THE IRRIGATION AGE. 



179 



AS AN ARTICLE OF FOOD. 



The subject deserves notice. Standing alone in the 

 vegetable world as containing the starch element in 

 common with cereals, has placed it beside wheat as one 

 of the standard articles of diet. In all probability the 

 potato will never be adulterated, its nature being such 

 that no process of manufacture is required to prepare 

 it for food. In its purity there can be nothing more 

 healthful. The various methods of cooking them rec- 

 ommend the valuable product to more extended use. 



L. A. ASPINWALL 

 President Aspinwal! Mfg, Co., Jackson, Mich. 



The element of value contained in the potato is stiiivh. 

 Although from 70 to 80 per cent of the potato is water, 

 there is about 18 per cent of starch. The elements be- 

 ing variable in different varieties of potatoes, the fol- 

 lowing table from Encyclopedia Americana may be con- 

 sidered a fair approximate: 



Water 78 



Starch 18 



Protein 2.2 



Ash ! 1 



Fat . 0.1 



99.3 



Starch being a carbohydrate, naturally includes a 

 trace of sugar (which is more abundant as they becpjne 

 soft in the late spring), also a fraction per cent of fiber, 

 which with a little undetermined matter go to make 

 the 100 per cent. The starch is contained in small cells, 

 and with the protein (albuminous matter), through the 

 action of heat when boiling the tubers, unite with the 

 water contained therein. These, including the water, 

 constitute the food elements of the potato. Unlike the 

 starch in rice, which unites with the water it is boiled 

 in, the starch of the potato unites with the water con- 

 tained in the tuber, thus bringing about a similar re- 

 sult in each. 



Figure 1 represents a transverse section of a po- 

 tato. The inner portion or medullary layer contains 

 the faintly visible channels through which the sap 



flows, and are more prominent at the stem end or source 

 of supply. These channels are variable in shape through- 

 out the potato, and are visible where, the cells which 

 contain the starch grains are apparently lengthened 

 by the flow of sap. This layer is rich in starch except 

 at the center. Surrounding this is the cortical layer 

 which is also rich in starch. It also contains rather 

 more fiber. 



Figure 1. 



The thin external layer just underneath the skin 

 contains the least starch. By reference to Figure 2, 

 which represents the starch cells magnified about 100 

 diameters, we will notice they are flattened or imper- 

 fectly developed near the skin, and contain comparatively 

 smaller grain of starch. As we penetrate the 'cortical 

 layer larger cells are found which abound with corres- 

 pondingly larger grains of starch, as shown at the cen- 

 ter of the figure. It is interesting to note that the 

 cells are mostly hexagon or pentagon in shape, although 

 many are found which are four-sided. These layers are 

 formed upon each other like a well-built wall, which 

 they also resemble. The cells are composed of fiber 

 and are alike found in all vegetables, although devoid 

 of starch. Just how the liquid flowing between these 

 cells percolates between the walls, or by a process of 

 osmose produces the starch grains within them I am 

 unable to explain. 



Figure 3 represents the starch grains magnified 

 about 400 diameters. In appearance they are much 

 like potatoes, both as to shape and variation in size. 



Figure 2. 



The outer layer or skin is exceedingly glossy and beau- 

 tiful when viewed by the aid of a microscope. 



The future of the potato must be exceedingly great 

 if we take into consideration the possibilities of increas- 

 ing the product by a further introduction of improved 



