser and more compact with subtle diverse effects.

CONCLUSION

Different meat or non-meat proteins as emulsifier have varied impacts on the rheology and microstructure of MP gels, indicating the potential and feasibility of these non-meat proteins as emulsifiers to modify the textural properties in comminuted meat products. © 2017 Society of Chemical Industry.