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.

Tailoring meat products for the elderly: A comprehensive review

The population of the elderly is projected to grow significantly in most of the developed countries in the near future. This should earn this demographic the title of 'Consumer of the future'. Meat has high quality proteins and essential vitamins which are important for all demographics but more so for the elderly due to their susceptibility to sarcopenia. This review explored the landscape of meat research and product development that meets the distinctive requirements of the elderly, drawing from published refereed articles, industry reports, and unpublished grey literature. The review emphasised the importance of understanding the evolving dietary and sensory requirements associated with ageing and how they intersect with meat consumption. One notable aspect observed is the diversity within the elderly population, which underscores the necessity for tailored approaches in meat product development to cater to the varying preferences and nutritional needs of different individuals. This review also highlights the ongoing efforts in developing meat-based products that span a spectrum of consistencies, ranging from solid to liquid forms, to accommodate the diverse needs of elderly consumers. Despite these advancements, the review found a discrepancy between the pace of meat product development for the elderly and the rapid advancements in kitchen-level technologies and suggests that further research is needed to bridge this gap and align product innovation with emerging technological trends.

Comparison of protein quality and digestibility between plant-based and meat-based burgers

Nowadays, consumers are increasingly inclined toward plant-based meat analogues for sake of food security, safety, and sustainability. This growing interest, not only from consumers but also from food companies, brought the offer on the market to be wide and vast. From our previous study it emerged that the market supply, especially the Italian one, is diversified both in terms of protein sources and nutrient content. Although these products are increasingly consumed, for most of the meat analogues today on the market, little is still known about their actual protein quality and digestibility. To fill this gap, in this study different commercial plant-based burgers (2 soy-based and 2 pea-based) were selected and compared to two beef burgers, as controls, in terms of protein quality and digestibility. The findings of this study demonstrated the essential amino acidic profile lacks lysine for almost all burgers (including the meat-based ones) compared to the amino acid scoring pattern set by FAO/WHO (for older children and adults), even if the sum of essential amino acids was within the range of sufficiency. All samples showed good initial protein integrity with low hydrolysis (above 6%) and percentage of D-enantiomers (above 15%). The study of the digestibility, performed by the validated INFOGEST in vitro model, showed better protein solubilisation in the case of meat burgers (63 ± 3% and 61 ± 8%), but a good digestibility also in the case of plant-based ones (from 55% to 40%). The degree of hydrolysis of the solubilised proteins was very high in all samples (from 65% to 40%) indicating a very good protein accessibility to digestive enzymes. The analysis of the peptide fraction of digestates indicated a high prevalence of collagen proteins in beef burgers and of reserve proteins in plant-based burgers. This study showed that the differences between these products are mostly dependent on the quality of the raw materials used, rather than on the vegetal or animal protein source. Therefore, to have a product with a good protein quality and digestibility, independently from the protein origin, the consumer needs to make an accurate choice, carefully reading the ingredient list.

Effect of Nitric Oxide and Its Induced Protein S-Nitrosylation on the Structures and In Vitro Digestion Properties of Beef Myofibrillar Protein

This study aimed to investigate the effects of nitric oxide (NO) and its induced protein S-nitrosylation on the structures and digestion properties of beef myofibrillar protein (MP). The MP was treated with 0, 50, 250, 500, and 1000 μM concentrations of NO-donor S-nitrosoglutathione (GSNO) for 30 min at 37 °C. The results indicated that GSNO treatment significantly decreased the sulfhydryl contents whereas the carbonyl contents increased. Meanwhile, compared with the control group, the surface hydrophobicity, the intrinsic fluorescence intensity, and the α-helix content of proteins were decreased significantly with the enhancement of GSNO concentrations. In addition, 250 μM GSNO treatment increased the gastric digestibility of MP, while the gastrointestinal digestibility and the release of peptides were both inhibited by 500 and 1000 μM GSNO treatments. These data demonstrate that protein S-nitrosylation can affect the in vitro digestion properties of proteins by altering the physicochemical properties and structure of MP.

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.

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.

In-Bag Dry- vs. Wet-Aged Lamb: Quality, Consumer Acceptability, Oxidative Stability and In Vitro Digestibility

The aim of this study was to produce in-bag dry-aged lamb and compare its meat quality, consumer acceptability, oxidative stability and in vitro digestibility to the wet-aged equivalents. Significantly higher pH, weight loss and reduced cook loss were observed in dry-aged lamb compared to the wet-aged (p < 0.0001). Dry-aged lamb had harder and chewier texture profiles and lower colour attributes (L*, a* and b*) than the wet-aged (p < 0.001). The dry-aged and wet-aged lamb were equally preferred (around 40% each) by the consumer panel, underpinning the niche nature of dry-aged meat. Significantly (p < 0.05) higher yeast and thiobarbituric acid reactive substances (TABRS) levels were observed in dry-aged lamb compared to the wet-aged. There was no difference in fatty acid profile, protein carbonyl content and pattern of proteolysis between ageing regimes (p > 0.05). Ageing regimes had no impact on overall digestibility; however, a greater gastric digestibility was observed in dry-aged lamb through the increased release of free amino acids (FAAs) compared to the wet-aged. Outcomes of this study demonstrated for the first time the possibility of producing dry-aged lamb legs of acceptable quality, oxidative stability and superior digestibility compared to the equivalent wet-aged lamb.

Oxidative stability, proteolysis, and in vitro digestibility of fresh and long-term frozen stored in-bag dry-aged lean beef

Effect of air velocities, stepwise in-bag ageing and ageing time on the oxidative stability, proteolysis and digestibility of fresh and long-term frozen-stored dry-aged lean beef were studied. Increased air velocities and stepwise ageing regime had no effect (P > 0.05) on dry-aged beef lipid and protein oxidative stabilities and proteolysis pattern compared to control straight-dry-ageing. TBARS, protein carbonyl and free amino acids (FAAs) increased (P > 0.05) with ageing time. In-bag dry-ageing of beef improved its lipids and protein oxidative stability during long-term frozen storage compared to unaged beef. Improvement in beef protein digestibility was observed through increased release of FAAs and appearance of small protein fragments from SDS-PAGE in dry-aged samples compared to the unaged. The high lipid and protein oxidative stability of long-term frozen lean beef produced using stepwise in-bag ageing process suggest potential for the process to be used for producing dry-aged meat for export.

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.

Factors Affecting the Digestibility of Beef and Consequences for Designing Meat-Centric Meals

The impact of the following on beef digestibility was determined by static in vitro methods: (1) age of cattle; (2) muscle rigor state, ultimate pH, and mincing/particle size; (3) muscle/meat cut; (4) organ meats; and (5) meat accompaniments. Results indicate that beef is more digestible from older compared to younger cattle; prerigor compared to postrigor meat; higher compared to lower ultimate pH meat; cuts with lower compared to higher collagen contents; finely compared to coarsely minced/ground meat; and organ (liver and kidney) compared to muscle meat. Beef digestibility is enhanced when cooked with mushroom and pumpkin and reduced with starchy foods such as rice and potatoes. The outcomes of this study provide a base for the scientific design of meals with beef as a central ingredient and digestibility as the main functionality of interest.

The effect of meat processing methods on changes in disulfide bonding and alteration of protein structures: impact on protein digestion products

We investigated the effects of different pork preparation methods (cooked pork, emulsion-type sausage, dry cured pork, and stewed pork) on protein structures and in vitro digestion. Compared with raw meat, processed meats contained lower levels of free sulfhydryl groups (P < 0.05). Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed different protein profiles for pork products treated without or with 5% βME, which indicated different extents of disulfide bond formation. Emulsion-type sausage showed significantly higher α-helix content and lower β-sheet, β-turn, and random coil contents than cooked pork (P < 0.05). Correspondingly, emulsion-type sausage and dry-cured pork had the highest values of surface hydrophobicity (P < 0.05). Proteome data showed that the long salting and drying times used for dry-cured pork as well as long-term high-temperature cooking of stewed pork might alter the accessibility of digestive proteolytic enzymes to the protein cleavage sites.

Processing caused different levels of formation of disulfide bonds, and associated it with protein structure changes and digested products.

Evaluation of the Digestibility of Korean Hanwoo Beef Cuts Using the in vitro Physicochemical Upper Gastrointestinal System

The aim of this study was to investigate the digestibility of different Korean Hanwoo beef cuts using an in vitro digestion model, in vitro physicochemical upper gastrointestinal system (IPUGS). The four most commonly consumed cuts - tenderloin, sirloin, brisket and flank, and bottom round - were chosen for this study. Beef samples (75 g) were cooked and ingested into IPUGS, which was composed of mouth, esophagus, and stomach, thereby simulating the digestion conditions of humans. Digested samples were collected every 15 min for 4 h of simulation and their pH monitored. Samples were visualized under a scanning electron microscope (SEM) to examine changes in the smoothness of the surface after digestion. Analysis of the amino acid composition and molecular weight (MW) of peptides was performed using reverse-phase high performance liquid chromatography and sodium dodecyl sulfate polyacrylamide gel electrophoresis, respectively. Following proteolysis by the gastric pepsin, beef proteins were digested into peptides. The amount of peptides with higher MW decreased over the course of digestion. SEM results revealed that the surface of the digested samples became visibly smoother. Total indispensable and dispensable amino acids were the highest for the bottom round cut prior to digestion simulation. However, the total amount of indispensable amino acids were maximum for the tenderloin cut after digestion. These results may provide guidelines for the elderly population to choose easily digestible meat cuts and products to improve their nutritional and health status.