Quantification of peptides released during in vitro digestion of cooked meat

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.

Comparison of nutritional profile between plant-based meat analogues and real meat: A review focusing on ingredients, nutrient contents, bioavailability, and health impacts

In order to fully understand the nutritional heterogeneity of plant-based meat analogues and real meat, this review summarized their similarities and differences in terms of ingredients, nutrient contents, bioavailability and health impacts. Plant-based meat analogues have some similarities to real meat. However, plant-based meat analogues are lower in protein, cholesterol and VB12 but higher in dietary fiber, carbohydrates, sugar, salt and various food additives than real meat. Moreover, some nutrients in plant-based meat analogues, such as protein and iron, are less bioavailable. There is insufficient evidence that plant-based meat analogues are healthier, which may be related to the specific attributes of these products such as formulation and degree of processing. As things stand, it is necessary to provide comprehensive nutrition information on plant-based meat products so that consumers can make informed choices based on their nutritional needs.

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.

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 β-turn contents in the myosin and actin fractions (P < 0.05), whilst increasing the β-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.

Musculus senhousei as a promising source of bioactive peptides protecting against alcohol-induced liver injury

Alcohol-induced liver injury has become a leading risk for human health, however, effective strategies for the prevention or treatment are still lacking. Hence, the present study explored the potential of Musculus senhousei as a source of hepatoprotective peptides against alcoholic liver injury using in vitro, in vivo and in silico methods. Results indicated that Musculus senhousei peptides (MSP, extracted by simulated gastrointestinal digestion of cooked mussel) exhibited notable antioxidant (ABTS and DPPH assays) and alcohol dehydrogenase (ADH) stabilizing activity in vitro. The ingestion of MSP markedly alleviated alcohol-induced liver injury in mice, as indicated by the decrease of serum transaminases (AST and ALT). In line with in vitro assays, significantly increased hepatic ADH activity and activated antioxidative defense system (GSH, SOD, GSH-Px and CAT) were observed, whereas the oxidative stress (MDA) was decreased. Peptidomic analysis revealed over 6000 peptides with favorable amino acid compositions, and a total of 20 potentially novel peptides with bioactivity and bioavailability were excavated among 746 of the most influential peptides using an in silico strategy. Peptides (i.e. WLPMKL, WLWLPA, RLC and RCL) were further synthesized and validated in vitro to be bioactive. These findings suggest that Musculus senhousei can be an ideal source of bioactive peptides for the prevention of alcoholic liver injury.

Dynamic alterations in protein, sensory, chemical, and oxidative properties occurring in meat during thermal and non-thermal processing techniques: A comprehensive review

Meat processing represents an inevitable part of meat and meat products preparation for human consumption. Both thermal and non-thermal processing techniques, both commercial and domestic, are able to induce chemical and muscle's proteins modification which can have implication on oxidative and sensory meat characteristics. Consumers' necessity for minimally processed foods has paved a successful way to unprecedented exploration into various novel non-thermal food processing techniques. Processing of meat can have serious implications on its nutritional profile and digestibility of meat proteins in the digestive system. A plethora of food processing techniques can potentially induce alterations in the protein structure, palatability, bioavailability and digestibility via various phenomena predominantly denaturation and Maillard reaction. Apart from these, sensory attributes such as color, crispness, hardness, and total acceptance get adversely affected during various thermal treatments in meat. A major incentive in the adoption of non-thermal food processing is its energy efficiency. Considering this, several non-thermal processing techniques have been developed for evading the effects of conventional thermal treatments on food materials with respect to Maillard reactions, color changes, and off-flavor development. Few significant non-thermal processing techniques, such as microwave heating, comminution, and enzyme addition can positively affect protein digestibility as well as enhance the value of the final product. Furthermore, ultrasound, irradiation, high-pressure processing, and pulsed electric fields are other pivotal non-thermal food processing technologies in meat and meat-related products. The present review examines how different thermal and non-thermal processing techniques, such as sous-vide, microwave, stewing, roasting, boiling, frying, grilling, and steam cooking, affect meat proteins, chemical composition, oxidation, and sensory profile.

Digestomic data of proteolysis during whether post rumen digestion after tannin supplementation

The protein degradation of alfalfa hay after tannin supplementation was monitored during wethers digestion. Three rumen-cannulated wethers were infused a tannin solution, and water for control, through the cannula. The digestion time-points samples were collected in vivo in the rumen and in vitro in the abomasum, and the small intestine compartments. The digestomic dataset was acquired by identifying and quantifying the peptides resulting from the protein degradation, using high-resolution LC-MS/MS mass spectrometry and label-free quantitation. The digestomic dataset is the compilation of proteomic data acquired in the rumen and peptidomic data acquired in the abomasum and in the small intestine. The proteomic analysis identified 20 Medicago proteins in the rumen fluid, based on 169 peptides of which 140 are unique. The peptidomic analysis identified 28 Medicago proteins in the abomasum, based on 575 peptides of which 363 are unique, and 11 Medicago proteins in the small intestine, based on 94 peptides of which 63 are unique. This digestomic dataset of proteolysis during sheep post rumen digestion after tannin supplementation reveals the protein regions protected by tannin supplementation, and could be reused in studies related to the protein use efficiency by ruminants.

Cooking affects pork proteins in vitro rate of digestion due to different structural and chemical modifications

The effect of thermal processing on the in vitro digestibility of pork proteins was studied. Raw samples were considered the control group, while the thermal treatments included 58, 80, 98 and 160 °C for 72 min, 118 °C for 8 min and 58 °C for 17 h, resembling a range of different cooking procedures. Samples were subsequently subjected to pepsin digestion at pH 3.00 in the gastric phase followed by trypsin and α-chymotrypsin at pH 8.00 in the intestinal phase. Pork cooked at 58 °C for 72 min had a significantly higher pepsin digestibility rate than meat cooked at 80 °C or 160 °C. The trend was similar in the intestinal phase, with samples cooked at 58 °C for 72 min having enhanced digestion rate over other treatments after 120 min of digestion. A PLS model pointed out to an inverse relationship between in vitro proteolysis rate and variables like Maillard reaction compounds or protein structural changes.

Transformation of highly marbled meats under various cooking processes

Cooking induces modifications in meat structure and composition, affecting its sensory and nutritional properties. These changes depend on the cooking method and meat characteristics. In the present study, beef were cooked in three different ways-grilling, boiling, and sous-vide cooking-with two endpoint temperatures, 55 °C and 77 °C, to better understand the general impact of cooking on the structure of fatty meat. Light microscopy was used to visualize muscle, connective, and adipose tissues. After cooking, muscle fibers were more compact, which can be attributed to perimysium shrinkage and water transfer, for all cooking processes except grilling at 55 °C. The cross-sectional area of muscle fibers was not impacted by cooking, regardless of the temperature or cooking method. Connective tissue between adipocytes was affected by cooking at 77 °C, but not at 55 °C. Despite the cooking method used, cooking to well-done (77 °C) clearly affected the structure of the perimysium of beef, possibly because of collagen denaturation.

Impact of Tannin Supplementation on Proteolysis during Post-Ruminal Digestion in Wethers Using a Dynamic In Vitro System: A Plant (Medicago sativa) Digestomic Approach

The aim of this study was to characterize the effects of tannins on plant protein during sheep digestion using a digestomic approach combining in vivo (rumen) conditions and an in vitro digestive system (abomasum and small intestine). Ruminal fluid from wethers infused with a tannin solution or water (control) was introduced into the digester, and protein degradation was followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Tannin infusion in the rumen led to a clear decrease in protein degradation-related fermentation end-products, whereas ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCo) protein was more abundant than in control wethers. In the simulated abomasum, peptidomic analysis showed more degradation products of RuBisCo in the presence of tannins. The effect of RuBisCo protection by tannins continued to impact Rubisco digestion into early-stage intestinal digestion but was no longer detectable in late-stage intestinal digestion. The peptidomics approach proved a potent tool for identifying and quantifying the type of protein hydrolyzed throughout the gastrointestinal tract.

Potential DPP IV Inhibitory Peptides from Dry-Cured Pork Loins after Hydrolysis: An In Vitro and In Silico Study

Peptidyl peptidase IV (DPP-IV) is a pharmacotherapeutic target in type 2 diabetes, and inhibitors of this enzyme are an important class of drugs for the treatment of type 2 diabetes. In the present study, peptides (<7 kDa) isolated from dry-cured pork loins after pepsin and pancreatin hydrolysis were identified by mass spectrometry and tested as potential inhibitors of DPP-IV by the in silico method. Two peptides, namely WTIAVPGPPHS from myomesin (water-soluble fraction, A = 0.9091) and FKRPPL from troponin (salt-soluble fraction, A = 0.8333), were selected as the most promising inhibitors of DPP-IV. Both peptides were subjected to ADMET analysis. Fragments of these peptides showed promising drug-likeness properties as well as favorable absorption, distribution, metabolism, excretion, and toxicity functions, suggesting that they are novel leads in the development of DPP-IV inhibitors from food.

Deciphering the protein digestion of meat products for the elderly by in vitro food oral processing and gastric dynamic digestion, peptidome analysis and modeling

The elderly population will increase sharply in the future, along with an emerging range of specific nutritional needs that include adapted food. We aimed to develop a workflow to study the fate of a food, objectify the bioavailability of nutrients in the case of the digestive physiology of the elderly, and model the fate of proteins in the stomach. Pork frankfurters were subjected to in vitro normal and deficient mastication and gastric digestion, mimicking adult and elderly food oral and digestive processing. Swallowable food boluses were characterized for granulometric and rheological properties. Biochemical analyses were conducted on the bolus and on the digesta. Macronutrients, label-free peptide quantification and identification were performed, and modeling was applied to protein digestion kinetics. After deficient mastication, the food bolus was harder with more large particles, lower free iron release and more protein oxidation. The amount of peptides released in the stomach progressively increased, but to a lower extent for the elderly digestive condition and irrespective of masticatory efficiency. 592 peptides were identified from 67 proteins. Different trajectories were observed for adult and elderly digestive conditions, and two groups of meat proteins were identified based on the rate of hydrolysis. Designing suitable foods requires in vitro tools to evaluate the possible benefit for the elderly. Besides the well-known notion of Food Oral Processing (FOP), our work broadens the concept by extending oral activity to digestion when working in a nutritional context. This new concept is named Food Oral and Digestive Processing, FODP.

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.

Sous Vide Cook Temperature Alters the Physical Structure and Lipid Bioaccessibility of Beef Longissimus Muscle in TIM-1

Changes in the physical states, induced with different sous vide cooking temperatures, significantly (P < 0.05) altered lipid bioaccessibility measured in the TNO-simulated gastrointestinal tract model-1 of AAA boneless beef striploin, containing the longissimus lumborum muscle. The denaturation of actin significantly correlates with the total cumulative free fatty acid (FFA) bioaccessibility, whereby the striploin cooked to 60 °C presents the maximum lipid bioaccessibility (15.8 ± 1.0%), rate constant (k_a) for FFA hydrolysis (0.087 ± 0.003 min^-1), and greatest actin denaturation enthalpy (-0.57 ± 0.06 ΔH). Thus, thermal treatments above 60 °C significantly decrease the kinetics of lipolysis (70 °C = 0.042 ± 0.002 min^-1 and 80 °C = 0.047 ± 0.002 min^-1) and the resultant total lipid bioaccessibility (70 °C = 8.6 ± 0.7 and 80 °C = 8.3 ± 0.5%). This research highlights the potential to manipulate the physical food structure to alter digestion kinetics, supporting the need to understand supramolecular structures in food and their nutritional outcomes.

Improvement of meat protein digestibility in infants and the elderly

Meat is a valuable protein source with a balanced composition of essential amino acids and various nutrients. This review aims to identify methods to improve digestion of meat proteins, as well as evaluate the digestive characteristics of infants and the elderly. Immature digestive conditions in infants, including a high gastric pH and low protease concentration, can hinder protein digestion, thus resulting in inhibited growth and development. Likewise, gastrointestinal (GI) tract aging and chronic health problems, including tooth loss and atrophic gastritis, can lead to reduction in protein digestion and absorption in the elderly compared with those in young adults. Moderate heating and several non-thermal technologies, such as aging, enzymatic hydrolysis, ultrasound, high-pressure processing, and pulsed electric field can alter protein structure and improve protein digestion in individuals with low digestive capacity.

Temperature-dependent in vitro digestion properties of isoelectric solubilization/precipitation (ISP)-isolated PSE-like chicken protein

The effects of various heating strategies (72 °C-20 min, 100 °C-60 min) on the digestibility of isoelectric solubilization/precipitation (ISP)-isolated pale, soft, exudative (PSE)-like chicken protein in an in vitro simulated gastrointestinal model were studied. Untreated PSE-like meat protein was used as the control. The hydrophobic groups were much more exposed in ISP-isolated protein than in the control protein, and the difference diminished after heating. The results of SDS-PAGE analyses and digestion kinetic parameters show the ISP isolates had higher digestibility than the control group when heated at 72 °C for 20 min (P < 0.05), but there was no significant difference between the 100 °C heated groups (P > 0.05). Additionally, all ISP-isolated groups showed higher peptide abundance than the control groups. In summary, heating at 72 °C for 20 min is beneficial to increase the digestion properties of ISP-isolated PSE-like chicken protein, but its gel properties are weaker than those of protein heated at 100 °C for 60 min.

Assessment of carbonic anhydrase 3 as a marker for meat authenticity and performance of LC-MS/MS for pork content

In recent years, food fraud is a global issue that has raised wide public concern. Mass spectrometry techniques have a significant advantage of qualitatively and quantitatively analyzing food authenticity, especially for highly processed meat products. In this work, a simple and specific, rapid resolution liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the determination of pork content in processed meat products according to internal standard (ISTD) method. To improve the efficiency of sample preparation, simplified bead-beating and enzymolysis process were investigated. In contrast with different heat-stable and specific porcine-peptides, EPITVSSDQMAK, GGPLTAAYR, HDPSLLPWTASYDPGSAK from Carbonic anhydrase 3 proved to have an excellent quantitative ability, thus obtaining good linear relationship and satisfactory recovery. This method was successfully applied to different types of meat products, thus demonstrating that complex mixtures of pork content can be accurately quantified.

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.

Sarcoplasmic Proteome Profile and Internal Color of Beef Longissimus Lumborum Steaks Cooked to Different Endpoint Temperatures

The complex relationship between endpoint temperature, sarcoplasmic proteome, and internal color in cooked steaks is yet to be examined. The objective of the present study was to characterize the changes in sarcoplasmic proteome and their influence on the internal color of beef longissimus lumborum (LL) steaks cooked to different endpoint temperatures. Two 2.5-cm-thick LL steaks were fabricated from 9 beef strip loins and were cooked to an internal endpoint temperature of either 60°C (C-60) or 71°C (C-71). Cooked steaks were cooled and sliced parallel to the grilled surface, and internal color was evaluated instrumentally. Sarcoplasmic proteome from the interiors of the cooked steaks was analyzed using two-dimensional electrophoresis, and the gel images were digitally analyzed. The protein spots exhibiting more than 2-fold intensity differences (P &lt; 0.05) were subjected to in-gel tryptic digestion and were identified by tandem mass spectrometry. The C-60 steaks demonstrated greater (P &lt; 0.05) redness and color stability than the C-71 ones. Eleven differentially abundant protein spots were identified, and they belonged to 6 functional groups (transport proteins, enzymes in energy metabolism, chaperones, antioxidant proteins, enzymes in amino acid metabolism, and glycolytic enzymes). While 10 spots were overabundant (P &lt; 0.05) in C-60 steaks, 1 spot was overabundant (P &lt; 0.05) in C-71 steaks. The spot overabundant in C-71 samples was identified as myoglobin, suggesting the possible role of post-translational modifications in the heme protein’s thermal stability. The results indicated that the endpoint cooking temperature influenced sarcoplasmic proteome profile and internal color of cooked beef LL steaks. The overabundant proteins in steaks cooked to 60°C may be exploited as potential biomarkers for undercooked beef, which is a source for foodborne infections.

The Role of Meat Protein in Generation of Oxidative Stress and Pathophysiology of Metabolic Syndromes

Various processing methods have a great impact on the physiochemical and nutritional properties of meat that are of health concern. Hence, the postmortem processing of meat by different methods is likely to intensify the potential effects on protein oxidation. The influence of meat protein oxidation on the modulation of the systemic redox status and underlying mechanism is well known. However, the effects of processed meat proteins isolated from different sources on gut microbiota, oxidative stress biomarkers, and metabolomic markers associated with metabolic syndromes are of growing interest. The application of advanced methodological approaches based on OMICS, and mass spectrometric technologies has enabled to better understand the molecular basis of the effect of processed meat oxidation on human health and the aging process. Animal studies indicate the involvement of dietary proteins isolated from different sources on health disorders, which emphasizes the impact of processed meat protein on the richness of bacterial taxa such as (Mucispirillum, Oscillibacter), accompanied by increased expression of lipogenic genes. This review explores the most recent evidences on meat processing techniques, meat protein oxidation, underlying mechanisms, and their potential effects on nutritional value, gut microbiota composition and possible implications on human health.

Low Protein Digestibility of Beef Puree in Infant In Vitro Digestion Model

This study investigated protein digestibility of beef puree in infant and adult in vitro digestion models. The simulated digestive juices for infant and adult were prepared. Protein digestibility of beef puree was calculated in the gastric and gastrointestinal compartments. The 10% trichloroacetic acid soluble nitrogen and α-amino group contents of gastric digesta were lower in the infant in vitro digestion model than those in the adult in vitro digestion model (p<0.05). In addition, the gastrointestinal digesta from the infant in vitro digestion model had lower value of the 10% trichloroacetic acid soluble nitrogen and α-amino group contents than those of the adult in vitro digestion model (p<0.05). The results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the remarkable bands of actin and myosin light chain B were found in the digesta of beef puree from the infant in vitro digestion model. The results of this study revealed the lower protein digestibility of beef puree in infants compared to that in adults. Therefore, the development of ways to increase digestibility of meat protein can improve the nutritional quality of meat products for infants.

Comparative peptidomic profile and bioactivities of cooked beef, pork, chicken and turkey meat after in vitro gastro-intestinal digestion

This study was designed to investigate the potential contribution of bioactive peptides to the biological activities related to the consumption of pork, beef, chicken and turkey meat following in vitro gastro-intestinal digestion. After extraction of the peptidic fractions from digested samples, the bioactivities were evaluated by in vitro antioxidant activity as well as angiotensin-converting enzyme (ACE) and dipeptidyl peptidase-IV (DPP-IV) inhibition assays. Pork and turkey meat appeared to be the best sources of antioxidant peptides. Pork was found to be the best source of DPP-IV-inhibitory peptides whereas chicken meat supplied peptides with the highest ACE-inhibitory activity. The comprehensive analysis of the peptidomic profile of digested samples was performed by nano-LC-ESI-QTOF MS/MS analysis. A total of 217, 214, 257 and 248 peptides were identified in digested pork, beef, chicken and turkey meat, respectively. Chicken and turkey meat showed the highest similarity in peptide sequences with 202 common peptides. Sixty-two peptides matched with sequences with previously demonstrated biological activity. In particular, 35 peptides showed ACE-inhibitory activity and 23 DPP-IV inhibitory activity. Twenty-two bioactive peptides were commonly released from the different types of meat. The relative amount of identified bioactive peptides were positively correlated to the biological activities of the different digested meats. BIOLOGICAL SIGNIFICANCE: The present study describes for the first time a comprehensive peptide profile of four types of meat after in vitro gastro-intestinal digestion. The peptide inventory was used to identify 62 bioactive peptides with ACE- and DPPIV-inhibitory and antioxidant activities. The bioactivity analysis revealed interesting and significant differences between the studied meats. The originality of this work lay in the description of intrinsic differences in physiological functions after the ingestion of meat proteins from different species. In a context in which the current research scene relates meat consumption to the onset of chronic pathologies, this peptide profiling and bioactivity analysis shed light on the possible health benefits of peptides released from meat proteins. In fact, this paper represents a sort of detailed peptide list that may help to predict which peptides could be generated after meat intake and detectable at gastro-intestinal level. It also provides a thorough investigation of novel biological activities associated to meat protein hydrolysates, giving a new positive aspect to meat consumption.

Processed Meat Protein Promoted Inflammation and Hepatic Lipogenesis by Upregulating Nrf2/Keap1 Signaling Pathway in Glrx-Deficient Mice

Oxidative stress may play a critical role in the progression of liver disorders. Increasing interest has been given to the associations among diet, oxidative stress, gut-liver axis, and nonalcoholic fatty liver disease. Here, we investigated the effects of processed meat proteins on biomarkers of lipid homeostasis, hepatic metabolism, antioxidant functions, and gut microbiota composition in glutaredoxin1 deficient (Glrx1^-/-) mice. The wild-type (WT) and Glrx1^-/- mice were fed a soy protein diet (SPD), a dry-cured pork protein diet (DPD), a braised pork protein diet (BPD), and a cooked pork protein diet (CPD) at a dose of 20% of protein for 3 months. Serum and hepatic total cholesterol, serum endotoxin, hepatic liver droplet %, and antioxidant capacity were significantly increased in the CPD fed WT mice. In addition, CPD fed Glrx1^-/- mice significantly increased total cholesterol, triacylglycerol, and pro-inflammatory cytokines which are accompanied by higher steatosis scores, intrahepatic lipid accumulation, and altered gene expression associated with lipid metabolism. Furthermore, hepatic gene expression of Nrf2/keap1 signaling pathway and its downstream signaling targets were determined using RT-qPCR. Glrx1 deficiency increased Nrf2 activity and expression of its target genes (GPx, catalase, SOD1, G6pd, and Bbc3), which was exacerbated by intake of CPD. Metagenomic analyses revealed that Glrx1^-/- mice fed meat protein diets had higher abundances of Mucispirillum, Oscillibacter, and Mollicutes but lower abundances of Bacteroidales S24-7 group_norank, Blautia, and Anaerotruncus than their wild-type counterparts. In summary, Glrx1 deficiency induced an increase in serum biomarkers for lipid homeostasis, gut microbiota imbalance, and upregulation of Nrf2/Keap1 and antioxidant defense genes, which was aggravated by cooked meat protein diet.

Specific Microbiota Dynamically Regulate the Bidirectional Gut-Brain Axis Communications in Mice Fed Meat Protein Diets

The purpose of this study was to characterize the dynamic changes of different protein diets to gut microbiota and explore the influence on communications between the gut and the brain. C57BL/6J mice were fed casein, soy protein, and four kinds of processed meat proteins at a normal dose of 20% for 8 months. Bacteroidales S24-7 abundance increased from 4 to 8 months, whereas the abundances of six genera including Akkermansia decreased remarkably. Lachnospiraceae Unclassified abundance in the emulsion-type sausage protein and stewed pork protein groups showed an opposite change from 4 to 8 months. Twenty-eight and 48 specific operational taxonomy units in cecum and colon respectively were involved in regulating serotonin, peptide YY, leptin, and insulin levels. Specific microbiota was involved, directly or indirectly through signaling molecules, in the regulation of body metabolism, which may affect the communications between the gut and brain and cause different growth performances.

Combined in vivo and in silico approaches for predicting the release of bioactive peptides from meat digestion

We studied the kinetics of peptide release during the gastric digestion of meat proteins in vivo, in view to predicting the release of bioactive peptides further on in the digestive tract. Six mini pigs fitted with gastric cannulas received a meal with cooked beef as protein source. Digesta was collected at regular time intervals up to 5½ h. The peptides generated by the gastric digestion of meat were identified and quantified using label-free LC MS, thereafter subjected to in silico digestion mimicking the action of intestinal enzymes. Three clusters of proteins presenting similar evolutions according to their dynamic hydrolysis were obtained. This study clearly improves the in silico prediction of the intestinal release of bioactive peptides by mapping meat protein degradation in the stomach in an in vivo model. Knowledge of the conformation of the peptides released in the stomach further improves this prediction.

Comparison of myosin heavy chain content determined by label-free quantification between porcine longissimus thoracis, psoas major and semimembranosus muscles

The present study was conducted to quantify MHCs in porcine longissimus thoracis (LT), psoas major (PM) and semimembranosus (SM) muscles through the label-free quantification (LFQ). To estimate the accuracy of LFQ, quantitative RT-PCR (qRT-PCR), immunohistochemistry (IHC), and Western-blotting (WB) were performed. MHCs 2x, 2a, 2b and slow were identified by LC-MS/MS analysis and 279 ion spectra were selected for LFQ analysis. The content of MHC 2b was higher in LT and in SM than in PM (p<0.05), while the content of MHC slow was highest in PM among the muscles (p<0.01) regardless of LFQ types. Positive correlation coefficients of MHC 2b and MHC slow between LFQ and IHC (relative area composition) and qRT-PCR results partially supported the LFQ results. Though low-abundant peptides should be considered to estimate MHC contents via the spectral count method, LFQ enables the determination of MHC contents at protein level regardless of LFQ types.

Global antioxidant response of meat

BACKGROUND

The global antioxidant response (GAR) method uses an enzymatic digestion to release antioxidants from foods. Owing to the importance of digestion for protein breakdown and subsequent release of bioactive compounds, the aim of the present study was to compare the GAR method for meat with the existing methodologies: the extraction-based method and QUENCHER. Seven fresh meats were analyzed using ABTS and FRAP assays.

RESULTS

Our results indicated that the GAR of meat was higher than the total antioxidant capacity (TAC) assessed with the traditional extraction-based method. When evaluated with GAR, the thermal treatment led to an increase in the TAC of the soluble fraction, contrasting with a decreased TAC after cooking measured using the extraction-based method. The effect of thermal treatment on the TAC assessed by the QUENCHER method seemed to be dependent on the assay applied, since results from ABTS differed from FRAP.

CONCLUSION

Our results allow us to hypothesize that the activation of latent bioactive peptides along the gastrointestinal tract should be taken into consideration when evaluating the TAC of meat. Therefore, we conclude that the GAR method may be more appropriate for assessing the TAC of meat than the existing, most commonly used methods. © 2016 Society of Chemical Industry.

Effect of cooking and in vitro digestion on the antioxidant activity of dry-cured ham by-products

Dry-cured ham by-products have been traditionally used in Mediterranean household cooking of broths and stews. The aim of this work was to evaluate the effect of cooking treatments and in vitro gastrointestinal digestion on the antioxidant activity of natural peptides found in bones from Spanish dry-cured hams. The antioxidant activity was tested using five different assays and results demonstrated that cooking using conventional household methods increased the antioxidant activity of ham by-products when assessed using different antioxidant assays with the exception of the ABTS radical scavenging measurement assay. Simulated gastrointestinal digestion showed no significant effect on the antioxidant activity of ham by-products and antioxidant activity decreased when assessed using the ORAC and β-carotene bleaching assays. Analysis by MALDI-TOF MS revealed a considerable breakdown of peptides due to the action of gastrointestinal enzymes, mainly in samples cooked at 100°C for 1h. In addition, 459 peptides derived from 57 proteins were identified and quantified using mass spectrometry in tandem, evidencing that peptides derived from collagen protein were responsible for the differences in antioxidant activities observed between the uncooked and cooked samples after digestion. The results show the potential of dry-cured ham bones as a source of antioxidant peptides that retain their bioactivity after household cooking preparations and gastrointestinal digestion.

Protein digestomic analysis reveals the bioactivity of deer antler velvet in simulated gastrointestinal digestion

Proteins are the most prominent bioactive component in deer antler velvet. The aim of the present study was to track the fate of protein of antler velvet by protein digestomics. The peptide profile identified by LC-MS/MS and the in vitro bioactivity of antler velvet aqueous extract (AAE) were investigated in simulated gastrointestinal digestion. A total of 23, 387 and 417 peptides in AAE, gastric and pancreatic digests were identified using LC-MS/MS, respectively. Collagens, the predominant proteins, released 34 peptides in gastric digests and 146 peptides in pancreatic digests. The gastric and pancreatic digests presented dipeptidyl peptidase IV (DPP-IV) and prolyl endopeptidase (PEP) inhibition activities. Four peptides from digests were proved to be DPP-IV and PEP inhibitory peptides. The results showed that the peptides released from antler velvet protein contributed to the bioactivity of antler velvet during digestion.

Effect of cooking and simulated gastrointestinal digestion on the activity of generated bioactive peptides in aged beef meat

Ageing is widely used in the meat industry to improve tenderness mainly as a result of the breakdown of muscular proteins through the action of endopeptidases during storage time.

Digestomics: an emerging strategy for comprehensive analysis of protein catabolism

When cells mobilize nutrients from protein, they generate a fingerprint of peptide fragments that reflects the net action of proteases and the identities of the affected proteins. Analyzing these mixtures falls into a grey area between proteomics and metabolomics that is poorly served by existing technology. Herein, we describe an emerging digestomics strategy that bridges this gap and allows mixtures of proteolytic fragments to be quantitatively mapped with an amino acid level of resolution. We describe recent successes using this technique, including a case where digestomics provided the link between hemoglobin digestion by the malaria parasite and the world-wide distribution of chloroquine resistance. We highlight other areas of microbiology and cancer research that are well-suited to this emerging technology.