Real-Time IoT Gaseous and Gravimetric Profiling Links Postharvest Respiratory Dynamics to Flavor Development in Vanilla planifolia

Abstract

The postharvest curing of Vanilla planifolia is a critical flavor-generating process, yet its real-time physiological and biochemical dynamics remain poorly characterized due to reliance on destructive sampling methods. To address this gap, we developed a novel dual-stage IoT multisensor framework integrating open-air gravimetric monitoring and hermetic gas profiling to continuously track the 34-day curing process non-destructively. High-frequency sensor data encompassing CO₂, O₂, ethylene, and total volatile organic compounds (TVOC) via metal oxide semiconductor cross-sensitivity were correlated with moisture loss and phenolic accumulation quantified by HPLC. Physical analysis of 50 individually tracked beans revealed a highly significant mean mass reduction of 73.58 ± 6.11% (t(49) = 33.89, p < 0.001). Controlled moisture retention (final mass ≥ 3.0 g) yielded the highest vanillin concentration (2.91 ± 0.15% w/dw), significantly exceeding over-dried beans (one-way ANOVA; F(3,8) = 6.45, p = 0.016, η² = 0.71), confirming a direct moisture–enzyme activity dependency. Gaseous profiling delineated three distinct curing phases: an acute stress-induced respiratory burst (CO₂ peak, 4322 ppm; O₂ nadir, 20.42%), a progressive metabolic decline, and a terminal biochemical equilibrium. Furthermore, a highly synchronized ethylene-TVOC correlation (r = 0.92) emerged as a robust real-time indicator of programmed cellular senescence and concurrent volatile precursor release. These results establish IoT-based multisensor monitoring as a scalable, precision tool for optimizing biochemical maturation, ensuring batch consistency, and elevating the commercial value of natural vanilla production.