Non-invasive determination of surface features of banana during ripening
Ripening of dessert banana (Musa sap.) is associated with changes in colour (green to yellow starting from the cente), softening, and surface features. These have mostly been investigated using distinct technologies. Hence, here changes in surface features were examined with two novel, non-invasive techniques: a luster sensor and a 3D profilometer. The profiler measures the 3D surface characteristics of an area, rather than a single profile line, and corrects data for curvature of the fruit. The luster sensor detected an increase in glossiness from stage 3 (green) to stage F7a (ripe) of ca. 35%, followed by a decrease in glossiness from stage F7a to F7b (overripe). The profilometer provided visual and parametric roughness values (Ra) for ripening. Cavendish bananas showed an increase from 2.5 to 6.6 µm during ripening stage 3 (green) to stage 7b (overripe). Another roughness value, Rz, increased concomitantly from 13.1 µm at stage 3 (green) to 26.9 µm at stage F7b (overripe). The study showed that the centre of the fruit was the best region for surface imaging, because it was the most advanced ripening part of the banana fruit, easily curved, and the region of the fruit can be accessed when a carton was opened. This study shows that it is now possible to monitor the changes in surface glossiness and roughness during the ripening of Cavendish bananas using two novel non-invasive technologies. The compact luster sensor may become a component of a portable probe and manual control of packing units. Differences in the predicted green life can be used to prioritize containers for unloading in the discharge port or to implement quality-based warehouse management strategies. Containers that arrive at banana ripening rooms before their green life ends, can be re-routed, in addition to the present, colour-based ripening scale.
KeywordsBanana (Musa sap.) Glossiness Micro-morphology Non-invasive measurement Optical examination Ripening Roughness
We are grateful to Bananenreiferei Walter Pott GmbH Leverkusen, Germany for the fresh samples, to Mr. René Koch (Keyence Co.) for the use of the 3D profilometer (VR-3000), to Ingo Henze for the use of his banana image in Fig. 2a, Prof. M. Watt, Australia for revising the English and to Mrs M. Förster for the graphics of Fig. 2a and b.
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