882 



SCIENCE 



[N. S. Vol. XXXVI. No. 939 



The fruit of the date palm is hard, green 

 and highly astringent, the approximately 

 oval shape and the size varying in the dif- 

 ferent varieties, of vrhich there are many. 

 When ripe they may be dry or very soft 

 and syrupy, again according to the va- 

 riety. The soft dates when ripe can not be 

 transported unless they are dried and 

 packed, and it is in this condition that we 

 are familiar with this fruit. In order to 

 market the soft varieties so that they may 

 be consumed in the fresh condition, the 

 Arabs have practised for many centuries 

 the art of artificial ripening. This con- 

 sists in exposing the bunches of unripe 

 fruit to the vapors of vinegar, of which the 

 active agent appears to be the acetic acid, 

 judging from the experiments of Vinson, 

 of the Arizona Agricultural Experiment 

 Station. Among other changes which take 

 place during the artificially induced ripen- 

 ing period, the most obvious is the rapid 

 disappearance of astringency, so that the 

 quite inedible fruit of to-day is ready to 

 the palate on the morrow or at latest the 

 following day. Vinson further found that 

 there is a great variety of chemicals which 

 can produce the same resiilt; so various in 

 kind indeed are the chemicals that the 

 changes in the fruit can not be explained 

 as ordinary chemical reactions. Supra- 

 normal temperatures up to 70 degrees 

 Fahr. may also be used, but higher tem- 

 peratures kill the fruit, after which it is 

 impossible to render them non-astringent. 

 There is, however, a distinction to be drawn 

 at this point between the effects of certain 

 ripening agents and others. Thus, when 

 some chemical substances, such as acetic 

 acid, nitrous ether, etc., are used, the tan- 

 nin changes from being colorless to red, 

 indicating that it has been oxidized. Oxi- 

 dized tannin is tasteless, so that in such 

 case the non-astringency is readily ex- 

 plained. If heat or alcohol be used, the 



tannin remains colorless, and as such is 

 astringent, so that, if it can not be detected 

 by the tongue, this is the result of some 

 other condition than oxidation. Indeed 

 the evidence is well nigh conclusive that 

 during the ripening of the date the tannin 

 remains unchanged chemically, but that its 

 collophysical relations have been changed. 

 That it is still present may at once be dem- 

 onstrated by the use of suitable chemical 

 reagents — their suitability depending on 

 whether the reaction produces a color 

 change or not. Thvis the salts of iron and 

 other metals produce the corresponding 

 color changes ; alkaloids produce no change. 

 It has been pointed out before, however, 

 that the reaction of alkaloids and tannin 

 may be prevented by means of a protector 

 and this leads us to the conclusion that 

 non-astringency in the ripe date is due not 

 to the destruction of the tannin or to any 

 chemical change in it, but to the presence 

 of an efficient protector. Further evidence 

 for this will be given further on. 



The persimmon occurs wild as a single 

 recognized species in North America, and 

 the fruit is known in the south as the 

 " 'possum persimmon" for the reason that 

 the opossum fattens on it in the autumn. 

 In China and Japan there are numerous 

 ciiltural varieties, most of which resemble 

 a ripe tomato in size, shape and color. 

 Certain kinds lose their astringency before 

 they soften, and can be eaten as we eat 

 apples, biting into a firm flesh. Others 

 become edible only after becoming quite 

 soft and watery, so that a spoon becomes 

 an appropriate implement for managing 

 them. Still another kind, described as an 

 "astringent variety" is used as the source 

 of a fluid, called " kaki-no-shihu," obtained 

 by mashing up the fruits in water and al- 

 lowing the mash to ferment. The product 

 is used for waterproofing fishing lines and 

 nets, and for coating wrapping paper, 



