Digestibility and metabolism of soluble amylose and amylopectin starches in the rat

Abstract

Modified water soluble potato (70-75 % amylopectin) and amylomaize-7 (70% amylose) starches were studied. Male rats were fed one of the 4 carbohydrates, commercial com starch, dextrose, modified potato starch, and modified amylomaize-7 starch at 55 g/100 g diet, from 5 to 9 wk of age. Body weights were similar in all groups. Food consumption was significantly higher in the two modified starch-fed groups. In the two experimental groups, especially in modified potato starch-fed group, high bulk feces were noticed, and the colons were fill of undigested starch and gas. Digestibilities were 100 ± 0 % for commercial com starch, 100 ± 0 % for dextrose, 69.0 ± 1.0 % for modified potato starch, and 91.5 ± 0.8 % for modified amylomaize-7 starch (n=9, X ± SEM). The modified potato starch-fed group deposited less fat, protein, and energy than the other three groups. Heart and epididymal fat pad weights were also lower in the modified potato starch-fed group. However, liver weights were elevated in the two groups fed the experimental starches. Mean fasting TG values were similar in all groups. Fasting serum free fatty acid concentration was higher in the modified potato starch-fed group than the two control groups. Free fatty acid concentrations were similar in the amylomaize-7 starch-fed group and the two control groups. Mean fasting serum protein concentration was significantly lower in the modified potato starch-fed group. Mean fasting serum glucose concentrations were significantly higher in the two experimental groups. The ratio o( insulin to glucagon was lowest in the modified potato starch-fed group; in the amylomaize-7 starch-fed group the ratio was lower than in the dextrose-fed group. The data indicate that the rats compensated for the lower digestibility of the two experimental starches by increasing food consumption. Products of fermentation might contribute to gluconeogenesis to account for the higher fasting serum glucose in the two experimental groups. These data indicate that only the modified amylomaize-7 starch may be useful to develop food product for liquid nutritional supplements.