12 



FROZEN POTATOES. 



In a memoir laid some months ago before the Institute 

 of France, M. Payen, the celebrated chemist, made some 

 valuable observations upon the subject of frozen Potatoes, 

 which are usually considered useless, and are consequently 

 thrown away. As it appears from his investigations that 

 Potatoes are in no material degree injured by frost, but that 

 they are as nutritious after being frozen as before, and in 

 some respects more useful as food, I translate literally the 

 report made to the Institute by Messrs. Turpin and Dutrochet 

 upon a subject of such vast importance to mankind ; pre- 

 mising only that it is the starch of the Potatoe which gives 

 it its nutritive qualities. 



Frozen potatoes are usually, after being thawed, thrown 

 away as altogether unfit for food, even for cattle ; they are 

 found to have acquired an acrid taste, and the makers of 

 starch know by experience that they do not yield more than 

 3 or 4 per cent, of starch instead of 16 or 17 per cent, which 

 they furnish in their uninjured state. M. Payen endeavoured 

 to ascertain the cause of this difference. It might be 

 supposed that the effect of a thaw would be to alter the 

 amylaceous matter, in consequence of which it might become 

 soluble. But M. Payen satisfied himself, by exact and 

 positive experiments, that thawed potatoes and those in the 

 natural state each contain exactly the same proportion of 

 soluble and insoluble matter. This being so, there ought to 

 be as much starch in a potatoe after being frozen as before ; 

 and consequently M. Payen suspected that the loss of starch 

 experienced by the starch-maker in frozen potatoes was 

 owing to some mechanical obstacle which opposes the ex- 

 traction and separation of this substance. This idea was 

 confirmed by a microscopical examination of the tissue of 

 the potatoe, thawed and rasped down. We know that the 

 starch is contained in the cells or vesicles of parenchyma, of 

 which the potatoe is composed ; the rasp, by tearing open 

 the cells, sets the starch at liberty. It is obvious that if the 

 rasp produces such an effect, the cells must be fixed firmly in 

 the tissue ; otherwise they would be only torn asunder by 

 the teeth of the rasp, and the starch which they contain 

 could not get out of the cells. Now M. Payen discovered 

 that this actually happens when a potatoe is successively 



