J. Ortiz-Cañavate

Development and implementation of an on-line impact sensor for firmness sensing of fruits

A prototype impact system for firmness sorting of fruits (TOUCHLINE), developed initially by Chen and Ruiz-Altisent (Paper presented at AgEng 96, Madrid, Paper no. 96F-003), has been modified and installed in an experimental fruit packing line. The system consists of a lateral impact sensor with a control electronic circuit, a control software and an ejection system with three outlets regulated by a microcontroller. The lateral impact sensor detects the presence of fruit by means of an optical sensor and impacts it. Impact signal is obtained by an accelerometer and sent to a PC where it is processed by specific software to yield a firmness index. According to this index the software gives an order to the microcontroller of the ejection system and fruit is sent to its corresponding outlet. Several tests were carried out with spherical balls of cork, tennis and rubber, showing a good performance of the sorting system.

Evaluation and correction of the mechanical aggressiveness of commercial sizers used in stone fruit packing lines

Abstract Three different types of sizers (two electronic cup sizers, one electronic finger sizer and one mechanical roller sizer) were analysed using an instrumented sphere IS 100 (62 mm ∅) in three cooperatives in the region of Valencia (Spain), handling peaches and apricots. In all three sizers the outlet transfer point “sizer-receiving belt” was responsible for the highest mean impact values: 31 g for the roller sizer, 60 g for the finger sizer, and 74 and 207 g for cup sizers. Several solutions (powered brush and elimination of structural elements under the receiving belt) were analysed to reduce such impacts to safe levels.

Instrumentation and procedures for commercial non-destructive determination of firmness of various fruits

A high interest in non-destructive instrumentation for firmness sensing of fruits is developing, and commercial laboratory and on-line equipment is already available. Many fruit handling lines offer NIR (plus VIS) systems, claiming that they can estimate firmness, in addition to chemical quality of fruits, as soluble solids. Optical firmness sensing is difficult or not feasible for many fruits, so that mechanical firmness devices are rapidly increasing presence in the market. Mechanical firmness devices, which can be used on-line, as well as table-top in laboratory, are based on either of two principles: deformation by contact or vibration response to contact. Contact is of the fast type, being an impact with low energy, with a duration of a few miliseconds. The vibration response spectrum is analized after transformation into frequency-domain, and characteristic frequency is determined. In both techniques, deformation of fruit is encountered, being this related to structure of fruit flesh, and therefore to firmness. Furthermore, both procedures can be (and are) combined in the same system. A review of the existing commercial equipment is made. Selected results on different fruits, which show experimental comparisons of different non-destructive with respect to destructive instruments are presented, showing the feasibility and better repeatability for non-destructive procedures. The need for standardising non-destructive firmness measurement of fruits is discussed.

Decelerator elements for ramp transfer points in fruit packing lines

Abstract Two different decelerator elements used to reduce impacts on fruits on ramp transfer points in fruit packing lines were designed and tested. The performance of these elements, a powered decelerator and a multiple curtain, was compared to commercial decelerators (blankets). A ramp of length 60 cm was placed at an angle of 30° in an experimental fruit packing line between a roller transporter and a conveyor. The decelerators were placed on top of the ramp. Different tests were carried out to study the performance of the decelerators using instrumented spheres (IS 100) of various sizes. Results showed that decelerators can reduce the impact intensity down to safe thresholds. The powered decelerator was the most effective because it reduced the speed of fruits and did not cause retention of the fruit, when correctly regulated.

Evaluation of a Non-Destructive Impact Sensor to Determine On-Line Fruit Firmness

A non-destructive impact sensor to measure on-line fruit firmness was evaluated. This sensor is an adaptation of a static model used in the laboratory to measure fruit quality and was installed in an experimental fruit packing line with a commercial sizer chain. The firmness index is related to the acceleration-time curve supplied by an accelerometer attached to an impacting arm. The main objective of this study was to evaluate sensor performance and sources of variation. We made classification trials on three fruits: peaches ( Prunus persica (L.) Batsch), apples (Malus domestica Borkh.), and pears (Pyrus communis L.), as well as working trials, such as placing the fruit, orientation, and others. The sensor works correctly at a speed of 7 fruits s -1 (0.63 m s -1 ) and allows fruit classification at three levels of firmness using specific software . Good discrimination was obtained only for soft peaches. There were variations in results between different fruits and different parts of the same fruit mainly due to the non-uniformity of fruit shape and lack of ripeness homogeneity of each one.