A portable, digital device for measuring tomato firmness

Mark A. Ritenour, Elizabeth M. Lamb, Peter J. Stoffella, Steven A. Sargent


Although fruit softness is used as an indicator of tomato (Lycopersicon esculentum) quality, no objective measurement of softness is included in the USDA quality standards. To aid the industry and tomato inspectors, a portable, low-cost digital firmness tester (IRREC tester) was developed to determine deformation. Comparisons of fruit deformation measurements were made between the IRREC tester using an 11-mm diameter probe with either a 9.8 or 4.9 N (1.0 or 0.5 kg) force, and a device developed in the Horticultural Sciences Department (IFAS tester) fitted with an analog meter using a 16-mm diameter probe and a 9.8 N (1.0 kg) force. 'FL 47' tomato fruit at mature-green, breaker ( 10% red) and ripe stages were harvested 1 day prior to the test and subjectively divided into five firmness classes (very firm, firm, medium firm, soft, and very soft). Eight to 20 fruit in each firmness class were tested with each device. The new IRREC tester was easier to read than the IFAS tester. However, fruit-to-fruit variability was often higher using the new device. There was no visible injury to tomato fruits following a single measurement, but repeated measurements with the 11-mm diameter probe and 9.8 N force on the same point resulted in some surface discoloration on the softest fruit after 3 days at room temperature. Both testers reliably measured increased deformation values with each progressively softer group of tomato fruit.


deformation; lycopersicon esculentum mill.; fruit quality; grade standards

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283