Isolation and identification of two novel umami and umami-enhancing peptides from peanut hydrolysate by consecutive chromatography and MALDI-TOF/TOF MS

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.

Insights on modulators in perception of taste modalities: a review

A major challenge in taste research is to overcome the flavour imperfections in food products and to build nutritious strategies to combat against obesity as well as other related metabolic syndromes. The field of molecular taste research and chemical senses has contributed to an enormous development in understanding the taste receptors and mechanisms of taste perception. Accordingly, the development of taste-modifying compounds or taste modulators that alter the perception of basic taste modalities has gained significant prominence in the recent past. The beneficial aspects of these substances are overwhelming while considering their potential taste-modifying properties. The objective of the present review is to provide an impression about the taste-modulating compounds and their distinctive taste-modifying properties with reference to their targets and proposed mechanisms of action. The present review also makes an effort to discuss the basic mechanism involved in oro-gustatory taste perception as well as on the effector molecules involved in signal transduction downstream to the activation of taste receptors.

Identification and comparison of oligopeptides during withering process of White tea by ultra-high pressure liquid chromatography coupled with quadrupole-orbitrap ultra-high resolution mass spectrometry

Peptides could have specific tastes or bioactivities depending on the length and sequence of amino acids. Till date it remains unknown what peptides are formed during the white tea manufacturing process and whether they contribute to the flavor or bio-activities of white tea. As a first step to address these questions, we applied ultra-high pressure liquid chromatography coupled with quadrupole-orbitrap ultra-high resolution mass spectrometry (UPLC-Quadrupole-Orbitrap-UHRMS) to monitor peptides dynamic changes during the withering process. A total of 196 abundant peptides were identified. Most of them were oligopeptides within a molecular weight of 1000 Da. Four of them were randomly selected, synthesized peptides were applied for further confirmation and quantification. Sequence analysis suggested that some of them were potential taste contributors. Proteinase cleave site analysis identified two separate periods of active proteins degradation at 0-12 h and 30-42 h of the withering processes. Further analysis of cleavage sites also suggested that protein degradation during withering steps were random rather than a stepwise reaction.

Identification and taste characteristics of novel umami and umami-enhancing peptides separated from peanut protein isolate hydrolysate by consecutive chromatography and UPLC-ESI-QTOF-MS/MS

Six novel peptides were separated from peanut protein isolate hydrolysate (PPIH) using ethanol precipitation and gel chromatography, and identified as DQR, NNP, EGF, EDG, TESSSE and RGENESEEEGAIVT by UPLC-ESI-QTOF-MS/MS. On the basis of sensory results, all peptides were perceived umami with threshold values from 0.39 to 1.11 mM and had umami-enhancing abilities simultaneously with threshold values from 0.33 to 0.82 mM. RGENESEEEGAIVT was the first discovered tetradecapeptide with umami and umami-enhancing ability. The dose-response test revealed that umami-enhancing activities of identified peptides were different: TESSSE and RGENESEEEGAIVT imparted better umami intensity when equimolar monosodium glutamate (MSG) was added into 0.5 g/L MSG solution. Taste profile analyses of complex mixtures with/without synthetic peptides were determined by both electronic tongue and human panellists, suggesting that umami peptides influence multiple tastes and electronic tongue has the potential to replace sensory test to distinguish taste attributes of foods rich in peptides.

Isolation and identification of the umami peptides from shiitake mushroom by consecutive chromatography and LC-Q-TOF-MS

Umami is critical to the taste of shiitake mushroom. To isolate and identify umami peptides, fractions from hydrolyzed dried shiitake mushroom were separated by ultrafiltration, gel filtration chromatography (GFC), and reversed-phase high-performance liquid chromatography (RP-HPLC). Separations were combined with sensory evaluations (grading and taste dilution analysis) and analysis of electronic tongue, which were used to identify the most umami component in shiitake mushroom. Low-molecular-weight fractions (MW < 3 kDa) have the strongest flavor in the shiitake mushroom hydrolysate. In the 3 subfractions separated from low-molecular-weight fractions (MW < 3 kDa) by GFC, the second subfraction (F2) was selected for RP-HPLC analysis. The first peak (G1) in RP-HPLC was identified by LC-Q-TOF-MS, and 2 tripeptides and 3 dipeptides were identified. The amino acid sequence of these peptides were Gly-Cys-Gly, Glu-Pro-Glu, Cys-Met, Val-Phe, and Gly-Glu.

Umami compounds present in low molecular umami fractions of asam sunti - A fermented fruit of Averrhoa bilimbi L

Salted fermented fruit known as asam sunti (Averrhoa bilimbi L.) in Indonesia has been used as a source of umami taste. This study was aimed to characterize the three types of asam sunti and their water soluble extracts, and to trace the compounds responsible for umami taste in umami fractions. Umami fractions were obtained by ultrafiltration followed by Sephadex G-15 chromatographic separation. The three types of samples could be differentiated by physicochemical and sensory analyses. Low molecular weight fraction had the highest umami intensity. Further chromatographic separation revealed three umami fractions, F-II, III and IV. Umami taste of F-III was due to the presence of free l-glutamic acid at 6 times, while FII and FIV were due to succinic acid at more than 30 times their respective umami thresholds. Organic acid as well as amino acid seemed to play an important role in the intense umami taste of asam sunti.

Analysis of Umami Taste Compounds in a Fermented Corn Sauce by Means of Sensory-Guided Fractionation

Corn sauce, an ingredient obtained from the fermentation of enzymatically hydrolyzed corn starch and used in culinary applications to provide savory taste, was investigated in this study. The links between its sensory properties and taste compounds were assessed using a combination of analytical and sensory approaches. The analyses revealed that glutamic acid, sodium chloride, and acetic acid were the most abundant compounds, but they could not explain entirely the savory taste. The addition of other compounds, found at subthreshold concentrations (alanine, glutamyl peptides, and one Amadori compound), contributed partly to close the sensory gap between the re-engineered sample and the original product. Further chemical breakdown, by a sensory-guided fractionation approach, led to the isolation of two fractions with taste-modulating effects. Analyses by mass spectrometry and nuclear magnetic resonance showed that the fractions contained glutamyl peptides, pyroglutamic acid, glutamic acid, valine, N-formyl-glutamic acid, and N-acetyl-glutamine.

Effect of Salt Reduction on Consumer Acceptance and Sensory Quality of Food

Reducing salt (NaCl) intake is an important public health target. The food industry and catering services are searching for means to reduce the salt content in their products. This review focuses on options for salt reduction in foods and the sensory evaluation of salt-reduced foods. Simple salt reduction, mineral salts and flavor enhancers/modifiers (e.g., umami compounds) are common options for salt reduction. In addition, the modification of food texture and odor-taste interactions may contribute to enhanced salty taste perception. Maintaining consumer acceptance of the products is a challenge, and recent examples of the consumer perception of salt-reduced foods are presented.

Comparison of non-volatile umami components in chicken soup and chicken enzymatic hydrolysate

Umami taste is an important part to the taste of chicken. To isolate and identify non-volatile umami compounds, fractions from chicken soup and hydrolysate were prepared and analyzed. Amino acids were analyzed by amino acid analyzer. Organic acids and nucleotides were determined by ultra-performance liquid chromatography. Separation procedures utilizing ultrafiltration, Sephadex G-15 and reversed-phase high-performance liquid chromatography were used to isolate umami taste peptides. Combined with sensory evaluation and LC-Q-TOF-MS, the amino acid sequences of 12 oligopeptides were determined. The amount of taste compounds was higher in chicken enzymatic hydrolysate than that of chicken soup. Eight oligopeptides from chicken enzymatic hydrolysate were identified, including Ala-Asp, Ala-Met, His-Ser, Val-Glu, Ala-Glu, Asp-Ala-Gly, Glu-Asp and Ala-Glu-Ala. Four oligopeptides from chicken soup were identified, including Val-Thr, Ala-His, Ala-Phe and Thr-Glu.

Novel Umami Ingredients: Umami Peptides and Their Taste

Umami substances are very important for food seasoning and healthy eating. In addition to monosodium glutamate and some nucleotides, recent investigations have revealed that several peptides also exhibit umami taste. In recent years, 52 peptides have been reported to show umami taste, including 24 dipeptides, 16 tripeptides, 5 octapeptides, 2 pentapeptides, 2 hexapeptides, 1 tetrapeptide, 1 heptapeptide, and 1 undecapeptide. Twenty of these peptides have been examined for the present of umami taste. In this review, we have listed these umami peptides based on their category, source, taste, and threshold concentration. The evidence for peptides showing umami taste, the umami taste receptors on the human tongue, and the peptides whose umami taste is controversial are also discussed.

The structure features of umami hexapeptides for the T1R1/T1R3 receptor

Umami is thought to be initiated by binding tastants to G-protein-coupled receptors in taste cells, while the structure and mechanism of the receptors are not clear. In this study, we summarized umami peptides and classified them roughly into two groups: the first group contains dipeptides and tripeptides with terminal Glu or Asp, while the second peptides comprises more amino acids without significant features. The research on the structure and taste characteristics of second group peptides are less studied, so we focus on this group. In this work, nine flavor peptides were newly identified from Takifugu obscurus, and among them, the umami hexapeptides KGRYER belong to the second group. Five hexapeptides from this study, our previous work and references were chosen to build a Three Dimensional Quantitative Structure-Activity Relationship model with q2 value as 0.964 successfully. Then the relationship between the structure and intensity of umami peptides were illustrated.

An Interesting Tour of New Research Results on Umami and Umami Compounds

Knowledge about the fifth basic taste, the umami taste, has been investigated by many scientists in the last years and continues to gain importance. Therefore, a lot of scientific studies were conducted to explore several effects influencing the mechanism of umami, which is elicited and enhanced by defined concentrations of MSG (monosodium glutamate) and umami compounds. This paper covers the most relevant scientific literature regarding umami, its use as a flavor enhancer, and the latest umami compounds, which have been released in the last ten years. The main goal of this overview was to summarize the most important results which were related to umami as one of the five basic tastes, the umami taste receptor, the essential role of umami in a great number of physiological mechanisms, and the MSG symptom complex. Furthermore, the function of umami in the interaction of taste, aftertaste and olfactory pathways has been discussed.

Food protein-originating peptides as tastants - Physiological, technological, sensory, and bioinformatic approaches

Taste is one of the factors based on which the organism makes the selection of what to ingest. It also protects humans from ingesting toxic compounds and is one of the main attributes when thinking about food quality. Five basic taste sensations are recognized by humans: bitter, salty, sour, sweet, and umami. The taste of foods is affected by some molecules of some specific chemical nature. One of them are peptides derived from food proteins. Although they are not the major natural compounds originating from food sources that are responsible for the taste, they are in the area of scientific research due to the specific composition of amino acids which are well-known for their sensory properties. Literature data implicate that sweet, bitter, and umami are the tastes attributable to peptides. Moreover, the bitter peptide tastants are the dominant among the other tastes. Additionally, other biological activities like, e.g., inhibiting enzymes that regulate the body functions and acting as preventive food agents of civilization diseases, are also associated with the taste of peptides. The advance in information technologies has contributed to the elaboration of internet archives (databases) as well as in silico tools for the analysis of biological compounds. It also concerns peptides - namely taste carriers originating from foods. Thus, our paper provides a summary of knowledge about peptides as tastants with special attention paid to the following aspects: a) basis of taste perception, b) taste peptides detected in food protein sequences with special emphasis put on the role of bitter peptides, c) peptides that may enhance/suppress the taste of foods, d) databases as well as bioinformatic approaches suitable to study the taste of peptides, e) taste-taste interactions, f) basis of sensory analysis in the evaluation of the taste of molecules, including peptides, and g) the methodology applied to reduce/eliminate the undesired taste of peptides. The list of taste peptides serving some biological functions is presented in the Supplement file. The information provided includes database resources, whereas peptide sequences are given with InChiKeys, which is aimed at facilitating the Google® search. Our collection of data regarding taste peptides may be supportive for the scientists working with the set of peptide data in the context of structure-function activity of peptides.

A novel multi-biofunctional protein from brown rice hydrolysed by endo/endo-exoproteases

Brown rice, which is a less allergenic food grain and contains essential amino acids, was hydrolysed by bromelain and PROTEASE FP51® to improve its functionalities and taste for food applications. The hydrolysate prepared by bromelain (eb-RPH) had high protein solubility, surface hydrophobicity, low molecular weight peptides, hydrophobic amino acids (leucine, valine and glycine) and flavor amino acids (glutamic acid and aspartic acid). The eb-RPH exhibited higher 1,1-diphenyl-2-picrylhydrazyl (DPPH˙) and 2,2'-azino-bis 3-ethylbenzthiazoline-6-sulfonic (ABTS˙(+)) radical-scavenging activities of 76.62% and 52.96%, respectively, and possessed a better foaming capacity (221.76%) and emulsifying capacity (32.34%) than the hydrolysate prepared by PROTEASE FP51® (ep-RPH) did. The eb-RPH gave the desired taste, which is attributed to volatile flavor compounds (benzaldehyde, benzeneacetaldehyde and 2-acetyl-1-pyrroline) and non-volatile flavor compounds, such as monosodium glutamate, 5'-guanosine monophosphate and 5'-inosine monophosphate (0.07, 0.03 and 0.05 mg mL(-1), respectively). Brown rice peptides generated by bromelain were novel bioactive peptides with multifunctional properties.

Preparation of gluten free bread enriched with green mussel (Perna canaliculus) protein hydrolysates and characterization of peptides responsible for mussel flavour

Green mussel protein hydrolysates (GMPH) utilization for the enrichment of gluten-free bread followed by characterization of flavour peptides using chromatography and electronic nose techniques have been done. The degree of hydrolysis was carried out in each protease digest, and the higher degree of hydrolysis was observed in pepsin digestion. Gluten-free (GF) bread was formulated by using buckwheat flour (BWF), rice flour (RF) and chickpea flour (CPF) (70:20:10) and GMPH were added in the range of 0-20% in the GF bread for enrichment with GMPH. Radar plot of the electronic nose analysis showed that the sensors P30/2, T30/1 and T70/2 had a higher response to the GF bread and GMPH. Consequently, the peptide sequence was obtained manually by ESI-MS spectra of GMPH (KGYSSYICDK) and F-II (SSYCIVKICDK). Flavour quality was 97% discriminately comparable to the GMPH and F-II fractions. Mussel flavoured GF bread can be included in the celiac diet.

In vitro angiotensin I converting enzyme inhibition by a peptide isolated from Chiropsalmus quadrigatus Haeckel (box jellyfish) venom hydrolysate

The anti-angiotensin I converting enzyme activity of box jellyfish, Chiropsalmus quadrigatus Haeckel venom hydrolysate was studied. The venom extract was obtained by centrifugation and ultrasonication. Protein concentration of 12.99 μg/mL was determined using Bradford assay. The pepsin and papain hydrolysate was tested for its toxicity by Limit test following the OECD Guideline 425 using 5 female Sprague-Dawley rats. Results showed that the hydrolysate is nontoxic with an LD50 above 2000 mg/kg. In vitro angiotensin I converting enzyme (ACE) inhibitory activity was determined using ACE kit-WST. Isolation of ACE inhibitory peptides using column chromatography with SP-Sephadex G-25 yielded 8 pooled fractions with fraction 3 (86.5%) exhibiting the highest activity. This was followed by reverse phase - high performance liquid chromatography (RP-HPLC) with an octadecyl silica column (Inertsil ODS-3) using methanol:water 15:85 at a flow rate of 1.0 mL/min. Among the 13 fractions separated with the RP-HPLC, fraction 3.5 exhibited the highest ACE inhibitory activity (84.1%). The peptide sequence ACPGPNPGRP (IC50 2.03 μM) from fraction 3.5 was identified using Matrix-assisted laser desorption/ionization with time-of-flight tandem mass spectroscopy analysis (MALDI-TOF/MS).

Sequence, taste and umami-enhancing effect of the peptides separated from soy sauce

Five tasty peptides were separated from soy sauce, by sensory-guided fractionation, using macroporous resin, medium-pressure liquid chromatography and reverse phase-high performance liquid chromatography, and identified by ultra-performance liquid chromatography tandem mass-spectrometry as ALPEEV, LPEEV, AQALQAQA, EQQQQ and EAGIQ (which originated from glycinin A1bB2-445, glycinin A1bB2-445, cobyric acid synthase, leucine-tRNA ligase and glycoprotein glucosyltransferase, respectively). LPEEV, AQALQAQA and EQQQQ tasted umami with threshold values of 0.43, 1.25 and 0.76mmol/l, respectively. ALPEEV and EAGIQ had minimal umami taste, but ALPEEV, EAGIQ and LPEEV showed umami-enhancement with a threshold estimated at 1.52, 1.94 and 3.41mmol/l, respectively. In addition, the synthetic peptides showed much better sensory taste than mixtures of their constitutive amino acids. It indicated that peptides might play an important role in the umami taste of soy sauce.

Discovery of kokumi peptide from yeast extract by LC-Q-TOF-MS/MS and sensomics approach

BACKGROUND

Yeast extract can impart thickness, complexity and long-lasting taste impression, coined kokumi taste, to blank chicken broth. In this research, the kokumi-active peptide in yeast extract was discovered by ultrafiltration, liquid chromatographic and quadrupole-time-of-flight-tandem mass spectrometric technologies. Furthermore, the sensory characters of these peptides were evaluated by a sensomics approach.

RESULTS

A total of 10 kokumi peptides were identified from yeast extract. They were γ-Glu-Cys-Gly, γ-Glu-Leu, γ-Glu-Val, γ-Glu-Tyr, Leu-Lys, Leu-Gln, Leu-Ala, Leu-Glu, Leu-Thr and Ala-Leu. Apart from the well-known kokumi-active glutathione and γ-glutamyl dipeptides, five leucyl dipeptides were first proposed having kokumi activity. Among them, Ala-Leu was found to have the highest kokumi threshold concentration (1.5 mmol L(-1) ) in the blank chicken broth, while Leu-Glu was the lowest (0.3 mmol L(-1) ). A subsequent dose-response experiment indicated that the bitter-tasting leucyl dipeptides could impart kokumi taste to chicken broth at low concentrations (less than bitter threshold concentrations). Interestingly, the kokumi sensation began to decrease when such peptides exceeded the threshold concentration by approximately 16-fold in the blank chicken broth.

CONCLUSION

Key kokumi-active fractions were purified from yeast extract. Among them, ten important kokumi peptides from yeast extract were identified.

Sensitivity and accuracy of organic matrix-assisted laser desorption and ionisation mass spectrometry of FeCl3 is higher than in in matrix-free approach

We compare the quality and reliability of laser desorption and ionisation mass spectra of FeCl3 acquired without the assistance of the matrix with the spectra acquired with different organic matrix molecules. Generally, inorganic salts tend to form clusters upon laser irradiation, the signals of which can be easily distinguished from ions arising from the matrix. In the presence of a matrix, cluster ions are, however, mostly suppressed. We have compared the number of analyte signals, accuracy of determination of isotope composition of the analyte and the sensitivity of FeCl3 detection between different approaches. The results obtained imply that the sensitivity of mass spectrometric analysis of FeCl3 is somewhat higher when matrices are applied than in the matrix-free approach. Among all matrices tested in this work, F20TPP seems to be the most promising for further applications as a matrix for mass spectrometry of inorganic salts.