Figure 1.- -"Mechanical thumb" fruit firmness tester. 



BN-18679 



down inside the sleeve or extend out to nearly the depth that the 

 plunger depresses the fruit tissue. It is critical that the head be uni- 

 form and that the instrument is set so that the plunger will depress 

 the fruit tissue to a uniform depth, in the case of apples 0.055 inch. 1 



2. The calibration adjusting screws should allow for at least .045-inch 

 sleeve movement. 



3. Exact specifications for the flashlight are not critical. All that is re- 

 quired is an indicator light which will go on when electrical contact 

 is made in the "thumb" accessory. 



Directions for use : 



To give accurate readings, the tester must be used carefully. It must be 

 held at a right angle to the surface of the product; otherwise erroneous read- 

 ings will be obtained. The product, such as an apple, may be held in one hand 



l Schomer, H. A., and Olsen, K. L. A Mechanical Thumb for Determining Firmness of Apples. ASHS, Vol. 81, 

 pp. 61-66, 1962. 



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