Identification and characterization of flavor precursor peptide from beef enzymatic hydrolysate by Maillard reaction

Key saltiness-enhancing substances in Maillard reaction products derived from chicken breast hydrolysate: Identification, saltiness-enhancing ability and mechanism

This work employs a saltiness-guided separation combined with UPLC-QTOF-MS to identify the key saltiness-enhancing substances in Maillard reaction products derived from chicken breast hydrolysate (CBH-MRPs). Thirteen compounds in the U3 fraction exhibited significant saltiness-enhancing abilities, which increased the saltiness intensity of NaCl (3 g/L) from 2.80 to 3.35-3.88. Interactions between the compounds and NaCl were evaluated using the S-curve method. The results showed that five compounds (5'-GMP, 5'-IMP, L-glutamic acid, L-lactic acid, and L-carnosine) and one compound (glutamine) exhibited synergistic and additive effects with NaCl, respectively, at tested concentrations. Notably, 5'-GMP/5'-IMP/glutamine and L-carnosine/L-lactic acid demonstrated better saltiness-enhancing abilities at their suprathreshold and subthreshold levels, respectively. Molecular docking results showed that hydrogen bonding was the key force for docking. Residues Cys475, Glu378, and Trp236 were the primary binding sites of the transmembrane channel-like protein 4 (TMC4). These results contribute to a better understanding of the saltiness modulating mechanisms of CBH-MRPs.

Identification of salty peptides from enzymolysis extract of oyster by peptidomics and virtual screening

Salty peptide as an important sodium substitute, which could reduce the risk of cardiovascular disease caused by excessive sodium intake. In this study, novel salty peptides were prepared and identified from enzymolysis extract of oysters by peptitomic identification, virtual screening and solid phase synthesis. Additionally, molecular simulation was used to study the taste mechanism of salty peptides. 316 peptides were identified in the enzymatic hydrolysates of oysters. 6 peptides, selected through virtual screening, were synthesized using solid-phase synthesis, and EK, LFE, LEY and DR were confirmed to possess a pleasing salty taste through electronic tongue evaluation. Molecular docking results indicated that these 4 peptides could enter the binding pocket within the transmembrane channel-like 4 (TMC4) cavity, wherein salt bridges, hydrogen bonds and attractive charges were the main binding forces. This study provides a rapid screening method for salty peptides in sea food products but possibly applied for other sources.

Advancements in production, assessment, and food applications of salty and saltiness-enhancing peptides: A review

Salt is important for food flavor, but excessive sodium intake leads to adverse health consequences. Thus, salty and saltiness-enhancing peptides are developed for sodium-reduction products. This review elucidates saltiness perception process and analyses correlation between the peptide structure and saltiness-enhancing ability. These peptides interact with taste receptors to produce saltiness perception, including ENaC, TRPV1, and TMC4. This review also outlines preparation, isolation, purification, characterization, screening, and assessment techniques of these peptides and discusses their potential applications. These peptides are from various sources and produced through enzymatic hydrolysis, microbial fermentation, or Millard reaction and then separated, purified, identified, and screened. Sensory evaluation, electronic tongue, bioelectronic tongue, and cell and animal models are the primary saltiness assessment approaches. These peptides can be used in sodium-reduction food products to produce "clean label" items, and the peptides with biological activity can also serve as functional ingredients, making them very promising for food industry.

Novel salty peptides derived from bovine bone: Identification, taste characteristic, and salt-enhancing mechanism

Excessive sodium intake is a major contributor to the incidence of cardiovascular diseases. The objective of this study was to prepare, isolate, and characterize peptides from bovine bone protein and investigate the salty/salt-enhancing mechanism of peptides. 1032 peptides were identified in the enzymatic hydrolysates of bovine bone protein and were further screened by the composition of amino acid residues and molecular docking analysis. 5 peptides were finally selected for solid-phase synthesis, and KER showed a better salty taste by sensory verification. Moreover, the synergistic effect of KER in NaCl and MSG solution could enhance the salty intensity by 65.26 %. The binding of KER to the salty receptor (TMC4) was driven by hydrogen bonding and electrostatic interactions with a binding energy of -88.0734 kcal/mol. This work may provide a new approach to efficiently screen salty peptides from natural food materials, which were expected as a taste enhancer used in salt-reducing foods.

Diversified Techniques for Restructuring Meat Protein-Derived Products and Analogues

Accompanied by the rapid growth of the global population and increasing public awareness of protein-rich foods, the market demand for protein-derived products is booming. Utilizing available technologies to make full use of meat by-products, such as scraps, trimmings, etc., to produce restructured meat products and explore emerging proteins to produce meat analogues can be conducive to alleviating the pressure on supply ends of the market. The present review summarizes diversified techniques (such as high-pressure processing, ultrasonic treatment, edible polysaccharides modification, enzymatic restructuring, etc.) that have been involved in restructuring meat protein-derived products as well as preparing meat analogues identified so far and classifying them into three main categories (physical, chemical and enzymatic). The target systems, processing conditions, effects, advantages, etc., of the included techniques, are comprehensively and systemically summarized and discussed, and their existing problems or developing trends are also briefly prospected. It can be concluded that a better quality of restructured products can be obtained by the combination of different restructuring technologies. This review provides a valuable reference both for the research and industrial production of restructured meat protein-derived products and analogues.

The application of protease in aquaculture: Prospects for enhancing the aquafeed industry

Low-fishmeal and protein-saving diets are two prominent nutritional strategies utilized to address challenges related to the scarcity and sustainability of protein sources in aquaculture. However, these diets have been associated with adverse effects on the growth performance, feed utilization, and disease resistance of aquatic animals. To mitigate these challenges, exogenous protease has been applied to enhance the quality of diets with lower protein contents or fishmeal alternatives, thereby improving the bioavailability of nutritional ingredients. Additionally, protease preparations were also used to enzymatically hydrolyze fishmeal alternatives, thus enhancing their nutritional utilization. The present review aims to consolidate recent research progress on the use of protease in aquaculture and conclude the benefits and limitations of its application, thereby providing a comprehensive understanding of the subject and identifying opportunities for future research.

Proteomics analysis of the influence of proteolysis on the subsequent glycation of myofibrillar protein

Proteomics was used to study the influence of proteolysis on the glycation of myofibrillar proteins (MPs). Proteolysis by papain and proteinase K generated the highest level of amino acids (AAs) and peptides, respectively. Both the glycation degree (A value increased from 0.173 to 0.202-0.348) and speed (k value increased from 0.0099 to 0.0132-0.0145) were enhanced by proteolysis using papain and proteinase K. Proteomics analysis revealed that proteolysis largely enhanced the glycation site number in Lys, Arg and N-terminal residues (eg. Leu, Gly, Thr, Ala, Met, Ile, Phe and Val residues in myosin light chain). Proteolysis by papain preferentially acted on actin and therefore specifically increased the glycation sites from actin. Proteolysis reduced the level of aldehydes but enhanced the aromatic E-nose signals, possibly due to the combination of aldehydes with released AAs/peptides. The proteomics analysis helped to detail the relationship between proteolysis and subsequent glycation/flavour formation.

Light-Colored Maillard Peptides: Formation from Reduced Fluorescent Precursors of Browning and Enhancement of Saltiness Perception

The browning formation and taste enhancement of peptides derived from soybean, peanut, and corn were studied in the light-colored Maillard reaction compared with the deep-colored reaction. The fluorescent compounds, as the browning precursors, were accumulated during the early Maillard reaction of peptides and subsequently degraded into dark substances, which resulted in a higher browning degree of deep-colored Maillard peptides (MPs), especially for the MPs derived from corn peptide. However, the addition of l-cysteine in light-colored Maillard reaction reduced the formation of deoxyosones and short-chain reactive α-dicarbonyls, thereby weakening the generation of fluorescent compounds and inhibited the browning of MPs. Synchronously, the peptides were thermally degraded into small peptides and amino acids, which were consumed less during light-colored thermal reaction due to its shorter reaction time at high temperature compared with deep-colored ones, thus contributing to a stronger saltiness perception of light-colored MPs than deep-colored MPs. Besides, the Maillard reaction products derived from soybean and peanut peptides possessed an obvious "kokumi" taste, making them suitable for enhancing the soup flavors.

Enhancing Kokumi Sensation and Reducing Bitterness in Acid-Hydrolyzed Vegetable Proteins through Lactate and Thermal Processing

Previous studies have demonstrated that thermal processing in the presence of lactate and amino acids can produce taste-active N-lactoyl amino acids. This study aimed to investigate the impact of lactate and thermal processing on the sensory characteristics of acid-hydrolyzed vegetable proteins (aHVP). The results showed that the processed aHVP exhibited enhanced kokumi, a milder umami taste, and reduced bitterness on treatment with 1% lactate at 110 °C for 3 h or 3% lactate at 120 °C for 2 h compared to the unprocessed samples. Partial or orthogonal least-squares discriminant analysis and variable importance in projection (VIP) analyses revealed the significant contributions of N-,l-Lac-l-hydrophobic AAs [-Met, -Ile, -Leu, -Val, and -Phe (VIP > 1.2)] to the observed differences between the processed and unprocessed samples. Electronic tongue analysis confirmed the sensory findings and indicated a decrease in the aftertaste of bitterness in the processed samples. Furthermore, the study identified the sensory characteristics of N-l-Lac-l-Met, -Ile, and -Leu, highlighting their potential to enhance salty, umami, and kokumi perception in simulated broth. Furthermore, the study incorporated the addition of bitter amino acids (Val, Ile, Leu, Tyr, Phe, Lys, His, and Arg) and the aforementioned N-l-Lac-l-AAs to aHVP, providing further evidence for their contributions to bitterness and aftertaste-B as well as the kokumi differences, respectively. This study provides valuable insights into the sensory effects of lactate and thermal processing on aHVP, facilitating the development of improved taste-enhancing strategies.

Identification and Characterization of Novel Umami Peptides from Protein Hydrolysates of Morchella esculenta and Their Interaction with T1R1/T1R3 Receptor

The study aimed to explore umami peptides derived from protein hydrolysates of Morchella esculenta. According to the electronic tongue and sensory evaluation, the ultrafiltration fractions (<3 kDa) of the protein hydrolysates exhibited the strongest umami taste. The overall flavor of the screened fractions was significantly improved after the Maillard reaction, based on the electronic nose and electronic tongue analyses, and the content of total free amino acid increased from 387.35 to 589.30 μg/mL. A total of 37 peptides with high confidence were identified from the fractions using LC-MS/MS. Additionally, two novel umami peptides were screened through bioinformatics and molecular docking, and their recognition threshold was 0.43 (EYPPLGRFA) and 0.52 mmol/L (TVIDAPGHRDFI), respectively. In addition, molecular docking analysis revealed that the key binding sites, such as Ser148, Leu51, Arg327, and Leu468 in T1R1/T1R3 contributed to docking, and hydrogen bonding and hydrophobic interactions were the dominant interaction forces between the two umami peptides and T1R1/T1R3 receptor. This study contributes to the development and utilization of Morchella esculenta in flavored foods.

Gradient Retention Factor Concept Applied to Method Development for Peptide Analysis by Means of RP-HPLC

Using the van Deemter model, the efficiency of three stationary phase systems in the analysis of a mixture of synthetic peptides was evaluated: (i) monolithic, (ii) packed, and (iii) core-shell columns, and it was shown that the efficiency of the monolithic column is superior to the others, specifically using it, the lowest values of H _min (0.03 and 0.1 mm) were obtained, and additionally its efficiency was not significantly affected by increasing the flow. Using the concept of the gradient retention factor (k*), a method for chromatographic separation of a peptide complex mixture was designed, implemented, and optimized and then transferred from a packed column to a monolithic one. The results showed that it was possible to separate all components of the mixture using both evaluated columns; moreover, the analysis time was reduced from 70 to 10 min, conserving the critical pair resolution (1.4), by the transfer method using the k* concept. The method developed was tested against a mixture of doping peptides, showing that this method is efficient for separating peptides of various natures. This investigation is very useful for the development of methods for the analysis of complex peptide mixtures since it provides a systematic approach that can be extrapolated to different types of columns and instrumentation.

Insights into flavor and key influencing factors of Maillard reaction products: A recent update

During food processing, especially heating, the flavor and color of food change to a great extent due to Maillard reaction (MR). MR is a natural process for improving the flavor in various model systems and food products. Maillard reaction Products (MRPs) serve as ideal materials for the production of diverse flavors, which ultimately improve the flavor or reduce the odor of raw materials. Due to the complexity of the reaction, MR is affected by various factors, such as protein source, hydrolysis conditions, polypeptide molecular weight, temperature, and pH. In the recent years, much emphasis is given on conditional MR that could be used in producing of flavor-enhancing peptides and other compounds to increase the consumer preference and acceptability of processed foods. Recent reviews have highlighted the effects of MR on the functional and biological properties, without elaborating the flavor compounds obtained by the MR. In this review, we have mainly introduced the Maillard reaction-derived flavors (MF), the main substances producing MF, and detection methods. Subsequently, the main factors influencing MF, from the selection of materials (sugar sources, protein sources, enzymatic hydrolysis methods, molecular weights of peptides) to the reaction conditions (temperature, pH), are also described. In addition, the existing adverse effects of MR on the biological properties of protein are also pointed out.

Producing beef flavors in hydrolyzed soybean meal-based Maillard reaction products participated with beef tallow hydrolysates

This work investigated the effect of oxidized beef tallow on the volatile compositions and sensory properties of soybean meal-based Maillard reaction products (MRPs). Various tallow oxidation methods included thermal treatment (TT), enzymatic hydrolysis (ET) and enzymatic hydrolysis combined with mild thermal (ETT) treatment. Results showed that all these oxidized tallow contained more types of volatile compounds than those of untreated tallow. Moreover, the composition of almost all types of volatile substances was greatly increased with the addition of the oxidized beef tallow into the hydrolyzed soybean meal-based Maillard reaction system. More importantly, the composition of oxygen-containing heterocycles (63.89 μg/mL), sulfur-containing compounds (76.64 μg/mL), and nitrogen-containing heterocycles (19.81 μg/mL) that contribute positively to sensory properties in ETT-MRPs was found to be the highest among all the MRPs. Correlation assessment revealed that ETT was closely related to the most typical volatile products and sensory attributes, indicating this approach can effectively enhance the sensory and flavor of hydrolyzed soybean meal derived MRPs.

Maillard reaction of food-derived peptides as a potential route to generate meat flavor compounds: A review

Plant-based meat analogues (PBMA) are promising foods to address the global imbalance between the supply and demand for meat products caused by the increasing environmental pressures and growing human population. Given that the flavor of PBMA plays a crucial role in consumer acceptance, imparting meat-like flavor is of great significance. As a natural approach to generate meat-like flavor, the Maillard reaction involving food-derived peptides could contribute to the required flavor compounds, which has promising applications in PBMA formulations. In this review, the precursors of meat-like flavor are summarized followed by a discussion of the reactions and mechanisms responsible for generation of the flavor compounds. The preparation and analysis techniques for food-derived Maillard reacted peptides (MRPs) as well as their taste and aroma properties are discussed. In addition, the MRPs as meat flavor precursors and their potential application in the formulation of PBMA are also discussed. The present review provides a fundamental scientific information useful for the production and application of MRPs as meat flavor precursors in PBMA.

EGCG-gelatin biofilm improved the protein degradation, flavor and micromolecule metabolites of tilapia fillets during chilled storage

The protein degradation, flavor and micromolecule metabolites changes of (-)-epigallocatechin gallate (EGCG)-gelatin biofilm treatment (EGT) on chilled tilapia fillets in 21 days were investigated. Morphology observations revealed EGT protected good connective myofibrillar protein. It maintained protein secondary structure by significantly increasing the proportion of α-helix (15.20%) and decreasing the ratio of random coils (22.02%) in the EGT group compared to the control (CON) group (P < 0.05). Metabolomics with UHPLC-Q-TOF/MS analysis indicated a distinct separation between the CON and treatment groups at the end of storage. Small peptides analysis demonstrated that the EGT group increased the level of sweet peptides. Additionally, the EGT group significantly reduced the formation of amino acid derivatives and esters and off-flavor development. Overall, EGT effectively improved flavor, inhibited fish protein oxidation/degradation, and verified metabolomics results. This study unveiled the potential of metabolomics to analyze metabolites determined by tilapia and monitor the changes during storage.

Structural characteristics and improved in vitro hepatoprotective activities of Maillard reaction products of decapeptide IVTNWDDMEK and ribose

Here, a novel decapeptide IVTNWDDMEK with Maillard reactivity derived from scallop Chlamys farreri mantle was identified. The structural characteristics and in vitro hepatoprotective effects of IVTNWDDMEK conjugated with ribose were further investigated. The changes in decapeptide structures were determined by ultraviolet-visible (UV-vis), Fourier transform infrared (FTIR), and atomic force microscopy (AFM), and the modification sites induced by Maillard reaction of IVTNWDDMEK and ribose were monitored by high performance liquid chromatography/tandem mass spectrometry (HPLC-MS/MS). Maillard reaction products (MRPs) of IVTNWDDMEK-ribose demonstrate hepatoprotective benefits through the suppression of DNA damage and apoptosis induced by oxidative stress in human HepG2 cells in addition to enhancing the antioxidant activities. Moreover, after treatment with decapeptide-ribose MRPs, the activities of cellular antioxidative enzymes, such as catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and glutathione reductase (GSH-Rx) were remarkably increased, while the content of malondialdehyde (MDA) was decreased compared with H₂ O₂ ^- treated group, thereby enhancing the intracellular antioxidant defenses. These findings demonstrate the potential utilization of decapeptide IVTNWDDMEK-ribose MRPs as food antioxidants to suppress oxidative damage. PRACTICAL APPLICATION: In recent years, several food-derived bioactive peptides and their derivatives are regarded as good dietary antioxidants for reducing oxidative stress and improving liver function. Here, a novel Maillard reactive decapeptide IVTNWDDMEK, identified from scallop mantle hydrolysates by peptidomics in the previous study was synthesized. Then, the correlation between intercellular antioxidant activities and chemical structure changes of IVTNWDDMEK-ribose Maillard reaction conjugates was further studied. The preferable hepatoprotective activities of decapeptide IVTNWDDMEK-ribose MRPs indicated that these MRPs could be potentially utilized as food antioxidants or additives in the production of nutritional foods.

Key lipid molecules in hepatopancreas of Eriocheir sinensis: Identification and thermal oxidative degradation characteristics

The hepatopancreas of Eriocheir sinensis are the key parts that form its unique flavor. Lipids are important parts of hepatopancreas; hence, this study used UHPLC-Q E Orbitrap mass spectrometer to investigate the changes in the lipid composition of crabs formed from thermal oxidation system. The results demonstrated that key lipids in the hepatopancreas of female Chinese mitten crabs were phosphatidylethanolamine (PE) and free fatty acid (FFA) during the steaming process. The key fatty acids of PE were C18:1, C18:3, C20:3, C20:4, C20:5, and C22:6. The degradation rate of C24:0 in FFA was greater than the synthesis rate. Principal component analysis, partial least square analysis combined with hierarchical cluster analysis found that PE (16:0/20:5), PE (18:1/20:4), PE (16:0/22:6), PE (16:0/20:4), PE (16:0 /16:1), PE (16:0/18:2), PE (18:0/20:5), PE (18:0/22:6), PE (18:0/20:4), PE (16:0/18:1), PE (18:0/18:2), PE (18:0/22:5), and PE (18:0/18:1) were the key PE molecular species. Simulating thermal oxidation to understand the dynamic change mechanism of lipids is meaningful for processing of Chinese mitten crab products and catering to public sensory orientation. PRACTICAL APPLICATIONS: In this study, the UHPLC-Q E Orbitrap method was used to detect and analyze the molecular species changes of Eriocheir sinensis in the simulated thermal oxidation system, and systematically analyzed the law of changes. Based on these results, we can expand our understanding of the changing characteristics of the hepatopancreas and pancreas of the river crab and provide a direction for the formation mechanism of the aroma substances of E. sinensis during the heat treatment and the improvement of the quality of its products.

Optimization of beef broth processing technology and isolation and identification of flavor peptides by consecutive chromatography and LC-QTOF-MS/MS

To investigate the flavor peptides of beef broth obtained under optimized stewing conditions, separation procedures such as ultrafiltration, Sephadex G-15 column chromatography, and reversed-phase high-performance liquid chromatography were employed to isolate the umami taste peptides. Sensory evaluation was combined with liquid chromatography-mass spectrometry to detect the flavor peptides. The optimization of the stewing process conditions was studied using the orthogonal method, which indicated that time had the most significant effect on the taste efficiency of sensory evaluation, followed by the mixed spices, sucrose, and salt. The optimized cooking conditions included 3.5 hr of cooking time, 1.800 g of sucrose, 2.125 g of salt, and 1.500 g of mixed spices. The results showed that six peptides, including SDEEVEH, AEVPEVH, GVDNPGHP, GSDGSVGPVGP, SDGSVGPVGP, and DEAGPSIVH, were detected in sample X1M1; and seven peptides, including VAPEEHPT, VVSNPVDIL, VGGNVDYK, PFGNTHN, EAGPSIVHR, VDFDDIQK, and DEAGPSIVH, were detected in sample X2M2. This study compared the flavor peptides in stewed beef before and after the optimization, and thus provided a basis for the improvement of beef processing technology.

Identification, taste characteristics and molecular docking study of novel umami peptides derived from the aqueous extract of the clam meretrix meretrix Linnaeus

To understand the delicious taste of the clam M. meretrix Linnaeus, the putative umami peptides from the aqueous extract of the cooked clam were obtained by ultrafiltration, gel filtration chromatography, and reversed-phase high-performance liquid chromatography. The isolated peptide fraction with the most intense umami taste was screened by sensory and electronic tongue analysis. Seven novel peptides, GLLPDGTPR, RPNPFENR, STMLLESER, ANPGPVRDLR, QVAIAHRDAK, VLPTDQNFILR, and VTADESQQDVLK, were identified and synthesized to verify their taste characteristics. The taste activity prediction and the sensory evaluation of the synthetic peptides revealed that those peptides were umami and umami-enhancing peptides. Docking of the synthesized peptides with the umami taste receptor T1R1/T1R3 indicated that the peptides could enter the binding pocket in the Venus flytrap domain of the T1R3 cavity, wherein Asp196 and Glu128 may play key roles in the synergism of umami taste and hydrogen bonding and electrostatic interactions are important interaction forces.