A PROBE IMPACT SENSOR FOR FRUIT FIRMNESS MEASUREMENT

A probe sensor was developed for measuring the impact characteristics of various fruits and predicting firmness. The sensor was operated by an air cylinder which released and returned an impact mass in the probe body. The acceleration of the mass was recorded. Algorithms were developed to analyze shape characteristics of the impact force (Vp=peak accelerometer output, tp=time to peak acceleration, and c2=Vp/tp2). Correlation coefficients between penetrometer firmness and Vp were 0.92, 0.80, and 0.55 for peaches, pears, and apples, respectively. Results for peaches and pears were slightly better than the previous system of a fruit striking a flat rigid surface. Local variations in firmness around the apple surface increased the variability in sensor response, resulting in low correlations with firmness measurements.