Ripening of avocado fruits studied by spectroscopic techniques. Issue 8 (5th June 2020) - Lin, Xiaobo
Abstract: Avocados are considered very healthy due to the high content mono‐unsaturated lipid, essential vitamins and minerals, minimal sugar and no cholesterol and are therefore sometimes referred to as "the perfect fruits". Avocados, mainly grown in Latin‐America, are harvested unripe and sent overseas. However, the ripening process is very difficult to assess visually and tactilely. A tool for precise noninvasive judgment of the status would be valuable as the fruit is too expensive to be cut open unripe or overdue. A white‐light source and a light‐emitting diode unit with four excitation wavelengths (365, 385, 395, and 405 nm) were used for reflectance and fluorescence spectroscopy in a fiber‐coupled set‐up for noninvasive monitoring. Twelve non‐ripe avocados, with approximately the same size and appearance, were studied and divided into three groups and kept at three different storage conditions; at room temperature, in a refrigerator and a combination of the two. We showed that fluorescence was useful for following the ripening process. A method, which compensates for the spatial variations in spectral properties around a fruit, is described. Remote fluorescence monitoring, intended for orchard use, was also demonstrated. A low‐cost device based on fluorescence for avocado ripeness assessment is proposed. Abstract : Avocados are fruits with extremely favorable properties for human health. Judging when they are ripe remains a challenge for consumers. Using biophotonics methods, a detailed spectroscopic study of the ripening process was performed, and useful parameters were found for monitoring the status of the fruits. A method to compensate for surface non‐uniformities was demonstrated, and a compact device for fruit assessment is proposed.