Development of Enzymatic Synthesis of γ-Glutamylcarnosine and Its Effects on Taste

Flavor and structure characteristics of egg white peptides based on γ-glutamylation modification: A promising flavor enhancement strategy

The widespread use of egg white peptides (EWP) in healthy foods is limited by undesirable flavors. In this study, transglutaminase (TG) was used to catalyze the γ-glutamylation reaction between glutamine (Gln) and EWP, modifying the structure and flavor of EWP. The interaction of Gln and EWP altered the primary structure and spatial conformation of EWP, thus increasing the solubility. γ-glutamylation reduced the bitterness and increased umami of EWP by consuming hydrophobic bitter amino acids and generating umami peptides. Twenty-one synthesized γ-glutamyl peptides were identified in G-EWP after γ-glutamylation, which could enhance the sweetness, saltiness, umami, and kokumi taste of basic substances. All of these peptides could enter the Venus flytrap (VFT) of calcium-sensing receptor (CaSR), which might be the mechanism of G-EWP with enhanced kokumi taste. Overall, this research provided the theoretical basis for flavor improvement of EWP.

Noteworthy Consensus Effects of D/E Residues in Umami Peptides Used for Designing the Novel Umami Peptides

Aspartic acid (D) and glutamic acid (E) play vital roles in the umami peptides. To understand their exact mechanism of action, umami peptides were collected and cut into 1/2/3/4 fragments. Connecting D/E to the N/C-termini of the fragments formed D/E consensus effect groups (DEEGs), and all fragments containing DEEG were summarized according to the ratio and ranking obtained in the above four situations. The interaction patterns between peptides in DEEG and T1R1/T1R3-VFD were compared by statistical analysis and molecular docking, and the most conservative contacts were found to be HdB_277_ARG and HdB_148_SER. The molecular docking score of the effector peptides significantly dropped compared to that of their original peptides (-1.076 ± 0.658 kcal/mol, p value < 0.05). Six types of consensus fingerprints were set according to the Top7 contacts. The exponential of relative umami was linearly correlated with ΔGbind (R2 = 0.961). Under the D/E consensus effect, the electrostatic effect of the umami peptide was improved, and the energy gap between the highest occupied molecular orbital-the least unoccupied molecular orbital (HOMO-LUMO) was decreased. The shortest path map showed that the peptides had similar T1R1-T1R3 recognition pathways. This study helps to reveal umami perception rules and provides support for the efficient screening of umami peptides based on the material richness in D/E sequences.

Protein Hydrolysates from Pleurotus geesteranus Modified by Bacillus amyloliquefaciens γ-Glutamyl Transpeptidase Exhibit a Remarkable Taste-Enhancing Effect

Long-term high salt intake exerts a negative impact on human health. The excessive use of sodium substitutes in the food industry can lead to decreased sensory quality of food. γ-Glutamyl peptides with pronounced taste-enhancing effects can offer an alternative approach to salt reduction. However, the content and yield of γ-glutamyl peptides in natural foods are relatively low. Enzyme-catalyzed synthesis of γ-glutamyl peptides provides a feasible solution. In this study, Pleurotus geesteranus was hydrolyzed by Flavourzyme to generate protein hydrolysates. Subsequently, they were modified by Bacillus amyloliquefaciens γ-glutamyl transpeptidase to generate γ-glutamyl peptides. The reaction conditions were optimized and their taste-enhancing effects were evaluated. Their peptide sequences were identified by parallel reaction monitoring with liquid chromatography-tandem mass spectrometry and analyzed using molecular docking. The optimal conditions for generation of γ-glutamyl peptides were a pH of 10.0, an enzyme condition of 1.2 U/g, and a reaction time of 2 h, which can elicit a strong kokumi taste. Notably, it exhibited a remarkable taste-enhancing effect for umami intensity (76.07%) and saltiness intensity (1.23-fold). Several novel γ-glutamyl peptide sequences were found by liquid chromatography-tandem mass spectrometry, whereas the binding to the calcium-sensing receptor was confirmed by molecular docking analysis. Overall, γ-glutamyl peptides from P. geesteranus could significantly enhance the umami and salt tastes, which can serve as promising taste enhancers.