A new wireless device for real-time mechanical impact evaluation in a citrus packing line

Postharvest operations of fresh fruits in packing lines are potential cause of bruising and damage with remarkable consequences for fruit quality and marketability. Different types of impact recording devices (the so-called electronic fruits or pseudo fruits) have been developed in the last thirty years with the aim of measuring the magnitude of the impacts experienced by fruits during postharvest operations. The aim of this study was to develop and test a novel wireless instrumented sphere in order to study the critical points in a citrus packing line, real-time measuring the impacts suffered by fruits during processing. The non-commercial device was based on a MEMS (Micro Electro Mechanical System) sensor node with sensing range from ±1 g to ± 400 g (g = 9.8 m s-2), a Ferroelectric RAM (FRAM) memory, a Radio Frequency (RF) transmitter, a microcontroller, a 75 mAh lithium battery. The sensor node was positioned inside a plastic ellipsoidic case with a total weight of 100 g in order to represent the cv. Tardivo di Ciaculli mandarin. A FR receiver allowed the real-time transmission of the measured data. The tests were performed in the “Consorzio del Mandarino Tardivo di Ciaculli” packing line (Palermo, Italy). Total acceleration values, representing the stresses suffered by the fruit inside the packing line, were studied using a variance component model. The results showed that in most of the measurements, total acceleration remained below 20 g but between the brushing and the waxing machine, considerably higher values were obtained, up to 80 g. In particular, waxing was identified as the most critical operation based on the impact magnitude transmitted to the fruit. Our system proved to be effective for performing the online assessment of the accelerations experienced by the fruits, immediately visualizing them with the opportunity of promptly deciding where to intervene to guarantee fruits’ quality in postharvest operations.