Evolution of freshness indicators and rapid sensing technologies for seafood: toward a global platform for quality evaluation

Abstract Declines in the freshness of seafood lead to deterioration in quality and taste, highlighting the need for scientific and consistent freshness management throughout the entire supply chain. This review summarizes the theoretical background, indicators, measurement methods, and the rapidly emerging rapid-sensing technologies related to seafood freshness evaluation. Conventional freshness assessment methods can be categorized into sensory, physicochemical, and microbiological evaluations. Among these, the K-value—based on the compositional ratio of adenosine triphosphate degradation products—has been widely used as a scientific indicator that allows quantitative assessment of freshness. Although high-performance liquid chromatography-based K-value measurements offer high reproducibility, they are not suitable for rapid evaluation in distribution settings or at points of consumption. In contrast, recent developments include portable biosensors targeting adenosine triphosphate metabolites and volatile basic nitrogen, such as enzyme-based, antibody-based, and electronic-nose-type devices. Coupled with AI-driven analysis and multimodal approaches integrating multiple sensors, these technologies are enabling increasingly accurate freshness assessments. Considering the challenges of insufficient temperature control in international distribution and the subjectivity inherent in sensory evaluations, standardized rapid assessment methods based on scientific indicators will play a crucial role in ensuring quality and enhancing the value of seafood in global supply chains. In this review, we provide an overview of postmortem biochemical changes in seafood, the framework of chemical freshness indicators, recent advances in rapid-sensing technologies, and perspectives on freshness management in international distribution. Finally, we discuss the remaining challenges and future directions for research and practical implementation.