Comparative Study on the Postmortem Proteolysis and Shear Force during Aging of Pork and Beef Semitendinosus Muscles.

The differences in the proteolytic patterns and shear force of pork and beef during aging were evaluated. Pork and beef semitendinosus muscles were obtained at 24 and 48 h postmortem, respectively, and aged at 4°C for 0 (Day 0), 7 (Day 7), and 14 days (Day 14). Changes in the electrical conductivity were observed in pork on Day 7 and beef on Day 14. The calpain activity increased in pork (p<0.05) after 14 days of aging, whereas that of beef decreased on Day 7 (p<0.05). The cathepsin B activity in pork and beef increased between Day 7 and 14 (p<0.05). The content of α-amino group in the 10% trichloroacetic acid-soluble fraction increased between Day 7 and 14 in pork (p<0.05), but increased steadily in beef throughout aging (p<0.05). The electrophoretogram of the myofibrillar proteins revealed a 30 kDa protein band only in the beef lane on Day 14. The cooked pork had no significant changes in the shear force during aging periods (p>0.05), while the gradual decrease in the shear force with the increasing aging periods was shown in the cooked beef (p<0.05). Circular dichroism analysis of myosin extracts from pork and beef revealed thermal denaturation temperatures of 55°C and 58°C, respectively. This study highlights the different post-mortem proteolytic patterns and thermal denaturation temperatures of myosin in pork and beef semitendinosus muscles, which contribute to distinct changes in the shear force during aging between pork and beef.

Reduction of N-nitrosamine in cured ham using atmospheric cold plasma-treated cauliflower powder.

The effects of cauliflower treated with atmospheric cold plasma (ACP), as a natural nitrite source, on the curing of ground ham and nitrosamine formation were investigated. Ground ham was prepared using sodium nitrite and ACP-treated cauliflower powder (PTCP) to achieve initial nitrite concentrations of 60 and 100 mg/kg, respectively. ACP treatment generated nitrite in cauliflower but significantly reduced the antioxidant activity (P < 0.05). As a nitrite source, PTCP had similar effects as sodium nitrite in the development of cured color in ground ham, with a comparable residual nitrite content (P ≥ 0.05). Three nitrosamines, N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), and N-nitrosopyrrolidine (NPYR), were detected in ground ham. NPYR formation was significantly lower in ground ham treated with PTCP at an initial nitrite concentration of 100 mg/kg (P < 0.05). Therefore, the use of a natural nitrite source manufactured through ACP treatment can prospectively achieve suitable curing efficiency while simultaneously suppressing nitrosamine formation.

Relationship between the pH of semispinalis capitis muscle and the quality properties of pork shoulder butt and belly slices.

This study investigated the relationship of carcass characteristics such as hot carcass weight and back fat thickness (BFT) and the pH of semispinalis capitis (SC) with the cooking loss (CL) of pork shoulder butt and the CL and Warner-Bratzler shear force (WBSF) of belly. BFT was correlated with the CLs of the butt slices (r s  = -0.30) and the belly slices (r s  = -0.27 to -0.32). The pH of the SC muscle showed a correlation with the CLs of the butt slices (r s  = -0.45) and the belly slices of the 6th and 11th thoracic vertebrae (r s  = -0.28 to -0.33). Additionally, the correlations (r s  = 0.62 to 0.77) were observed in the CLs among the belly slices. However, the WBSF of the belly slices did not show correlations with others. Therefore, the pH of the SC muscle as well as BFT can be used to obtain information on the CL of shoulder butts and bellies in carcasses.

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.

The Effect of Irradiation on Meat Products.

The effects of irradiation on meat constituents including water, proteins, and lipids are multifaceted. Irradiation leads to the decomposition of water molecules, resulting in the formation of free radicals that can have both positive and negative effects on meat quality and storage. Although irradiation reduces the number of microorganisms and extends the shelf life of meat by damaging microbial DNA and cell membranes, it can also accelerate the oxidation of lipids and proteins, particularly sulfur-containing amino acids and unsaturated fatty acids. With regard to proteins, irradiation affects both myofibrillar and sarcoplasmic proteins. Myofibrillar proteins, such as actin and myosin, can undergo depolymerization and fragmentation, thereby altering protein solubility and structure. Sarcoplasmic proteins, including myoglobin, undergo structural changes that can alter meat color. Collagen, which is crucial for meat toughness, can undergo an increase in solubility owing to irradiation-induced degradation. The lipid content and composition are also influenced by irradiation, with unsaturated fatty acids being particularly vulnerable to oxidation. This process can lead to changes in the lipid quality and the production of off-odors. However, the effects of irradiation on lipid oxidation may vary depending on factors such as irradiation dose and packaging method. In summary, while irradiation can have beneficial effects, such as microbial reduction and shelf-life extension, it can also lead to changes in meat properties that need to be carefully managed to maintain quality and consumer acceptability.

Tracking bioactive peptides and their origin proteins during the in vitro digestion of meat and meat products.

Existing reviews address bioactive peptides of meat proteins; however, comprehensive reviews summarizing the released sequences and their corresponding parent meat proteins in the digesta are limited. This review explores the bioactive peptides released during the in vitro gastrointestinal (GI) digestion of meat, connecting with parent proteins. The primary bioactivities of meat-derived peptides include angiotensin-converting enzyme (ACE) and dipeptidyl peptidase (DPP)-IV inhibition and antioxidant effects. Myofibrillar, sarcoplasmic, and stromal proteins play a significant role in peptide release during digestion. The release of bioactive peptides varies according to the parent protein and cryptides had short chains, non-toxicity, and great bioavailability and GI absorption scores. Moreover, the structural stability and bioactivities of peptides can be influenced by the digestive properties and amino acid composition of parent proteins. Investigating the properties and origins of bioactive peptides provides insights for enhancing the nutritional quality of meat and understanding its potential health benefits.

Effects of myofibril-palatinose conjugate as a phosphate substitute on meat emulsion quality.

The objective of this study was to investigate a replacement for phosphate in meat products. Protein structural modification was employed in this study, and grafted myofibrillar protein (MP) with palatinose was added to meat emulsion without phosphate. Here, 0.15% of sodium polyphosphate (SPP) was replaced by the same (0.15%) concentration and double (0.3%) the concentration of grafted MP. Although the thermal stability was decreased, the addition of transglutaminase could increase stability. The rheological properties and pH also increased with the addition of grafted MP and transglutaminase. The addition of grafted protein could be perceived by the naked eye by observing a color difference before cooking, but it was not easy to detect after cooking. The cooking loss, emulsion stability, water holding capacity, lipid oxidation, and textural properties improved with the addition of grafted MP. However, the excessive addition of grafted MP and transglutaminase was not recommended to produce a high quality of phosphate replaced meat emulsion, and 0.15% was identified as a suitable addition ratio of grafted MP.

Characterization of peptides released from frozen-then-aged beef after digestion in an in vitro infant gastrointestinal model.

This study investigated whether the freezing-then-aging treatment of beef affects protein digestibility and release of potentially bioactive peptides using an in vitro infant digestion model. After 28 days of storage, aged-only (AO) and frozen-then-aged (FA) beef exhibited higher α-amino group contents in the 10% trichloroacetic acid-soluble fraction compared to day 0 (P < 0.05). Following in vitro digestion in the infant model, FA showed higher contents of α-amino groups and smaller proteins (<3 and 1 kDa) than day 0 and AO (P < 0.05). Relative contributions of myofibrillar, sarcoplasmic, and stromal proteins to the bioactive peptides released from AO and FA differed from those of day 0. In addition, FA exhibited a higher proportion of potential bioactive peptide sequences. Overall, freezing-then-aging treatment can enhance the potential health benefits of beef to be used as a protein source for complementary foods.

Heat-induced gelation of egg white proteins depending on heating temperature: Insights into protein structure and digestive behaviors in the elderly in vitro digestion model.

This study investigated the effects of heating temperature of egg white gels (EWGs) on the digestive characteristics by heating egg white (EW) to reach 75 °C (EWG-75) and 95 °C (EWG-95). The gel protein structure showed a decrease in the maximum tryptophan fluorescence intensity and a significant increase in the surface hydrophobicity of EWGs compared to EW (P < 0.05). The total and reactive free sulfhydryl groups were higher in the EWGs than in the EW (P < 0.05). While the proportions of α-helical and ß-sheet structures remained similar in EW and EWG-75 (P > 0.05), EWG-95 exhibited a notable decrease in α-helix content (P < 0.05) and an increase in ß-sheet content (P < 0.05). Furthermore, EWG-95 displayed higher hardness and cohesiveness than EWG-75 (P < 0.05). In the adult and elderly in vitro digestion models, EWG-95 exhibited the highest protein digestibility (50.44 % and 54.65 % in the models of elderly and adult subjects, respectively) after GI digestion (P < 0.05), followed by EWG-75 and EW. The electrophoretogram of the digesta revealed more intense protein bands in the elderly digestion model, particularly in the gastric digesta of EW, indicating slower digestion compared to the adult model. Therefore, EW should be appropriately heated before consumption, especially for elderly individuals, to facilitate efficient protein digestion and absorption.

Effects of konjac glucomannan as a freeze-denaturation inhibitor or binder on the physiochemical properties of heat-induced gel of freeze-dried duck blood.

During freeze-drying, the degradation or eutectic melting of duck blood proteins can reduce the quality of duck blood gels. However, the interaction between proteins and polysaccharides during drying can improve protein-based gel quality. Therefore, here, we investigated the physicochemical properties of heat-induced gels of freeze-dried duck blood (FDB) and FDB with different proportions of the polysaccharide konjac glucomannan (KG), which serves as a freeze-denaturation inhibitor agent (FDA) or binder (BG). The pH and water-holding capacity (WHC) of FDB + KG gels were higher than those of FDB gel without KG (control). Especially, the WHC increased from 11.00% for control to 55.65% for FDB gel with 1% KG as a BG. Consequently, cooking loss and texture parameters of FDB + KG gels decreased. The hardness of control was 2.14 kg, which significantly reduced to 0.12-0.87 kg with KG addition. The highest carbonyl content was observed in control gel, and the thiobarbituric acid reactive substance content was reduced by the addition of 1% KG as an FDA (T1) or 0.8% KG as an FDA with 0.2% KG as a BG (T2) (p < 0.05). These changes might be induced by the alteration of tertiary structure and thermodynamic stability of gels. In conclusion, 1% KG can be used as an FDA to improve the quality and physicochemical properties of heat-induced gels of FDB. Optimized FDB gels with KG can be used as an innovative food ingredient to fortify nutrition and develop special dietary purposes.

Differences in pork myosin solubility and structure with various chloride salts and their property of pork gel.

The solubility and structure of myosin and the properties of pork gel with NaCl, KCl, CaCl2, and MgCl2 were investigated. Myofibrillar proteins (MPs) with phosphate were more solubilized with NaCl than with KCl (p < 0.05). CaCl2 and MgCl2 showed lower MP solubilities than those of NaCl and KCl (p < 0.05). The α-helix content of myosin was lower in KCl, CaCl2, and MgCl2 than in NaCl (p < 0.05). The pH of pork batter decreased in the order of KCl, NaCl, MgCl2, and CaCl2 (p < 0.05). The cooking yield of the pork gel manufactured with monovalent salts was higher than that of the pork gel manufactured with divalent salts (p < 0.05). The pork gel manufactured with KCl and MgCl2 showed lower hardness than that of the pork gel manufactured with NaCl. The solubility and structure of myosin were different with the different chloride salts and those led the different quality properties of pork gel. Therefore, the results of this study can be helpful for understanding the quality properties of low-slat meat products manufactured by replacing sodium chloride with different chloride salts.

Recent strategies for improving the quality of meat products.

Processed meat products play a vital role in our daily dietary intake due to their rich protein content and the inherent convenience they offer. However, they often contain synthetic additives and ingredients that may pose health risks when taken excessively. This review explores strategies to improve meat product quality, focusing on three key approaches: substituting synthetic additives, reducing the ingredients potentially harmful when overconsumed like salt and animal fat, and boosting nutritional value. To replace synthetic additives, natural sources like celery and beet powders, as well as atmospheric cold plasma treatment, have been considered. However, for phosphates, the use of organic alternatives is limited due to the low phosphate content in natural substances. Thus, dietary fiber has been used to replicate phosphate functions by enhancing water retention and emulsion stability in meat products. Reducing the excessive salt and animal fat has garnered attention. Plant polysaccharides interact with water, fat, and proteins, improving gel formation and water retention, and enabling the development of low-salt and low-fat products. Replacing saturated fats with vegetable oils is also an option, but it requires techniques like Pickering emulsion or encapsulation to maintain product quality. These strategies aim to reduce or replace synthetic additives and ingredients that can potentially harm health. Dietary fiber offers numerous health benefits, including gut health improvement, calorie reduction, and blood glucose and lipid level regulation. Natural plant extracts not only enhance oxidative stability but also reduce potential carcinogens as antioxidants. Controlling protein and lipid bioavailability is also considered, especially for specific consumer groups like infants, the elderly, and individuals engaged in physical training with dietary management. Future research should explore the full potential of dietary fiber, encompassing synthetic additive substitution, salt and animal fat reduction, and nutritional enhancement. Additionally, optimal sources and dosages of polysaccharides should be determined, considering their distinct properties in interactions with water, proteins, and fats. This holistic approach holds promise for improving meat product quality with minimal processing.

Level Optimization of Beet Powder and Caramel Color for Beef Color Simulation in Meat Analogs before and after Cooking.

In this study, concentration levels of beet powder (BP) and caramel color (CC) were optimized to simulate beef color in meat analogs before and after cooking. The central composite design of response surface methodology (RSM) was used to set the levels of BP and CC, and the CIE L*, CIE a*, and CIE b* were selected as the responses for RSM. After optimization, myoglobin-free beef patties were prepared with three optimized levels of BP and CC. When raw, all the patties had the same color as natural beef; however, CIE L*, CIE a*, and CIE b* were statistically different from those of beef after cooking (p<0.05). Moreover, the use of BP and CC induced "browning" after the cooking process, with no excessive yellow color. Therefore, based on the overall desirability in the color optimization using RSM, the combination of BP (1.32%) and CC (1.08%) with the highest overall desirability can be used to simulate the color change of beef in meat analogs.

High-pressure processing of beef increased the in vitro protein digestibility in an infant digestion model.

Beef is an ideal protein source for use as a complementary food in infants. Considering the limited protein-digesting capacity of infants, it is required to enhance protein digestibility while minimizing the deterioration of beef quality. Thus, this study aimed to determine the effects of high-pressure processing (HPP) on the physicochemical properties and in vitro digestibility of beef proteins in an infant digestion model. HPP at 200 and 300 MPa decreased the tryptophan fluorescence intensity of the myosin and actin fractions relative to that at 0.1 MPa (P < 0.05). Compared to treatment at 0.1 and 100 MPa, HPP at 300 MPa decreased α-helix and ß-turn contents in the myosin and actin fractions (P < 0.05), whilst increasing the ß-sheet content (P < 0.05). Beef actomyosin content decreased (P < 0.05) during HPP at 200 and 300 MPa (c.f., 0.1 and 100 MPa). After in vitro digestion of beef, HPP at 200 and 300 MPa increased the α-amino group content and the abundance of proteins below 3 kDa in the digesta (P < 0.05). However, due to the considerable lipid oxidation at 300 MPa, HPP at 200 MPa is ideal for improving the protein digestibility of beef when incorporated into complementary foods for infants.

Strategies for modulating the lipid digestion of emulsions in the gastrointestinal tract.

The structural changes in emulsion products can be used to control the bioavailability of fatty acids and lipophilic compounds. After ingestion, lipid droplets undergo breakdown and structural changes as they pass through the gastrointestinal tract. The oil-water interface plays a critical role in modulating the digestive behavior of lipid droplets because changes in the interfacial layer control the adsorption of lipase and bile salts and determine the overall rate and extent of lipid digestion. Therefore, lipid digestibility can be tuned by selecting the appropriate types and levels of stabilizers. The stabilizer can change the lipase accessibility and exposure of lipid substrates, resulting in variable digestion rates. However, emulsified lipids are not only added to food matrixes but are also co-ingested from other dietary components. Therefore, overall consumption behaviors can affect the digestion rate and digestibility of emulsified lipids. Although designing an emulsion structure is challenging, controlling lipid digestion can improve the health benefits of products. Therefore, a thorough understanding of the process of emulsified lipid digestion is required to develop food products that enable specific physiological responses. The targeted or delayed release of lipophilic molecules and fatty acids through emulsion systems has significant applications in healthcare and pharmaceuticals.

Structural and Functional Changes in Soybean Protein via Remote Plasma Treatments.

To the best of our knowledge, few studies have utilized cold plasma to improve soybean protein extraction yield and the functional properties of soybean protein. In this study, we aimed to assess the benefits of remote plasma treatments on soybean with respect to the utilization of soybean protein. This study involved two different sample forms (whole and crushed beans), two different plasma chemistry modes (ozone and nitrogen oxides [NOx = NO + NO2]), and a novel pressure-swing reactor. Crushed soybeans were significantly affected by NOx-mode plasma treatment. Crushed soybeans treated with NOx-mode plasma had the best outcomes, wherein the protein extraction yield increased from 31.64% in the control to 37.90% after plasma treatment. The water binding capacity (205.50%) and oil absorption capacity (267.67%) of plasma-treated soybeans increased to 190.88% and 246.23 % of the control, respectively. The emulsifying activity and emulsion stability slightly increased compared to those of the control. The secondary structure and surface hydrophobicity were altered. The remote plasma treatment of crushed soybeans increased soybean protein extraction yield compared to plasma-treated whole beans as well as untreated beans and altered the structural and physicochemical properties of soybean proteins.

Changes in beef protein digestibility in an in vitro infant digestion model with prefreezing temperatures and aging periods.

The protein digestibility of beef at three prefreezing temperatures (freezing at -20 °C, F20; freezing at -50 °C, F50; and freezing at -70 °C, F70) and aging periods (4, 14, and 28 days) was investigated using an in vitro infant digestion model. The increased cathepsin B activity in the frozen-then-aged treatments (P < 0.05) resulted in a higher content of 10% trichloroacetic acid-soluble α-amino groups than in the aged-only group on days 14 and 28 (P < 0.05). F50 had the most α-amino groups in the digesta and digested proteins under 3 kDa on day 28 (P < 0.05), with the disappearance of actin band in the digesta electrophoretogram. The secondary and tertiary structures of myofibrillar proteins revealed that F50 underwent irreversible denaturation (P < 0.05), especially in the myosin fraction, while F20 and F70 showed protein renaturation during aging (P < 0.05). In general, prefreezing at -50 °C then aging can improve the in vitro protein digestibility of beef through freezing-induced structural changes.

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 ß-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.

Utilization of Electrical Conductivity to Improve Prediction Accuracy of Cooking Loss of Pork Loin.

This study investigated the predictability of cooking loss of pork loin through relatively easy and quick measurable quality properties. The pH, color, moisture, protein content, and cooking loss of 100 pork loins were measured. The explanatory variables included in all linear regression models with an adjust-r2 value of ≥0.5 were pH and the protein content. In the linear regression model predicting cooking loss, the highest adjust-r2 value was 0.7, with pH, CIE L*, CIE b*, moisture, and protein content as the explanatory variables. In 30 pork loins, electrical conductivity was additionally measured, and as a result of linear regression analysis for predicting cooking loss, the highest adjust-r2 value was 0.646 with electrical conductivity measured at 40 Hz, with pH and color as the explanatory variables. Ordinal logistic regression analysis was performed to predict the three grades (low, middle, and high) of loin cooking loss using pH, color, and 40 Hz electrical conductivity as the explanatory variables, and the percent concordance was 93.8%. In conclusion, the addition of electrical conductivity as an explanatory variable did not increase the prediction accuracy of the linear regression model for predicting cooking loss; however, it was demonstrated that it is possible to predict and classify the cooking loss grade of pork loin through quality properties that can be measured quickly and easily.

Understanding protein digestion in infants and the elderly: Current in vitro digestion models.

The last decades have witnessed a surge of interest in the fate of dietary proteins during gastrointestinal (GI) digestion. Although several in vitro digestion models are available as alternatives to clinical experiments, most of them focus on the digestive conditions of healthy young adults. This study investigates the static/dynamic models used to simulate digestion in infants and the elderly and considers the related in vivo conditions. The in vitro digestive protocols targeting these two groups are summarized, and the challenges associated with the further development of in vitro digestion models are discussed. Static models rely on several factors (e.g., enzyme concentration, pH, reaction time, and rotation speed) to differentiate digestive conditions depending on age. Dynamic models can more accurately simulate the complex digestion process and allow the inclusion of further parameters (sequential secretion of digestive fluids, gradual changes in pH, peristaltic mixing, GI emptying, and the inoculation of luminal microbiota). In the case of infants, age or growth stage clarification and the differentiation of digestive protocols between full-term and preterm infants are required, whereas protocols dealing with various health statuses are required in the case of the elderly, as this group is prone to oral cavity and GI function deterioration.