Kokumi substances as taste modulators: Sensory properties and molecular mechanisms

Oral perception during food and beverage consumption results from the integration of multiple sensory processes and is inherently complex. Current knowledge of oral perception is primarily derived from studies of stimuli and compounds that evoke specific sensory modalities, including taste, mouthfeel-related somatosensory sensations, and chemesthesis. Difficulties are associated with defining and characterising each sensation because they involve multiple chemosensory systems. This review focuses on kokumi substances, taste modulators that have been increasingly examined in recent years, and oral perception, which is now globally called kokumi, and is modulated by kokumi substances. Here, we review the concept of kokumi and studies on the functionality of kokumi substances, their chemical diversity, and the molecular mechanisms of their action. We mainly investigated oral perception modified by kokumi substances using γ-glutamyl kokumi peptides, which are well-known kokumi substances, and the molecular mechanisms of action mediated by the activation of the calcium-sensing receptor (CaSR), a receptor for kokumi substances. Previous findings on kokumi substances other than γ-glutamyl peptides and other receptors that may be involved in this perception are also summarised. A more detailed scientific understanding of kokumi substances may contribute to improvements in food palatability and the development of foods with less salt, sugar, and fat, providing health benefits. This may also lead to the design of new foods that contribute to sustainability. Systematic investigations of kokumi substances, their perception, and their molecular mechanisms of action will drive future research directions and investigations.