Re: what chemical reaction occurs when persimmon is mixed w/baking soda

Aloha, Celeste,

     I'm sorry to have taken so long in answering your interesting question 
about persimmons and baking soda.  I had asked a colleague of mine over a 
week ago to help me with the answer, since I am a nutritionist, not a food 
scientist.  I finally got a response from him today.
     According to Dr. Alvin Huang, a food scientist on our faculty here at 
the University of Hawaii at Manoa, persimmons are high in a particular 
soluble dietary fiber called pectin...the same stuff you might have added 
to fruit juice to make it gel when you were making jelly (actually it 
probably was extracted from apples, since they are also high in pectins).  
Anyway, the pectin reacts with the calcium salts found in baking powder 
(double-acting baking powder is a mixture of calcium acid phosphate, baking 
soda...sodium bicarbonate...and sodium aluminum sulfate) and a gel is 
produced.
     You might try an experiment.  Take some apple juice (high in pectin) 
and add some baking soda...let it stand for awhile.  I'll bet that it gels 
up, also.  I fancy myself a pretty good cook, but have never run into this 
problem, although I use persimmons during the holidays in my baking, too.