Digestibility Of Meat Proteins Research Articles

In vitro gastrointestinal digestibility and peptidomic analysis of frankfurters as influenced by different forms of κ-carrageenan

We used peptide profiling to investigate the effects of different forms of κ-carrageenan (a typical hydrocolloid) on the in vitro gastrointestinal digestibility of frankfurters. All incorporated forms of κ-carrageenan were found to decrease the digestibility of meat proteins in the frankfurters, although the effects varied for some peptide fragments. Particle size analysis and super-resolution microscopy revealed that addition of κ-carrageenan in a water suspension resulted in the lowest protein digestibility for frankfurters, followed by κ-carrageenan in a powder form and in a brine suspension. Peptide profiling identified 63 peptides common to all frankfurters after gastrointestinal digestion. In addition, 9 new peptide fragments related to myofibrillar proteins and sarcoplasmic proteins were observed in digestion products from frankfurters that contained κ-carrageenan. Addition of the κ-carrageenan water suspension resulted in a unique pattern of peptide abundance after gastrointestinal digestion of the frankfurters. This pattern was not observed with the powder or brine suspension, both of which contained higher abundances of myosin peptides. However, it is still unclear how different forms of κ-carrageenan caused changes in specific digestion sites, and further investigation is needed to understand this phenomenon. These findings provide novel insights into the effects of various forms of κ-carrageenan on the digestibility of meat proteins in emulsified meat products.

Tenderness and physicochemical characteristics of meat treated by recombinant bromelain of MD2 pineapple from a codon-optimized synthetic gene

Bromelain is a complex of cysteine proteases from pineapple (Ananas comosus) which was widely used in meat tenderizers. Earlier, using a synthetic optimized gene approach, recombinant bromelain of MD2-pineapple (MD2-MBro) was successfully produced in a fully soluble form. Nevertheless, the use of MD2-MBro to tenderize the meat has never been examined. Indeed, no report on the meat tenderization activity using recombinant bromelain was found. The aim of the current study is to determine the effect of MD2-MBro on meat tenderness and its physicochemical properties. To address this, MD2-MBro was over-expressed in Escherichia coli BL21 CodonPlus(DE3), followed by purification using a single step of Ni-NTA affinity chromatography. Fresh lamb shoulder meat from a local market in Kota Kinabalu, Sabah, Malaysia, was then treated with MD2-MBro at the concentration of 0 (B0), 0.01 (B1), 0.05 (B2), and 0.1% (B3). The meat tenderness was measured using Warner-Bratzler shear forces, indicating that the addition of MD2-MBro had significantly (P < 0.01) reduced the shear force value from 8.80kg/cm2 to the range of 6.01 to 6.92 kg/cm2, which falls under the category of tender. The ability of MD2-MBro to tenderize meat might be related to its ability to degrade myofibril protein, as demonstrated by the formation of a clear zone under an agar plate system and scanning electron microscopy. Besides, the total protein or sarcoplasmic protein solubility was significantly enhanced by the MD2-MBro treatments, along with soluble peptides, free amino acids, collagen content, and collagen solubility, which indicated the improvement in meat protein digestibility. Other physicochemical properties (color, pH, water-holding capacity, and cooking loss) of the meat were affected by MD2-MBro treatments yet remained in the normal range. Altogether, while MD2-MBro consisted of only a single cysteine protease enzyme, this protein can tenderize meat and increase protein digestibility, with acceptable changes in the overall physicochemical properties.
 Keywords: bromelain, cysteine protease, meat tenderizer, recombinant protein, pineapple

Influence of hydrophilic polysaccharide fat replacers on the in vitro digestibility of protein in emulsion-type sausage

Hydrophilic polysaccharides have been widely applied as fat replacers in meat products, but their effects on the digestibility of meat proteins has seldom been studied. Replacement of backfat in emulsion-type sausage with konjac gum (KG), sodium alginate (SA) and xanthan gum (XG) were found to reduce the released amino group (–NH2) during simulated gastric digestion and initial intestinal digestion. The suppressed gastric digestibility of protein was verified by the denser structures of protein gastric digests and reduced generation of peptides in gastric digestion when a polysaccharide was added. After the whole gastrointestinal digestion, high level of SA and XG resulted in larger digests and a more obvious SDS-PAGE band between 5 and 15 kDa, and KG and SA significantly reduced the total release of –NH2. Additional of KG, SA and XG were found to the increase the viscosity of the gastric digests mixture, which could account for the reduced hydrolysis efficiency of pepsin during the gastric digestion, as evidenced in the pepsin activity study (decreased by 12.2–39.1%). This work highlights the influence of polysaccharide fat replacer on the digestibility of meat protein by changing the matrix characteristics.

Moderate Protein Oxidation Improves Bovine Myofibril Digestibility by Releasing Peptides in the S2 Region of Myosin: A Peptidomics Perspective.

This study aimed to investigate the influence of protein oxidation on the digestive properties of beef myofibrillar protein (MP). MP was treated with a hydroxyl radical-generating system containing various concentrations of H2O2. The increased content in a free sulfhydryl group and surface hydrophobicity indicated that oxidation treatment with 1 mM H2O2 induced unfolding of MP. Reducing and nonreducing SDS-PAGE results suggested that 10 mM H2O2 oxidation treatment resulted in aggregation of MP; meanwhile, the disulfide bond was the major covalent bond involved in aggregation. Peptidomics showed that peptides in the digestion products of MP were mainly derived from myosin tail. Moderate oxidation (1 mM H2O2) facilitated the release of peptide in the rod portion (S2) of myosin, whereas excessive oxidation (10 mM H2O2) inhibited peptide release in the light meromyosin region. This work presents insightful information for the crucial impact of oxidation on meat protein digestibility from the peptidomics perspective.

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.

The degree of doneness affected molecular changes and protein digestibility of pork.

The degree of doneness has been shown to have a great impact on eating quality of meat, however, it is little known whether it affects protein digestibility of meat. In this study, we explored molecular changes and protein digestibility of pork under different degree of doneness. Pork chops were cooked in a 100°C water bath for about 26 min and a gradient decrease in doneness was obtained from outer to inner layers of samples. Compared with the raw samples, the cooked samples' active and total sulfhydryl contents, surface hydrophobicity, and turbidity increased but its solubility decreased. The inner layers with lower doneness contained higher α-helix, and fluorescence intensities of tryptophan and tyrosine residues than the outer layers with higher doneness. The pepsin and pancreatin digestibility of meat proteins in the inner layers were higher than those of the outer layers. Molecular simulation analysis showed that the most abundant protein in pork, i.e., myosin in the outer layers were more stable with an increased number of hydrogen bonds, making it difficult to be digested. These findings provided a new insight into the heterogeneity of meat nutritional quality due to the existence of doneness gradient.

Methods for improving meat protein digestibility in older adults

This review explores the factors that improve meat protein digestibility and applies the findings to the development of home meal replacements with improved protein digestion rates in older adults. Various methods improve the digestion rate of proteins, such as heat, ultrasound, high pressure, or pulse electric field. In addition, probiotics aid in protein digestion by improving the function of digestive organs and secreting enzymes. Plant-derived proteases, such as papain, bromelain, ficin, actinidin, or zingibain, can also improve the protein digestion rate; however, the digestion rate is dependent on the plant enzyme used and protein characteristics. Sous vide processing improves the rate and extent of protein digestibility, but the protein digestion rate decreases with increasing temperature and heating time. Ultrasound, high pressure, or pulsed electric field treatments degrade the protein structure and increase the proteolytic enzyme contact area to improve the protein digestion rate.

Digestibility of Meat Mineral and Proteins from Broilers Fed with Graded Levels of Chlorella vulgaris.

The incorporation of sustainable protein sources in animal feeding is a growing trend. So far, no study has investigated in vitro digestion of meat, from broilers fed microalgae, in a human model. This research aimed to evaluate the effect of incorporating Chlorella vulgaris in the broilers diet on human protein digestibility, and mineral bioaccessibility. The study used 240 male Ross 308 broilers randomly allocated to groups fed a control diet or a diet where soybean meal was replaced with 10% (CV10%), 15% (CV15%), or 20% (CV15%) of C. vulgaris for 40 days. The microalga supplementation increased the protein and lowered the fat content in the muscle. Results on the percentages of amino acids highlighted that arginine and threonine proportions increased and lysine and cysteine proportions decreased with microalga inclusion. CV15% and CV20% meat had higher amount of K, Ca, Mg, P, and Fe in raw breasts, improving the nutrient composition of the meat. Cooking caused a decrease in Na and K and an increase in other minerals. CV20% had higher bioaccessibility of K, Ca, Mg, P, and Mg, compared to the control. Replacing soybean meal in broiler feed with higher concentrations of C. vugaris could improve the digestibility of meat protein and minerals.

Effect of different κ-carrageenan incorporation forms on the gel properties and in vitro digestibility of frankfurters

This study demonstrated that the addition of different forms (dry powder and pre-suspended in water) of κ-carrageenan at an intermediate concentration (0.2%, w/w) significantly improved the textural and gel properties of frankfurters, as well as the rheological behaviour of meat batter (P < 0.05). Moreover, microstructural images revealed that the interaction between meat proteins and κ-carrageenan were closely associated with the distinct dispersed state of each incorporation form of κ-carrageenan in the meat protein gel network. Meanwhile, hydrogen bonding was the major molecular force in frankfurters in the present of κ-carrageenan, which could be altered with the incorporation forms and concentrations of κ-carrageenan. Additionally, incorporation of κ-carrageenan gradually decreased the in vitro digestibility of meat proteins in the frankfurters in a dose-dependent manner (P < 0.05). However, each addition form of κ-carrageenan had no obvious differences of protein digestibility (P > 0.05). The main conclusions of present work provided the vital understanding for the applications of κ-carrageenan in emulsified meat products.

Impact of common gastrointestinal disorders in elderly on in vitro meat protein digestibility and related properties

This study aimed to in vitro evaluate the impact of common gastrointestinal (GI) alterations appearing with aging on protein digestibility, and functional related properties, in four different meats (chicken, turkey, pork and beef). Thus, three elderly digestion models were stated as long as altered GI conditions affected at oral (E1), oral and gastric (E2) and oral, gastric and intestinal stages (E3). Healthy adult GI conditions were also mimicked as standard control model (C). A notable trichloroacetic acid (TCA) soluble protein and the free amino acids (FAA) release reduction (p<0.05) were found under intestinal suboptimal conditions (E3), being more accused in beef than in other meats. Thus, chicken intake would be more advisable, than other meats, in terms of protein digestibility; while beef would provide a greater net supply of FAA under E3 model conditions. Gastric altered conditions, seem to favor protein solubility. Finally, while gastric and intestinal suboptimal conditions diminish the angiotensin converting enzyme (ACE) inhibition of meat digesta, their antioxidant activity was only negatively affected by intestinal altered conditions.

Monitoring molecular composition and digestibility of ripened bresaola through a combined foodomics approach

In this work, the effects of maturation time and simulated gastrointestinal digestion on the molecular and peptide profiles of “Bresaola Valtellina” were assessed through the foodomics approach, in this case food proteomics and peptidomics combined to other analytical and biological assays, aiming at depicting a holistic food quality. Human digestion of this Italian cured meat product was simulated using an in vitro static protocol and the degree of proteolysis and the in vitro bioactivity of the soluble free compounds in the digestates were evaluated by biochemical assays, e.g. SDS-PAGE, size exclusion HPLC, HPLC/MS, 1H NMR, enzymatic and antioxidant activities. The obtained results demonstrated that in vitro gastrointestinal digestion contributed to a considerable release of myofibrillar proteins by the muscle tissue. Data from SDS-PAGE, peptidomic and size exclusion HPLC assays showed that the in vitro digestion largely degraded proteins of muscle tissue to peptides smaller than 250 Da. The released peptides were likely responsible for the inhibitory activity on amylolytic enzymes and for the antioxidant properties elicited by the gastric digestates of Bresaola. Overall, the results demonstrated the negligible role of ripening in making meat proteins more bioaccessible, whereas they confirmed the highly in vitro digestibility of meat proteins from Bresaola. This study represents a new approach merging proteomics and foodomics to evaluate the effect of ripening and in vitro digestion on the bioactivity and bioaccessibility of proteins and peptides of meat products.

Actinidin pretreatment and sous vide cooking of beef brisket: Effects on meat microstructure, texture and in vitro protein digestibility

The application of actinidin to beef brisket followed by thermal inactivation (by sous vide cooking) was studied for its effects on textural attributes, microstructure and protein digestibility under simulated gastric conditions. The optimal processing of meat was achieved by injecting 5% of a 3 mg/mL solution of commercial actinidin extract (Actazin™ from Anagenix Ltd.) into brisket steaks, followed by vacuum tumbling and cooking under sous vide conditions at 70 °C for 30 min. This cooking time is considerably less than sous vide cooking times normally used in the food service industry. The actinidin-treated meat had no change in pH, colour and cook loss, but showed improved sensory scores for tenderness, juiciness and flavour compared with the untreated meat. Transmission electron micrographs showed considerable breakdown of the myofibrillar structure, particularly around the Z-discs. An enhanced initial rate of muscle protein breakdown under simulated gastric conditions was observed using SDS-PAGE, demonstrating positive effects of the actinidin treatment on meat protein digestibility.

In vitro protein digestibility of pork products is affected by the method of processing

Processing contributes to different flavors and textures of pork products. However, processing methods have also showed a great impact on meat nutrition. In this study, protein digestibility and digested products were compared among four kinds of processed pork products (cooked pork, emulsion-type sausage, dry-cured pork and stewed pork). Cooked samples were homogenized and digested by pepsin and trypsin. The digestibility of meat proteins was evaluated by particle size measurement, SDS–PAGE, and LC-MS/MS. Emulsion-type sausage had the highest digestibility and the lowest particle size (P<0.05), while stewed pork showed the opposite results (P<0.05). Band profiling on SDS-PAGE gels were significantly different before and after digestion, and between pork products as well. LC-MS/MS analysis revealed that stewed pork samples had the greatest number of 750–3500Da Mw peptides in digested products, while emulsion-type sausage had the smallest number of peptides between 750 and 3500Da. Long-time salting and drying, and long-time and high-temperature cooking may induce pork proteins to being less susceptible to pepsin digestion.

Compared with Raw Bovine Meat, Boiling but Not Grilling, Barbecuing, or Roasting Decreases Protein Digestibility without Any Major Consequences for Intestinal Mucosa in Rats, although the Daily Ingestion of Bovine Meat Induces Histologic Modifications in the Colon

Background: Cooking may impair meat protein digestibility. When undigested proteins are fermented by the colon microbiota, they can generate compounds that potentially are harmful to the mucosa.Objectives: This study addressed the effects of typical cooking processes and the amount of bovine meat intake on the quantity of undigested proteins entering the colon, as well as their effects on the intestinal mucosa.Methods: Male Wistar rats (n = 88) aged 8 wk were fed 11 different diets containing protein as 20% of energy. In 10 diets, bovine meat proteins represented 5% [low-meat diet (LMD)] or 15% [high-meat diet (HMD)] of energy, with the rest as total milk proteins. Meat was raw or cooked according to 4 processes (boiled, barbecued, grilled, or roasted). A meat-free diet contained only milk proteins. After 3 wk, rats ingested a 15N-labeled meat meal and were killed 6 h later after receiving a 13C-valine injection. Meat protein digestibility was determined from 15N enrichments in intestinal contents. Cecal short- and branched-chain fatty acids and hydrogen sulfide were measured. Intestinal tissues were used for the assessment of protein synthesis rates, inflammation, and histopathology.Results: Meat protein digestibility was lower in rats fed boiled meat (94.5% ± 0.281%) than in the other 4 groups (97.5% ± 0.0581%, P < 0.001). Cecal and colonic bacterial metabolites, inflammation indicators, and protein synthesis rates were not affected by cooking processes. The meat protein amount had a significant effect on cecal protein synthesis rates (LMD > HMD) and on myeloperoxidase activity in the proximal colon (HMD > LMD), but not on other outcomes. The ingestion of bovine meat, whatever the cooking process and the intake amount, resulted in discrete histologic modifications of the colon (epithelium abrasion, excessive mucus secretion, and inflammation).Conclusions: Boiling bovine meat at a high temperature (100°C) for a long time (3 h) moderately lowered protein digestibility compared with raw meat and other cooking processes, but did not affect cecal bacterial metabolites related to protein fermentation. The daily ingestion of raw or cooked bovine meat had no marked effect on intestinal tissues, despite some slight histologic modifications on distal colon.

Digestion of cooked meat proteins is slightly affected by age as assessed using the dynamic gastrointestinal TIM model and mass spectrometry.

In humans, meat ensures the supply of proteins with high nutritional value and indispensable amino acids. The main goal of the present study was to compare the degradation of meat proteins in adult and elderly digestive conditions. Cooked meat was subjected to in vitro digestion in the dynamic multi-compartmental TIM (TNO gastroIntestinal Model) system. Digestibility and bioaccessibility were determined using nitrogen balance and digestion products were identified using mass spectrometry. The TIM model was adapted according to in vivo data to mimic the specific digestive conditions of elderly people. Meat protein digestibility and bioaccessibility were around 96 and 60% respectively and were not influenced by age (P > 0.05). As much as 800 peptides were identified in the duodenal and jejunal compartments issued from 50 meat proteins with a percentage of coverage varying from 13 to 69%. Six proteins, mainly from the cytosol, were differentially hydrolyzed under the adult and elderly digestive conditions. Pyruvate kinase was the only protein clearly showing a delay in its degradation under elderly digestive conditions. This study provides significant insights into the understanding of meat protein dynamic digestion. Such data will be helpful to design in vivo studies aiming to evaluate dietary strategies that can attenuate muscle mass loss and more generally maintain a better quality of life in the elderly population.

High True Ileal Digestibility but Not Postprandial Utilization of Nitrogen from Bovine Meat Protein in Humans Is Moderately Decreased by High-Temperature, Long-Duration Cooking1–3

Background: Meat protein digestibility can be impaired because of indigestible protein aggregates that form during cooking. When the aggregates are subsequently fermented by the microbiota, they can generate potentially harmful compounds for the colonic mucosa.Objective: This study evaluated the quantity of bovine meat protein escaping digestion in the human small intestine and the metabolic fate of exogenous nitrogen, depending on cooking processes.Methods: Sixteen volunteers (5 women and 11 men; aged 28 ± 8 y) were equipped with a double lumen intestinal tube positioned at the ileal level. They received a test meal exclusively composed of 120 g of intrinsically 15N-labeled bovine meat, cooked either at 55°C for 5 min (n = 8) or at 90°C for 30 min (n = 8). Ileal effluents and blood and urine samples were collected over an 8-h period after the meal ingestion, and 15N enrichments were measured to assess the digestibility of meat proteins and the transfer of dietary nitrogen into the metabolic pools.Results: Proteins tended to be less digestible for the meat cooked at 90°C for 30 min than at 55°C for 5 min (90.1% ± 2.1% vs. 94.1% ± 0.7% of ingested N; P = 0.08). However, the particle number and size in ileal digesta did not differ between groups. The appearance of variable amounts of intact fibers was observed by microscopy. The kinetics of 15N appearance in plasma proteins, amino acids, and urea were similar between groups. The amount of exogenous nitrogen lost through deamination did not differ between groups (21.2% ± 0.8% of ingested N).Conclusions: Cooking bovine meat at a high temperature for a long time can moderately decrease protein digestibility compared with cooking at a lower temperature for a short time and does not affect postprandial exogenous protein metabolism in young adults. The study was registered at www.clinicaltrials.gov as NCT01685307.

Effect of dry-cured ham maturation time on simulated gastrointestinal digestion: Characterization of the released peptide fraction

This study deals with the identification of the peptides released after in vitro simulated gastrointestinal digestion of dry-cured Parma hams, using a physiological digestion model in terms of number of steps and composition of digestive juices. The obtained peptide mixture was analysed by ultra-high performance liquid chromatography with single quadrupole mass spectrometer detector and liquid chromatography hyphenated with triple quadrupole mass spectrometry and LTQ-orbitrap. This approach allowed for the identification of up to 81 different peptide sequences, mainly originating not only from myofibrillar proteins but also from sarcoplasmic proteins: the MW range spans between 200 and 1700Da, with a high number of very short sequences (21 dipeptides and 12 tripeptides). Several identified released peptides are precursors of potentially bioactive sequences. The effect of the maturation time of the ham on the peptide profile obtained upon digestion was assessed: Principal Component Analysis allows for differentiating between 18months and 24months aged hams, underlying the importance of maturation on the digestibility of meat proteins and on the eventual release of bioactive sequences.

Influence of Heat on the Digestibility of Meat Proteins

Influence of Heat on the Digestibility of Meat Proteins