ศูนย์นวัตกรรมเทคโนโลยีหลังการเก็บเกี่ยว

Evaluating apple firmness sensors.

Pitts, M.; Cavalieri, R.; Drake, S.; Fellman, J.;

Tree Fruit Postharvest Journal Year: 1997 Vol: 8 Issue: 4 Pages: 13-22

1997

บทคัดย่อ

This study aimed to devise and conduct an objective evaluation that would allow the industry to compare the performance of proposed sensors in side-by-side comparisons of the Magness-Taylor Penetrometer Test (MTPT), using Washington State (USA) apples. Sensors were evaluated each spring during 1991-94. Three procedures were followed in every evaluation: many apples (approx equal to 3000) were tested to give a wide range of apple size and firmness; the firmness of each apple was measured by each sensor under evaluation, carefully following the inventors' instructions and ensuring that all measurements were taken on precisely the same location on every apple; the MTPT was performed on each apple using a standard 11 mm diameter tip mounted on an Instron force measurement system at a rate of 25 mm/min. Sensor performance was measured using 3 criteria: could the sensor estimate MTPT values to within 1 lb (0.45 kg) in the critical regions of 8-14 lb (3.6-6.4 kg)?; did the sensor bruise any apples?; co

uld the sensor be integrated into typical packing line systems? None of the 5 sensors tested met this criteria. None of the sensors were able to estimate the MTPT in the critical region. It is concluded that the critical assumptions made by the sensor designers were not valid for apple tissue: apple tissue elastic modulus is not constant; apple tissue elastic modulus is not the same for compressive and tensile stress; and the elastic modulus is not a good predictor of 'firmness' - only the elastic modulus at near destructive levels is related to human-perceived firmness. A computer based model of Delicious-type apples was developed which can help optimize the design of nondestructive apple firmness sensors.