1.j6 



THE POTATO. 



same circumstances. The results are contained in tlie following 

 table : 



In the particular circumstances under which this experiment was 

 made, therefore, it is obvious that the Rohan variety contained the 

 lartrest quantity of nutritive matter and starch. 



Potatoes which have been exposed to a temperature a few degrees 

 bolow the freezing point of water, undergo so great a change in their 

 texture, that it becomes dillicult afterwards to extract the starch 

 which they contain. Tliey besides acquire so disagreeable a flavor, 

 as all the world knows, that cattle sometimes refuse to eat them. 

 After having ascertained that a potato has the same chemical com- 

 position before and after congelation, M. Payen examined the starchy 

 siibstance under the microscope, and found that the starch obtained 

 from a frozen tuber presented itself in compound granular masses. 

 four or five times the size of the largest natural grains of starch. 

 'rii(3 pulp which remained upon the sieve in the preparation of thi.s 

 starch, was formed by a collection of cells, for the most part full of 

 starch. It would therefore appear, that in consequence of iho 

 changes of volume of the tluid successively congealed and liquefied 

 y\\v. adhesion between the cells was destroyed : they become separa- 

 l)lc with the slightest force, ant! merely part one from another by 

 ilie action of the grater without being torn ; the larger number re- 

 MKiin unbroken and still filled with starch. This fact enables us to 

 understand how potatoes, which have been frozen, will yield nearly 

 ihc whole of their starch if they be treated before they are thawed. 

 The cells then sealed up by the congealed water resist suflicienlly 

 to be broken by the teeth of the grater. Potatoes which have been 

 iVozen, are generally less farinaceous, at the same time that they have 

 a decidedly sweet taste, which, according to M. Payen, is owing to 

 vegetation having already made some progress in the tubers before 

 congelation ; and we know that durmg germination there is always 

 a formation of sugar at the expense of the fecula. Frosted potatoes 

 have always a disagreeable taste, and a most unpleasant smell, so 

 that in many places they are thrown upon the dunghill. The elfecl 

 of the frost, in fact, is to set the juices which are enclosed in the 

 tissue of the potato at liberty, and the higher temperature which ac- 

 companies Tiid tnllows a thaw, exposes those juices to he acted upon 



