Fig. 40.—Potato Starch under Polarized Light (× 200).—(Courtesy Bureau of Chemistry.)
Average composition:
Frazier, of the Cornell station, has collected analyses of a large number of different varieties of potatoes, and finds them to have the following average composition:
| Water, | 75.00 | percent |
| Starch, | 19.87 | „ |
| Sugars and dextrin, | .77 | „ |
| Fat, | .08 | „ |
| Cellulose, | .33 | „ |
| Ash, | 1.00 | „ |
The following analyses show in detail the composition of potatoes from different localities:
Analysis of Maine potatoes:
The Bureau of Chemistry a few years ago made an investigation in connection with the experiment station in Maine of the composition of potatoes grown in that state used for table purposes and for starch making. Some of the best varieties grown in different parts of the state were subjected to analysis, and the following results show them to be of quite uniform composition:
Analyses of Maine Potatoes.[29]
| Variety. | Water. | Starch. | Fiber. | Protein (Nitrogen × 6.25). | Ash. | Specific Gravity. |
|---|---|---|---|---|---|---|
| Percent. | Percent. | Percent. | Percent. | Percent. | ||
| Hebron, | 79.72 | 16.94 | 0.90 | 2.12 | 0.76 | 1.0604 |
| Do. | 78.13 | 18.59 | .72 | 2.06 | .78 | 1.0795 |
| White Elephant, | 76.81 | 19.96 | .84 | 2.19 | .99 | 1.0867 |
| Do. | 76.92 | 20.38 | .90 | 2.31 | .87 | 1.0742 |
| Do. | 78.74 | 15.96 | .64 | 2.25 | .92 | 1.0803 |
| Do. | 75.21 | 19.31 | .61 | 2.12 | .83 | 1.1058 |
| Do. | 75.88 | 18.81 | .56 | 2.25 | .96 | 1.0921 |
| Do. | 77.44 | 18.12 | .63 | 2.06 | .88 | 1.0906 |
| Do. | 75.56 | 18.14 | .56 | 1.81 | 1.04 | 1.1129 |
| Do. | 78.13 | 18.62 | .63 | 1.75 | .98 | 1.0881 |
| Delaware, | 76.02 | 19.20 | .61 | 2.06 | 1.01 | 1.0852 |
| Do. | 76.93 | 18.63 | .61 | 2.19 | .94 | 1.0904 |
| Do. | 75.72 | 18.63 | .55 | 2.31 | .95 | 1.0745 |
| Do. | 77.64 | 16.26 | .61 | 2.56 | .91 | 1.1120 |
| Carmen, | 76.87 | 18.03 | .66 | 2.06 | .90 | 1.0967 |
| Do. | 76.57 | 17.07 | .59 | 2.38 | .76 | 1.0804 |
| Average, | 77.02 | 18.29 | .66 | 2.16 | .91 | 1.0881 |