Dynamic migration of free amino acids from garlic in light soy sauce and its impact on taste formation.

INTRODUCTION: Garlic-flavored light soy sauce is a representative composite seasoning whose taste formation depends not only on fermentation-derived components in light soy sauce but also on the time-dependent transfer of garlic-derived taste substances. However, evidence regarding the dynamic migration of non-volatile taste-active compounds-particularly free amino acids (FAAs)-and their roles in taste formation during soaking remains limited. This study aimed to elucidate the time-dependent migration of garlic-derived FAAs during soaking and their contribution to taste formation, and to assess a practical soaking endpoint.

METHODS: Samples at different soaking times were evaluated using electronic tongue analysis and targeted FAA quantification. The soaking procedure was used to establish a controlled experimental model rather than to represent an industrial standard protocol. Taste activity values (TAVs) and orthogonal partial least squares-discriminant analysis (OPLS-DA) with variable importance in projection (VIP) values were used to identify key taste-active and discriminating amino acids and to assess a practical soaking endpoint.

RESULTS: Electronic tongue analysis showed that sourness and bitterness gradually decreased, whereas sweetness and umami exhibited an overall increasing trend with soaking time; the 30- and 40-day samples exhibited highly similar global taste profiles, indicating stabilization of the taste profile. A total of 16 FAAs were detected: total FAAs reached a maximum at day 20, whereas glutamic acid accumulated continuously and reached its highest level at day 30. TAV analysis indicated multiple taste-active amino acids, with glutamic acid making the greatest contribution, and OPLS-DA (VIP values) likewise highlighted glutamic acid among the discriminating variables. These taste shifts were consistent with the time-dependent migration and accumulation of garlic-derived taste-active FAAs, particularly glutamic acid.

CONCLUSION: Under the tested conditions, glutamic acid is the key driver of umami enhancement and taste stabilization in the garlic-light soy sauce soaking system. A soaking period of approximately 30 days can be considered a practical soaking endpoint to achieve a relatively stable and reproducible taste profile, supporting process optimization and standardization of garlic-flavored light soy sauce.