Evaluation of Two Objective Methods and a Subjective Rating Scale for Measuring Tomato Fruit Firmness1

Abstract

Tomato fruit firmness is closely associated with its ripeness stage; as the fruit ripens it softens. Correct usage of the UC Fruit Firmness Tester requires that such variables as location of measurement on the fruit, removal of skin, and plunger (tip) diameter be specified. A negative and highly significant correlation (r = −0.75) exists between firmness measurements with the UC Firmness Tester (a destructive method) and the compression testing device (a nondestructive method). Values obtained by both methods were also highly correlated (r = 0.79, UC Firmness Tester; r = −0.81, compression testing device) with subjective evaluation scores based on finger feel. Two possible minimum firmness limits are suggested for tomato fruits at shipping point and at retail.