Discrimination of in vitro and in vivo digestion products of meat proteins from pork, beef, chicken, and fish

The formation of sulfur metabolites during in vitro gastrointestinal digestion of fish, white meat and red meat is affected by the addition of fructo-oligosaccharides

The formation of sulfur metabolites during large intestinal fermentation of red meat may affect intestinal health. In this study, four muscle sources with varying heme-Fe content (beef, pork, chicken and salmon), with or without fructo-oligosaccharides (FOS), were exposed to an in vitro gastrointestinal digestion and fermentation model, after which the formation of sulfur metabolites, protein fermentation metabolites, and short (SCFA) and branched (BCFA) chain fatty acids was assessed. When FOS were present during muscle fermentation, levels of SCFA (+54%) and H2S (+36%) increased, whereas levels of CS2 (-37%), ammonia (-60%) and indole (-30%) decreased, and the formation of dimethyl sulfides and phenol was suppressed. Red meat fermentation was not accompanied by higher H2S formation, but beef ferments tended to contain 33 to 49% higher CS2 levels compared to the ferments of other muscle sources. In conclusion, there is a greater effect on sulfur fermentation by the addition of FOS to the meats, than the intrinsic heme-Fe content of meat.

Nutritional and physicochemical characteristics of Asiatic hard clam powder prepared by different cook-drying processes: a comparative study

BACKGROUND

Asiatic hard clam (Meretrix meretrix) is an underutilized bivalve resource. This study discusses dried clam powders prepared from this resource to enhance its utilization and improve nutritional security in protein-deficient populations. Dried clam powder was prepared from Asiatic hard clam and the effects of different pre-cooking methods (boil-dried clam powder, BDCP; steam-dried clam powder, SDCP; and microwave-dried clam powder, MDCP) on nutritional (proximate composition, amino acid profiling, mineral profiling, fatty acid profiling) and physicochemical qualities were investigated.

RESULTS

Different pre-cooking methods significantly influenced the characteristics of the clam powder. The MDCP sample showed the highest concentration of amino acids, polyunsaturated fatty acids, Na, K, Ca and Mg content compared to BDCP and SDCP. The boiling process led to a loss of nutritional quality in terms of amino acids and macrominerals. The MDCP displayed the highest solubility in water (30.10%) but its oil and water absorption characteristics were the lowest among all the samples. Boil-cooked clam powder displayed the highest oil binding (2.03 mL g-1 protein) capacity. Boiling and steaming processes resulted in malondialdehyde generation compared to microwaving. Different pre-cooking processes did not influence the colour attributes significantly, but the control sample prepared without pre-cooking (CCP) had a significantly lower L* value (32.34), resulting in a darker product. In vitro digestibility of the clam powder varied in the order MDCP > SDCP > BDCP > CCP.

CONCLUSION

The study demonstrated that nutritionally rich protein powder can be prepared from Asiatic hard clam. Based on the results, microwave pre-cooking is considered the best pre-cooking method to preserve the nutritional qualities of clam powder. © 2024 Society of Chemical Industry.

Analytical Methods and Effects of Bioactive Peptides Derived from Animal Products: A Mini-Review

Peptides with bioactive effects are being researched for various purposes. However, there is a lack of overall research on pork-derived peptides. In this study, we reviewed the process of obtaining bioactive peptides, available analytical methods, and the study of bioactive peptides derived from pork. Pepsin and trypsin, two representative protein digestive enzymes in the body, are hydrolyzed by other cofactors to produce peptides. Bicinchoninic acid assay, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, chromatography, and in vitro digestion simulation systems are utilized to analyze bioactive peptides for protein digestibility and molecular weight distribution. Pork-derived peptides mainly exhibit antioxidant and antihypertensive activities. The antioxidant activity of bioactive peptides increases the accessibility of amino acid residues by disrupting the three-dimensional structure of proteins, affecting free radical scavenging, reactive oxygen species inactivation, and metal ion chelating. In addition, the antihypertensive activity decreases angiotensin II production by inhibiting angiotensin converting enzyme and suppresses blood pressure by blocking the AT1 receptor. Pork-derived bioactive peptides, primarily obtained using papain and pepsin, exhibit significant antioxidant and antihypertensive activities, with most having low molecular weights below 1 kDa. This study may aid in the future development of bioactive peptides and serve as a valuable reference for pork-derived peptides.

Novel antioxidant peptides from sheep plasma protein hydrolysates: Purification, identification and cytoprotective effects against H2O2-induced oxidative stress

This study sought to purify and identify antioxidant peptides from sheep (Ovis aries) plasma protein hydrolysates and assess their protective impacts on H2O2-induced Caco-2 cells. The purification process involved reversed high-performance liquid chromatography, anion-exchange chromatography, and Sephadex G-25. Three peptides, namely Trp-Glu-Glu-Pro-Ala-Met (WEEPAM), Ser-Leu-His-Phe-Met-Glu (SLHFME), and His-Cys-Thr-Thr-Phe-Met-Ile, with molecular weights of 761.84, 762.87, and 852.03 Da, respectively, were identified by liquid chromatography with tandem mass spectrometry. Among the three antioxidant peptides, superoxide radical (O2 -) radical scavenging capacity of WEEPAM and SLHFME was not significantly different from glutathione (GSH) (p > 0.05), while their 1,1-diphenyl-2-picrylhydrazyl radical scavenging capacity was greater than GSH (p < 0.05). WEEPAM revealed increased antioxidant activity after pepsin and trypsin hydrolysis under an in vitro digestion model. In addition, WEEPAM inhibited oxidative damage in Caco-2 cells by significantly reducing reactive oxygen species accumulation, early apoptosis, malondialdehyde formation, and increasing intracellular superoxide dismutase, glutathione peroxidase, and catalase activities.

Association of Dietary Protein Sources and Their Adequacy, Body Composition and Risk of Sarcopenic Obesity in South Korean Populations: A Cross-Sectional Study

Dietary protein sources and protein adequacy are crucial modulators of muscle quality and body composition. We investigated the association between dietary protein sources (and their adequacy) and body composition and the risk of sarcopenic obesity (SO) in South Korean populations. The participants (n = 1967) were classified into SO, obese, sarcopenia, and normal groups. A cross-sectional survey was conducted using the KS-15 questionnaire, short-form food frequency questionnaire, and anthropometric measurements. The percentage of body fat (male: 35.36 ± 0.51%; female: 44.14 ± 0.36%) was significantly high, while appendicular skeletal muscle (ASM; male: 36.39 ± 0.30%, female: 30.32 ± 0.19%) was low in the SO group. Beef and pork consumption was negatively associated with ASM (%) but positively associated with body fat (%) in the normal group and positively associated with ASM (kg/m2: beta = 0.002, p = 0.02) and BFM (kg: beta = 0.012, p = 0.03) in the SO group, respectively. The highest quintile (Q5: 173.6 g/day) showed a decreased risk of SO prevalence (AORs: 0.46, CI: 0.22-0.94) compared with that in the lowest quintile (Q1: 21.6 g/day) among the people with inadequacy protein intake. Daily poultry and egg intake was positively linked with body composition in the participants with SO, while red meat showed a negative effect on imbalanced body composition in participants in the normal and SO groups. Furthermore, a lower intake of poultry and eggs was strongly associated with SO prevalence in people who consumed inadequate amounts of daily dietary protein.

Protein oxidation-mediated changes in digestion profile and nutritional properties of myofibrillar proteins from bighead carp (Hypophthalmichthys nobilis)

Digestibility is an important factor in accessing the nutritional quality and potential health benefits of protein. In this study, exudates were utilized to incubate myofibrillar proteins (MPs) for simulating the oxidation of MPs in frozen-thawed fish fillets. An in vitro gastrointestinal system was used to investigate the effect of protein oxidation on the digestion profile and nutritional properties of MPs. Results showed that exudates treatment caused the moderate oxidation of MPs and its digestibility thus increased, hydroxyl radical generation system treatment reduced the digestibility significantly. The analysis of SDS-PAGE, tricine-SDS-PAGE, amino acid composition, and peptidomics of digestion products indicates that protein oxidation decreases digestibility by causing protein cross-linking, degradation, and amino acid residues conversion. Additionally, protein oxidation reduces nutritional value of MPs via several ways including loss of essential amino acids, the proportion increase of macromolecular peptides (>2 kDa) in digests, and the percentage decrease of potential bioactive peptides in digests. The present study provides an intuitive insight into the impact of protein oxidation in frozen/thawed fillets on the digestibility of MPs, emphasizing the importance of mitigating protein oxidation to preserve their nutritional quality.

Dietary components regulate chronic diseases through gut microbiota: a review

In recent years, gut microbiota as an immune organ has gradually become the mainstream of research. When the composition of the gut microbiota is changed significantly, this may affect human health. This review details the major microbiota composition and metabolites in the gut and discusses chronic diseases based on gut dysbiosis, including obesity, liver injury, colon cancer, atherosclerosis, and central nervous system diseases. We comprehensively summarize the changes in abundance of relevant gut microbiota by ingesting different diet components (such as food additives, dietary polyphenols, polysaccharides, fats, proteins) and their influence on the microbial quorum sensing system, thereby regulating related diseases. We believe that quorum sensing can be used as a new entry point to explain the mechanism of ingesting dietary components to improve gut microbiota and thereby regulate related diseases. This review hopes to provide a theoretical basis for future research on improving disease symptoms by ingesting functional foods containing dietary components. © 2023 Society of Chemical Industry.

Analysis and Comparison of Proteomics of Placental Proteins from Cows Using Different Proteases

Newly found biochemical characteristics of the placenta can provide new insights for further studies on the possible markers of physiological/pathological pregnancy or the function of the placenta. We compared the proteome of the dairy cow placenta after enzymatic hydrolysis by three different proteases using a label-free mass spectrometry approach. In total, 541, 136, and 86 proteins were identified in the trypsin group (TRY), pepsin group (PEP), and papain group (PAP). By comparing the proteome of the PAP and TRY, PEP and TRY, and PEP and PAP groups, 432, 421, and 136 differentially expressed proteins were identified, respectively. We compared the up-regulated DEPs and down-regulated DEPs of each comparison group. The results show that the proteins identified by papain were mostly derived from the extracellular matrix and collagen, and were enriched in the relaxin signaling pathway and AGE-RAGE signaling pathway in diabetic complications; pepsin digestion was able to identify more muscle-related proteins, which were enriched in the lysosome, platelet activation, cardiac muscle contraction, the bacterial invasion of epithelial cells, and small cell lung cancer; trypsin mainly enzymatically degraded the extracellular matrix, blood particles, and cell-surface proteins that were enriched in arginine and proline metabolism, olfactory transduction proteasome, protein processing in the endoplasmic reticulum, pyruvate metabolism, and arrhythmogenic right ventricular cardiomyopathy (ARVC). In summary, these results provide insights into the discovery of the physiological functions of dairy cow placenta and the selection of proteases in dairy cow placenta proteomics.

Dietary Protein, Chronic Salt-Sensitive Hypertension, and Kidney Damage

It has been estimated that over a fifth of deaths worldwide can be attributed to dietary risk factors. A particularly serious condition is salt-sensitive (SS) hypertension and renal damage, participants of which demonstrate increased morbidity and mortality. Notably, a large amount of evidence from humans and animals has demonstrated that other components of the diet can also modulate hypertension and associated end-organ damage. Evidence presented in this review provides support for the view that immunity and inflammation serve to amplify the development of SS hypertension and leads to malignant disease accompanied by tissue damage. Interestingly, SS hypertension is modulated by changes in dietary protein intake, which also influences immune mechanisms. Together, the evidence presented in this review from animal and human studies indicates that changes in dietary protein source have profound effects on the gut microbiota, microbiota-derived metabolites, gene expression, immune cell activation, the production of cytokines and other factors, and the development of SS hypertension and kidney damage.

Consumption Patterns and the Nutritional Contribution of Total, Processed, Fresh, and Fresh-Lean Pork to the U.S. Diet

Pork has the potential to provide several macro and micronutrients to the diet, as it is a commonly consumed protein in the United States and across many cultures worldwide. There is an absence of clinical and observational studies that isolate the nutritional contribution of various types of pork intake from that of other red and/or processed meats. The objective of this study was to assess consumption patterns and the nutritional contribution of total, processed, fresh, and fresh-lean pork to the diets of participants aged 2+ years enrolled in the National Health and Nutrition Examination Survey (NHANES) 2007-2018 data cycles. The recent National Cancer Institute method was used to disaggregate fresh and processed pork intake from the USDA Food Patterns Equivalents Database. The mean intake of total pork among consumers was estimated to be 79.5 ± 0.82, 54.2 ± 0.69, 54.6 ± 0.93, and 45.9 ± 0.73, g/d for men, women, boys, and girls, respectively. Total pork consumption subtly increased intakes of total energy and several macro and micronutrients, decreased diet quality (HEI-2015) scores (adults only), and consumption of other "healthful" food groups. Only subtle but clinically insignificant effects of pork intake on biomarkers of nutritional status were shown. These trends were largely driven by processed pork consumption and the co-consumption of foods such as condiments. Increasing the availability and education around fresh-lean cuts may help to increase intake of protein and other key nutrients across certain subpopulations, without adversely affecting diet quality and biomarkers of health status.

Overview of omics applications in elucidating the underlying mechanisms of biochemical and biological factors associated with meat safety and nutrition

Over the years, significant technological discoveries have facilitated the improvement of meat-related research. Recent studies of complex and interactive factors contributing to variations in meat safety are increasingly focused on data-driven omics approaches such as proteomics. This review highlighted omics advances in elucidating the biochemical and biological actions on meat safety. Also, the impacts of the nutritional characteristics of meat and meat products on human health are emphasized. Future perspectives should explore multi-omics and in situ investigations to elucidate the implications in microbiological studies, including nutritional and health-related assessments. Also, creating meat safety assessment and prediction models based on biomarkers of meat safety traits will help to mitigate application constraints, thereby evaluating meat quality more accurately. This could provide a scientific basis for increasing the meat industry's profitability and producing high-quality meat and meat products for consumers. SIGNIFICANCE OF THE REVIEW: This review highlighted omics advances in elucidating underlying mechanisms of biochemical and biological factors associated with meat safety. Also, the impacts of meat proteins on human health are emphasized. Future perspectives should explore multi-omics and in situ investigations to elucidate the implications in microbiological studies, including nutritional and health-related assessments. Also, creating meat safety assessment and prediction models based on biomarkers of meat safety traits will help to mitigate application constraints, thereby evaluating meat quality more accurately. This could provide a scientific basis for increasing the meat industry's profitability and producing high-quality meat and meat products for consumers.

Antioxidant activity of venison subjected to in vitro cooking and gastrointestinal digestion and isolation of its 2,2-diphenyl-1-picrylhydrazyl radical scavenging peptides

Venison, a type of game meat, has several health benefits because it contains not only high protein and low fat but also bioactive peptides with several physiological properties, including antioxidative and angiotensin-converting enzyme inhibitory properties. The aim of the present study was to investigate the antioxidant activity of venison treated by in vitro cooking and gastrointestinal digestion. We subjected venison along with pork and beef to in vitro cooking and digestion and assessed their antioxidant activity via 2,2-diphenyl-1-picrylhydrazyl radical scavenging (DPPH-RS) and hydrophilic oxygen radical absorbance capacity (H-ORAC) assays. The peptide contents of all types of cooked and digested meat samples were higher than those of the untreated and cooked samples. The DPPH-RS activities and H-ORAC of digested venison, pork, and beef were increased compared with those of untreated samples. DPPH-RS activity was significantly higher in the digested venison samples than in the digested pork and beef samples. In this study, several fractions of digested venison from the chromatography exhibited DPPH-RS activity. Peptide analysis, using liquid-chromatography with tandem mass spectrometry, unveiled two peptides DIDDLELTLAK and TQTVCNFTDGALVQHQEWDGK with high DPPH-RS activities. Thus, venison is a rich source of antioxidant peptides and potentially demonstrate an antioxidation ability by digestive enzymes in vivo.

Use of Tuna Visceral Pepsin in Combination with Trypsin as Digestion Aid: Enhanced Protein Hydrolysis and Bioavailability

Freeze-dried tuna pepsin powder (TPP) was prepared using maltodextrin (10%) and trehalose (5%), while trypsin-loaded beads (TLB) with 5% glycerol were obtained via chitosan/alginate ionotropic gelation. The storage stability of TPP and TLB and their proteolytic activity toward red kidney bean protein (RKB), threadfin bream surimi (TBS) and egg white protein (EWP) in varying simulated in vitro gastrointestinal (GI) tract conditions were studied. The intestinal transepithelial transportation of generated peptides was also carried out through Caco-2 cell monolayers after the cytotoxicity test. Enzyme activity was dropped when TPP and TLB in blister packs were kept for 10 weeks of storage at room (28 °C) and refrigerated (4 °C) temperatures. TPP and TLB at a level of 50% (w/w of proteins) effectively hydrolyzed RKB, TBS and EWP in a simulated in vitro GI tract, as indicated by marked protein degradation and increased degree of hydrolysis. Some peptides generated after GI digestion could transport through Caco-2 cell monolayers. Those peptides had different molecular size distribution and antioxidant activities. The highest antioxidant activity was observed for RKB hydrolysate after passing through the Caco-2 cell monolayer. Therefore, TPP and TLB from skipjack tuna viscera could potentially be used for enzyme supplementation to help digest food proteins. Food-derived bioactive peptides generated after GI digestion could assist in improving human health due to their antioxidant activity.

Purification and identification of a novel hypotensive and antioxidant peptide from porcine plasma

BACKGROUND

Pig plasma contains a large amount of protein. Porcine plasma polypeptide can be prepared by the enzymatic hydrolysis of porcine plasma protein. The present study investigated the function, structure, and mechanisms of porcine plasma peptides.

RESULTS

The results showed that WVRQAPGKGL had a major ability to scavenge hydroxyl radical scavenging activity (HRSA) (35.25%), 2,2'-azino-bis (3-ethylbenzothiazo line-6-sulfonic acid) diammonium salt radical scavenging activity (ABTS RSA) (93.09%) and 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity (DPPH RSA) (25.72%), as well as in angiotensin converting enzyme (ACE) inhibition (91.64%). WVRQAPGKGL could inactivate ACE by binding to Zn2+ because of the presence of carboxyl in WVRQAPGKGL. The ACE inhibition, HRSA, and DPPH of synthetic WVRQAPGKGL were improved by 12.70%, 16.06%, and 117.11% respectively after in vitro digestion. It (0.1 mg mL^-1 ) also increased superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) by 59.78%, 69.05%, and 59.06%, and decreased reactive oxygen species (ROS) and malondialdehyde (MDA) by 22.08% and 50.59%, respectively, to protect HepG2 cells induced by H₂ O₂ . Furthermore, in a spontaneously hypertensive rat (SHR) model, the systolic blood pressure (SBP) and diastolic blood pressure (DBP) of the peptide group (30 mg kg^-1 ) both decreased by about 33.33% in comparison with captopril.

CONCLUSION

A new difunctional (antioxidant and hypotensive) peptide, WVRQAPGKGL, derived from porcine plasma hydrolyzate was isolated by gel filtration and reverse phase chromatography, and identified by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS)^-1 . The difunctional peptide WVRQAPGKGL from porcine plasma could therefore be used in formulating functional foods or pharmaceuticals. © 2022 Society of Chemical Industry.

Freeze-Dried Tuna Pepsin Powder Stabilized by Some Cryoprotectants: In Vitro Simulated Gastric Digestion toward Different Proteins and Its Storage Stability

The impact of maltodextrin (10%) in combination with trehalose or glycerol at different levels (2.5% and 5%) and their mixture on the stability of freeze-dried pepsin from skipjack tuna stomach was studied. Addition of 5% trehalose and 10% maltodextrin yielded the powder (TPP-T5) with highest relative pepsin activity (p < 0.05). TPP-T5 had different shapes and sizes, with mean particle size of 65.42 ± 57.60 μm, poly-dispersity index of 0.474, and zeta potential of −19.95. It had bulk density of 0.53 kg m−3 and possessed fair flowability. The wetting time for TPP-T5 was 16.36 ± 0.73 min, and solubility was 93.58%. TPP-T5 stored at room temperature under different relative humidities could maintain proteolytic activity up to 4 weeks. Commercial porcine pepsin (CP) and crude tuna pepsinogen had molecular weights of 35.2 and 43.3 kDa, respectively, when analyzed using gel filtration (Sephadex G-50) and SDS-PAGE. Tuna pepsin had comparable hydrolysis toward threadfin bream muscle protein, whey protein isolate, and kidney bean protein isolate to commercial pepsin, especially at a higher level (15 units/g protein). Digested proteins contained peptides with varying molecular weights as determined by MALDI-TOF. Therefore, pepsin from skipjack tuna stomach could replace commercial porcine pepsin and was beneficial supplement for patients with maldigestion, particularly the elderly.

Effect of gastrointestinal alterations mimicking elderly conditions on in vitro digestion of meat and soy proteins

Among the physiological functions declining with aging, decreased secretion of gastric fluid, achlorhydria, is commonly observed. We evaluated the digestion of meat (chicken, beef, and pork) and soy proteins using in vitro conditions mimicking gastrointestinal (GI) digestion in adults (control, C) and elderly individuals with achlorhydria (EA). Changes in degrees of hydrolysis (DH), SDS-PAGE profiles, peptide concentrations, and proteomic profiles during digestion were investigated. Digestion under the EA conditions markedly decreased DH, especially for soy proteins. SDS-PAGE profiling and proteomics showed that myofibrillar/sarcoplasmic proteins from meat and glycinin/beta-conglycinin from soy were most affected by digestion conditions. Our results indicated that differences in the digestibility of meat protein between EA and control conditions gradually narrowed from the gastric to the intestinal phase for meat protein, while a pronounced difference persisted in the intestinal phase for soy protein. Our work provides new insight of value for future dietary recommendations for elderly individuals.

Identification of a novel hypotensive peptide from porcine plasma hydrolysate by in vitro digestion and rat model

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Porcine plasma was enzymatically hydrolyzed with different times.

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The hydrolysate with high hydrolysis degree was isolated and purified by G-15 gel chromatography and HPLC.

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The ace inhibition rates of different purified compounds were determined.

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The sequence of the polypeptide with best ace inhibition (IFPPKPKDTL) was determined by Q exactive LC-MS / MS.

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The hypotensive function of synthetic peptide IFPPKPKDTL was also determined in spontaneously hypertensive rat.

We separated a novel functional peptide IFPPKPKDTL from porcine plasma hydrolysate by chromatography, HPLC, and identified by Q Exactive LC-MS/MS. Results showed that IFPPKPKDTL had a significant ability of ACE inhibition (76.6%) likely due to the presence of hydrophobic, aromatic, and acidic amino acids that can inactivate ACE by binding Zn²⁺, providing a hydrogen atom to maintain the link between ACE and the peptide. Furthermore, the ACE inhibition of synthetic IFPPKPKDTL was improved by 15.6% after in vitro digestion. Additionally, the systolic blood pressure and diastolic blood pressure of spontaneously hypertensive rats gavaged by the peptide (30 mg/kg). Thereby, ACE inhibitory peptide IFPPKPKDTL from porcine plasma was stable and has potential functional value.

Body weight index indicates the responses of the fecal microbiota, metabolome and proteome to beef/chicken-based diet alterations in Chinese volunteers

Relationships between meat consumption and gut diseases have been debated for decades, and the gut microbiota plays an important role in this interplay. It was speculated that the gut microbiota and relevant indicators of hosts with different body weight indexes (BMIs) might respond differentially to meat-based diet alterations, since lean and obese hosts have different gut microbiota composition. Forty-five young Chinese volunteers were recruited and assigned to high-, middle- and low-BMI groups. All of the volunteers were given a beef-based diet for 2 weeks and subsequently with a chicken-based diet for another 2 weeks. Body weight and blood indexes were measured, and fecal samples were obtained for 16S rRNA sequencing, metabolome and proteome analyses. The fecal metabolites of the low-BMI volunteers showed greater sensitivity to meat-based diet alterations. In contrast, the fecal proteome profiles and blood indexes of the high- and middle-BMI volunteers indicated greater sensitivity to meat-based diet alterations. Replacing the beef-based diet with the chicken-based diet largely changed operational taxonomic units of Bacteroides genus, and thus probably induced downregulation of immunoglobulins in feces. Compared with the beef-based diet, the chicken-based diet decreased inflammation-related blood indexes, especially in high- and middle-BMI volunteers. This work highlighted the role of BMI as an important factor predicting changes in gut homeostasis in response to meat consumption. Compared with the chicken-based diet, the beef-based diet may induce more allergic and inflammation-related responses in high- and middle- BMI Chinese at the current level.

Peptidomic Characteristic of Peptides Generated in Dry-Cured Loins with Probiotic Strains of LAB during 360-Days Aging

Peptidomics refers to the comprehensive profiling of endogenous peptides obtained from biological sources. The formation of endogenous peptides is dependent on not only endogenous factors but also exogenous factors such as microbial proteases or process conditions, including fermentation. This study analyzed the probiotic strains of Lactobacillus rhamnosus LOCK900 (LOCK), Bifidobacterium animalis ssp. lactis BB-12 (BB12), and potential probiotic Lactobacillus acidophilus Bauer Ł0938 (BAUER) to assess their ability of fermentation and peptide production in dry-cured pork loin. The peptides obtained after in vitro digestion were characterized by liquid chromatography–tandem mass spectrometry. Based on the sequences identified, the degree of similarity or differences between the peptides was determined and presented graphically on the factor plane. The charts showed that the meat products aged for 180 and 270 days were the most diverse when BB12 or BAUER were used as starter cultures. Myosin and keratin were identified as the most likely precursors of bioactive peptides in products obtained using this strain of lactic acid bacteria (LAB). The knowledge acquired from this study may contribute to the design of functional meat products as the results revealed not only the peptidogenic potential of the LAB strains indicated on their beneficial effect on the bioactivity of peptides.

Reconsidering Meat Intake and Human Health: A Review of Current Research

Meat consumption is gradually increasing and its impact on health has attracted widespread attention, resulting in epidemiological studies proposing a reduction in meat and processed meat intake. This review briefly summarizes recent advances in understanding the effects of meat or processed meat on human health, as well as the underlying mechanisms. Meat consumption varies widely among individuals, populations, and regions, with higher consumption in developed countries than in developing countries. However, increasing meat consumption may not be the main cause of increasing incidence of chronic disease, since the development of chronic disease is a complex physiological process that involves many factors, including excessive total energy intake and changes in food digestion processes, gut microbiota composition, and liver metabolism. In comparison, unhealthy dietary habits and a sedentary lifestyle with decreasing energy expenditure are factors more worthy of reflection. Meat and meat products provide high-value protein and many key essential micronutrients. In short, as long as excessive intake and overprocessing of meats are avoided, meat remains an indispensable source of nutrition for human health.

Matter Flow Through an Animal Model Feed With Grasshopper Sphenarium purpurascens: Evidence of a Sustainable and Nutritious Protein Production System

The demand for food and the environmental damage linked to its production will increase significantly; thus, the need for protein sources that are nutritious, digestible, and sustainable in environmental terms is rising. Many bromatological studies show that insects possess high protein amounts, becoming an alternative to conventional livestock. However, in vivo studies on digestibility are scarce (either on humans or laboratory animals), particularly when analyzing assimilation efficiency. In this work, we measured weight gain, food intake, feces and urine quantification, protein assimilation efficiency, and food conversion ratio in Wistar rats fed with five different diets for 5 weeks. Three diets were based on different concentrations of orthopteran protein (Sphenarium purpurascens) and were compared against a control diet and a highly caloric treatment, which was heavy in sugar and refined flours. The diet based on 23% of S. purpurascens protein resulted in 2.0 and 20.8% more biomass accumulation than the control and the highly caloric diet, respectively. The diets with 18% and 23% insect protein exhibited an average feed conversion of 6.3, while the control group resulted in 8.5 and the caloric diet in 42.7. These results show that S. purpurascens protein yields higher or equal conversion values than a conventional diet, indicating that grasshoppers can be a sustainable and nutritious food for humans and an alternative to livestock. On the other hand, even if feeding insects to farm animals for human consumption is considered an option, it seems highly inefficient, mainly because this practice increases one trophic level in the energy flow. Therefore, incorporating insect protein into human diets represents a sustainable alternative to face future feeding and environmental challenges. Proposals like the one we present here have yet to be evaluated; however, our findings in laboratory animals project a promising future for human populations, where low environmental cost proteins could be obtained sustainably.

Effect of air fryer frying temperature on the quality attributes of sturgeon steak and comparison of its performance with traditional deep fat frying

In this study, the influence of air-frying temperature on the physical properties of sturgeon steaks was explored. Meanwhile, the comparison of traditional deep fat frying (TF) and air fryer frying (AFF) methods on the quality, flavor, and digestibility of sturgeon steaks were investigated. The results indicated that along with the increase of temperature (130, 160, and 190℃) for 15 min, the moisture content of AFF sturgeon steak surface decreased dramatically while that of interior was well preserved. The applied texture property analysis exhibited that AFF sturgeon steak showed the enhanced elasticity, low hardness, and soft texture. The results indicated that AFF sturgeon steak contained higher essential amino acid content than TF sturgeon steak. More flavor compounds (aldehydes, alcohols, and esters) were produced after AFF than TF. Although the digestibility of fried sturgeon steaks decreased after frying, AFF sturgeon steaks were digested rapidly in the stomach and intestine. Conclusively, AFF sturgeon steaks exhibited a crispy texture, appealing flavor, and low oil content. This work provides a certain reference for the suitable frying methods in the processing industry of sturgeon products.

Effect of processing on in vitro digestibility (IVPD) of food proteins

Proteins are important macronutrients for the human body to grow and function throughout life. Although proteins are found in most foods, their very dissimilar digestibility must be taking into consideration when addressing the nutritional composition of a diet. This review presents a comprehensive summary of the in vitro digestibility of proteins from plants, milk, muscle, and egg. It is evident from this work that protein digestibility greatly varies among foods, this variability being dependent not only upon the protein source, but also the food matrix and the molecular interactions between proteins and other food components (food formulation), as well as the conditions during food processing and storage. Different approaches have been applied to assess in vitro protein digestibility (IVPD), varying in both the enzyme assay and quantification method used. In general, animal proteins tend to show higher IVPD. Harsh technological treatments tend to reduce IVPD, except for plant proteins, in which thermal degradation of anti-nutritional compounds results in improved IVPD. However, in order to improve the current knowledge about protein digestibility there is a vital need for understanding dependency on a protein source, molecular interaction, processing and formulation and relationships between. Such knowledge can be used to develop new food products with enhanced protein bioaccessibility.

Thermal processing implications on the digestibility of meat, fish and seafood proteins

Thermal processing is an inevitable part of the processing and preparation of meat and meat products for human consumption. However, thermal processing techniques, both commercial and domestic, induce modifications in muscle proteins which can have implications for their digestibility. The nutritive value of muscle proteins is closely related to their digestibility in the gastrointestinal tract and is determined by the end products that it presents in the assimilable form (amino acids and small peptides) for the absorption. The present review examines how different thermal processing techniques, such as sous-vide, microwave, stewing, roasting, boiling, frying, grilling, and steam cooking, affect the digestibility of muscle proteins in the gastrointestinal tract. By altering the functional and structural properties of muscle proteins, thermal processing has the potential to influence the digestibility negatively or positively, depending on the processing conditions. Thermal processes such as sous-vide can induce favourable changes, such as partial unfolding or exposure of cleavage sites, in muscle proteins and improve their digestibility whereas processes such as stewing and roasting can induce unfavourable changes, such as protein aggregation, severe oxidation, cross linking or increased disulfide (S-S) content and decrease the susceptibility of proteins during gastrointestinal digestion. The review examines how the underlying mechanisms of different processing conditions can be translated into higher or lower protein digestibility in detail. This review expands the current understanding of muscle protein digestion and generates knowledge that will be indispensable for optimizing the digestibility of thermally processed muscle foods for maximum nutritional benefits and optimal meal planning.

Changes in the digestion properties and protein conformation of sturgeon myofibrillar protein treated by low temperature vacuum heating during in vitro digestion

The digestion properties of sturgeon myofibrillar protein (MF) treated by low temperature vacuum heating (LTVH) at different processing temperatures (50, 60 and 70 °C) and times (15 and 30 min) were studied and compared with those of sturgeon MF treated by traditional cooking (TC). The results showed that as the temperature and time increased, the protein digestibility decreased, whereas the particle size and protein aggregation increased. It was observed that the band intensity of myosin heavy chain and myosin heavy chain 7 weakened; however, the band intensity of actin showed little change. MALDI-TOF-MS analysis revealed that the digested products of the samples treated by LTVH had a larger proportion of 750-1000 Da peptides than those treated by TC, which was consistent with the trend of the number of unique peptides identified in each group. Fourier transmission infrared (FT-IR) spectroscopy showed that the contents of α-helices and β-sheets exhibited negative and positive correlations with the temperature, respectively. Overall, compared to TC, LTVH can relieve the heat stress of protein conformation, reduce protein aggregation to improve the accessibility of the protein to digestive protease, and increase digestibility.

Identification of novel antioxidant peptide from porcine plasma hydrolysate and its effect in in vitro digestion/HepG2 cells model

A novel antioxidant peptide EDEQKFWGK from porcine plasma hydrolysate (PPH) was separated by chromatography, HPLC, and identified by LC-MS/MS. Results showed that EDEQKFWGK had better antioxidant ability (Hydroxyl RAS 32.19%, ABTS RAS 92.93% and DPPH RAS 26.76%) compared with glutathione (30.11%, 82.01%, 26.44%) due to the presence of hydrophobic, aromatic acids (F, W) and acidic amino acids (E, D), decreasing ROS by providing hydrogen atom and chelating metal ions. Furthermore, the antioxidant properties of synthetic EDEQKFWGK still significant despite in vitro digestion because of the production of smaller active peptide. Additionally, it could increase SOD, CAT, GSH-Px to resist oxidative damage in HepG2 cells by inhibiting ROS (O₂ ^- , OH·), forming complexes to prevent OH· from destroying DNA and binding to ARE to promote antioxidase expression. Thereby, the novel peptide EDEQKFWGK from porcine plasma had much stable antioxidant properties and hade great potential in formulating functional foods. PRACTICAL APPLICATIONS: This research isolated a novel antioxidant peptide. Moreover, the antioxidant effects of peptide were confirmed under the in vitro digestion model and oxidative damage HepG2 cells model. The results showed the antioxidant peptide could play better effect after digestion and protect the cells from oxidative damage. These data could expand the sequence data of antioxidant peptides and promote the high-value utilization of PPH.

Animal by-products collagen and derived peptide, as important components of innovative sustainable food systems-a comprehensive review

In 2020, the world's food crisis and health industry ushered into a real outbreak. On one side, there were natural disasters such as the novel coronavirus (2019-nCoV), desert locusts, floods, and droughts exacerbating the world food crisis, while on the other side, the social development and changes in lifestyles prompted the health industry to gradually shift from a traditional medical model to a new pattern of prevention, treatment, and nourishment. Therefore, this article reviews animal by-products collagen and derived peptide, as important components of innovative sustainable food systems. The review also considered the preparation, identification, and characterization of animal by-product collagen and collagen peptides as well as their impacts on the food system (including food processing, packaging, preservation, and functional foods). Finally, the application and research progress of animal by-product collagen and peptide in the food system along with the future development trend were discussed. This knowledge would be of great significance for a comprehensive understanding of animal by-product collagen and collagen peptides and would encourage the use of collagen in food processing, preservation, and functional foods.

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.

Characterization of the mercury-binding proteins in tuna and salmon sashimi: Implications for health risk of mercury in food

Fish consumption is one of the major ways through which humans receive exposure to mercury (Hg). The existing forms of Hg in food, particularly Hg bound to proteins, may affect the absorption of Hg by humans and subsequently its potentially toxic effects. However, the knowledge regarding Hg-binding proteins in edible fish muscle is scarce. In the present study, salmon and tuna fish muscles, collected from seven different regions and countries, were analyzed using metallomics- and proteomics-based techniques. The concentration of Hg in sashimi samples ranged from 4.4 to 317.4 ng/g. Size exclusion chromatography (SEC) coupled with inductively coupled plasma mass spectrometer (ICP-MS) showed that beta-actin was a novel Hg-binding protein from the fish muscles, and this protein could also bind bismuth (Bi), silver (Ag), and copper (Cu). Hg bound to beta-actin accounted for approximately 30.2-37.6% of the total Hg in the tuna muscles and was significantly correlated to total Hg in the fish muscles (r = 0.98, p < 0.01) and in the fraction of soluble proteins (r = 0.94, p < 0.01). These findings suggest that proteins act as the main Hg accumulation sites in edible fish; thus, increasing human exposure to Hg following gastrointestinal digestion.

Stability of tuna trypsin-loaded alginate-chitosan beads in acidic stomach fluid and the release of active enzyme in a simulated intestinal tract environment

Encapsulation properties of trypsin from tonggol tuna (Thunnus tonggol) spleen using different materials including alginate (AG), low and high molecular weight chitosan (LC and HC, respectively), and soy lecithin (SL) were studied. The highest encapsulation efficiency and greatest relative activity were found in AG/LC beads after simulated gastric phase (p < .05). AG/LC encapsulated trypsin was used in simulated in vitro gastrointestinal tract for hydrolysis of sodium caseinate, soy protein isolate and fish mince, in which all protein samples were hydrolyzed as indicated by the increased α-amino group content (p < .05). Higher degradation was attained when beads containing trypsin were added. When AG/LC beads packed in blister pack were stored for 8 weeks at refrigerated temperature, a 26% decrease in activity occurred. Therefore, encapsulated tonggol tuna spleen trypsin can be prepared using AG/LC to withstand structural breakdown in stomach, but be released as an active protease within intestinal tract. PRACTICAL APPLICATION: Spleen from tonggol tuna is a by-product, which can be used as a source of trypsin, a proteolytic enzyme. The trypsin that was encapsulated within alginate and low molecular weight chitosan beads was released in the intestinal phase and was retained proteolytic activity. Therefore, this encapsulated trypsin can be packaged in capsules and taken as a supplement to aid protein digestion in the gastrointestinal tract, especially for people that need such digestive aids.

Changes in the extent and products of In vitro protein digestion during the ripening periods of Chinese dry-cured hams

A long ripening period is essential for developing dry-cured ham flavor, but the effect of ripening process on its in vitro digestion product has not been extensively studied. Here, we investigated the in vitro digestion profiles from Chinese dry-cured ham (Jinhua, Rugao and Xuanwei) with different ripening periods by particle size measurement, gel eletrophoresis analysis and nano liquid chromatography-tandem mass spectrometry. The results showed that the in vitro digestibility of ham was in a good agreement with the particle size of digestion products. Among the three types dry-cured ham, Xuanwei showed the highest digestibility (93.46%), followed by Jinhua (74.46%). In term of ripening period, the 2-year Xuanwei and Jinhua showed the diversity of peptides (especially for peptide with molecular weight < 2500 Da), besides their good digestibility. Moreover, the highest amount of peptides (404) was observed in 2-year Jinhua compared to other hams. Our finding gave a new insight into the digestion profiles and nutritional properties of Chinese dry-cured hams.

Isolation, Evaluation, and Identification of Angiotensin I-Converting Enzyme Inhibitory Peptides from Game Meat

Game meat has been underutilized, while it offers the potential to diversify not only the human diet but also increase food production and the nutritional value of meat products. This study aimed to determine the angiotensin I-converting enzyme (ACE) inhibitory activities of the digested game meats (venison and boar meat) compared with those of livestock meats (beef and pork). Through the sodium dodecyl sulfate polyacrylamide gel electrophoresis and size chromatography results, we found that the digested products from each meat had different molecular weights. The ACE inhibitory ratio in all tested samples had gradually increased following by the enzyme treatments. ACE inhibitory ratios and the half maximal inhibitory concentration values indicated that digested venison was the most potent inhibitor of ACE activity, followed by the digested boar meat. The level of anserine in digested venison was higher than that in the other meats, but the carnosine level was lower. Through fractionations and liquid chromatography-tandem mass spectrometry analysis, five ACE inhibitory peptides were identified from the digested venison. Of these peptides, Isoleucine-Lysine- Glutamic Acid-Valine-Threonine-Glutamic Acid-Arginine (IKEVTER) demonstrated the highest ACE inhibitory activity. Therefore, the game meat is food that is believed potentially to offer high bioactivities, particularly antihypertensive forces.

Gastrointestinally Digested Protein from the Insect Alphitobius diaperinus Stimulates a Different Intestinal Secretome than Beef or Almond, Producing a Differential Response in Food Intake in Rats

In this study we compare the interaction of three protein sources—insect, beef, and almond—with the gastrointestinal tract. We measured the enterohormone secretion ex vivo in human and pig intestine treated with in vitro digestions of these foods. Insect and beef were the most effective in inducing the secretion of CCK, while almond was the most effective in inducing PYY in pig duodenum. In the human colon, almond was also the most effective in inducing PYY, and GLP-1 levels were increased by insect and beef. The three digested proteins reduced ghrelin secretion in pig duodenum, while only insect reduced ghrelin secretion in human colon. We also found that food intake in rats increased in groups fed a raw insect pre-load and decreased when fed raw almond. In conclusion, the insect Alphitobius diaperinus modulates duodenal and colonic enterohormone release and increases food intake in rats. These effects differ from beef and almond.

Gastrointestinal digestion and cecal fermentation of a mixed gel of lean pork meat and resistant starch in mice

The sensitivity of meat gel to digestive enzymes and the overall digestion pattern of the meat product is vital, and exerts an important influence on the growth and metabolism of mice. In order to provide a comprehensive understanding for better usage of resistant starch (RS) in functional meat products, the effects of a mixed gel (MS, a cooked mixture) of lean pork meat and RS on the gastrointestinal digestion and cecal fermentation of mice were investigated via comparing with those of RS-free meat gel (M) and the addition of RS to meat gel (M + S). The results showed that both M + S and MS promoted gastrointestinal digestion and cecal fermentation in mice. Specifically, the MS diet contributed to the hydrolysis of proteins, the formation of beneficial amino acids, and cecal health in spite of the larger particle size for digestion than that of the M + S group. Collectively, mixed gels of meat and RS are prospective for developing healthier meat products.

Long-Term Intake of Pork Meat Proteins Altered the Composition of Gut Microbiota and Host-Derived Proteins in the Gut Contents of Mice

SCOPE

This study is to investigate the effects of long-term intake of pork protein on the composition of gut microbiota and proteins in mice.

METHODS AND RESULTS

C57BL/6J mice are fed pork meat protein diets for 240 days, and the composition of gut microbiota and proteins in luminal contents from the duodenum to the colon are analyzed by 16S rRNA gene sequencing and LC-MS/MS. The stewed pork protein diet group has a highly similar microbiota composition to that of the cooked pork protein diet group, but different from the pork emulsion sausage or dry-cured pork protein diet groups. Lachnospiraceae NK4A136, Odoribacter, Defluviitaleaceae UCG-011, Ruminiclostridium 9, Blautia, Lachnoclostridium, and Ruminococcaceae UCG-010 play an important role in response to changes in gut luminal proteins. Specific microbes are significantly correlated with the Cela3b and Cpa1 that are derived from the host and involve protein digestion and absorption.

CONCLUSIONS

Pork meat protein diets alter the gut microbiota composition and specific gut microbes may have a great impact on protein digestion and absorption by regulating the secretion of digestive proteins from the host. These findings provide a new insight into the associations of long-term intake of meat protein diet with gut microbiota and host.

High-Meat-Protein High-Fat Diet Induced Dysbiosis of Gut Microbiota and Tryptophan Metabolism in Wistar Rats

Meat-diet-induced changes in gut microbiota are often accompanied with the development of various metabolic and inflammatory disorders. The exact biochemical mechanism underlying these effects is not well elucidated. This study aims to evaluate how meat proteins in high-fat diets affect tryptophan metabolism in rats. The high-chicken-protein (HFHCH) or high-pork-protein (HFHP) diets increased levels of skatole and indole in cecal and colonic contents, feces, and subcutaneous adipose tissue. The HFHCH and HFHP diets also increased the abundance of Lactobacillus, the Family XIII AD3011 group, and Desulfovibrio in the cecum and colon, which may be involved in the production of skatole and indole. Additionally, high-meat-protein diets induced lower activity of skatole- and indole-metabolizing enzyme CYP2E1 in liver compared with low-meat-protein diets. This work highlights the negative impact of high meat proteins on physiological responses by inducing dysbiosis of gut microbiota and tryptophan metabolism.

Dietary Protein: Mechanisms Influencing Hypertension and Renal Disease

PURPOSE OF REVIEW

This review will provide an in-depth coverage of the epidemiological and pre-clinical literature surrounding the role of dietary protein in hypertension, with a special emphasis on the history of our work on the Dahl salt-sensitive rat.

RECENT FINDINGS

Our studies have dedicated much effort into understanding the relationship between dietary protein and its effect on the development of salt-sensitive hypertension and renal injury. Our evidence over the last 15 years have demonstrated that both the source and amount of dietary protein can influence the severity of disease, where we have determined mechanisms related to immunity, the maternal environment during pregnancy, and more recently the gut microbiota, which significantly contribute to these diet-induced effects. Deeper understanding of these dietary protein-related mechanisms may provide insight on the plausibility of dietary modifications as future therapeutic avenues for hypertension and renal disease.