First, i wonder whether persimmons(D.kaki L. f.) are cultivated in north America?

Several days ago,I picked a green persimmon,in the dorm,I cut it into two halves using a small knife so as to see inside.Nothing clear or special indeed,but several seconds later,I found that the "juices" on the knife turned into black-blue!!

We discussed this phenomenon on our BBS,and a guy in the chemistry department suggested that it may due to certain chemical reactions between tannin and ion,and neckle may be involved,too.

Interesting indeed,hope to see some further explainations or other similar interesting experiences.

Hui Gao(Tianjin,China)