was something very similar to DPA, but not DPA itself. 

 This does not mean that apples and pears do not contain 

 natural DPA. If only half of the derivatized material in 

 the Delicious extract was DPA, it could produce the ion 

 ratio that was obtained. Therefore, our results leave 

 imanswered the question, "Is DPA a natural compound 

 in apples?" Clearly, something very similar to DPA is 

 produced, and possibly some of what we were measur- 

 ing was DPA. 



There is an important ramification of this study. 

 Clearly, DPA or DPA-like compounds are being mea- 

 sured on fruit that have not been treated with this 

 chemical. It is present at harvest and accumulates 

 during storage, since our fruit out of storage showed 10- 

 times the concentrations of the fruit picked directly off 

 the tree. 



DPA is a somewhat volatile compound, and the 

 abundant residues we measured on the walls of our 

 storage rooms show that there is likelihood of contami- 

 nation of untreated fruit with DPA from the atmosphere 

 in the storage or possibly from contact with bins and 

 other equipment. Large quantities of DPA are used in 

 industry as an antioxidant/stabilizer. For example, 

 rubber products commonly contain DPA. Thus, fruit 

 may absorb some DPA directly or indirectly from 



industrial products. If a test of fruit indicates the 

 presence of DPA, its source could be any or all of the 

 following: 



1 . DPA application. 



2. Contamination from residues in fruit storages, 

 containers, or equipment. 



3. Contamination from industrial use of DPA. 



4. A natural product in apples that while not being 

 DPA, is being measured as DPA. 



5. Possibly, natural-product DPA in the fruit. 

 Therefore, measurement of "DPA" in fruit is not proof 

 that fruit were treated with DPA. There apparently is no 

 such thing as "zero DPA" in apples. Conclusions must 

 be based on the quantity ofDPA present in the fruit, not 

 on its absolute presence. 



In conclusion, we have not resolved the question of 

 whether or not DPA is a natural product in apples and 

 pears. Small quantities of something very similar to 

 DPA, and possibly of DPA itself, is/are naturally occur- 

 ring, but remain to be identified. However, we have 

 shown clearly that conclusions drawn from DPA resi- 

 due analyses must be based on quanfities measured, not 

 on its presence in the fruit. An analysis showing the 

 presence of DPA in fruit is not positive evidence of 

 DPA application to the fruit. 



•X» *^ •X* *J>* *-£-• 

 ry% •^ rp» #Y* •T* 



14 



Fruit Notes, Fall, 1994 



