Bioactivities generated from meat proteins by enzymatic hydrolysis and the Maillard reaction

Application of experimental design as a statistical approach to recover bioactive peptides from different food sources

Bioactive peptides (BAPs) derived from samples of animals and plants have been widely recommended and consumed for their beneficial properties to human health and to control several diseases. This work presents the applications of experimental designs (DoE) used to perform factor screening and/or optimization focused on finding the ideal hydrolysis condition to obtain BAPs with specific biological activities. The collection and discussion of articles revealed that Box Behnken Desing and Central Composite Design were the most used. The main parameters evaluated were pH, time, temperature and enzyme/substrate ratio. Among vegetable protein sources, soy was the most used in the generation of BAPs, and among animal proteins, milk and shrimp stood out as the most explored sources. The degree of hydrolysis and antioxidant activity were the most investigated responses in obtaining BAPs. This review brings new information that helps researchers apply these DoE to obtain high-quality BAPs with the desired biological activities.

Effect of Conventional Humid-Dry Heating through the Maillard Reaction on Chemical Changes and Enhancement of In Vitro Bioactivities from Soy Protein Isolate Hydrolysate-Yeast Cell Extract Conjugates

This study investigated the formation of soy protein isolate hydrolysate-yeast cell extract (SPIH-YCE) conjugates through a humid-dry heating process and their impact on bioactivity. The incubation of SPIH-YCE samples at 60 °C and ~75% humidity for varying durations (0, 5, 10, 15, and 20 days) resulted in a significant decrease in reducing sugars and free amino acids, while the degree of glycation increased by approximately 65.72% after 10 days. SDS-PAGE analysis and size exclusion chromatography revealed the presence of peptides and glycoprotein molecules, with an increase in the distribution of larger peptide size chains. The conjugated SPIH-YCE (10 days) exhibited the highest antioxidant capacity compared to the other samples at different incubation times. A comparative study between SPIH-YCE (day 0) and SPIH-YCE after 10 days of incubation showed significantly higher anti-inflammatory and ACE inhibitory activities for the conjugates subjected to the humid-dry heating process. This suggests that SPIH-YCE conjugates could serve as an alternative substance with the potential to provide health benefits by mitigating or preventing non-communicable diseases (NCDs). This research highlights the importance of the Maillard reaction in enhancing bioactivity and offers insights into the alterations of the chemical structure of these conjugates.

Flavor Characterization of Traditional Fermented Soybean Pastes from Northeast China and Korea

This study compares the physicochemical properties, taste, and volatile compounds of Northeastern Chinese dajiang (C) and Korean doenjang (K) and distinguishes the discriminant volatile metabolites between them. The result revealed that compared to group C, group K exhibited more similar physicochemical properties and had lower pH, moisture, and amino acid nitrogen content, while demonstrating higher titratable acidity, salt content, and reduced sugar content. The electronic tongue analysis showed that the saltiness and umami of soybean pastes had high response values, enabling clear differentiation of the overall taste between the two types of soybean pastes. A total of 71 volatile substances from the soybean pastes were identified through solid-phase microextraction gas chromatography-mass spectrometry. Furthermore, orthogonal partial least squares discriminant analysis revealed 19 volatile compounds as differentially flavored metabolites. Our study provides a basis for explaining the differences in flavor difference of Northeastern Chinese dajiang and Korean doenjang from the perspective of volatile metabolites.

Effects of the dipeptides comprising leucine and lysine on lifespan and age-related stress in Caenorhabditis elegans

The aging process is affected by various stressors. An increase in oxidative stress is related to the impairment of physiological functions and enhancement of glycative stress. Food-derived bioactive peptides have various physiological functions, including antioxidant activities. Dipeptides comprising Leu and Lys (LK and KL, respectively) have been isolated from foods; however, their physiological properties remain unclear. In this study, we investigated the antioxidant/antiglycation activity of dipeptides and their antiaging effects using Caenorhabditis elegans (C. elegans). Both dipeptides showed antioxidant activities against several reactive oxygen species (ROS) in vitro. In particular, the scavenging activity of LK against superoxide radicals was higher than KL did. Moreover, dipeptides suppressed advanced glycation end products (AGEs) formation in the BSA-glucose model. In the lifespan assays using wild-type C. elegans, both LK and KL significantly prolonged the mean lifespan by 20.9% and 11.7%, respectively. In addition, LK decreased intracellular ROS and superoxide radical levels in C. elegans. Blue autofluorescence, an indicator of glycation in C. elegans with age, was also suppressed by LK. These results suggest that dipeptides, notably LK, show an antiaging effect by suppressing oxidative and glycative stress. Our findings suggest that such dipeptides can be used as a novel functional food ingredient. Food-derived dipeptide Leu-Lys (LK) and Lys-Leu (KL) exert antioxidant and antiglycation activity in vitro. Treatment with LK prolonged the mean lifespan and maximum lifespan of C. elegans more than that of KL. Intracellular ROS and blue autofluorescence levels (indicator of aging) were suppressed by LK.

Role of Enzymatic Reactions in Meat Processing and Use of Emerging Technologies for Process Intensification

Meat processing involves different transformations in the animal muscle after slaughtering, which results in changes in tenderness, aroma and colour, determining the quality of the final meat product. Enzymatic glycolysis, proteolysis and lipolysis play a key role in the conversion of muscle into meat. The accurate control of enzymatic reactions in meat muscle is complicated due to the numerous influential factors, as well as its low reaction rate. Moreover, exogenous enzymes are also used in the meat industry to produce restructured products (transglutaminase), to obtain bioactive peptides (peptides with antioxidant, antihypertensive and gastrointestinal activity) and to promote meat tenderization (papain, bromelain, ficin, zingibain, cucumisin and actinidin). Emerging technologies, such as ultrasound (US), pulsed electric fields (PEF), moderate electric fields (MEF), high-pressure processing (HPP) or supercritical CO₂ (SC-CO₂), have been used to intensify enzymatic reactions in different food applications. This review aims to provide an overview of the enzymatic reactions taking place during the processing of meat products, how they could be intensified by using emerging technologies and envisage potential applications.

Comparison of 2,5-dimethyl-4-hydroxy-3(2H)-furanone, a volatile odor compound generated by the Maillard reaction, in cooked meat of various animal species and parts

2,5-Dimethyl-4-hydroxy-3(2H)-furanone (DMHF), a compound having a sweet caramel-like odor, is one of the major compounds generated by the Maillard reaction. DMHF could affect the palatability of cooked and processed foods such as meat, while its inhalation induces several physiological functions. However, basic findings of DMHF generation in meat remain unclear. In this study, we compared the amount of DMHF in cooked meat of various animal meat (Japanese black cattle beef, Australian beef, pork, and chicken) and parts (round, loin, thigh, and breast). Meat samples were heated at 230°C, and then the amount of DMHF was measured using the solvent extraction methods. Moreover, the substrates (total free amino acid and glucose) used for the Maillard reaction were also measured to elucidate the relation between DMHF generation and nutrients in meat. DMHF was detected in all cooked meat samples, suggesting that DMHF is generated in meat regardless of animal species and parts. A significant positive correlation was observed between the DMHF generation and glucose content in the round and thigh parts. Our results suggest that DMHF generation during meat cooking would be regulated by the glucose content.

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.

Quantitative metabolome analysis of boiled chicken egg yolk

Boiling has important effects on the texture of chicken eggs, but its effects on egg nutrients have not been systematically investigated. In this study, changes in the metabolites of egg yolks boiled under different heating intensities were quantified and compared by metabolomic analysis. A total of 797 metabolites were identified, and the abundance of 162 metabolites changed significantly after boiling. The significant reduction of L-lysine and D-fructose suggested that Maillard reactions occurred in over-boiled egg yolks. Egg yolk endogenous enzymes might induce a partial hydrolysis of proteins and phospholipids during the warm-up period of boiling, as the abundance of dipeptides, lysophospholipids, and free fatty acids was significantly increased in boiled egg yolks. Boiling increased the detectable abundance of fat-soluble vitamins, riboflavin, and biotin, possibly by altering the complex structure of protein-lipid-lipophilic compounds or denaturing vitamin-binding proteins. The results of metabolomic analyses provide important information for understanding the nutritional changes of egg yolk boiled under different heating intensities.

Bioactive peptides from meat: Current status on production, biological activity, safety, and regulatory framework

By-products of the meat processing industry which are often discarded as waste are excellent protein substrates for producing bioactive peptides through enzymatic hydrolysis. These peptides have tremendous potential for the development of functional food products but there is scanty information about the regulations on bioactive peptides or products in various parts of the world. This review focuses on the diverse bioactive peptides identified from different meat and meat by-products, their bioactivity and challenges associated in their production as well as factors limiting their effective commercialization. Furthermore, this report provides additional information on the possible toxic peptides formed during production of the bioactive peptides, which enables delineation of associated safety and risk. The regulatory framework in place for bioactive peptide-based foods in different jurisdictions and the future research directions are also discussed. Uniform quality, high cost, poor sensory acceptance, lack of toxicological studies and clinical evidence, paltry stability, and lack of bioavailability data are some of the key challenges hindering commercial advancement of bioactive peptide-based functional foods. Absorption, distribution, metabolism and excretion (ADME) studies in rodents, in vitro genotoxicity, and immunogenicity data could be considered as absolute pre-requisites to ensure safety of bioactive peptides. In the absence of ADME and genotoxicity data, long term usage to evaluate safety is highly warranted. Differences in legislations among countries pose challenge in the international trade of bioactive peptides-based functional foods. Harmonization of regulations could be a way out and hence further research in this area is encouraged.

Physicochemical, Functional, and Technological Properties of Protein Hydrolysates Obtained by Microbial Fermentation of Broiler Chicken Gizzards

Fermentation is an economical method for obtaining protein hydrolysates. The purpose of the scientific research was to perform a comprehensive analysis of the physicochemical, technological, and functional properties of protein hydrolysates obtained by microbial fermentation. The research results showed that hydrolysates fermented with propionic acid bacteria and bifidobacteria have better physicochemical and technological indicators compared to the control sample. Significant increases in water-holding and fat-holding capacities (by 1.8–2.1 times and 1.5–2.5 times, respectively), as well as fat-emulsifying ability (by 12.8–29.8%) in experimental samples were found. Hydrolysates obtained by fermentation effectively inhibit the growth of Escherichia coli and Staphylococcus aureus. The thermal analysis showed a sufficiently high-thermal stability of the obtained protein hydrolysates. In hydrolysates fermented by bacterial culture, the removal of physico-mechanical and osmotically bound moisture occurred at temperatures of 110 °C and 115 °C, respectively, and in whey protein hydrolysate at a temperature of 100 °C. The release of chemically bound moisture was observed at a temperature of 170 °C for fermented hydrolysates and at 155 °C for the control sample. The results proved that fermented protein products are characterized by high functional properties, antioxidant and antimicrobial activity, and can be used as natural food additives and preservatives.

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.

The effect of hydrolysis pre-treatment by flavourzyme on meat quality, antioxidative profiles, and taste-related compounds in Samgyetang breast supplemented with black garlic

This study aimed to carefully investigate the effect of hydrolysis using Flavourzyme on meat quality, antioxidative status, and taste-related compounds in breast of Samgyetang that was supplemented with black garlic (BG). Four different treatment groups were compared: (1) conventional Samgyetang (control), (2) Samgyetang hydrolyzed with Flavourzyme (1%, v/w) (FS), (3) Samgyetang made with the BG extract without hydrolysis (NBG), and (4) BG samgyetang pre-treated with Flavourzyme (1%, v/w) in a water bath at 55°C for 2.5 h and hydrolyzed before being processed (HBG). All the treatment groups were cooked by retorting at conditions 121°C and 1.5 kg/cm² for 1 h. Improved umami profiles through the increase of umami-related nucleotides (5’-GMP, 5’-IMP) and free amino acids—aspartic acid and glumtamic acid, in Samgyetang breast was recorded following hydrolysis. The HBG group tended to impart stronger scavenging activity toward free radicals compared with the other two groups, while not differing with NBG group regarding suppressing malondialdehyde. Textural properties were improved through hydrolysis, wherein the shear force value decreased from 2.29 kgf in the control to 1.19 and 1.25 kgf in the FS and HBG group. Moisture percentages were highly retained, with the redness score increasing and the lightness color decreasing following hydrolysis. In conclusion, the results of this study can be a preliminary information of the effect of hydrolysis pre-treatment for BG samgyetang. Further experiments are required to compare various enzymes along with its organoleptic acceptances.

Valorization of municipal organic waste into purified lactic acid

Municipal organic waste (biowaste) consists of food derived starch, protein and sugars, and lignocellulose derived cellulose, hemicellulose, lignin and pectin. Proper management enables nutrient recycling and sustainable production of platform chemicals such as lactic acid (LA). This review gathers the most important information regarding use of biowaste for LA fermentation covering pre-treatment, enzymatic hydrolysis, fermentation and downstream processing to achieve high purity LA. The optimal approach was found to treat the two biowaste fractions separately due to different pre-treatment and enzyme needs for achieving enzymatic hydrolysis and to do continues fermentation to achieve high cell density and high LA productivity up to 12 g/L/h for production of both L and D isomers. The specific productivity was 0.4 to 0.5 h^-1 but with recalcitrant biomass, the enzymatic hydrolysis was rate limiting. Novel purification approaches included reactive distillation and emulsion liquid membrane separation yielding purities sufficient for polylactic acid production.

Antihypertensive and Antioxidant Activity of Chia Protein Techno-Functional Extensive Hydrolysates

Twelve high-quality chia protein hydrolysates (CPHs) were produced from chia protein isolate (CPI) in a pilot plant of vegetable proteins. To obtain functional hydrolysate, four CPHs were hydrolyzed by the action of Alcalase, an endoprotease, and the other eight CPHs were hydrolyzed by the action of Flavourzyme, an exoprotease. Alcalase-obtained CPHs showed significant antihypertensive properties particularly, the CPH obtained after 15 min of hydrolysis with Alcalase (CPH15A), which showed a 36.2% hydrolysis degree. In addition, CPH15A increased the antioxidant capacity compared to CPI. The CPH15A physicochemical composition was characterized and compared to chia defatted flour (CDF) and CPI, and its techno-functional properties were determined by in vitro experiments through the analysis of its oil absorption capacity, as well as the capacity and stability of foaming and emulsifying, resulting in an emulsifier and stabilizer better than the intact protein. Therefore, the present study revealed that CPH15A has potent antihypertensive and antioxidant properties and can constitute an effective alternative to other plant protein ingredients sources that are being used in the food industry.

Effect of Microbial Enzymes on the Changes in the Composition and Microstructure of Hydrolysates from Poultry By-Products

Poultry by-products are promising for the production of protein hydrolysates by enzymatic hydrolysis. The aim of the study is to research the effect of bacterial concentrates on the changes in the amino acid composition and microstructure of poultry by-products during fermentation. Hydrolysis of the gizzards and combs was carried out with a liquid concentrate of bifidobacteria and propionic acid bacteria. As a result of microstructural study of fermented by-products, a decrease in the perception of histological dyes, poor visualization of the cell elements and blurring of the connective tissue matrix were established. During morphometric analyses, we found a reduction in the specific area of connective tissue, the diameter of collagen fibers and the thickness of muscle fibers. A significant effect of the fermentation on the particle size distribution was noted; samples hydrolyzed by microbial enzymes were characterized by a high uniformity of particle sizes and a large number of small particles. Our research revealed an increase in the concentration of free amino acids in the hydrolysates during the fermentation period. The results of biochemical and microscopic analysis confirm the good hydrolysability of hen combs and gizzards under the action of microbial enzymes.