Spatio-temporal monitoring of maturation, ripening, and fungal rot development in “Hass” avocados using quantitative magnetic resonance imaging

Abstract

Maturity, ripeness, and fungal rot are key quality attributes of avocados that interact to determine consumer acceptance, market value, and postharvest losses. We applied quantitative magnetic resonance imaging (MRI) techniques to simultaneously and non-invasively assess these three internal attributes. Healthy, fungal-inoculated, and naturally infected “Hass” avocados were ripened under controlled conditions and scanned with a 1.5 T whole-body system to generate transverse relaxation time (T₂) maps, lipid fraction maps, apparent micro-porosity maps, and vascular structure images. Linear regression between lipid fraction and dry matter content yielded a root mean squared error (RMSE) of 2.8 %, indicating that MRI can reliably assess fruit maturity. In contrast, neither T₂, apparent micro-porosity, nor lipid fraction values captured changes in mesocarp firmness during ripening. In infected tissue, T₂ initially increased and subsequently decreased, whereas apparent micro-porosity increased at later stages. Elevated T₂ values delineated lesion peripheries before visible pulp discoloration or histological damage occurred. Furthermore, serial MRI monitoring from unripe to overripe stages enabled tracking of fungal development within individual fruit, revealing distinct morphological patterns: stem-end rots advanced longitudinally along vascular bundles, whereas body rots spread radially through parenchyma. These findings demonstrate that MRI is a suitable tool for postharvest quality monitoring and for studying fruit–pathogen interactions in avocados and other fleshy fruit.