Utilization of Sweet Potato Starch by Rats and Its Effect on the Digestion of Dietary Protein

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Abstract
The digestibility of sweet potato starch and the degree of its effect upon the digestion of dietary protein were compared with those of cornstarch and potato starch, by feeding adult white rats diets containing one of these starches as the sole source of carbohydrate. The coefficients of digestibility of corn, sweet potato and potato starch were found to be 99, 97 and 57%, respectively. The differences are statistically significant. When the diets were steamed, all starches were utilized nearly perfectly and no significant differences were observed. Raw sweet potato starch caused diarrhea and markedly decreased the apparent digestibility of dietary protein. This effect was decreased when sweet potato starch was purified, and disappeared when it was steamed. It is suggested that some component of the sweet potato which caused diarrhea is carried along with the starch, and that it would appear to be heat labile and can be removed by washing with certain solvents. Raw potato starch was little utilized and it also lowered the apparent digestibility of the dietary protein. It is sugested that the main reason for this is the heat-labile digestion-resistant property of the potato starch granule.