A Study of Native and Chemically Modified Potato Starch. Part II: Digestibility in the Rat Intestinal Tract

The in vivo digestibility of the following chemically modified potato starch derivatives was evaluated in rats; distarch phosphate (DSP), acetyl di‐starch phosphate (ADSP) and hydroxypropyl di‐starch phosphate (HPDSP). Unmodified potato starch was used as reference. The starches were studied raw and after gelatinization by drum‐drying. The extent of in vivo digestion was evaluated through balance experiments in normal rats (apparent digestibility) and in rats treated with an antibiotic drug to suppress hind‐gut fermentation (true digestibility). Starch digestibility was calculated from direct measurement of starch in feed and faeces. Three different methods for starch analysis were compared. The apparent digestibility of raw potato starches was low, ranging from 50 (HPDSP) to 84% (ADSP). The true digestibility of gelatinized unmodified potato starch was essentially complete and was not affected to any appreciable extent as a result of cross‐linking or acetylation. In contrast, etherification with hydroxypropyl significantly reduced the extent of digestion and absorption to a low level, about 50%, which was not significantly different from that with the corresponding raw material. Thus, the digestibility of the HPDSP derivative was not improved by gelatinization. The maldigested hydroxypropylated starch fraction was only metabolized to a limited degree by the hind‐gut microorganisms.