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BACKGROUND: Morden advanced analytical tools offer valuable information into the understanding of molecular mechanism of traditional food processing. Chopping temperature is well‐known to affect the surimi gel quality of silver carp, but the detailed molecular mechanism is not very clear. In this study, a gel‐based proteomics was performed on the extracted surimi proteins under different chopping temperatures (0, 5, 10, and 25 °C) along with other physicochemical characterization of surimi proteins and gels. RESULTS: With increased chopping temperature, protein extractability (in 3% sodium chloride) generally decreased, while the extracted protein generally exhibited larger surface hydrophobicity, reduced intrinsic fluorescence intensity, lower sulfhydryl content. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) profile of extracted protein showed a clear difference at 25 °C when compared with the other three temperatures, and more protein fragmentation occurred. Proteomic analysis of selected bands indicated that major myofibrillar proteins react differently with chopping temperatures, especially at 25 °C. The selected bands contained a variety of other proteins or their fragments, including adenosine triphosphate (ATP) synthase, glyceraldehyde‐3‐phosphate dehydrogenase, glucose‐6‐phosphate isomerase, heat shock protein, parvalbumin, collagen, and so forth. For the surimi gel, water‐holding capacity and gel strength generally decreased with increased chopping temperature. CONCLUSION: Our results suggested that chopping at 0–10 °C is acceptable for the production of silver carp surimi in terms of gel strength and water‐holding capacity. However, a chopping temperature near 0 °C led to less protein oxidation and denaturation. The inferior gel quality at 25 °C is linked to a decreased concentration of extracted protein and degradation of major myofibrillar protein, the latter is likely crosslinked with sarcoplasmic proteins. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

This study investigated the effects of ultrasound treatment at different powers (0, 150, 300, 450 and 600 W) and a 20 kHz frequency for different durations (0, 5, 10 and 15 minutes) on the structure, physicochemical properties and emulsifying performance of sarcoplasmic proteins (SP) extracted from pale, soft and exudative (PSE)-like chicken meat. The results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed no significant changes in the composition of SP before and after ultrasound treatment. Circular dichroism (CD) spectroscopy showed that sonication did not alter the secondary structure of PSE-like chicken SP. Both ultrasonic treatment time and power had significant effects on the particle size, turbidity, potential, surface hydrophobicity, fluorescence intensity, ultraviolet (UV) absorption spectrum, solubility, and emulsifying properties of SP. With increasing ultrasonication time and ultrasonic power, the average particle size and turbidity of SP decreased significantly (P < 0.05), reaching minimum values of 237.2 nm and 0.018, respectively. The absolute value of zeta potential, solubility, surface hydrophobicity, and fluorescence intensity significantly increased. Experimental results showed that the most pronounced effects were observed at a 600 W power and 15 min, resulting in an up to 44.72% increase in solubility compared with the control group. In addition, ultrasonication could significantly increase the emulsifying activity index (EAI) and emulsion stability index (ESI) of SP, and reduced the turbiscan stability index (TSI) of the emulsion stabilized by SP (P < 0.05). The highest emulsifying performance of SP was observed after ultrasonication at 20 kHz, 300 W for 15 min, with a 79.18% increase in EAI and a 44.87% increase in ESI. In summary, ultrasonication changed the structural properties of PSE-like chicken SP and effectively improved its solubility and emulsifying properties.

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Yanbian cattle have a unique meat flavor, and high-grade meat is in short supply. Therefore, in this study, we aimed to improve the added value of Yanbian cattle low-fat meat and provide a theoretical reference for the subsequent development of an excellent starter. Rump meat from Yanbian cattle was dry-aged and then screened for protease-producing fungi. Three protease-producing fungi (Yarrowia hollandica (D4 and D11), Penicillium oxalicum (D5), and Meesziomyces ophidis (D20)) were isolated from 40 d dry-aged beef samples, and their ability to hydrolyze proteins was determined using bovine sarcoplasmic protein extract. SDS-PAGE showed that the ability of Penicillium oxalicum (D5) to degrade proteins was stronger than the other two fungi. In addition, the volatile component content of sarcoplasmic proteins in the D5 group was the highest (45.47%) and comprised the most species (26 types). Metabolic pathway analysis of the fermentation broth showed that phenylalanine, tyrosine, and tryptophan biosynthesis was the most closely related metabolic pathway in sarcoplasmic protein fermentation by Penicillium oxalicum (D5). Dry-aged beef-isolated Penicillium oxalicum serves as a potential starter culture for the fermentation of meat products. [ABSTRACT FROM AUTHOR]

To determine whether sarcoplasmic proteins affected water migration in myofibrils during air-drying, with protein denaturation as an indicator of sarcoplasmic protein changes, the extent of sarcoplasmic protein changes in lamb during air-drying was first studied. The results showed that sarcoplasmic protein’s thermal stability decreased and secondary structure changed, indicating sarcoplasmic protein denatured in lamb during air-drying (35 °C, 60% RH, 3 m/s wind speed). Subsequently, the effect of sarcoplasmic protein solutions, dried at different times and rates, on myofibril protein–water interaction was studied in vitro. Two sets of sarcoplasmic protein solutions were dried for 0, 3, 6, and 9 h in a drying oven, resulting in different degrees of change. These two sets with higher or lower drying rates were achieved by controlling the contact area between sarcoplasmic protein solution and air. These dried sarcoplasmic protein solutions were then mixed with extracted myofibril and incubated for 2 h. The results showed a significant increase in T21 relaxation time of the incubation system when sarcoplasmic protein solution was dried at 35 °C for 3 h. This indicated that myofibrillar protein–water interaction was weakened, facilitating water migration from the inside to the outside of myofibrils. The denaturation degree of sarcoplasmic proteins was slowed by a higher drying rate, thereby alleviating the increase in the amount of immobile water within myofibrils when dried for 6 h. In conclusion, the properties of sarcoplasmic proteins were influenced by both drying rate and time, thereby influencing the water migration within myofibrils during air-drying. [ABSTRACT FROM AUTHOR]

Summary: This study aimed to evaluate the protease activity of freeze‐dried kiwifruits as affected by the various colours and the antioxidant activities of protein hydrolysates from pork loin protein (sarcoplasmic and myofibrillar proteins) containing different freeze‐dried kiwifruit powder during incubation times. The protease activity of freeze‐dried kiwifruit powders was determined using casein and meat protein as substrates. Gold and green kiwifruit powders showed higher protease activity than red kiwifruit powders. Each type of kiwifruit showed different hydrolysis degrees for myofibrillar and sarcoplasmic proteins. The myofibrillar and sarcoplasmic proteins with kiwifruit powder showed increased antioxidant activity compared to the control. The protein hydrolysates obtained from pork loins treated with green and gold kiwifruit powders increased antioxidant activity with increased incubation time. These results suggested that the protein hydrolysates of pork loins containing freeze‐dried kiwifruit powders had potential antioxidant activity, resulting in maintaining meat product quality during storage. [ABSTRACT FROM AUTHOR]

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Sarcoplasmic proteins (SP) derived from yak meat were oxidized by malondialdehyde (MDA) at different concentrations. The effects of lipid oxidation on physicochemical properties and color stability of SP were investigated by evaluating side-chain amino acid oxidation, protein structure and color of SP and the oxidation status of myoglobin (Mb). The results showed that after MDA oxidation, the a* value, b* value, C* value, and deoxymyoglobin and oxymyoglobin contents of SP significantly decreased (P < 0.05), and the L* value, metmyoglobin content, and ferrylmyoglobin concentration significantly increased (P < 0.05), indicating that MDA oxidation lowered color stability. The contents of carbonyl groups and dimeric tyrosine, the fluorescence intensity of SP-MDA adducts, and the relative contents of β-helix and β-turn significantly increased (P < 0.05), and total sulfhydryl content, surface hydrophobicity, intrinsic fluorescence intensity, and the relative contents of α-helix and random coil significantly declined (P < 0.05). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed blurred expansion of small molecule bands and the formation of macromolecular aggregates, suggesting that MDA promoted the oxidation and aggregation of SP. Pearson correlation analysis revealed significant correlations between MDA oxidation and physicochemical properties and color stability of SP (P < 0.05). This study reveals that MDA alters the structure of SP by directly oxidizing it or mediating Mb oxidation, causing cross-linked aggregation of SP and reducing its color stability.

The interaction between muscle proteins and aroma compounds during processing can lead to a loss of aroma in the meat products, thereby altering the aroma profile for the consumer preference. Heat treatment has been commonly used in meat processing. The addition of spices during stewing meat can be used to eliminate the off-flavor for the enhanced color and the fragrance. Among them, terpenoid compounds are the key volatile flavor compounds in spices. But it is unclear on the mechanism of their interaction with muscle proteins. Myofibrillar protein (MP) and sarcoplasmic protein (SP) also play important roles as components of muscle proteins. This study aims to clarify the patterns and mechanisms of the interaction between muscle proteins and terpenoid compounds during heat treatment. Various physicochemical properties of MP and SP were determined at different heating times, such as surface hydrophobicity, total sulfhydryl content, particle size, and secondary structure content. Three terpenoid compounds (3-carene, limonene, and linalool) which significantly contributed to the aroma of stewed pork, were selected to investigate the interaction between aroma compounds and muscle proteins. Solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) was used to study the changes in the aroma absorption ability of proteins with heating time. The correlation was examined between aroma absorption and conformational changes of MP and SP. Moreover, the molecular docking analysis was also implemented to reveal the mechanism of muscle proteins binding to the terpenoid compounds. The results indicated that the heat treatment significantly altered the conformation of MP and SP. The surface hydrophobicity and total sulfhydryl content of MP and SP initially increased and then decreased, as the heating time increased, due to their unfolding and aggregation behaviors. Both MP and SP exhibited an increase in particle sizes during heating, particularly with a higher degree of SP aggregation, due to the lower thermal stability. Furthermore, the secondary structure content analysis showed that the intramolecular hydrogen bond of proteins was rearranged into intermolecular hydrogen bond, and then the ordered structure was transformed into a random coil conformation following heating, resulting in a decrease of α -helix structure content and an increase of β -sheet and random coil structure content. MP and SP demonstrated enhanced aroma adsorption during the initial 5 min of heating, due to their unfolded secondary structures and exposed binding sites. However, the continued heating led to the aggregation of MP and SP, burying the binding sites, and reducing their adsorption ability. Although the MP and SP exhibited similar adsorption within 0- 5 min of heating, the SP displayed weaker adsorption than the MP after 10-60 min of heating. This difference was attributed to the higher degree of aggregation in the SP, which resulted in greater steric hindrance and the burial of more aroma-binding sites. Molecular docking results demonstrated that the hydrophobic interactions dominated the interactions between 3- carene/limonene and muscle proteins, whereas the linalool bound to muscle proteins through hydrophobic interactions and hydrogen bonds. Overall, the heat treatment can be expected to modify the conformation of muscle proteins, and then regulate the exposure or burial of aroma binding sites. Consequently, there was some impact on the interaction between muscle proteins and terpenoid compounds. The findings can provide theoretical guidance to control the aroma retention/release behavior during the thermal processing of meat products for the higher quality of meat products. [ABSTRACT FROM AUTHOR]

Yanbian cattle have a unique meat flavor, and high-grade meat is in short supply. Therefore, in this study, we aimed to improve the added value of Yanbian cattle low-fat meat and provide a theoretical reference for the subsequent development of an excellent starter. Rump meat from Yanbian cattle was dry-aged and then screened for protease-producing fungi. Three protease-producing fungi (Yarrowia hollandica (D4 and D11), Penicillium oxalicum (D5), and Meesziomyces ophidis (D20)) were isolated from 40 d dry-aged beef samples, and their ability to hydrolyze proteins was determined using bovine sarcoplasmic protein extract. SDS-PAGE showed that the ability of Penicillium oxalicum (D5) to degrade proteins was stronger than the other two fungi. In addition, the volatile component content of sarcoplasmic proteins in the D5 group was the highest (45.47%) and comprised the most species (26 types). Metabolic pathway analysis of the fermentation broth showed that phenylalanine, tyrosine, and tryptophan biosynthesis was the most closely related metabolic pathway in sarcoplasmic protein fermentation by Penicillium oxalicum (D5). Dry-aged beef-isolated Penicillium oxalicum serves as a potential starter culture for the fermentation of meat products.

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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. [ABSTRACT FROM AUTHOR]

This research aimed to monitor the shelf-stability of sarcoplasmic protein powder (SPP) derived from silver carp and to determine consumer acceptability of aquatic-based protein powders. Soluble proteins were extracted, freeze-dried and powdered. Each powder was packaged, stored at 20 °C and 30 °C, and analyzed at 0, 3, 6, and 9 months. Storage of SPP at 30 °C resulted in the greatest changes: water activity increased (p

• Oxidative stability of myoglobin (Mb) was investigated under magnetic field treatment. • The central iron was protected for porphyrin ring first oxidized by hydroxyl radical. • 12 mT magnetic field could slow down oxidation damage of hydroxyl radical to Mb. • Sarcoplasmic protein shielded Mb from oxidation damage caused by magnetic fields. This study aimed to investigate the effect of magnetic fields (0, 3, 6, 12 mT) on the oxidation characteristics of myoglobin (Mb) in the sarcoplasmic protein (SP) system and to understander the underlying mechanism. The metmyoglobin content, Soret band of heme iron porphyrin, protein conformation and molecular weight distribution were measured in different Mb and SP samples. The results showed that the primary oxidation site of hydroxyl radical on Mb was likely to be the porphyrin ring structure and the side chain group of protein rather than the central iron atoms, what's more, 12 mT magnetic field treatment had an inhibitory effect on the oxidative damage induced by hydroxyl radical. [ABSTRACT FROM AUTHOR]

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To determine whether sarcoplasmic proteins affected water migration in myofibrils during air-drying, with protein denaturation as an indicator of sarcoplasmic protein changes, the extent of sarcoplasmic protein changes in lamb during air-drying was first studied. The results showed that sarcoplasmic protein's thermal stability decreased and secondary structure changed, indicating sarcoplasmic protein denatured in lamb during air-drying (35 °C, 60% RH, 3 m/s wind speed). Subsequently, the effect of sarcoplasmic protein solutions, dried at different times and rates, on myofibril protein-water interaction was studied in vitro. Two sets of sarcoplasmic protein solutions were dried for 0, 3, 6, and 9 h in a drying oven, resulting in different degrees of change. These two sets with higher or lower drying rates were achieved by controlling the contact area between sarcoplasmic protein solution and air. These dried sarcoplasmic protein solutions were then mixed with extracted myofibril and incubated for 2 h. The results showed a significant increase in T 21 relaxation time of the incubation system when sarcoplasmic protein solution was dried at 35 °C for 3 h. This indicated that myofibrillar protein-water interaction was weakened, facilitating water migration from the inside to the outside of myofibrils. The denaturation degree of sarcoplasmic proteins was slowed by a higher drying rate, thereby alleviating the increase in the amount of immobile water within myofibrils when dried for 6 h. In conclusion, the properties of sarcoplasmic proteins were influenced by both drying rate and time, thereby influencing the water migration within myofibrils during air-drying.

BACKGROUND Protein modification is used to improve emulsion properties. However, there are limited reports on the effect of methylglyoxal (MGO) modification on emulsifying properties and on the production of advanced glycation end‐products (AGEs) in chicken sarcoplasmic protein emulsion (SPE). In this study, MGO solution was dispersed into prepared emulsion (17 mg mL−1 sarcoplasmic–soybean oil (v/v 5:1)) at 0, 0.5, 5, 10, 30 and 50 mmol L‐1 concentrations. Emulsifying activity index (EAI), emulsifying stability index (ESI), Z‐average diameter, polydispersity index (PDI), zeta potential, rheological behavior (thermal condensation characteristics and fluidity) and AGEs in different concentrations of MGO SPE were measured. In addition, the effect of MGO on the levels of AGEs, lipid and protein oxidation of the emulsion as well as their relationship has also been analyzed. RESULTS: Our findings showed that ESI had the lowest value when MGO was added at a concentration of 10 mmol L‐1, while Z‐average, PDI, carbonyl and AGEs had the highest value at the same concentration. Also, 10 mmol L‐1 MGO played an important role in affecting the rheology of the emulsion. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE) results showed that the presence of myofibrillar proteins (MPs) in SPE was the main reason for the crosslinking of polymers which could be damaged by high concentration of MGO (>10 mmol L‐1). CONCLUSION: Different concentration of MGO showed varying effects on emulsion properties and on the formation of AGEs in chicken SPE. Pearson's correlation analysis concluded that protein oxidation played a significant positive role during MGO modification. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Copyright of Food Research & Development is the property of Food Research & Development Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Skeletal muscle is highly adaptable and has consistently been shown to morphologically respond to exercise training. Skeletal muscle growth during periods of resistance training has traditionally been referred to as skeletal muscle hypertrophy, and this manifests as increases in muscle mass, muscle thickness, muscle area, muscle volume, and muscle fiber cross-sectional area (fCSA). Delicate electron microscopy and biochemical techniques have also been used to demonstrate that resistance exercise promotes ultrastructural adaptations within muscle fibers. Decades of research in this area of exercise physiology have promulgated a widespread hypothetical model of training-induced skeletal muscle hypertrophy; specifically, fCSA increases are accompanied by proportional increases in myofibrillar protein, leading to an expansion in the number of sarcomeres in parallel and/or an increase in myofibril number. However, there is ample evidence to suggest that myofibrillar protein concentration may be diluted through sarcoplasmic expansion as fCSA increases occur. Furthermore, and perhaps more problematic, are numerous investigations reporting that pre-to-post training change scores in macroscopic, microscopic, and molecular variables supporting this model are often poorly associated with one another. The current review first provides a brief description of skeletal muscle composition and structure. We then provide a historical overview of muscle hypertrophy assessment. Next, current-day methods commonly used to assess skeletal muscle hypertrophy at the biochemical, ultramicroscopic, microscopic, macroscopic, and whole-body levels in response to training are examined. Data from our laboratory, and others, demonstrating correlations (or the lack thereof) between these variables are also presented, and reasons for comparative discrepancies are discussed with particular attention directed to studies reporting ultrastructural and muscle protein concentration alterations. Finally, we critically evaluate the biological construct of skeletal muscle hypertrophy, propose potential operational definitions, and provide suggestions for consideration in hopes of guiding future research in this area.

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Highlights • Sarcoplasmic protein was treated by isoelectric solubilization/precipitation. • Sarcoplasmic protein aggregates flocculently after denaturation. • Hydrophobicity of alkali-treated sarcoplasmic protein kept constant during heating. • Adding alkali-treated sarcoplasmic protein promotes myofibrillar protein gelation. • Sarcoplasmic protein decreased the heat stability of myofibrillar protein. Abstract The sarcoplasmic protein from pale, soft and exudative -like chicken breast meat was modified using an isoelectric solubilization/precipitation process. After the modification, the sarcoplasmic protein obtained a larger particle distribution than the nontreated sample, indicating a severe aggregation. The isoelectric solubilization/precipitation-treated sarcoplasmic protein aggregates exhibited a flocculated and amorphous shape stabilized by the hydrophobic interactions. The hydrophobic interactions of alkali-treated sarcoplasmic proteins were relatively constant during heating, while they dramatically increased in nontreated sample. The alkali-treated sarcoplasmic protein could promote myofibrillar protein gelation properties, as proved by the higher breaking force and lower cooking loss. According to our results, it is hypothesized that the alkali-treated sarcoplasmic protein likely does not interfere in the gelation behavior of myofibrillar protein but does fill in the pores of the three-dimensional network, thereby strengthening its gelation elasticity. Overall, the alkali-treated sarcoplasmic protein exhibits the potential to improve the myofibrillar protein gelation properties. [ABSTRACT FROM AUTHOR]

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Abstract This study investigated the effects of sarcoplasmic protein (SP) on myofibrillar protein (MP) gel properties by adding different concentrations of SP (0, 10, 20 and 30 g/100 g) into MP, with both of them isolated from pork. The interaction between MP and SP and the potential mechanism were also explored. When compared with the untreated MP, adding 20 g/100 g SP showed the maximum water-holding capacity, with an increase of 31.74%, as well as the most compact and densest MP gel network as indicated by the scanning electron microscopy. SP addition could also increase the binding water capacity of the gel due to shorter T 22 and less free water. Furthermore, adding 20 g/100 g SP increased the values of springiness, hardness and chewiness from 0.35 to 0.70, 142.86 to 581.63, and 11.88 to 92.55, while adding 10 g/100 g SP increased the cohesiveness value from 0.17 to 0.25. These results indicated that moderate SP addition can improve the gel properties of MP. Highlights • Sarcoplasmic protein (SP) notably affects myofibrillar protein (MP) gel property. • 20% SP addition largely improves MP gel texture property and water-holding capacity. • SEM showed the most compact and dense MP gel network by 20% SP addition. • Moderate SP could improve MP gel texture and WHC by padding the network and increasing the hydration. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Skeletal muscle is highly adaptable and has consistently been shown to morphologically respond to exercise training. Skeletal muscle growth during periods of resistance training has traditionally been referred to as skeletal muscle hypertrophy, and this manifests as increases in muscle mass, muscle thickness, muscle area, muscle volume, and muscle fiber cross-sectional area (fCSA). Delicate electron microscopy and biochemical techniques have also been used to demonstrate that resistance exercise promotes ultrastructural adaptations within muscle fibers. Decades of research in this area of exercise physiology have promulgated a widespread hypothetical model of training-induced skeletal muscle hypertrophy; specifically, fCSA increases are accompanied by proportional increases in myofibrillar protein, leading to an expansion in the number of sarcomeres in parallel and/or an increase in myofibril number. However, there is ample evidence to suggest that myofibrillar protein concentration may be diluted through sarcoplasmic expansion as fCSA increases occur. Furthermore, and perhaps more problematic, are numerous investigations reporting that pre-to-post training change scores in macroscopic, microscopic, and molecular variables supporting this model are often poorly associated with one another. The current review first provides a brief description of skeletal muscle composition and structure. We then provide a historical overview of muscle hypertrophy assessment. Next, current-day methods commonly used to assess skeletal muscle hypertrophy at the biochemical, ultramicroscopic, microscopic, macroscopic, and whole-body levels in response to training are examined. Data from our laboratory, and others, demonstrating correlations (or the lack thereof) between these variables are also presented, and reasons for comparative discrepancies are discussed with particular attention directed to studies reporting ultrastructural and muscle protein concentration alterations. Finally, we critically evaluate the biological construct of skeletal muscle hypertrophy, propose potential operational definitions, and provide suggestions for consideration in hopes of guiding future research in this area. [ABSTRACT FROM AUTHOR]

Abstract Beef colour is essential to consumer acceptability with dark muscle colours being problematic. Dark meat has less light scattering but the mechanisms are unknown. We hypothesise that three mechanisms are responsible for decreased light scattering in dark meat, namely (i) larger lateral separation of myofilaments, (ii) decreased optical protein density in the I-band and (iii) decreased denaturation of sarcoplasmic proteins. Nineteen beef longissimus thoracis muscles, divided into 'light', 'medium' and 'dark' colour groups, were assessed for light scattering by reflectance confocal microscopy, sarcomere length, and myofilament lattice spacing by small-angle X-ray diffraction. Dark muscles had a longer lattice spacing, shorter sarcomeres and wider muscle fibre diameters compared to lighter colour groups, indicating that the transverse spacing of muscle fibres that occurs post-mortem, with pH decline, is central to light scattering development. Dark muscles also had more degradation of the Z -disc and higher sarcoplasmic protein activities, which could impact on the optical density and contribute to lower light scattering. Highlights • Dark muscles have a longer myofilament lattice spacing compared to light muscles. • Dark muscles have short sarcomere lengths compared to light muscles. • Myosin-myosin myofilament spacing is central to colour and light scattering. • Dark muscles have a higher sarcoplasmic enzyme activity. • Titin and four and a half LIM domains (FHL1) are implicated in dark meat colour. [ABSTRACT FROM AUTHOR]

The combined effect of farm management practices, transport time, and ageing time on the electrophoretic changes of sarcoplasmic (SPP) and myofibrillar (MFP) protein fractions of goat kids was studied. A total of 64 suckling goat kids were withdrawn from two farms with “high” (GW) and “low” (DW) welfare-friendly management practices, and they were transported for 2 or 6 h immediately before slaughtering. Longissimus lumborum samples were obtained at 3, 8, and 21 days post-mortem, and muscle proteins were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis SDS-PAGE. Both protein extracts displayed significant changes attributable to meat maturation. Managing conditions of kids in DW farms increased the post-mortem susceptibility of muscle proteins. Some MFP of Longissimus lumborum muscle, such as troponin T, as well as 26–30 and 35–37 kDa fractions were influenced significantly by deficient on-farm management, and therefore, these protein fragments might be considered as indicators of low-welfare on-farm management in goat kids.

Resistance training generally increases skeletal muscle hypertrophy, whereas aging is associated with a loss in muscle mass. Interestingly, select studies suggest that aging, as well as resistance training, may lead to a reduction in the abundance of skeletal muscle myofibrillar (or contractile) protein (per mg tissue). Proteomic interrogations have also demonstrated that aging, as well as weeks to months of resistance training, lead to appreciable alterations in the muscle proteome. Given this evidence, the purpose of this small pilot study was to examine total myofibrillar as well as total sarcoplasmic protein concentrations (per mg wet muscle) from the vastus lateralis muscle of males who were younger and resistance-trained (denoted as YT, n = 6, 25 ± 4 years old, 10 ± 3 self-reported years of training), younger and untrained (denoted as YU, n = 6, 21 ± 1 years old), and older and untrained (denoted as OU, n = 6, 62 ± 8 years old). The relative abundances of actin and myosin heavy chain (per mg tissue) were also examined using SDS-PAGE and Coomassie staining, and shotgun proteomics was used to interrogate the abundances of individual sarcoplasmic and myofibrillar proteins between cohorts. Whole-body fat-free mass (YT > YU = OU), VL thickness (YT > YU = OU), and leg extensor peak torque (YT > YU = OU) differed between groups (p < 0.05). Total myofibrillar protein concentrations were greater in YT versus OU (p = 0.005), but were not different between YT versus YU (p = 0.325). The abundances of actin and myosin heavy chain were greater in YT versus YU (p < 0.05) and OU (p < 0.001). Total sarcoplasmic protein concentrations were not different between groups. While proteomics indicated that marginal differences existed for individual myofibrillar and sarcoplasmic proteins between YT versus other groups, age-related differences were more prominent for myofibrillar proteins (YT = YU > OU, p < 0.05: 7 proteins; OU > YT = YU, p < 0.05: 11 proteins) and sarcoplasmic proteins (YT = YU > OU, p < 0.05: 8 proteins; OU > YT&YU, p < 0.05: 29 proteins). In summary, our data suggest that modest (~9%) myofibrillar protein packing (on a per mg muscle basis) was evident in the YT group. This study also provides further evidence to suggest that notable skeletal muscle proteome differences exist between younger and older humans. However, given that our n-sizes are low, these results only provide a preliminary phenotyping of the reported protein and proteomic variables.

To investigate the effects of conformational changes and thermal degradation of myofibrillar protein (MP), sarcoplasmic protein (SP), and collagen (CO) on the binding ability for aroma compounds during heating. Using SDS-PAGE, HPLC, and LC-MS/MS, a consistent rise in the total concentration of peptides and free amino acids formed by the thermal degradation of proteins was observed. The surface hydrophobicity, total sulfhydryl content, particle size, and secondary structure content of proteins changed significantly over time. Furthermore, the aroma binding ability of proteins was determined by gas chromatography-mass spectrometry. The results revealed an increase in binding ability during 5 or 10 min of heating due to protein unfolding and the accumulation of degradation products. However, the binding ability decreased due to protein aggregation with prolonged heating. Notably, all proteins exhibited strong affinity toward ( E )-2-octenal, ( E , E )-2,4-decadienal, 2-methyl-3-furanthiol, and dimethyl trisulfide. The binding ability of MP and SP was similar but differed significantly from that of CO, which had lower binding ability for hexanal, ( E )-2-octenal, ( E , E )-2,4-decadienal, and dimethyl trisulfide compared to MP and SP.

This study investigated the proteome basis for color stability variations in beef steaks packaged under two modified atmosphere packaging (MAP) methods: HiOx-MAP (80% O 2 /20% CO 2 ) and CO-MAP (0.4% CO/30% CO 2 /69.6% N 2 ) during 15 days of storage. The color stability, pH, and sarcoplasmic proteome analysis of steaks were evaluated on days 0, 5, 10 and 15 of storage. Proteomic results revealed that the differential expression of the sarcoplasmic proteome during storage contributed to the variations in meat color stability between the two MAP methods. Compared with HiOx-MAP steaks, some glycolytic and energy metabolic enzymes important in NADH regeneration and antioxidant processes, antioxidant peroxiredoxins (thioredoxin-dependent peroxide reductase, peroxiredoxin-2, peroxiredoxin-6) and protein DJ-1 were more abundant in CO-MAP steaks. The over-expression of these proteins could induce CO-MAP steaks to maintain high levels of metmyoglobin reducing activity and oxygen consumption rate, resulting in CO-MAP steaks exhibiting better color stability than HiOx-MAP steaks during storage. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this study was to evaluate the nutritional quality and physical characteristics of soluble proteins separated from silver carp at 4, 20, and 40 °C. Ground silver carp was diluted, and soluble proteins were separated by centrifugation and dried. The proximate composition (dry wt) of the protein powders averaged 82.42% protein, 3.25% lipid, and 14.50% ash. Average protein recovery yield was 11.78% with the better yields occurring at 20 °C (P < 0.05). Mineral profile revealed greater concentrations of Fe, Mg, P, and Na when compared to the initial homogenate. More saturated and monounsaturated fatty acids were recovered in the 4 °C powder and the least in the 40 °C powder (P < 0.05). Polyunsaturated fatty acids displayed a reverse trend, with the greatest concentration in the 40 °C powder and the least in the 4 °C powder (P < 0.05). The amino acid profile revealed that the protein powder met all FAO/WHO/UNO amino acid requirements for adults. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) revealed high amounts of low and medium molecular weight (MW) proteins (10–15 and 25–50 kDa, respectively). Two‐dimensional (2‐D) electrophoresis indicated that the low MW proteins possessed a neutral isoelectric point relative to that of the medium MW proteins. The protein powder was significantly less soluble (P < 0.05) than whey protein concentrate 80 at every pH tested (pH 3.0 to 11.0). Similar tendencies were seen when ionic strength was shifted (0.0 to 1.1 I; P < 0.05). Soluble protein powders derived from silver carp are nutrient rich and have physical characteristics resembling whey protein concentrate. Changes in process temperature had limited effects on protein powder composition. Practical Application: Soluble proteins contribute to 20 to 40% of fish protein and are soluble in neutral salt solutions. Much of the sarcoplasmic proteins are lost when they solubilize in processing water and are discarded similarly to how whey protein was once discarded during dairy processing. When government regulations on whey disposal were implemented, the dairy industry responded by repurposing the high‐quality protein for human use and it is now a billion dollar industry. The aim of this research project was to verify the composition of an otherwise overlooked protein source. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Yuzuncu Yil Universitesi Journal of Agricultural Sciences (YYU J Agr Sci) is the property of Yuzuncu Yil University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Sodium reduction in meat products has been a strategic goal for decades, but the progress has been slow due to compromised functionality of myofibrillar protein (MP). The present study attempted to accentuate emulsifying activity of sarcoplasmic protein (SP) and understand the inter-relationship of SP and MP in mixed soluble muscle protein (SMP) extracted under simulated salt-reducing meat processing conditions. The SMP extracts with various " in situ " SP:MP ratios and structurally modified (ultrasound and pH 12 -shifting) pea protein supplements were subjected to interfacial analysis and emulsion preparation at salt concentrations of 0.1–0.6 M NaCl. In low-salt conditions (0.1–0.3 M NaCl), the SP-rich SMP exhibited strong initial interfacial adsorptivity compared with high-salt conditions (0.4–0.6 M NaCl), and the inclusion of 2% pea protein further improved (P < 0.05) the surface hydrophobicity (170–260%), interfacial pressure (2–11%), emulsifying activity (11–65%), and emulsion stability (7–35%). SP was responsible for emulsifying properties of SMP at < 0.4 M NaCl and had no appreciable effect on emulsifying activity of MP-dominated meat extract under higher-salt conditions. Results from this simulated SP/MP extract study indicate the feasibility to produce low-salt meat emulsions when aided by structurally modified pea protein. [Display omitted] • Sarcoplasmic protein (SP) in low-salt meat is surface active. • SP adsorbs more rapidly than myofibrillar protein (MP) at the oil-water interface. • Pea protein enhances interfacial rheology of SP-based films at <0.4 M NaCl. • SP when combined with MP stabilizes O/W emulsions in reduced-salt conditions. [ABSTRACT FROM AUTHOR]