Abstract
It has long been known that both the total dry matter and the starch content of potato tubers are proportional to the specific gravity; in fact in factory practice Märker's 1 table of specific gravities is commonly used in assaying potatoes for starch. Also, the starch content and dry matter are correlated positively with mealiness, whereas high protein causes sogginess. According to American standards mealiness is desirable; in Europe the reverse is true. Therefore it would seem that attempts to develop a high protein potato and still to maintain desirable culinary properties were doomed to failure, although East 2 was convinced otherwise, provided a high dry-matter content be maintained.
In 1911 56 samples of potatoes, representing 4 varietal groups, and grown under various conditions in different parts of Minnesota, were collected and analyzed at this station, with a view to determining the factors which affect the composition. It seemed desirable to utilize these data still further by calculating the coefficients of correlation among all the constituents of the tubers. The results of these calculations appear in Table I. Both starch and soluble sugars were determined, but the sum of the two only is here presented. The starch represents about 95 per cent. of the two.
It will be seen that there is an intimate relation between specific gravity and dry matter, which is to be expected. It will be further noticed that there is no correlation whatsoever between carbohydrate and dry matter and between nitrogen and dry matter. This is not contrary to the relation stated above between specific gravity and starch, since in factory practice the starch content is considered on the wet basis, and in this table all calculations are on the dry basis.
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