PROBLEM TO BE SOLVED: To measure the hardness of vegetables to the like accurately and nondestructively for application to a site for breeding varieties of plants by a method wherein the hardness testing machine is constituted of a portable sealing gun and of a digital force gage.
SOLUTION: A simple hardness testing machine 1 which evaluates the hardness of vegetables, fruits and the like is constituted in such a way that a digital force gage 4 which comprises a pressure sensing shaft 8, a compressed distance pointer 9 and the like is attached to a gun shaft 3 at a portable and rechargeable sealing gun 2 which comprises a grip 5, a speed adjusting knob 6, a switch 7 and the like. A base frame 11 in which a sample base is installed is attached to a truck tube part 10 at the sealing gun 2, the force gage 4 is slidable with reference to the frame 11, and a compressed distance scale 13 is installed between them. Then, a sample which is placed on the sample base is compressed by a prescribed distance of about 3 mm in the case of, e.g. an onion, a gradation on the force gage 4 whose peak is held is read out, and the hardness of the sample is measured.