Decoding quality and metabolic shifts in truss tomato during ripening and cold storage for precision harvesting

Whole-truss harvesting is complicated by asynchronous ripening, which can decouple external maturity from internal quality. Truss tomato 'Qingfan No. 3' was evaluated at green (GS), turning (TS), mature (MS), and short-term cold storage stages (SS3 and SS6) by integrating harvest-related traits, internal quality, and sensory assessment. Ripening was characterized by softening, increased soluble solids content (SSC), sugars, lycopene, antioxidant capacity, and umami-related amino acids, together with decreased L-malic acid and titratable acidity. Cold storage further altered color and metabolism and increased weight loss and cracking. A non-color partial least-squares discriminant analysis (PLS-DA) model discriminated preharvest maturity, whereas an exploratory partial least-squares regression (PLSR) model linked firmness and SSC to a multivariate internal-quality score and defined an empirical MS harvest boundary (SSC ≥ 6.975 + 0.133 × firmness). These findings provide a preliminary cultivar-specific framework for maturity classification, harvest-readiness assessment, and precision harvesting of truss tomato.