Abstract
The contents of dietary fiber (DF : cellulose, hemicellulose, lignin and pectin) in sweet potatoes (SP) of 15 varieties were determined. Analyses were carried out by the method of Southgate with some modification made by Mori et al., Van Soest and m-hydroxydiphenyl method, respectively. t-test was applied to know whether there was any difference in DF contens among various SP; improved and YEN (D. E. Yen collection introduced from New Zealand) races, different flesh colors of tuberous roots, production place and harvest years.
1) Contents of DF of the SP in 1981. year were as follows : cellulose, 2. 28±0. 87 %; hemicellulose, 1. 11±0. 67 %; lignin, 0. 04±0. 11 %; pectin, 0. 92±0. 64 %; crude starch, 69. 2±10.2%; crude fiber (CF), 2.64±0.43%; total DF/CF, 1.84±0.84%; respectively (mean±S. D., on dry matter basis).
2) Contents of cellulose, hemicellulose, lignin and total DF (total contents of cellulose, hemicellulose, lignin and pectin) were significantly lower in the leading cultivation races of Japan than in the YEN races.
3) There were significant differences in the DF contents among SP with various flesh colors of tuberous roots : in pectin content, white yellow flesh< red purple one; in cellulose and hemicellulose, white yellow flesh < orange one; in hemicellulose contents, red purple < orange one.
4) Cellulose, hemicellulose and pectin contents were significantly higher in the SP of the leading cultivation races of Japan in harvest year of 1982 than in ones of 1981.
5) Hemicellulose contents were significantly higher in the SP of the leading cultivation races of Japan of Chiba cultivated fields than in ones of Gunma. ADF-lignin contents were significantly higher in SP from Gunma cultivated fields than ones from Chiba.
6) The DF contents were negatively correlated with the starch contents in the SP of 1981 and 1982.
