Abstract
Background and Objective: Postharvest deterioration after ripening severely limits the marketability of 'Kluai Khai' banana (Musa acuminata, AA group). This study evaluated whether an indole-3-acetic acid (IAA)-containing, cell-free solution produced by Micrococcus yunnanensis P2-23 and temperature phasing (TP) could maintain postharvest quality.Methodology: A 4 × 2 factorial completely randomized design with three biological replicates combined with four nominal Salkowski-estimated IAA-equivalent concentrations (0, 250, 500, and 1,000 ppm) with non-TP and TP regimes. After a 3-min dip and storage at 12 ± 2°C for 14 days, fruit were ripened either continuously at 25°C or under TP (25, 22, 20, and 18°C on days 1–4, respectively, followed by 25°C). Visual quality, physicochemical characteristics, CO₂ production, and antioxidant-related attributes were evaluated through day 10.Main Results: All fruits were fully yellow by day 6, with no treatment differences in final total soluble solids. By day 10, TP-treated fruit had brighter peel, higher titratable acidity and firmness (118.0–132.7 versus 56.9–66.6 N), and lower weight loss (5.55–7.03 versus 8.28–9.13%) than non-TP fruit. The 1,000 ppm crude solution under TP maintained visual acceptability four days longer than the untreated non-TP control. TP also maintained higher late-stage ferric-reducing antioxidant power and total phenolic content, whereas non-TP fruit had higher DPPH activity. Respiration and crude-solution effects varied with time and concentration, with no consistent additional benefit or general synergy. HPLC-measured authentic IAA was 43.86% of the Salkowski estimate.Conclusions: TP most consistently slowed late-stage deterioration without disrupting ripening and is therefore the best-supported practical treatment for ‘Kluai Khai’ bananas. The crude bacterial solution provided no consistent additional benefit, and its effects cannot be assigned solely to IAA because authentic IAA was lower than the Salkowski estimate and other metabolites may have been present.