FIRMNESS MEASUREMENT OF FRESHLY HARVESTED DELICIOUS APPLES BY SENSORYMETHODS, SONIC TRANSMISSION, MAGNESS-TAYLOR, AND COMPRESSION

A rapid nondestructive method for measuring apple texture using sonic vibrational characteristics of intact apples was tested on freshly har vested 'Delicious' apples from major U.S. production areas. Sonic tran smission spectra and Magness-Taylor (MT) firmness were measured on who le apples and compression measurements were made on excised tissue. Tw o experienced Agricultural Marketing Service apple inspectors assessed each apple and assigned a ripeness score according to U.S. Dept. of A griculture grades and standards inspection procedures (based primarily on texture). Sonic functions correlated significantly with ripeness s cores, MT firmness, and forces to rupture or crush the tissue in compr ession. Ripeness scores were more closely correlated with the destruct ive firmness measurements than with sonic functions. However, sonic me asurement has the advantage of being nondestructive, whereas MT and ti ssue compression are inherently destructive. Further research is neede d to modify the Instrumentation and Sensing Laboratory's sonic techniq ue to improve the prediction of apple firmness before it can be adapte d for on-line sorting.