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Peptides derived from whole proteins in beef tenderloin (M. psoas major, PM) and striploin (M. longissimus lumborum, LL) associated with meat quality and muscle fiber composition were identified and quantified during 21 days of aging. Peptide quantification revealed 40-43 proteins to be significantly degraded during all aging time, and these were mostly sarcoplasmic proteins. Cooking loss of both muscles was not changed by aging (P > 0.05), whereas Warner-Bratzler shear force and meat color were affected by aging. Sensory tenderness increased in PM after 14 days of aging (P < 0.05). PM had a higher type I fiber content, whereas LL had a higher type IIX fiber content (P < 0.05), resulting in differences in proteolysis during all aging periods tested. These findings improve our understanding of different biochemical and physicochemical changes in aged meat according to the muscle type., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

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., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Lactobacillus sakei is a heterofermentative species of lactic acid bacteria that is used in industrial meat fermentation. To investigate adaptation in a meat environment, whole-genome DNA microarrays were used to analyze the gene expression related to growth and survival of L. sakei strain La22 when grown in sarcoplasmic (S-) or myofibrillar (M-) protein-supplemented chemically defined medium (CDM). Differential expression was detected in 551 genes. Genes encoding enzymes involved in peptide hydrolysis were differentially upregulated in M-CDM or/and S-CDM, and only oppB and oppC, involved in the amino acid and peptide transport system, were upregulated. Most genes related to metabolism of peptides, amino acids and related molecules were over-expressed in M-CDM and S-CDM, except for glnA and metK. Expression of certain genes was according to the differential substrate environment. The expression of genes involved in the stress response was not induced by growth in M-CDM., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Recently, white striations parallel to muscle fibers direction have been observed on the surface of chicken breast, which could be ascribed to intensive growth selection. The aim of this study was to evaluate the effect of white striping on chemical composition with special emphasis on myofibrillar and sarcoplasmic protein fractions that are relevant to the processing features of chicken breast meat. During this study, a total of 12 pectoralis major muscles from both normal and white striped fillets were used to evaluate chemical composition, protein solubility (sarcoplasmic, myofibrillar, and total protein solubility), protein quantity (sarcoplasmic, myofibrillar, and stromal proteins), water holding capacity, and protein profile by SDS-PAGE analysis. White-striped fillets exhibited a higher percentage of moisture (75.4 vs. 73.8%; P < 0.01), intramuscular fat (2.15 vs. 0.98%; P < 0.01), and collagen (1.36 vs. 1.22%; P < 0.01), and lower content of protein (18.7 vs. 22.8%; P < 0.01) and ash (1.14 vs. 1.34%; P < 0.01), in comparison with normal fillets. There was a great decline in myofibrillar (14.0 vs. 8.7%; P < 0.01) and sarcoplasmic (3.2 vs. 2.6%; P < 0.01) content and solubility as well as an increase in cooking loss (33.7 vs. 27.4%; P < 0.05) due to white striping defects. Moreover, gel electrophoresis showed that the concentration of 3 myofibrillar proteins corresponding to actin (42 kDa); LC1, slow-twitch light chain myosin (27.5 kDa); and LC3, fast-twitch light chain myosin (16 kDa), and almost all sarcoplasmic proteins were lower than normal. In conclusion, the findings of this study revealed that chicken breast meat with white striping defect had different chemical composition (more fat and less protein) and protein quality and quantity (low content of myofibrillar proteins and high content of stromal proteins) with respect to normal meat. Furthermore, white striped fillets had lower protein functionality (higher cooking loss). All the former changes indicate that white striping has great impact on quality characteristics of chicken breast meat., (© Poultry Science Association Inc.)

This study determined the effects of extraction buffer pH and postmortem aging on the extraction of salt-soluble and water-soluble proteins from broiler pectoralis muscle. Deboned broiler breast fillets were collected at 4 h postmortem, packaged, and then stored at 4°C until 1, 5, or 8 d postmortem. After the designated aging period, salt-soluble and water-soluble protein extractions were performed using buffers at 7 different pH levels (pH 5.4, 6.4, 6.9, 7.2, 7.5, 8.0, 9.0). Protein concentrations of the extracts were measured and SDS-PAGE analysis was performed. Salt-soluble protein concentration increased (P < 0.0001) as buffer pH increased from pH 5.4 to 6.9 and then remained unchanged from pH 6.9 to 9.0. Water-soluble protein concentration increased (P < 0.0001) as buffer pH increased from pH 5.4 to 7.2 and then remained unchanged from pH 7.2 to 9.0. There was not a significant extraction buffer pH by aging treatment interaction for the total protein concentration of either the salt-soluble or water-soluble protein extracts. The protein concentrations of salt-soluble extracts were similar at both 1 and 8 d postmortem but lower (P < 0.0001) at 5 d postmortem. The protein concentrations of water-soluble extracts were similar at both 1 and 5 d postmortem, but higher (P < 0.0001) at 8 d. Both extraction buffer pH and postmortem aging influenced the SDS-PAGE protein profiles of salt-soluble and water-soluble protein extracts from breast muscles. Data demonstrate that postmortem aging and extraction buffer pH influence both the total amount and the composition of the myofibrillar and sarcoplasmic proteins that can be extracted from broiler breast fillets., (© 2014 Poultry Science Association Inc.)

Unlabelled: The objective of this study was to determine the relationship between the protein composition of muscle exudates and meat tenderness in beef. Frozen, intact beef strip loins (n = 24) were each divided into 3 equal portions (anterior, middle, and posterior). Steaks were removed from each portion, individually vacuum packaged, thawed at 4 °C, and aged for 0, 7, or 14 d. After the designated aging period, exudate was collected from the packaging and 1 steak from each strip loin portion was utilized for shear force measurements. Muscle exudates were analyzed for protein content (biuret assay) and composition (sodium dodecyl sulfate-polyacrylamide gel electrophoresis). Shear force decreased (P < 0.0001) with aging from 0 to 14 d. The protein concentrations of the muscle exudates were not influenced by the aging period and were not related to the amount of exudate expressed. Electrophoretic analyses of the muscle exudates indicated that with aging the relative abundance of 4 proteins decreased (P < 0.01) and 10 proteins increased (P < 0.05) within the protein profiles of the exudates. The relative abundance of the 167, 97, and 47 kDa proteins in exudates at day 0 were significantly correlated (|r| = 0.57 to 0.77) to shear force at day 14. These data demonstrate that exudate protein composition changes with postmortem aging and beef tenderness., Practical Application: This research showed that the protein profiles of exudates that accumulate on the surface and in the packaging of beef change with meat aging and tenderness. These data suggest that muscle exudates may be a good source of protein markers that are useful in the development of rapid, noninvasive methodologies for predicting beef tenderness., (Published 2014. This article is a U.S. Government work and is in the public domain in the USA.)

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]

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]

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]

We investigated the physicochemical properties of the thermal gel of water-washed pork meat (WWM) in the presence of the soluble fraction of porcine sarcoplasmic protein (SP) obtained with ammonium sulfate at 75 percent saturation. Two precipitated fractions of SP were obtained at 0–50 percent and 50–75 percent saturation, named SP-f1 and SP-f2, respectively, and the soluble fraction obtained at 75 percent saturation, SP-f3, was used. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that SP-f3 contained mainly glyceraldehyde-3-phosphate dehydrogenase (GAPDH), while SP-f1 and SP-f2 had other SPs such as phosphorylase b, enolase, actin and phosphoglycerate mutase. The gel strength of WWM was greater when SP-f3 rather than one of various animal proteins such as bovine plasma (BP), egg white, or whey protein isolates (WPI), was added and SP-f3 had a gel-enhancing effect as good as that of polyphosphate (PP). The gel strength of WWM with added SP-f3 increased significantly with NaCl at 0.15 mol/L or more, but not in the absence of NaCl (0 mol/L). The effect of SP-f3 was evident at neutral pH and maximum gel strength was obtained at a pH above 6.0. Differential scanning calorimetric (DSC) analysis showed that an endothermic peak corresponding to myosin heads in WWM shifted to a lower temperature with the addition of SP-f3, as in the case of PP, though there was no such shift in the presence of other animal proteins (BP, egg white and WPI), suggesting that SP-f3 increases the gel strength of WWM through the dissociation of actomyosin similar to PP. Scanning electron microscopy (SEM) revealed wall-like structures among the protein strands in the WWM gel matrix in the presence of SP-f3. The results of DSC and SEM indicated that the formation of a gel network in meat products is reinforced with GAPDH in SP after the interaction between GAPDH and myofibrillar protein. [ABSTRACT FROM AUTHOR]