RESISTANCE TO WOUNDING OF CERTAIN FRUITS. 



DISCUSSION OF RESULTS. 



Table I shows that the average pressure required to puncture 

 berries that have been cooled is considerably more than that required 

 for warm berries. This is true not only for the freshly picked fruit 

 but also holds for the berries that were maintained at ice-box tem- 

 perature (about 16° C.) for 24 hours. 



Section A of Table I shows the average pressure in grams required 

 to puncture strawberries freshly picked and treated in various ways. 

 With the freshly picked fruit the pressures required (with a 636-micron 

 needle) are from 0.76 to 2.96 grams higher with the cooled berries 

 than with fruit from the same lots tested immediately at room tem- 

 perature. This is a marked increase in the resistance of the epidermis 

 to puncture. Washing in tap water without lowering the tempera- 

 ture did not apparently increase the resistance of the berries to punc- 

 ture, as is shown by the 14 determinations under that heading in the 

 table. Berries maintained in the ice box for 24 hours and then tested 

 as soon as they were removed and after they had been warmed to 

 room temperature gave results comparable to those obtained when 

 freshly picked berries were tested and then cooled for a few hours 

 and tested. again; that is, the pressure required to puncture the cold 

 fruit was greater than that required for the warm fruit. 



The results with black and red raspberries, shown in sections B 

 and C of Table I, were very similar to those obtained with straw- 

 berries. With black raspberries an average of 1.2 grams more pres- 

 sure was required, with a 121-micron needle, to puncture the cold 

 berries than those at room temperature. Only one variety of black 

 raspberries was tested. Two varieties of red raspberries were used, 

 the Ranere (St Regis) and an undetermined variety. The pressure 

 necessary to puncture the freshly picked Ranere berries was 1.55 

 grams less than that required for the same lot of fruit cooled in the 

 ice box. A 313-micron needle was used with this fruit. With the 

 undetermined variety the difference was 1.73 grams, or practically 

 the same as for the Ranere. Similar differences in the pressure 

 required for puncturing these berries were observed in berries of the 

 same lots cooled in the ice box for 24 hours and tested immediately 

 on removal and after warming to room temperature. It was notice- 

 able, however, that the pressures required to puncture the epidermis 

 after the 24-hour period in the ice box were not so high as with the 

 freshly picked fruit. It is possible that the storing of this fruit tends 

 to make the epidermis tender and more easily ruptured. 



Experiments- were carried out with four varieties of blackberries, 

 the Erie, Lawton, Wachusett, and one undetermined variety. The 

 results of the determinations were very similar to those obtained in 

 the work with the other berries. The average increase in pressure 

 necessary to puncture the freshly picked cooled fruit over that required 



