Dual regulation of raw Pu-erh tea aging by storage time and water activity: Evidence from a controlled storage study

Storage is regarded as a continuation of raw Pu-erh tea (RPT) processing, improving sensory quality and market value. However, studies based on naturally aged teas from different batches confound storage effects with variation in raw materials, processing, and storage history. Here, the same RPT batch was stored for three years at controlled temperature and water activity (Aw) levels of 0.53, 0.61, and 0.71. Storage time defined the aging trajectory of 122 annotated non-volatile metabolites (NVMs), characterized by puerin, amino acid derivative, and lipid accumulation, together with catechin and catechin oligomer depletion. Higher Aw accelerated the aging trajectories of 73 NVMs. Fungal communities became increasingly dominated by Cladosporium, Setophoma, and Papiliotrema with storage time and increasing Aw. Papiliotrema flavescens RPT (PF-RPT) inoculation under natural storage conditions accelerated L-theanine depletion and puerin accumulation, supporting a partial microbial basis for Aw-accelerated RPT aging and its potential for improving aging efficiency and process controllability.