The growing production volume of the meat industry has increased the need for revalorization of meat by-products to reduce economic and environmental impacts. Enzymatic hydrolysis of protein-rich meat by-products is an effective strategy for producing hydrolyzates with bioactive potential. Combining sequential enzymatic hydrolysis with γ-glutamyl transpeptidase activity can promote the formation of γ-glutamyl peptides associated with koku perception, a sensory attribute that increases taste intensity, continuity, and palatability. This study aimed to develop porcine liver hydrolyzates enriched in koku-related peptides through enzymatic hydrolysis followed by post-treatment with the transpeptidase Protana Uboost. Substrate specificity assays showed that a 0.2 U/mL enzyme concentration maximized γ-glutamyl dipeptide formation. Sequential hydrolysis using Alcalase and Protana Prime followed by Protana Uboost post-treatment generated the highest levels of koku-related peptides. Moreover, post-treatment significantly enhanced antioxidant capacity in the resulting hydrolyzates, supporting their potential as a functional ingredient.

Taste strongly influences food acceptance and purchase intention. Beyond the five basic tastes, oral sensations such as astringency or koku modulate overall taste perception. Both umami and koku act as taste enhancers, increasing mouthfeel and savoriness. While the taste of most proteogenic amino acids is well established, non-proteogenic amino acids and related protein derivatives remain insufficiently characterized. This study analyzes the taste profile of seventeen underexplored amino acids and protein derivatives using the PredMol in silico tool and quantitative descriptive analysis (QDA), with particular emphasis on their umami and koku potential. In silico evaluation identified bitterness and sweetness as the predominant tastes and predicted carnosine, theanine, citrulline, and ornithine to have koku potential with values higher than 0.44. Principal Component Analysis of the QDA revealed that sweetness, bitterness, and sourness were the main drivers of sample differentiation. Ornithine, glutamine, citrulline, pyroglutamic acid, and theanine exhibited a positive dose–response in umami perception, with potential synergistic effects observed in the presence of 0.5 mmol/L IMP. Additionally, theanine, citrulline, and ornithine enhanced koku-related attributes, particularly aftertaste and continuity, in aqueous model solutions. Overall, these findings suggest that these compounds can have a taste influence in food products and potential to be used as taste enhancers.