Abstract
Potatoes and legume seeds have been used as main food stuffs for human beings. However, there is little information as to the effects on the digestibilities of their starches by cell wall polysaccharides, which surround the starch granules.
In the present study, we examined chemically, in vitro, the cell wall polysaccharides and their effects on the digestibilities of gelatinized starches, using different kinds of potatoes, i. e., potato (Solanum tuberosum), yamanoimo (Dioscorea Batatas) and sweet potato (Ipomoea Batatas).
The cell wall polysaccharides of each potato were fractionated by successive extractions with cold water, hot water, 0.5% ammonium oxalate, 5% sodium hydroxide, 24% potassium hydroxide and 90% dimethylsulfoxide.
The result obtained were as follows:
1. The presence of cell wall polysaccharides which surround starch granules suppressed significantly the digestibility of gelatinized starches by porcine pancreatic α-amylase. The suppression rate was the highest in the case of sweet potato and the lowest in yamanoimo.
2. The amounts of hemicellulose and cellulose were found to be the lowest in yamanoimo and the highest in sweet potato. A structural weakness of the cell wall was observed in yamanoimo.
3. Inhibitory activity by each cell wall polysaccharide on porcine pancreatic α-amylase was not observed.
4. The constitution of cell, wall polysaccharides surrounding heat-gelatinized starches may affect in vitro the digestibility of starches by α-amylase.
