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31 Jul 2019
avocado ripeness inspection

Avocado Ripeness Inspection – Automatic X-ray Detection of Internal Damage

DETERMINE AVOCADO RIPENESS

Quality, price, and overall sales parameters for avocados and other fruits are related to their ripeness and damages that they may have suffered upon transport. Avocado is especially vulnerable to become overripe, a condition which may be difficult to distinguish from ripe fruits, and a condition which makes the fruit worthless.

Fig. 0 Two avocados that look identical from outside, but are at very different ripeness stages.

Low-energy X-ray scanning of e.g. avocado fruits can be accomplished with the fruit travelling past an X-ray scanner on a conveyor belt. A sorting mechanism based on the ripe condition and possible damages can be positioned immediately after the X-ray scanner. This sorting mechanism reacts on the basis of the real-time image processing and image quantification of the X-ray scanner.

AVOCADO X-RAY INSPECTION

Fig. 1 Low-energy X-ray image showing the avocado with obvious internal structural deterioration (the white areas and uneven structure).

The X-ray images unveil that the ripe fruits correlate with a void development around the inner core, at the early stages of the ripe. Later, an uneven internal structure with cracks seems to correlate with the further ripe of the fruit, and this can also be correlated to a softer feel of the ripe avocado.

AUTOMATIC DETECTION OF INTERNAL DAMAGE

A typical solution involves the scanning of the products being fed into the X-ray system on a conveyor belt. The speed of belt is typically about 12
m/min (limit is 27 m/min), and the inspection speed is around 1 avocado per second for each lane, or about 4 avocados per second at 12 m/min.

For fruits, the conveying method involves a special conveyor with side guides, and the sorting method is based on 4 output signals (on PLC to potential free relays for mounting of reject/sorting devices) for each lane, e.g.: Over-ripe, ripe, un-ripe, and not assessed (other damage, movement during imaging, other). Typical operation duty cycle is up to 24/7. Typical error conditions involves: rolling during imaging, dirt accumulation, wrong orientation, jamming of conveyor, bad conveyor adjustment.

QUALITY SELECTION BASED ON X-RAY INSPECTION

This study has unveiled that the internal structure of avocado can be traced to its stage of ripe, or damage state. This may have important applications, since the fruit quality can be difficult to evaluate on the exterior. Possible throughput may be 2-4 avocado per second, as a minimum. The inherent high contrast, high resolution, and high sensitivity, achieved by the low energy technology is fundamental for the application.

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