Protein, Peptide, and Amino Acid
Proteins, peptides, and amino acids share interconnectedness in their chemical structure and biological function. Here are some important considerations:
Proteins are intricate, large molecules composed of lengthy chains of amino acids. The specific sequence of amino acids within a protein determines its three-dimensional structure and its biological role.
Peptides are smaller than proteins, typically comprising 2 to 50 amino acids. Peptides often possess less well-defined structures compared to proteins, which can adopt complex conformations known as secondary, tertiary, and quaternary structures.
Amino acids serve as the foundational building blocks of proteins and peptides. With 20 different types available, amino acids can be combined in various ways to generate diverse proteins and peptides. The arrangement of amino acids and the order in which they are linked by peptide bonds in a peptide or protein is referred to as the primary structure.
Proteins and peptides play crucial roles within cells, fulfilling essential biological functions. For instance, proteins contribute to cellular shape and respond to signals from the extracellular environment. Certain peptides are involved in regulating the activities of other molecules.
Peptide, Amino Acid, and Umami
The enhancement of taste is associated with increased levels of free amino acids and peptides in meat. Peptides can influence the perception of umami taste. A umami peptide, Lys-Gly-Asp-Glu-Glu-Ser-Leu-Ala, consists of eight amino acids and is known to be found in beef hydrolysate.
Peptides exhibit greater stability compared to individual amino acids and play a significant role in taste perception. Bitterness and umami are the primary taste qualities often associated with peptides. While individual amino acids have a tendency to form aromatic compounds through thermal and microbiological processes, peptides maintain their stability and make a substantial contribution to taste.
Other functionalities of Peptide
The role of peptides is rather complex, and they are known for the ability to interact with certain taste receptors, such as those for bitterness, effectively reducing the perception of bitterness in food. A dipeptide (a peptide consisting of two amino acids,) Trp-Trp, was found to inhibit certain human bitter taste receptors (hTAS2Rs) and may be used as a bitterness-masking agent.
Peptides also have the ability to modify the rheological properties of food systems, thereby improving the overall texture. For instance, peptides can increase the viscosity of food systems, leading to an enhanced mouthfeel when consumed.
Another role peptides play is in improving the emulsification properties of food. Emulsification involves the blending of two immiscible liquids, such as oil and water, to create a stable emulsion. Peptides act as emulsifiers by reducing the surface tension between these liquids, thereby contributing to the stability of the emulsion.
Peptides also contribute to enhancing the water-holding capacity of food. Water-holding capacity refers to a food’s ability to retain moisture during processing and storage. Peptides achieve this by forming complexes with water molecules, which aids in preventing water loss and maintaining the desired moisture content in the food product.
All above functionalities affect the perception of tastes including umami; while amino acids are primarily concerned when we discuss umami and other tastes in food, peptides, small compounds of amino acids, also contribute to and affect the food tastes.
Reference
Ojiro, I., Nishio, H., Yamazaki-Ito, T., Nakano, S., Ito, S., Toyohara, Y., … & Ito, K. (2021). Trp-Trp acts as a multifunctional blocker for human bitter taste receptors, hTAS2R14, hTAS2R16, hTAS2R43, and hTAS2R46. Bioscience, Biotechnology, and Biochemistry, 85(6), 1526–1529.
Temussi, P. A. (2012). The good taste of peptides. Journal of Peptide Science, 18(2), 73–82.
Zhang, Y., Venkitasamy, C., Pan, Z., Liu, W., & Zhao, L. (2017). Novel umami ingredients: Umami peptides and their taste. Journal of food science, 82(1), 16–23.
