Smart-HAND: a simplified LED device for intact olives quality evaluation

The peculiar sensory and nutritional characteristics of olive fruits have led to a sharp boost of the demand for the main derivative products in traditional producing areas and elsewhere in the world. Several destructive, expensive, time-consuming and not sustainable techniques have been used to assess the degree of olives ripeness. To at least partially replace these types of analyses, Uceda and Frias (1975) proposed the Maturity Index (MI), a cheap and easy destructive technique for the visual determination of the best harvesting moment. This method, based on the color changes of skin and pulp, classifies 100 olives into eight groups or categories from intense green (category 0) to black with 100% purple flesh (category 7). Although it is the most used method, MI depends on the operator experience and it’s subjective and strongly affected by human error. Besides, color changes in olives are dramatically different among cultivars and during ripening process. The aim of this research was to design, build and test cost-effective and user-friendly devices able to optically predict the olive oil and moisture content in olive fruits in order to support small-scale growers in planning the optimal harvest date. A first version of a fully integrated, stand-alone LED prototype was built and now results patent-pending under the name of Smart-HAND (Smart Handheld Analyzer Non Destructive). The new device is composed by tuned photodiode arrays, interference filters, LEDs, optics and incorporates MEMS (Micro Electro-Mechanical Systems) sensors equipped with 6-channel digital sensors each one (AMS, models AS7262 visible and AS7263 NIR, Premstaetten, Austria-Europe) for spectral measurement in the visible (vis) and Short Wave Near-infrared (SW-NIR) region. The vis and SW-NIR sensors are 4.5 × 4.4 mm in size and are classified as ultra-low power consumption sensors, they have a 16-bit radiometric resolution and they cover 12 independent on-device optical filters from 450 to 860 nm. The six-channel vis sensor is sensitive to the 400 - 700 nm spectral range and is specific to get optical info at 450 nm, 500 nm, 550 nm, 570 nm, 600 nm, and 650 nm (interesting to get color information, a crucial feature to get indications regarding ripening progress). The full-width half-maximum of the sensors is 40 nm. The six-channel SW-NIR sensor is sensitive to the 600 - 900 nm spectral range and measures at 610 nm, 680 nm, 730 nm, 760 nm, 810 nm, and 860 nm. The full-width half-maximum of these sensors is 20 nm. Therefore, the vision on the application of this sensor can solve several problems in the field of olive growing. Firstly, it can objectify the evaluation of the quality of the olives in the field (to identify the ideal moment of harvesting) and before the milling process to define the correct price of the olives. Secondly, the logistics inside the mill is not easy to be managed. For instance, a preventive evaluation of the maturation parameters could avoid prolonged stop of olives bins in the receiving areas which causes the deterioration of the product. Finally, Smart-HAND could address to olives classification (in terms of qualitative attributes) which is useful for high added value olive oil productions.