Determination of Modified Atmosphere Critical Limits to Minimize Postharvest Decay and Quality Loss in Red Chili Pepper

Respiratory responses of individual chili pepper based on anatomical structures are remain poorly understood. Characterizing these responses is essential for determining the critical oxygen level (COL) and understanding tissue-specific O₂ limitations under modified atmospheres. This study quantified O₂ consumption and CO₂ production in intact fruits and individual anatomical structures using a gas analyser and integrated respiration modelling with X-ray computed tomography (CT) to characterize internal pathways for gas transport. Intact fruits and pericarp showed a rapid decrease in O₂ concentration, whereas seeds and pedicels exhibited slower O₂ declines without complete depletion. Michaelis–Menten modelling revealed anatomical structure- and maturity-dependent differences in COL. The COL of intact fruits decreased from 0.44% O₂ at the green stage to 0.12% at the orange stage and 0.08% at the red stage, whereas the pedicel showed substantially higher COL values (2.13–11.51% O₂) than the seed (0.17–1.80% O₂) and pericarp (0.02–0.07% O₂). X-ray CT revealed internal air spaces connected to the pedicel, providing structural evidence of a potential pathway for O₂ transport towards internal tissues. By integrating COL of individual anatomical structures with three-dimensional internal architecture, this study extends conventional intact chili respiration approaches and provides a physiological basis for defining modified-atmosphere conditions that minimize localized O₂ limitation in chili pepper.