Mapping Taste-Relevant Food Peptidomes by Means of Sequential Window Acquisition of All Theoretical Fragment Ion-Mass Spectrometry

MS based foodomics: An edge tool integrated metabolomics and proteomics for food science

Foodomics has become a popular methodology in food science studies. Mass spectrometry (MS) based metabolomics and proteomics analysis played indispensable roles in foodomics research. So far, several methodologies have been developed to detect the metabolites and proteins in diets and consumers, including sample preparation, MS data acquisition, annotation and interpretation. Moreover, multiomics analysis integrated metabolomics and proteomics have received considerable attentions in the field of food safety and nutrition, because of more comprehensive and deeply. In this context, we intended to review the emerging strategies and their applications in MS-based foodomics, as well as future challenges and trends. The principle and application of multiomics were also discussed, such as the optimization of data acquisition, development of analysis algorithm and exploration of systems biology.

Physicochemical and Sensory Characterization of Whey Protein-Enriched Semihard Cheese

In view of potential future changes of German food legislation with regard to cheese product quality parameters, this study aimed to evaluate the quality of whey protein-enriched semihard cheese (WPEC). Model WPEC was produced in a pilot plant and on an industrial scale by adding defined amounts of high-heat (HH) milk to the cheese milk and comprehensively analyzed during cheese processing. The dry matter, total protein, pure protein, fat, and sodium chloride content of six-week ripened cheese samples were not significantly different (p < 0.05) when the technologically necessary heating of the curd was adapted to the amount of HH milk. However, the ripening, firmness, and melting behavior of WPEC was different compared to cheese without HH milk. During ripening, no formation of whey protein peptides was observed, but differences in the amount of some bitter peptides deriving from the casein fraction were found. Sensory data suggested a slightly more bitter taste perception by the panelists for the WPEC. Further technological adjustments are recommended to obtain marketable WPEC.

Identification and prediction of milk-derived bitter taste peptides based on peptidomics technology and machine learning method

Bitter taste peptides (BPs) are vital for drug and nutrition research, but large-scale screening of them is still time-consuming and costly. This study developed a complete workflow for screening BPs based on peptidomics technology and machine learning method. Using an expanded dataset and a new combination of BPs' characteristic factors, a novel classification prediction model (CPM-BP) based on the Light Gradient Boosting Machine algorithm was constructed with an accuracy of 90.3 % for predicting BPs. Among 724 significantly different peptides between spoiled and fresh UHT milk, 180 potential BPs were predicted using CPM-BP and eleven of them were previously reported. One known BP (FALPQYLK) and three predicted potential BPs (FALPQYL, FFVAPFPEVFGKE, EMPFPKYP) were verified by determination of calcium mobilization of HEK293T cells expressing human bitter taste receptor T2R4 (hT2R4). Three potential BPs could activate the hT2R4 and are demonstrated to be BPs, which proved the effectiveness of CPM-BP.

A comprehensive database of cheese-derived bitter peptides and correlation to their physical properties

Bitterness is a common flavor attribute of aged cheese associated with the peptide fraction, but excessive levels are a defect leading to consumer rejection. Bitterness in cheese has been primarily associated with peptides that arise from the breakdown of casein. The last review of bitter peptides was published in 1992. This updated review compiled information about the bitter peptides published up to 2022. Our comprehensive search of the literature compiled 226 peptides associated with bitterness and cheese protein origins into a database (Supplemental Materials). The influences of a peptide's physical properties, such as molecular weight, average hydrophobicity, peptide length, number of prolines and the presence of hydrophobic amino acids in the peptide's terminus, were assessed for correlation with bitterness threshold values this assessment found that, among variables considered, higher molecular weight had the strongest correlation with higher bitterness among known peptides. Heatmaps of bitter peptides and their bitterness threshold values highlight β-casein as the primary source of known bitter peptides in cheese. This comprehensive database of cheese protein-derived bitter peptides and this discovery of the correlation of a peptide's physical properties to bitterness will aid future researchers in the identification and discovery of contributors to cheese bitterness.

Isolation, identification and sensory evaluation of kokumi peptides from by-products of enzyme-modified butter

BACKGROUND

Enzyme-modified butter is used as a common raw material to obtain a natural milk flavor. Butter protein is a by-product in butter processing that can be used as substrate to produce taste-active peptides, which can create additional value and new application opportunities, making the method more environmentally friendly.

RESULTS

Putative kokumi peptides from hydrolysates of protein by-products were isolated by gel filtration chromatography and reversed-phase high-performance liquid chromatography. The isolated peptide fraction with the most pronounced kokumi taste was screened by sensory evaluation and electronic tongue analysis. Eleven peptides were identified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry. Six peptides were synthesized to verify their taste characteristics. Five synthetic peptides (FTKK, CKEVVRNANE, EELNVPG, VPNSAEER and YPVEPFTER) showed different intensity levels of kokumi taste. Of these peptides, the decapeptide CKEVVRNANE had the highest kokumi intensity.

CONCLUSION

The newly identified kokumi peptides increased the kokumi taste intensity and showed some synergistic effect with umami taste. Both termini of the peptides seem to play an important role in taste characteristic. Glu residue at both termini can increase the kokumi taste intensity. This work indicated that it was feasible to produce kokumi peptides by enzymatic hydrolysis of the protein by-products of butter. © 2022 Society of Chemical Industry.

Bitter Peptides YFYPEL, VAPFPEVF, and YQEPVLGPVRGPFPIIV, Released during Gastric Digestion of Casein, Stimulate Mechanisms of Gastric Acid Secretion via Bitter Taste Receptors TAS2R16 and TAS2R38

Eating satiating, protein-rich foods is one of the key aspects of modern diet, although a bitter off-taste often limits the application of some proteins and protein hydrolysates, especially in processed foods. Previous studies of our group demonstrated that bitter-tasting food constituents, such as caffeine, stimulate mechanisms of gastric acid secretion as a signal of gastric satiation and a key process of gastric protein digestion via activation of bitter taste receptors (TAS2Rs). Here, we tried to elucidate whether dietary non-bitter-tasting casein is intra-gastrically degraded into bitter peptides that stimulate mechanisms of gastric acid secretion in physiologically achievable concentrations. An in vitro model of gastric digestion was verified by casein-fed pigs, and the peptides resulting from gastric digestion were identified by liquid chromatography-time-of-flight-mass spectrometry. The bitterness of five selected casein-derived peptides was validated by sensory analyses and by an in vitro screening approach based on human gastric parietal cells (HGT-1). For three of these peptides (YFYPEL, VAPFPEVF, and YQEPVLGPVRGPFPIIV), an upregulation of gene expression of TAS2R16 and TAS2R38 was observed. The functional involvement of these TAS2Rs was verified by siRNA knock-down (kd) experiments in HGT-1 cells. This resulted in a reduction of the mean proton secretion promoted by the peptides by up to 86.3 ± 9.9% for TAS2R16kd (p < 0.0001) cells and by up to 62.8 ± 7.0% for TAS2R38kd (p < 0.0001) cells compared with mock-transfected cells.

Typical Umami Ligand-Induced Binding Interaction and Conformational Change of T1R1-VFT

Umami taste receptor type 1 member 1/3 (T1R1/T1R3) heterodimer has multiple ligand-binding sites, most of which are located in T1R1-Venus flytrap domain (T1R1-VFT). However, the critical binding process of T1R1-VFT/umami ligands remains largely unknown. Herein, T1R1-VFT was prepared with a sufficient amount and functional activity, and its binding characteristics with typical umami molecules (monosodium l-glutamate, disodium succinate, beefy meaty peptide, and inosine-5'-monophosphate) were explored via multispectroscopic techniques and molecular dynamics simulation. The results showed that, driven mainly by hydrogen bond, van der Waals forces, and electrostatic interactions, T1R1-VFT bound to umami compound at 1:1 (stoichiometric interaction) and formed T1R1-VFT/ligand complex (static fluorescence quenching) with a weak binding affinity (K_a values: 252 ± 19 to 1169 ± 112 M^-1). The binding process was spontaneous and exothermic (ΔG, -17.72 to -14.26 kJ mol^-1; ΔH, -23.86 to -12.11 kJ mol^-1) and induced conformational changes of T1R1-VFT, which was mainly reflected in slight unfolding of α-helix (Δα-helix < 0) and polypeptide chain backbone structure. Meanwhile, the binding of the four ligands stabilized the active conformation of the T1R1-VFT pocket. This work provides insight into the binding interaction between T1R1-VFT/umami ligands and improves understanding of how umami receptor recognizes specific ligand molecules.

An aqueous extract of the brown alga Eisenia bicyclis extends lifespan in a sex-specific manner by interfering with the Tor-FoxO axis

Food has a decisive influence on our health, to the extent where even lifespan can be directly affected by it. In the present work, we have examined the effects of an aqueous extract of the marine brown alga Eisenia bicyclis in terms of its potential to extend lifespan. For this purpose, we used the fruit fly Drosophila melanogaster as a model. The experiments showed that small amounts of Eisenia extract can extend lifespan by up to 40%. This effect is not only related to the median but also to the maximum lifespan. Interestingly, this life-extending effect is sex-specific, i.e. it occurs exclusively in females. Even under stressful nutritional conditions such as a high sugar diet, this effect is detectable. Mechanistic studies showed that this life-prolonging effect depends on a functional Tor and a functional FoxO signaling pathway. It can be concluded that components of the Eisenia extract prolong lifespan by interacting with the Tor-FoxO axis. This study may serve to stimulate further investigations, which on the one hand show such a life-prolonging effect also in other organisms and on the other hand identify the substances responsible for this effect. Finally, it may also encourage the increased use of arame as a health-promoting food supplement.

Application of Large-Scale Molecular Prediction for Creating the Preferred Precursor Ions List to Enhance the Identification of Ginsenosides from the Flower Buds of Panax ginseng

This work was designed to evaluate the coverage of data-dependent acquisition (DDA) extensively utilized in the untargeted metabolite/component identification in the food sciences and pharmaceutical analysis. Using saponins from the flower buds of Panax ginseng (PGF) as an example, precursor ions list (PIL)-including DDA on a Q-Orbitrap mass spectrometer could enable higher coverage than the other four MS² acquisition approaches in characterizing PGF ginsenosides. A "Virtual Library of Ginsenoside" containing 13,536 ginsenoside molecules was established by C-language-programmed large-scale molecular prediction, which in combination with mass defect filtering could create a new PIL involving 1859 PGF saponin precursors. We could newly obtain the MS² spectra of at least 17 components and characterize 36 ginsenosides with unknown masses, among the 164 compounds identified from PGF. Conclusively, a molecular-prediction-oriented PIL in DDA can assist to discover more potentially novel molecules benefiting to the development of functional foods and new drugs.

Identification and Quantitation of Taste-Active Compounds in Dried Scallops by Combined Application of the Sensomics and a Quantitative NMR Approach

Application of the sensomics concept on dried scallops, a Japanese specialty produced from the adductor muscle of scallops, revealed after activity-guided fractionation with subsequent (comparative) taste dilution analyses besides nucleotides, amino acids, organic acids, and inorganic ions, the presence of taste-modulating quaternary ammonium compounds and opines in highly taste-active fractions. In order to recreate the taste of dried scallops, two independent quantitation approaches were applied and compared. The first approach used multiple targeted UHPLC-MS/MS and high-performance ion chromatography methods. Besides already established quantitation methods for basic taste compounds, a new HILIC-UHPLC-MS/MS_MRM method for the quantitation of chromatographically challenging opines, using synthesized stable isotope-labeled standards, was developed. Furthermore, a qHNMR approach was applied, enabling a direct identification and quantitation of organic taste compounds in a food extract without prior fractionation using a reference ¹H NMR database. Both methods yielded similar quantitative results of taste-active compounds in dried scallop extracts and subsequent taste recombination experiments based on these data were able to recreate the taste of dried scallops.

Application of the UHPLC-DIA-HRMS Method for Determination of Cheese Peptides

Until now, cheese peptidomics approaches have been criticised for their lower throughput. Namely, analytical gradients that are most commonly used for mass spectrometric detection are usually over 60 or even 120 min. We developed a cheese peptide mapping method using nano ultra-high-performance chromatography data-independent acquisition high-resolution mass spectrometry (nanoUHPLC-DIA-HRMS) with a chromatographic gradient of 40 min. The 40 min gradient did not show any sign of compromise in milk protein coverage compared to 60 and 120 min methods, providing the next step towards achieving higher-throughput analysis. Top 150 most abundant peptides passing selection criteria across all samples were cross-referenced with work from other publications and a good correlation between the results was found. To achieve even faster sample turnaround enhanced DIA methods should be considered for future peptidomics applications.